Nano-Micro Letters

Precision-Engineered Construction of Proton-Conducting Metal–Organic Frameworks

Liyu Zhu, Hongbin Yang, Ting Xu, Feng Shen, Chuanling Si — Wed, 11 Dec 2024 00:00:00 +0000

Proton-conducting materials have attracted considerable interest because of their extensive application in energy storage and conversion devices. Among them, metal–organic frameworks (MOFs) present tremendous development potential and possibilities for constructing novel advanced proton conductors due to their special advantages in crystallinity, designability, and porosity. In particular, several special design strategies for the structure of MOFs have opened new doors for the advancement of MOF proton conductors, such as charged network construction, ligand functionalization, metal-center manipulation, defective engineering, guest molecule incorporation, and pore-space manipulation. With the implementation of these strategies, proton-conducting MOFs have developed significantly and profoundly within the last decade. Therefore, in this review, we critically discuss and analyze the fundamental principles, design strategies, and implementation methods targeted at improving the proton conductivity of MOFs through representative examples. Besides, the structural features, the proton conduction mechanism and the behavior of MOFs are discussed thoroughly and meticulously. Future endeavors are also proposed to address the challenges of proton-conducting MOFs in practical research. We sincerely expect that this review will bring guidance and inspiration for the design of proton-conducting MOFs and further motivate the research enthusiasm for novel proton-conducting materials.

Highlights:
1 The effects of the size structure and stability of metal–organic frameworks (MOFs) on proton conduction are comprehensively summarized.
2 Advanced strategies for constructing proton conduction MOFs are critically discussed.
3 Challenges and opportunities for the development of novel proton-conducting MOFs are further outlined.

Tailoring Cathode–Electrolyte Interface for High-Power and Stable Lithium–Sulfur Batteries

Wed, 04 Dec 2024 00:00:00 +0000

Global interest in lithium–sulfur batteries as one of the most promising energy storage technologies has been sparked by their low sulfur cathode cost, high gravimetric, volumetric energy densities, abundant resources, and environmental friendliness. However, their practical application is significantly impeded by several serious issues that arise at the cathode–electrolyte interface, such as interface structure degradation including the uneven deposition of Li₂S, unstable cathode–electrolyte interphase (CEI) layer and intermediate polysulfide shuttle effect. Thus, an optimized cathode–electrolyte interface along with optimized electrodes is required for overall improvement. Herein, we comprehensively outline the challenges and corresponding strategies, including electrolyte optimization to create a dense CEI layer, regulating the Li₂S deposition pattern, and inhibiting the shuttle effect with regard to the solid–liquid–solid pathway, the transformation from solid–liquid–solid to solid–solid pathway, and solid–solid pathway at the cathode–electrolyte interface. In order to spur more perceptive research and hasten the widespread use of lithium–sulfur batteries, viewpoints on designing a stable interface with a deep comprehension are also put forth.

Highlights:
1 This review delves into the mechanism of the state-of-the-art lithium–sulfur batteries from a novel perspective of cathode–electrolyte interface.
2 It provides extensive strategies to construct a stable cathode–electrolyte interphase layer and improve the uneven deposition of Li₂S, enhancing the stability of the interface structure.
3 It proposes an in-depth and comprehensive research on how to inhibit the shuttle effect at the cathode–electrolyte interface with regard to distinct reaction pathways.

Atomically Precise Cu Nanoclusters: Recent Advances, Challenges, and Perspectives in Synthesis and Catalytic Applications

Tue, 03 Dec 2024 00:00:00 +0000

Atomically precise metal nanoclusters are an emerging type of nanomaterial which has diverse interfacial metal–ligand coordination motifs that can significantly affect their physicochemical properties and functionalities. Among that, Cu nanoclusters have been gaining continuous increasing research attentions, thanks to the low cost, diversified structures, and superior catalytic performance for various reactions. In this review, we first summarize the recent progress regarding the synthetic methods of atomically precise Cu nanoclusters and the coordination modes between Cu and several typical ligands and then discuss the catalytic applications of these Cu nanoclusters with some explicit examples to explain the atomical-level structure–performance relationship. Finally, the current challenges and future research perspectives with some critical thoughts are elaborated. We hope this review can not only provide a whole picture of the current advances regarding the synthesis and catalytic applications of atomically precise Cu nanoclusters, but also points out some future research visions in this rapidly booming field.

Highlights:
1 Summarizing recent advances on synthesis and catalytic applications of Cu nanoclusters.
2 The structure–property–functionality relationship is clearly elucidated.
3 Critical analysis of the current challenges and future perspectives.

Advances in the Development of Gradient Scaffolds Made of Nano-Micromaterials for Musculoskeletal Tissue Regeneration

Wed, 27 Nov 2024 00:00:00 +0000

The intricate hierarchical structure of musculoskeletal tissues, including bone and interface tissues, necessitates the use of complex scaffold designs and material structures to serve as tissue-engineered substitutes. This has led to growing interest in the development of gradient bone scaffolds with hierarchical structures mimicking the extracellular matrix of native tissues to achieve improved therapeutic outcomes. Building on the anatomical characteristics of bone and interfacial tissues, this review provides a summary of current strategies used to design and fabricate biomimetic gradient scaffolds for repairing musculoskeletal tissues, specifically focusing on methods used to construct compositional and structural gradients within the scaffolds. The latest applications of gradient scaffolds for the regeneration of bone, osteochondral, and tendon-to-bone interfaces are presented. Furthermore, the current progress of testing gradient scaffolds in physiologically relevant animal models of skeletal repair is discussed, as well as the challenges and prospects of moving these scaffolds into clinical application for treating musculoskeletal injuries.

Highlights:
1 This review highlights the gradient variations in the structural composition of musculoskeletal tissues and comprehensively examines recent progress in the fabrication and application of biomimetic gradient scaffolds for musculoskeletal repair.
2 The challenges and prospects of gradient scaffolds for clinical application are discussed.

Recent Strategies and Advances in Hydrogel-Based Delivery Platforms for Bone Regeneration

Xiao Wang, Jia Zeng, Donglin Gan, Kun Ling, Mingfang He, Jianshu Li, Yongping Lu — Wed, 27 Nov 2024 00:00:00 +0000

Bioactive molecules have shown great promise for effectively regulating various bone formation processes, rendering them attractive therapeutics for bone regeneration. However, the widespread application of bioactive molecules is limited by their low accumulation and short half-lives in vivo. Hydrogels have emerged as ideal carriers to address these challenges, offering the potential to prolong retention times at lesion sites, extend half-lives in vivo and mitigate side effects, avoid burst release, and promote adsorption under physiological conditions. This review systematically summarizes the recent advances in the development of bioactive molecule-loaded hydrogels for bone regeneration, encompassing applications in cranial defect repair, femoral defect repair, periodontal bone regeneration, and bone regeneration with underlying diseases. Additionally, this review discusses the current strategies aimed at improving the release profiles of bioactive molecules through stimuli-responsive delivery, carrier-assisted delivery, and sequential delivery. Finally, this review elucidates the existing challenges and future directions of hydrogel encapsulated bioactive molecules in the field of bone regeneration.

Highlights:
1 Recent advances in the combined delivery platform that integrate nano-/microscale carriers and with 3D hydrogel network for bone regeneration are summarized.
2 The strategies for bioactive molecules delivery involving nanoparticles, nanosheets, and microspheres, along with extra stimuli such as near-infrared light, temperature changes, ultrasonication, and inflammatory conditions, are introduced.
3 The prospects and challenges for the clinical translation and the development of nano-/microscale incorporated hydrogel-based delivery platform are discussed.

Recent Advances in Artificial Sensory Neurons: Biological Fundamentals, Devices, Applications, and Challenges

Shuai Zhong, Lirou Su, Mingkun Xu, Desmond Loke, Bin Yu, Yishu Zhang, Rong Zhao — Wed, 13 Nov 2024 00:00:00 +0000

Spike-based neural networks, which use spikes or action potentials to represent information, have gained a lot of attention because of their high energy efficiency and low power consumption. To fully leverage its advantages, converting the external analog signals to spikes is an essential prerequisite. Conventional approaches including analog-to-digital converters or ring oscillators, and sensors suffer from high power and area costs. Recent efforts are devoted to constructing artificial sensory neurons based on emerging devices inspired by the biological sensory system. They can simultaneously perform sensing and spike conversion, overcoming the deficiencies of traditional sensory systems. This review summarizes and benchmarks the recent progress of artificial sensory neurons. It starts with the presentation of various mechanisms of biological signal transduction, followed by the systematic introduction of the emerging devices employed for artificial sensory neurons. Furthermore, the implementations with different perceptual capabilities are briefly outlined and the key metrics and potential applications are also provided. Finally, we highlight the challenges and perspectives for the future development of artificial sensory neurons.

Highlights:
1 Biological fundamentals and recent progress of artificial sensory neurons are systematically reviewed.
2 Basic device, performance metrics, and potential applications of artificial sensory neurons are summarized.
3 Challenges for the future development of artificial sensory neurons are discussed.

Smart Gas Sensors: Recent Developments and Future Prospective

Boyang Zong, Shufang Wu, Yuehong Yang, Qiuju Li, Tian Tao, Shun Mao — Mon, 04 Nov 2024 00:00:00 +0000

Gas sensor is an indispensable part of modern society with wide applications in environmental monitoring, healthcare, food industry, public safety, etc. With the development of sensor technology, wireless communication, smart monitoring terminal, cloud storage/computing technology, and artificial intelligence, smart gas sensors represent the future of gas sensing due to their merits of real-time multifunctional monitoring, early warning function, and intelligent and automated feature. Various electronic and optoelectronic gas sensors have been developed for high-performance smart gas analysis. With the development of smart terminals and the maturity of integrated technology, flexible and wearable gas sensors play an increasing role in gas analysis. This review highlights recent advances of smart gas sensors in diverse applications. The structural components and fundamental principles of electronic and optoelectronic gas sensors are described, and flexible and wearable gas sensor devices are highlighted. Moreover, sensor array with artificial intelligence algorithms and smart gas sensors in “Internet of Things” paradigm are introduced. Finally, the challenges and perspectives of smart gas sensors are discussed regarding the future need of gas sensors for smart city and healthy living.

Highlights:
1 Recent developments of advanced electronic and optoelectronic gas sensors are introduced.
2 Sensor array with artificial intelligence algorithms and smart gas sensors in “Internet of Things” paradigm are highlighted.
3 Applications of smart gas sensors in environmental monitoring, medical and healthcare applications, food quality control, and public safety are described.

Solution-Processed Thin Film Transparent Photovoltaics: Present Challenges and Future Development

Wed, 23 Oct 2024 00:00:00 +0000

Electrical energy is essential for modern society to sustain economic growths. The soaring demand for the electrical energy, together with an awareness of the environmental impact of fossil fuels, has been driving a shift towards the utilization of solar energy. However, traditional solar energy solutions often require extensive spaces for a panel installation, limiting their practicality in a dense urban environment. To overcome the spatial constraint, researchers have developed transparent photovoltaics (TPV), enabling windows and facades in vehicles and buildings to generate electric energy. Current TPV advancements are focused on improving both transparency and power output to rival commercially available silicon solar panels. In this review, we first briefly introduce wavelength- and non-wavelength-selective strategies to achieve transparency. Figures of merit and theoretical limits of TPVs are discussed to comprehensively understand the status of current TPV technology. Then we highlight recent progress in different types of TPVs, with a particular focus on solution-processed thin-film photovoltaics (PVs), including colloidal quantum dot PVs, metal halide perovskite PVs and organic PVs. The applications of TPVs are also reviewed, with emphasis on agrivoltaics, smart windows and facades. Finally, current challenges and future opportunities in TPV research are pointed out.

Highlights:
1 Recent advancement in solution-processed thin film transparent photovoltaics (TPVs) is summarized, including perovskites, organics, and colloidal quantum dots.
2 Pros and cons of the emerging TPVs are analyzed according to the materials characteristics and the application requirements on the aesthetics and energy generation.
3 Promising TPV applications are discussed with emphasis on agrivoltaics, smart windows and facades.

Unleashing the Potential of Electroactive Hybrid Biomaterials and Self-Powered Systems for Bone Therapeutics

Thu, 17 Oct 2024 00:00:00 +0000

The incidence of large bone defects caused by traumatic injury is increasing worldwide, and the tissue regeneration process requires a long recovery time due to limited self-healing capability. Endogenous bioelectrical phenomena have been well recognized as critical biophysical factors in bone remodeling and regeneration. Inspired by bioelectricity, electrical stimulation has been widely considered an external intervention to induce the osteogenic lineage of cells and enhance the synthesis of the extracellular matrix, thereby accelerating bone regeneration. With ongoing advances in biomaterials and energy-harvesting techniques, electroactive biomaterials and self-powered systems have been considered biomimetic approaches to ensure functional recovery by recapitulating the natural electrophysiological microenvironment of healthy bone tissue. In this review, we first introduce the role of bioelectricity and the endogenous electric field in bone tissue and summarize different techniques to electrically stimulate cells and tissue. Next, we highlight the latest progress in exploring electroactive hybrid biomaterials as well as self-powered systems such as triboelectric and piezoelectric-based nanogenerators and photovoltaic cell-based devices and their implementation in bone tissue engineering. Finally, we emphasize the significance of simulating the target tissue’s electrophysiological microenvironment and propose the opportunities and challenges faced by electroactive hybrid biomaterials and self-powered bioelectronics for bone repair strategies.

Highlights:
1 Introduce the role of bioelectricity and the endogenous electric field in bone tissue and summarize different techniques to electrically stimulate cells and tissue.
2 Highlight the latest progress in exploring electroactive hybrid biomaterials as well as self-powered systems such as triboelectric and piezoelectric-based nanogenerators and photovoltaic cell-based devices in bone tissue engineering.
3 Emphasize the significance of simulating the target tissue’s electrophysiological microenvironment and propose the opportunities and challenges faced by electroactive hybrid biomaterials and self-powered bioelectronics.

Molecular Structure Tailoring of Organic Spacers for High-Performance Ruddlesden–Popper Perovskite Solar Cells

Thu, 10 Oct 2024 00:00:00 +0000

Layer-structured Ruddlesden–Popper (RP) perovskites (RPPs) with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell (PSC) technology. However, two-dimensional (2D) or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy, blocked charge transport and poor film quality, which restrict their photovoltaic performance. Fortunately, these issues can be readily resolved by rationally designing spacer cations of RPPs. This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications. We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics, charge transporting ability and stability of RPPs. Then we brought three aspects to attention for designing organic spacers. Finally, we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs. These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.

Highlights:
1 Organic spacers in Ruddlesden–Popper (RP) perovskites play a vital role in tuning crystallization, charge transport and photovoltaic performance for RP perovskite solar cells (PSCs).
2 Fundamental understanding of the functions of molecular structure of organic spacers is the prerequisite to design high-performance PSCs.
3 This review proposes practical design strategies in seeking RP molecular structure to maximize its photovoltaic performance for PSCs.

Flexible Graphene Field-Effect Transistors and Their Application in Flexible Biomedical Sensing

Mon, 07 Oct 2024 00:00:00 +0000

Flexible electronics are transforming our lives by making daily activities more convenient. Central to this innovation are field-effect transistors (FETs), valued for their efficient signal processing, nanoscale fabrication, low-power consumption, fast response times, and versatility. Graphene, known for its exceptional mechanical properties, high electron mobility, and biocompatibility, is an ideal material for FET channels and sensors. The combination of graphene and FETs has given rise to flexible graphene field-effect transistors (FGFETs), driving significant advances in flexible electronics and sparked a strong interest in flexible biomedical sensors. Here, we first provide a brief overview of the basic structure, operating mechanism, and evaluation parameters of FGFETs, and delve into their material selection and patterning techniques. The ability of FGFETs to sense strains and biomolecular charges opens up diverse application possibilities. We specifically analyze the latest strategies for integrating FGFETs into wearable and implantable flexible biomedical sensors, focusing on the key aspects of constructing high-quality flexible biomedical sensors. Finally, we discuss the current challenges and prospects of FGFETs and their applications in biomedical sensors. This review will provide valuable insights and inspiration for ongoing research to improve the quality of FGFETs and broaden their application prospects in flexible biomedical sensing.

Highlights:
1 The review provides a brief overview of the basic structure, operating mechanism, and key performance indicators of flexible graphene field-effect transistors.
2 The review details the preparation strategy of flexible graphene field-effect transistors focusing on material selection and patterning techniques.
3 The review analyzes the latest strategies for developing wearable and implantable flexible biomedical sensors based on flexible graphene field-effect transistors.

Optimization Strategies of Na3V2(PO4)3 Cathode Materials for Sodium-Ion Batteries

Fri, 04 Oct 2024 00:00:00 +0000

Na₃V₂(PO₄)₃ (NVP) has garnered great attentions as a prospective cathode material for sodium-ion batteries (SIBs) by virtue of its decent theoretical capacity, superior ion conductivity and high structural stability. However, the inherently poor electronic conductivity and sluggish sodium-ion diffusion kinetics of NVP material give rise to inferior rate performance and unsatisfactory energy density, which strictly confine its further application in SIBs. Thus, it is of significance to boost the sodium storage performance of NVP cathode material. Up to now, many methods have been developed to optimize the electrochemical performance of NVP cathode material. In this review, the latest advances in optimization strategies for improving the electrochemical performance of NVP cathode material are well summarized and discussed, including carbon coating or modification, foreign-ion doping or substitution and nanostructure and morphology design. The foreign-ion doping or substitution is highlighted, involving Na, V, and PO₄³⁻ sites, which include single-site doping, multiple-site doping, single-ion doping, multiple-ion doping and so on. Furthermore, the challenges and prospects of high-performance NVP cathode material are also put forward. It is believed that this review can provide a useful reference for designing and developing high-performance NVP cathode material toward the large-scale application in SIBs.

Highlights:
1 Optimization strategies for high-performance Na₃V₂(PO₄)₃ (NVP) cathode material are well summarized and discussed, including carbon coating or modification, foreign-ion doping or substitution and nanostructure and morphology design.
2 The foreign-ion doping or substitution is highlighted, involving the Na, V, and PO₄³⁻ sites, which include single-site doping, multiple-site doping, single-ion doping and multiple-ion doping.
3 Challenges and future perspectives for high-performance NVP cathode material are presented.

Engineered Cancer Nanovaccines: A New Frontier in Cancer Therapy

Yijie Wang, Congrui Liu, Chao Fang, Qiuxia Peng, Wen Qin, Xuebing Yan, Kun Zhang — Mon, 30 Sep 2024 00:00:00 +0000

Vaccinations are essential for preventing and treating disease, especially cancer nanovaccines, which have gained considerable interest recently for their strong anti-tumor immune capabilities. Vaccines can prompt the immune system to generate antibodies and activate various immune cells, leading to a response against tumor tissues and reducing the negative effects and recurrence risks of traditional chemotherapy and surgery. To enhance the flexibility and targeting of vaccines, nanovaccines utilize nanotechnology to encapsulate or carry antigens at the nanoscale level, enabling more controlled and precise drug delivery to enhance immune responses. Cancer nanovaccines function by encapsulating tumor-specific antigens or tumor-associated antigens within nanomaterials. The small size of these nanomaterials allows for precise targeting of T cells, dendritic cells, or cancer cells, thereby eliciting a more potent anti-tumor response. In this paper, we focus on the classification of carriers for cancer nanovaccines, the roles of different target cells, and clinically tested cancer nanovaccines, discussing strategies for effectively inducing cytotoxic T lymphocytes responses and optimizing antigen presentation, while also looking ahead to the translational challenges of moving from animal experiments to clinical trials.

Highlights:
1 We classified the carriers that built cancer nanovaccines, discussed their diversified applications and coincidently compared their advantages and disadvantages.
2 Various cellular targets that guide the design and engineering of cancer nanovaccines are categorized and their characteristics and benefits are highlighted.
3 The clinical cases and encountered challenges in cancer nanovaccines are discussed, during which reasonable solutions and future research direction are provided.

Recent Advances in Fibrous Materials for Hydroelectricity Generation

Mon, 30 Sep 2024 00:00:00 +0000

Depleting fossil energy sources and conventional polluting power generation pose a threat to sustainable development. Hydroelectricity generation from ubiquitous and spontaneous phase transitions between liquid and gaseous water has been considered a promising strategy for mitigating the energy crisis. Fibrous materials with unique flexibility, processability, multifunctionality, and practicability have been widely applied for fibrous materials-based hydroelectricity generation (FHG). In this review, the power generation mechanisms, design principles, and electricity enhancement factors of FHG are first introduced. Then, the fabrication strategies and characteristics of varied constructions including 1D fiber, 1D yarn, 2D fabric, 2D membrane, 3D fibrous framework, and 3D fibrous gel are demonstrated. Afterward, the advanced functions of FHG during water harvesting, proton dissociation, ion separation, and charge accumulation processes are analyzed in detail. Moreover, the potential applications including power supply, energy storage, electrical sensor, and information expression are also discussed. Finally, some existing challenges are considered and prospects for future development are sincerely proposed.

Highlights:
1 Fundamental principles and characteristics of fibrous materials-based hydroelectricity generation (FHG) are thoroughly reviewed.
2 Fabrication strategies and advanced functions of FHG are discussed and summarized in detail.
3 Challenges and perspectives of the next-generation development of FHG are discussed.

Exploring Nanoscale Perovskite Materials for Next-Generation Photodetectors: A Comprehensive Review and Future Directions

Mon, 30 Sep 2024 00:00:00 +0000

The rapid advancement of nanotechnology has sparked much interest in applying nanoscale perovskite materials for photodetection applications. These materials are promising candidates for next-generation photodetectors (PDs) due to their unique optoelectronic properties and flexible synthesis routes. This review explores the approaches used in the development and use of optoelectronic devices made of different nanoscale perovskite architectures, including quantum dots, nanosheets, nanorods, nanowires, and nanocrystals. Through a thorough analysis of recent literature, the review also addresses common issues like the mechanisms underlying the degradation of perovskite PDs and offers perspectives on potential solutions to improve stability and scalability that impede widespread implementation. In addition, it highlights that photodetection encompasses the detection of light fields in dimensions other than light intensity and suggests potential avenues for future research to overcome these obstacles and fully realize the potential of nanoscale perovskite materials in state-of-the-art photodetection systems. This review provides a comprehensive overview of nanoscale perovskite PDs and guides future research efforts towards improved performance and wider applicability, making it a valuable resource for researchers.

Highlights:
1 Innovative synthesis method for nanoscale-based perovskites with enhanced stability and efficiency.
2 Novel application of nanoscale-based perovskites in optoelectronics with superior performance metrics.
3 Comprehensive analysis of the structure–property relationships in perovskite nanomaterials.

High-Entropy Electrode Materials: Synthesis, Properties and Outlook

Fri, 27 Sep 2024 00:00:00 +0000

High-entropy materials represent a new category of high-performance materials, first proposed in 2004 and extensively investigated by researchers over the past two decades. The definition of high-entropy materials has continuously evolved. In the last ten years, the discovery of an increasing number of high-entropy materials has led to significant advancements in their utilization in energy storage, electrocatalysis, and related domains, accompanied by a rise in techniques for fabricating high-entropy electrode materials. Recently, the research emphasis has shifted from solely improving the performance of high-entropy materials toward exploring their reaction mechanisms and adopting cleaner preparation approaches. However, the current definition of high-entropy materials remains relatively vague, and the preparation method of high-entropy materials is based on the preparation method of single metal/low- or medium-entropy materials. It should be noted that not all methods applicable to single metal/low- or medium-entropy materials can be directly applied to high-entropy materials. In this review, the definition and development of high-entropy materials are briefly reviewed. Subsequently, the classification of high-entropy electrode materials is presented, followed by a discussion of their applications in energy storage and catalysis from the perspective of synthesis methods. Finally, an evaluation of the advantages and disadvantages of various synthesis methods in the production process of different high-entropy materials is provided, along with a proposal for potential future development directions for high-entropy materials.

Highlights:
1 The developmental history of high-entropy materials and the conceptual origin of “high entropy” is comprehensively reviewed.
2 The preparation methods of various high-entropy electrode materials are comprehensively reviewed.
3 The application properties of various high-entropy electrode materials in electrocatalysis and energy storage are comprehensively reviewed, with a prospective outlook on the future development of such materials.

Advances in Graphene-Based Electrode for Triboelectric Nanogenerator

Fri, 27 Sep 2024 00:00:00 +0000

With the continuous development of wearable electronics, wireless sensor networks and other micro-electronic devices, there is an increasingly urgent need for miniature, flexible and efficient nanopower generation technology. Triboelectric nanogenerator (TENG) technology can convert small mechanical energy into electricity, which is expected to address this problem. As the core component of TENG, the choice of electrode materials significantly affects its performance. Traditional metal electrode materials often suffer from problems such as durability, which limits the further application of TENG. Graphene, as a novel electrode material, shows excellent prospects for application in TENG owing to its unique structure and excellent electrical properties. This review systematically summarizes the recent research progress and application prospects of TENGs based on graphene electrodes. Various precision processing methods of graphene electrodes are introduced, and the applications of graphene electrode-based TENGs in various scenarios as well as the enhancement of graphene electrodes for TENG performance are discussed. In addition, the future development of graphene electrode-based TENGs is also prospectively discussed, aiming to promote the continuous advancement of graphene electrode-based TENGs.

Highlights:
1 Comprehensively reviewed the progress in research on graphene electrode-based triboelectric nanogenerators (TENGs) from two dimensions, including precision processing methods of graphene electrodes and applications of TENGs.
2 Discussed the various applications of graphene electrode-based TENGs in different scenarios, as well as the ways in which graphene electrodes enhance the performance of TENGs.
3 Offered a prospective discussion on the future development of graphene electrode-based TENGs, with the aim of promoting continuous advancements in this field.

Prussian Blue Analogue-Templated Nanocomposites for Alkali-Ion Batteries: Progress and Perspective

Jian‑En Zhou, Yilin Li, Xiaoming Lin, Jiaye Ye — Thu, 26 Sep 2024 00:00:00 +0000

Lithium-ion batteries (LIBs) have dominated the portable electronic and electrochemical energy markets since their commercialisation, whose high cost and lithium scarcity have prompted the development of other alkali-ion batteries (AIBs) including sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). Owing to larger ion sizes of Na⁺ and K⁺ compared with Li⁺, nanocomposites with excellent crystallinity orientation and well-developed porosity show unprecedented potential for advanced lithium/sodium/potassium storage. With enticing open rigid framework structures, Prussian blue analogues (PBAs) remain promising self-sacrificial templates for the preparation of various nanocomposites, whose appeal originates from the well-retained porous structures and exceptional electrochemical activities after thermal decomposition. This review focuses on the recent progress of PBA-derived nanocomposites from their fabrication, lithium/sodium/potassium storage mechanism, and applications in AIBs (LIBs, SIBs, and PIBs). To distinguish various PBA derivatives, the working mechanism and applications of PBA-templated metal oxides, metal chalcogenides, metal phosphides, and other nanocomposites are systematically evaluated, facilitating the establishment of a structure–activity correlation for these materials. Based on the fruitful achievements of PBA-derived nanocomposites, perspectives for their future development are envisioned, aiming to narrow down the gap between laboratory study and industrial reality.

Highlights:
1 The synthetic protocols of various Prussian blue analogue (PBA)-templated nanocomposites are discussed.
2 Alkali-ion storage mechanisms based on intercalation, alloying, or conversion reactions are analysed.
3 The properties of PBA-templated nanocomposites in alkali-ion batteries (AIBs) are evaluated and compared to outline the structure–activity correlation.
4 Perspectives for the future development of PBA-templated AIB electrodes are envisaged.

Defect Engineering: Can it Mitigate Strong Coulomb Effect of Mg2+ in Cathode Materials for Rechargeable Magnesium Batteries?

Zhengqing Fan, Ruimin Li, Xin Zhang, Wanyu Zhao, Zhenghui Pan, Xiaowei Yang — Wed, 25 Sep 2024 00:00:00 +0000

Rechargeable magnesium batteries (RMBs) have been considered a promising “post lithium-ion battery” system to meet the rapidly increasing demand of the emerging electric vehicle and grid energy storage market. However, the sluggish diffusion kinetics of bivalent Mg²⁺ in the host material, related to the strong Coulomb effect between Mg²⁺ and host anion lattices, hinders their further development toward practical applications. Defect engineering, regarded as an effective strategy to break through the slow migration puzzle, has been validated in various cathode materials for RMBs. In this review, we first thoroughly understand the intrinsic mechanism of Mg²⁺ diffusion in cathode materials, from which the key factors affecting ion diffusion are further presented. Then, the positive effects of purposely introduced defects, including vacancy and doping, and the corresponding strategies for introducing various defects are discussed. The applications of defect engineering in cathode materials for RMBs with advanced electrochemical properties are also summarized. Finally, the existing challenges and future perspectives of defect engineering in cathode materials for the overall high-performance RMBs are described.

Highlights:
1 The underlying migration mechanism of Mg²⁺ in cathode materials and roles of defects in Mg²⁺ migration in cathode materials were studied.
2 Applications of defect engineering to Mg²⁺ migration in cathode materials and the strategies for introducing various defects were summarized.
3 New development directions of defect engineering in cathode materials for rechargeable magnesium battery were prospected.

Advanced Functional Electromagnetic Shielding Materials: A Review Based on Micro-Nano Structure Interface Control of Biomass Cell Walls

Wed, 25 Sep 2024 00:00:00 +0000

Research efforts on electromagnetic interference (EMI) shielding materials have begun to converge on green and sustainable biomass materials. These materials offer numerous advantages such as being lightweight, porous, and hierarchical. Due to their porous nature, interfacial compatibility, and electrical conductivity, biomass materials hold significant potential as EMI shielding materials. Despite concerted efforts on the EMI shielding of biomass materials have been reported, this research area is still relatively new compared to traditional EMI shielding materials. In particular, a more comprehensive study and summary of the factors influencing biomass EMI shielding materials including the pore structure adjustment, preparation process, and micro-control would be valuable. The preparation methods and characteristics of wood, bamboo, cellulose and lignin in EMI shielding field are critically discussed in this paper, and similar biomass EMI materials are summarized and analyzed. The composite methods and fillers of various biomass materials were reviewed. this paper also highlights the mechanism of EMI shielding as well as existing prospects and challenges for development trends in this field.

Highlights:
1 The advantages of biomass materials for electromagnetic interference (EMI) shielding are analyzed, the mechanism of EMI shielding is summarized, and the factors affecting EMI shielding are analyzed systematically.
2 Various biomass materials (wood, bamboo, lignin, cellulose) were modified to obtain unique structures and improve EMI shielding performance.
3 The problems encountered in the application of biomass materials for EMI shielding are summarized, and the potential development and application in the future are prospected.

Advancements and Challenges in Organic–Inorganic Composite Solid Electrolytes for All-Solid-State Lithium Batteries

Wed, 25 Sep 2024 00:00:00 +0000

To address the limitations of contemporary lithium-ion batteries, particularly their low energy density and safety concerns, all-solid-state lithium batteries equipped with solid-state electrolytes have been identified as an up-and-coming alternative. Among the various SEs, organic–inorganic composite solid electrolytes (OICSEs) that combine the advantages of both polymer and inorganic materials demonstrate promising potential for large-scale applications. However, OICSEs still face many challenges in practical applications, such as low ionic conductivity and poor interfacial stability, which severely limit their applications. This review provides a comprehensive overview of recent research advancements in OICSEs. Specifically, the influence of inorganic fillers on the main functional parameters of OICSEs, including ionic conductivity, Li⁺ transfer number, mechanical strength, electrochemical stability, electronic conductivity, and thermal stability are systematically discussed. The lithium-ion conduction mechanism of OICSE is thoroughly analyzed and concluded from the microscopic perspective. Besides, the classic inorganic filler types, including both inert and active fillers, are categorized with special emphasis on the relationship between inorganic filler structure design and the electrochemical performance of OICSEs. Finally, the advanced characterization techniques relevant to OICSEs are summarized, and the challenges and perspectives on the future development of OICSEs are also highlighted for constructing superior ASSLBs.

Highlights:
1 The lithium-ion conduction mechanism of organic-inorganic composite solid electrolytes (OICSEs) is thoroughly conducted and concluded from the microscopic perspective based on filler content, type, and system.
2 The classic inorganic filler types, including inert and active fillers, are categorized with special emphasis on the relationship between inorganic filler structure design and the electrochemical performance of OICSEs.
3 Advanced characterization techniques for OICSEs are discussed, and the challenges and prospects for developing superior all-solid-state lithium batteries are highlighted.

Bimetallic Single-Atom Catalysts for Water Splitting

Megha A. Deshmukh, Aristides Bakandritsos, Radek Zbořil — Wed, 25 Sep 2024 00:00:00 +0000

Green hydrogen from water splitting has emerged as a critical energy vector with the potential to spearhead the global transition to a fossil fuel-independent society. The field of catalysis has been revolutionized by single-atom catalysts (SACs), which exhibit unique and intricate interactions between atomically dispersed metal atoms and their supports. Recently, bimetallic SACs (bimSACs) have garnered significant attention for leveraging the synergistic functions of two metal ions coordinated on appropriately designed supports. BimSACs offer an avenue for rich metal–metal and metal–support cooperativity, potentially addressing current limitations of SACs in effectively furnishing transformations which involve synchronous proton–electron exchanges, substrate activation with reversible redox cycles, simultaneous multi-electron transfer, regulation of spin states, tuning of electronic properties, and cyclic transition states with low activation energies. This review aims to encapsulate the growing advancements in bimSACs, with an emphasis on their pivotal role in hydrogen generation via water splitting. We subsequently delve into advanced experimental methodologies for the elaborate characterization of SACs, elucidate their electronic properties, and discuss their local coordination environment. Overall, we present comprehensive discussion on the deployment of bimSACs in both hydrogen evolution reaction and oxygen evolution reaction, the two half-reactions of the water electrolysis process.

Highlights:
1 Bimetallic single-atom catalysts (bimSACs) have garnered significant attention for leveraging the synergistic functions of the two metal active centers.
2 This review focuses on the advancements in the field of bimSACs and their pivotal role in hydrogen generation via water splitting.
3 State-of-the-art computational and physicochemical techniques for the analysis of bimSACs and their application in electrocatalytic water splitting are discussed.

Concurrently Boosting Activity and Stability of Oxygen Reduction Reaction Catalysts via Judiciously Crafting Fe–Mn Dual Atoms for Fuel Cells

Mon, 16 Dec 2024 00:00:00 +0000

The ability to unlock the interplay between the activity and stability of oxygen reduction reaction (ORR) represents an important endeavor toward creating robust ORR catalysts for efficient fuel cells. Herein, we report an effective strategy to concurrent enhance the activity and stability of ORR catalysts via constructing atomically dispersed Fe–Mn dual-metal sites on N-doped carbon (denoted (FeMn-DA)–N–C) for both anion-exchange membrane fuel cells (AEMFC) and proton exchange membrane fuel cells (PEMFC). The (FeMn-DA)–N–C catalysts possess ample dual-metal atoms consisting of adjacent Fe-N₄ and Mn-N₄ sites on the carbon surface, yielded via a facile doping-adsorption-pyrolysis route. The introduction of Mn carries several advantageous attributes: increasing the number of active sites, effectively anchoring Fe due to effective electron transfer to Mn (revealed by X-ray absorption spectroscopy and density-functional theory (DFT), thus preventing the aggregation of Fe), and effectively circumventing the occurrence of Fenton reaction, thus reducing the consumption of Fe. The (FeMn-DA)–N–C catalysts showcase half-wave potentials of 0.92 and 0.82 V in 0.1 M KOH and 0.1 M HClO₄, respectively, as well as outstanding stability. As manifested by DFT calculations, the introduction of Mn affects the electronic structure of Fe, down-shifts the d-band Fe active center, accelerates the desorption of OH groups, and creates higher limiting potentials. The AEMFC and PEMFC with (FeMn-DA)–N–C as the cathode catalyst display high power densities of 1060 and 746 mW cm⁻², respectively, underscoring their promising potential for practical applications. Our study highlights the robustness of designing Fe-containing dual-atom ORR catalysts to promote both activity and stability for energy conversion and storage materials and devices.

Highlights:
1 Fe–Mn dual-atom catalysts exhibit superior oxygen reduction reaction (ORR) activity and stability, with high half-wave potentials in both alkaline and acidic conditions.
2 Synergistic Mn incorporation effectively anchors Fe atoms, mitigates the Fenton reaction, and enhances the durability of ORR catalysts.
3 Advanced characterization and density-functional theory calculations reveal Mn-induced electronic structure modifications, promoting superior ORR kinetics and active site performance.
4 (FeMn-DA)-N-C catalysts show remarkable potential for practical fuel cell applications.

Unlocking Novel Functionality: Pseudocapacitive Sensing in MXene-Based Flexible Supercapacitors

Mon, 09 Dec 2024 00:00:00 +0000

Extensively explored for their distinctive pseudocapacitance characteristics, MXenes, a distinguished group of 2D materials, have led to remarkable achievements, particularly in the realm of energy storage devices. This work presents an innovative Pseudocapacitive Sensor. The key lies in switching the energy storage kinetics from pseudocapacitor to electrical double layer capacitor by employing the change of local pH (-log[H⁺]) in MXene-based flexible supercapacitors during bending. Pseudocapacitive sensing is observed in acidic electrolyte but absent in neutral electrolyte. Applied shearing during bending causes liquid-crystalline MXene sheets to increase in their degree of anisotropic alignment. With blocking of H⁺ mobility due to the higher diffusion barrier, local pH increases. The electrochemical energy storage kinetics transits from Faradaic chemical protonation (intercalation) to non-Faradaic physical adsorption. We utilize the phenomenon of capacitance change due to shifting energy storage kinetics for strain sensing purposes. The developed highly sensitive Pseudocapacitive Sensors feature a remarkable gauge factor (GF) of approximately 1200, far surpassing conventional strain sensors (GF: ~ 1 for dielectric-cap sensor). The introduction of the Pseudocapacitive Sensor represents a paradigm shift, expanding the application of pseudocapacitance from being solely confined to energy devices to the realm of multifunctional electronics. This technological leap enriches our understanding of the pseudocapacitance mechanism of MXenes, and will drive innovation in cutting-edge technology areas, including advanced robotics, implantable biomedical devices, and health monitoring systems.

Highlights:
1 We have discovered a novel phenomenon where the pseudocapacitance of flexible MXene supercapacitors changes sensitively in response to bending, leading to the development of Pseudocapacitive Sensors.
2 Pseudocapacitive Sensors repurpose supercapacitors as strain sensors, detecting capacitance changes from shifts between pseudocapacitance and electrical double layer capacitor. These highly sensitive sensors have a gauge factor of about 1200, far exceeding that of conventional strain sensors.

Revealing the Role of Hydrogen in Highly Efficient Ag-Substituted CZTSSe Photovoltaic Devices: Photoelectric Properties Modulation and Defect Passivation

Tue, 03 Dec 2024 00:00:00 +0000

The presence of Sn_Zn-related defects in Cu₂ZnSn(S,Se)₄ (CZTSSe) absorber results in large irreversible energy loss and extra irreversible electron–hole non-radiative recombination, thus hindering the efficiency enhancement of CZTSSe devices. Although the incorporation of Ag in CZTSSe can effectively suppress the Sn_Zn-related defects and significantly improve the resulting cell performance, an excellent efficiency has not been achieved to date primarily owing to the poor electrical-conductivity and the low carrier density of the CZTSSe film induced by Ag substitution. Herein, this study exquisitely devises an Ag/H co-doping strategy in CZTSSe absorber via Ag substitution programs followed by hydrogen-plasma treatment procedure to suppress Sn_Zn defects for achieving efficient CZTSSe devices. In-depth investigation results demonstrate that the incorporation of H in Ag-based CZTSSe absorber is expected to improve the poor electrical-conductivity and the low carrier density caused by Ag substitution. Importantly, the C=O and O–H functional groups induced by hydrogen incorporation, serving as an electron donor, can interact with under-coordinated cations in CZTSSe material, effectively passivating the Sn_Zn-related defects. Consequently, the incorporation of an appropriate amount of Ag/H in CZTSSe mitigates carrier non-radiative recombination, prolongs minority carrier lifetime, and thus yields a champion efficiency of 14.74%, showing its promising application in kesterite-based CZTSSe devices.

Highlights:
1 The Ag/H co-doping strategy has been proposed to promote the performance of Cu₂ZnSn(S,Se)₄ (CZTSSe) devices.
2 The incorporation of H in Ag-based CZTSSe photovoltaic absorber is expected to improve the poor electrical conductivity and the low carrier density caused by Ag substitution.
3 Benefiting from the synergism of the excellent defect passivation effect and photoelectric properties complementary effect enabled by Ag/H co-doping, a champion device with 14.74% efficiency is achieved.

Hierarchical Polyimide Nonwoven Fabric with Ultralow-Reflectivity Electromagnetic Interference Shielding and High-Temperature Resistant Infrared Stealth Performance

Tue, 03 Dec 2024 00:00:00 +0000

Designing and fabricating a compatible low-reflectivity electromagnetic interference (EMI) shielding/high-temperature resistant infrared stealth material possesses a critical significance in the field of military. Hence, a hierarchical polyimide (PI) nonwoven fabric is fabricated by alkali treatment, in-situ growth of magnetic particles and "self-activated" electroless Ag plating process. Especially, the hierarchical impedance matching can be constructed by systematically assembling Fe₃O₄/Ag-loaded PI nonwoven fabric (PFA) and pure Ag-coated PI nonwoven fabric (PA), endowing it with an ultralow-reflectivity EMI shielding performance. In addition, thermal insulation of fluffy three-dimensional (3D) space structure in PFA and low infrared emissivity of PA originated from Ag plating bring an excellent infrared stealth performance. More importantly, the strong bonding interaction between Fe₃O₄, Ag, and PI fiber improves thermal stability in EMI shielding and high-temperature resistant infrared stealth performance. Such excellent comprehensive performance makes it promising for military tents to protect internal equipment from electromagnetic interference stemmed from adjacent equipment and/or enemy, and inhibit external infrared detection.

Highlights:
1 Hierarchical polyimide (PI) nonwoven fabric is fabricated by alkali treatment, in-situ growth of magnetic particles, and "self-activated" electroless Ag plating process.
2 Impedance matching structure by assembling Fe₃O₄/Ag-loaded PI nonwoven fabric (PFA) and pure Ag-coated PI nonwoven fabric (PA) induces more electromagnetic waves enter PFA/PA and be dissipated.
3 The fluffy 3D space structure of PFA with strong adhesion interaction and low infrared emissivity of PA endow PFA/PA with excellent thermal stability in electromagnetic interference shielding and high-temperature resistant infrared stealth performance.

Anti-Swelling Polyelectrolyte Hydrogel with Submillimeter Lateral Confinement for Osmotic Energy Conversion

Tue, 03 Dec 2024 00:00:00 +0000

Harvesting the immense and renewable osmotic energy with reverse electrodialysis (RED) technology shows great promise in dealing with the ever-growing energy crisis. One key challenge is to improve the output power density with improved trade-off between membrane permeability and selectivity. Herein, polyelectrolyte hydrogels (channel width, 2.2 nm) with inherent high ion conductivity have been demonstrated to enable excellent selective ion transfer when confined in cylindrical anodized aluminum pore with lateral size even up to the submillimeter scale (radius, 0.1 mm). The membrane permeability of the anti-swelling hydrogel can also be further increased with cellulose nanofibers. With real seawater and river water, the output power density of a three-chamber cell on behalf of repeat unit of RED system can reach up to 8.99 W m⁻² (per unit total membrane area), much better than state-of-the-art membranes. This work provides a new strategy for the preparation of polyelectrolyte hydrogel-based ion-selective membranes, owning broad application prospects in the fields of osmotic energy collection, electrodialysis, flow battery and so on.

Highlights:
1 Ionic polymers can directly serve as high-performance ion-selective membranes when it was physically confined within submillimeter-sized cylindrical pore.
2 The universality of this strategy is demonstrated in preparing cation/anion-selective membrane.
3 With real seawater and river water, the output power density of a three-chamber cell on behalf of repeat unit of reverse electrodialysis system can reach up to 8.99 W m⁻².

Carbon Nanofiber/Polyaniline Composite Aerogel with Excellent Electromagnetic Interference Shielding, Low Thermal Conductivity, and Extremely Low Heat Release

Mon, 02 Dec 2024 00:00:00 +0000

The rapid development of communication technology and high-frequency electronic devices has created a need for more advanced electromagnetic interference (EMI) shielding materials. In response to this demand, a study has been conducted to develop multifunctional carbon nanofibers (CNFs)/polyaniline (PANI) aerogels with excellent electromagnetic interference shielding, flame retardancy, and thermal insulation performance. The process involved freeze-drying of electrospun CNFs and PANI nanoparticles followed by in situ growth PANI to coat the CNFs, creating the core–shell structured CNFs/PANI composite fiber and its hybrid aerogels (CP-3@PANI). The interaction between PANI and aniline (ANI) provides attachment sites, allowing additional ANI adsorption into the aerogel for in situ polymerization. This results in PANI uniformly covering the surface of the CNFs, creating a core–shell composite fiber with a flexible CNF core and PANI shell. This process enhances the utilization rate of the ANI monomer and increases the PANI content loaded onto the aerogel. Additionally, effective connections are established between the CNFs, forming a stable, conductive three-dimensional network structure. The prepared CP-3@PANI aerogels exhibit excellent EMI shielding efficiency (SE) of 85.4 dB and specific EMI SE (SE d⁻¹) of 791.2 dB cm³ g⁻¹ in the X-band. Due to the synergistic flame-retardant effect of CNFs, PANI, and the dopant (phytic acid), the CP-3@PANI aerogels demonstrate outstanding flame-retardant and thermal insulation properties, with a peak heat release rate (PHRR) as low as 7.8 W g⁻¹ and a total heat release of only 0.58 kJ g⁻¹. This study provides an effective strategy for preparing multifunctional integrated EMI shielding materials.

Highlights:
1 Using electrospun high-strength carbon nanofibers as the aerogel scaffold, high loading of polyaniline in the aerogel was achieved through seed polymerization, forming the core–shell structure fibers and simultaneously connecting the fibers as a stable conductive network.
2 Combining carbon-based materials with conductive polymers like polyaniline significantly improves shielding performance, achieving electromagnetic interference shielding efficiency of up to 84.5 dB and SE d⁻¹ values greater than 791.2 dB cm3 g⁻¹. Flame retardancy reduces PHRR by 65.8%, and thermal insulation with low thermal conductivity of 0.104 W m⁻¹ K⁻¹.

Ultrahigh Energy and Power Density in Ni–Zn Aqueous Battery via Superoxide-Activated Three-Electron Transfer

Yixue Duan, Bolong Li, Kai Yang, Zheng Gong, Xuqiao Peng, Liang He, Derek Ho — Fri, 29 Nov 2024 00:00:00 +0000

Aqueous Ni–Zn microbatteries are safe, reliable and inexpensive but notoriously suffer from inadequate energy and power densities. Herein, we present a novel mechanism of superoxide-activated Ni substrate that realizes the redox reaction featuring three-electron transfers (Ni ↔ Ni³⁺). The superoxide activates the direct redox reaction between Ni substrate and KNiO₂ by lowering the reaction Gibbs free energy, supported by in-situ Raman and density functional theory simulations. The prepared chronopotentiostatic superoxidation-activated Ni (CPS-Ni) electrodes exhibit an ultrahigh capacity of 3.21 mAh cm⁻² at the current density of 5 mA cm⁻², nearly 8 times that of traditional one-electron processes electrodes. Even under the ultrahigh 200 mA cm⁻² current density, the CPS-Ni electrodes show 86.4% capacity retention with a Columbic efficiency of 99.2% after 10,000 cycles. The CPS-Ni||Zn microbattery achieves an exceptional energy density of 6.88 mWh cm⁻² and power density of 339.56 mW cm⁻². Device demonstration shows that the power source can continuously operate for more than 7 days in powering the sensing and computation intensive practical application of photoplethysmographic waveform monitoring. This work paves the way to the development of multi-electron transfer mechanisms for advanced aqueous Ni–Zn batteries with high capacity and long lifetime.

Highlights:
1 Efficient activation of Ni electrode employs chronopotentiostatic superoxidation.
2 Novel superoxide activation mechanism realizes the redox reaction with three-electron transfer (Ni ↔ Ni³⁺).
3 As-prepared CPS-Ni||Zn batteries exhibit simultaneously ultrahigh energy and power densities.

RGB Color-Discriminable Photonic Synapse for Neuromorphic Vision System

Fri, 29 Nov 2024 00:00:00 +0000

To emulate the functionality of the human retina and achieve a neuromorphic visual system, the development of a photonic synapse capable of multispectral color discrimination is of paramount importance. However, attaining robust color discrimination across a wide intensity range, even irrespective of medium limitations in the channel layer, poses a significant challenge. Here, we propose an approach that can bestow the color-discriminating synaptic functionality upon a three-terminal transistor flash memory even with enhanced discriminating capabilities. By incorporating the strong induced dipole moment effect at the excitation, modulated by the wavelength of the incident light, into the floating gate, we achieve outstanding RGB color-discriminating synaptic functionality within a remarkable intensity range spanning from 0.05 to 40 mW cm⁻². This approach is not restricted to a specific medium in the channel layer, thereby enhancing its applicability. The effectiveness of this color-discriminating synaptic functionality is demonstrated through visual pre-processing of a photonic synapse array, involving the differentiation of RGB channels and the enhancement of image contrast with noise reduction. Consequently, a convolutional neural network can achieve an impressive inference accuracy of over 94% for Canadian-Institute-For-Advanced-Research-10 colorful image recognition task after the pre-processing. Our proposed approach offers a promising solution for achieving robust and versatile RGB color discrimination in photonic synapses, enabling significant advancements in artificial visual systems.

Highlights:
1 Photonic synapse capable of multispectral color discrimination is demonstrated.
2 Strong excited-state dipoles enable remarkable discrimination intensity (0.05–40 mW cm^-2).
3 This approach is not restricted to a specific medium in the channel layer, and convolutional neural network with synapses array achieves over 94% inference accuracy for Canadian-Institute-For-Advanced-Research-10 images.

Ligand Engineering Achieves Suppression of Temperature Quenching in Pure Green Perovskite Nanocrystals for Efficient and Thermostable Electroluminescence

Thu, 28 Nov 2024 00:00:00 +0000

Formamidinium lead bromide (FAPbBr₃) perovskite nanocrystals (NCs) are promising for display and lighting due to their ultra-pure green emission. However, the thermal quenching will exacerbate their performance degradation in practical applications, which is a common issue for halide perovskites. Here, we reported the heat-resistant FAPbBr₃ NCs prepared by a ligand-engineered room-temperature synthesis strategy. An aromatic amine, specifically β-phenylethylamine (PEA) or 3-fluorophenylethylamine (3-F-PEA), was incoporated as the short-chain ligand to expedite the crystallization rate and control the size distribution of FAPbBr₃ NCs. Employing this ligand engineering approach, we synthesized high quality FAPbBr₃ NCs with uniform grain size and reduced long-chain alkyl ligands, resulting in substantially suppressed thermal quenching and enhanced carrier transportation in the perovskite NCs films. Most notably, more than 90% of the room temperature PL intensity in the 3-F-PEA modified FAPbBr₃ NCs film was preserved at 380 K. Consequently, we fabricated ultra-pure green EL devices with a room temperature external quantum efficiency (EQE) as high as 21.9% at the luminance of above 1,000 cd m⁻², and demonstrated less than 10% loss in EQE at 343 K. This study introduces a novel room temperature method to synthesize efficient FAPbBr₃ NCs with exceptional thermal stability, paving the way for advanced optoelectronic device applications.

Highlights:
1 The innovative synthesis of pure green FAPbBr₃ nanocrystals at room temperature was exploited by employing aromatic amine ligands to refine the perovskite nanocrystals with high quality and excellent optoelectronic properties.
2 The proposed ligand engineering strategy firstly realized the suppression of emission thermal quenching effect in the organic-inorganic hybrid FAPbBr₃ nanocrystals.
3 It was demonstrated that the FAPbBr₃ based light-emitting diodes achieved a room temperature external quantum efficiency (EQE) of 21.9% at the luminance of 1580 cd m^-2, and only presented less than 10% loss in EQE at a higher temperature of 343 K.

A Multifunctional Hydrogel with Multimodal Self-Powered Sensing Capability and Stable Direct Current Output for Outdoor Plant Monitoring Systems

Xinge Guo, Luwei Wang, Zhenyang Jin, Chengkuo Lee — Wed, 27 Nov 2024 00:00:00 +0000

Smart farming with outdoor monitoring systems is critical to address food shortages and sustainability challenges. These systems facilitate informed decisions that enhance efficiency in broader environmental management. Existing outdoor systems equipped with energy harvesters and self-powered sensors often struggle with fluctuating energy sources, low durability under harsh conditions, non-transparent or non-biocompatible materials, and complex structures. Herein, a multifunctional hydrogel is developed, which can fulfill all the above requirements and build self-sustainable outdoor monitoring systems solely by it. It can serve as a stable energy harvester that continuously generates direct current output with an average power density of 1.9 W m⁻³ for nearly 60 days of operation in normal environments (24 °C, 60% RH), with an energy density of around 1.36 × 10⁷ J m⁻³. It also shows good self-recoverability in severe environments (45 °C, 30% RH) in nearly 40 days of continuous operation. Moreover, this hydrogel enables noninvasive and self-powered monitoring of leaf relative water content, providing critical data on evaluating plant health, previously obtainable only through invasive or high-power consumption methods. Its potential extends to acting as other self-powered environmental sensors. This multifunctional hydrogel enables self-sustainable outdoor systems with scalable and low-cost production, paving the way for future agriculture.

Highlights:
1 A simple and scalable fabricated hydrogel with multiple functionalities to realize self-sustainable outdoor monitoring solely by it for large-scale applications in precision agriculture.
2 Stable direct-current output without requirement on stochastic or temporal environmental energies, achieving an energy density of 1.36 × 10⁷ J m^–3 with continuous operation of 56.25 days in normal outdoor environment.
3 Self-powered noninvasive leaf relative water content monitoring and environmental sensing to evaluate plant health status with high durability and self-recoverability in severe environments.

Efficient and Stable Photoassisted Lithium-Ion Battery Enabled by Photocathode with Synergistically Boosted Carriers Dynamics

Wed, 27 Nov 2024 00:00:00 +0000

Efficient and stable photocathodes with versatility are of significance in photoassisted lithium-ion batteries (PLIBs), while there is always a request on fast carrier transport in electrochemical active photocathodes. Present work proposes a general approach of creating bulk heterojunction to boost the carrier mobility of photocathodes by simply laser assisted embedding of plasmonic nanocrystals. When employed in PLIBs, it was found effective for synchronously enhanced photocharge separation and transport in light charging process. Additionally, experimental photon spectroscopy, finite difference time domain method simulation and theoretical analyses demonstrate that the improved carrier dynamics are driven by the plasmonic-induced hot electron injection from metal to TiO₂, as well as the enhanced conductivity in TiO₂ matrix due to the formation of oxygen vacancies after Schottky contact. Benefiting from these merits, several benchmark values in performance of TiO₂-based photocathode applied in PLIBs are set, including the capacity of 276 mAh g⁻¹ at 0.2 A g⁻¹ under illumination, photoconversion efficiency of 1.276% at 3 A g⁻¹, less capacity and Columbic efficiency loss even through 200 cycles. These results exemplify the potential of the bulk heterojunction strategy in developing highly efficient and stable photoassisted energy storage systems.

Highlights:
1 Developing a universal bulk heterojunction strategy to create oxygen vacancies by embedding laser-manufactured metal nanocrystals into the TiO₂ matrix.
2 Proposing a new mechanism based on plasmonic-induced hot electron injection and enhanced conductivity from Schottky contact-derived oxygen vacancies.
3 Establishing several benchmark values for the performance of TiO₂-based photocathodes in photoassisted lithium-ion batteries.

Dual-Donor-Induced Crystallinity Modulation Enables 19.23% Efficiency Organic Solar Cells

Wed, 27 Nov 2024 00:00:00 +0000

Trap-assisted charge recombination is one of the primary limitations of restricting the performance of organic solar cells. However, effectively reducing the presence of traps in the photoactive layer remains challenging. Herein, wide bandgap polymer donor PTzBI-dF is demonstrated as an effective modulator for enhancing the crystallinity of the bulk heterojunction active layers composed of D18 derivatives blended with Y6, leading to dense and ordered molecular packings, and thus, improves photoluminescence quenching properties. As a result, the photovoltaic devices exhibit reduced trap-assisted charge recombination losses, achieving an optimized power conversion efficiency of over 19%. Besides the efficiency enhancement, the devices comprised of PTzBI-dF as a third component simultaneously attain decreased current leakage, improved charge carrier mobilities, and suppressed bimolecular charge recombination, leading to reduced energy losses. The advanced crystalline structures induced by PTzBI-dF and its characteristics, such as well-aligned energy level, and complementary absorption spectra, are ascribed to the promising performance improvements. Our findings suggest that donor phase engineering is a feasible approach to tuning the molecular packings in the active layer, providing guidelines for designing effective morphology modulators for high-performance organic solar cells.

Highlights:
1 By modulating the crystalline properties of the active layer with dual donors, the efficiency of organic solar cells reaches 19.23%.
2 The introduction of PTzBI-dF suppresses the accumulation of traps and charge recombination, allowing ternary devices to maintain 82% of their initial power conversion efficiency (PCE) after illumination for 800 h.
3 The dual-donor strategy for modulating the crystallinity of the active layer is applicable to a variety of Y6 derivatives, and the increase in PCE exceeds 1%.

A Fully-Printed Wearable Bandage-Based Electrochemical Sensor with pH Correction for Wound Infection Monitoring

Tue, 26 Nov 2024 00:00:00 +0000

Wearable sensing systems have been designed to monitor health conditions in real-time by detecting analytes in human biofluids. Wound diagnosis remains challenging, necessitating suitable materials for high-performance wearable sensors to offer prompt feedback. Existing devices have limitations in measuring pH and the concentration of pH-dependent electroactive species simultaneously, which is crucial for obtaining a comprehensive understanding of wound status and optimizing biosensors. Therefore, improving materials and analysis system accuracy is essential. This article introduces the first example of a flexible array capable of detecting pyocyanin, a bacterial virulence factor, while correcting dynamic pH fluctuations. We demonstrate that this combined sensor enhances accuracy by mitigating the impact of pH variability on pyocyanin sensor response. Customized screen-printable inks were developed to enhance analytical performance. The analytical performances of two sensitive sensor systems (i.e., fully-printed porous graphene/multiwalled carbon nanotube (CNT) and polyaniline/CNT composites for pyocyanin and pH sensors) are evaluated. Partial least square regression is employed to analyze nonzero-order data arrays from square wave voltammetric and potentiometric measurements of pyocyanin and pH sensors to establish a predictive model for pyocyanin concentration in complex fluids. This sensitive and effective strategy shows potential for personalized applications due to its affordability, ease of use, and ability to adjust for dynamic pH changes.

Highlights:
1 The first example of a flexible array capable of detecting pyocyanin, a bacterial virulence factor, while correcting dynamic pH fluctuations.
2 Developed a screen-printable conductive nanocomposite ink for fabricating the pyocyanin sensor and utilized a polyaniline/carbon nanocomposite as a pH-sensitive film for the pH sensor.
3 Customized inks are advantageous in terms of flexible printed sensing array integrated onto a bandage surface, capable of monitoring both pyocyanin and pH levels in wound exudate.

Deciphering Water Oxidation Catalysts: The Dominant Role of Surface Chemistry over Reconstruction Degree in Activity Promotion

Tue, 26 Nov 2024 00:00:00 +0000

Water splitting hinges crucially on the availability of electrocatalysts for the oxygen evolution reaction. The surface reconstruction has been widely observed in perovskite catalysts, and the reconstruction degree has been often correlated with the activity enhancement. Here, a systematic study on the roles of Fe substitution in activation of perovskite LaNiO₃ is reported. The substituting Fe content influences both current change tendency and surface reconstruction degree. LaNi_0.9Fe_0.1O₃ is found exhibiting a volcano-peak intrinsic activity in both pristine and reconstructed among all substituted perovskites in the LaNi_1-xFe_xO₃ (x = 0.00, 0.10, 0.25, 0.50, 0.75, 1.00) series. The reconstructed LaNi_0.9Fe_0.1O₃ shows a higher intrinsic activity than most reported NiFe-based catalysts. Besides, density functional theory calculations reveal that Fe substitution can lower the O 2p level, which thus stabilize lattice oxygen in LaNi_0.9Fe_0.1O₃ and ensure its long-term stability. Furthermore, it is vital interesting that activity of the reconstructed catalysts relied more on the surface chemistry rather than the reconstruction degree. The effect of Fe on the degree of surface reconstruction of the perovskite is decoupled from that on its activity enhancement after surface reconstruction. This finding showcases the importance to customize the surface chemistry of reconstructed catalysts for water oxidation.

Highlights:
1 Demonstrate that the key factor to determine the activity of reconstructed surfaces is the surface chemistry, instead of reconstruction degree using the popular perovskite LaNi_1-xFe_xO₃ oxides as model materials.
2 Fe content can influence both the surface reconstruction degree, the activation degree, and the activity of reconstructed surfaces.
3 The oxygen evolution reaction activity of reconstructed catalysts is primarily governed by the chemistry of the reconstructed surface species.

Wafer-Scale Ag2S-Based Memristive Crossbar Arrays with Ultra-Low Switching-Energies Reaching Biological Synapses

Yuan Zhu, Tomas Nyberg, Leif Nyholm, Daniel Primetzhofer, Xun Shi, Zhen Zhang — Fri, 22 Nov 2024 00:00:00 +0000

Memristive crossbar arrays (MCAs) offer parallel data storage and processing for energy-efficient neuromorphic computing. However, most wafer-scale MCAs that are compatible with complementary metal-oxide-semiconductor (CMOS) technology still suffer from substantially larger energy consumption than biological synapses, due to the slow kinetics of forming conductive paths inside the memristive units. Here we report wafer-scale Ag₂S-based MCAs realized using CMOS-compatible processes at temperatures below 160 °C. Ag₂S electrolytes supply highly mobile Ag⁺ ions, and provide the Ag/Ag₂S interface with low silver nucleation barrier to form silver filaments at low energy costs. By further enhancing Ag⁺ migration in Ag₂S electrolytes via microstructure modulation, the integrated memristors exhibit a record low threshold of approximately − 0.1 V, and demonstrate ultra-low switching-energies reaching femtojoule values as observed in biological synapses. The low-temperature process also enables MCA integration on polyimide substrates for applications in flexible electronics. Moreover, the intrinsic nonidealities of the memristive units for deep learning can be compensated by employing an advanced training algorithm. An impressive accuracy of 92.6% in image recognition simulations is demonstrated with the MCAs after the compensation. The demonstrated MCAs provide a promising device option for neuromorphic computing with ultra-high energy-efficiency.

Highlights:
1 Wafer-scale integration of Ag₂S-based memristive crossbar arrays was demonstrated using complementary metal–oxide–semiconductor (CMOS) compatible processes below 160 °C.
2 A record-low threshold voltage for filament formation and an ultra-low switching-energy reaching that of biological synapses in wafer-scale CMOS-compatible memristive units were achieved.
3 The energy-efficient resistance switching was enabled by self-supply of mobile Ag⁺ ions in Ag₂S electrolytes and low silver-nucleation barrier at Ag/Ag₂S interface.

Bioinspired Ultrasensitive Flexible Strain Sensors for Real-Time Wireless Detection of Liquid Leakage

Fri, 22 Nov 2024 00:00:00 +0000

Liquid leakage of pipeline networks not only results in considerable resource wastage but also leads to environmental pollution and ecological imbalance. In response to this global issue, a bioinspired superhydrophobic thermoplastic polyurethane/carbon nanotubes/graphene nanosheets flexible strain sensor (TCGS) has been developed using a combination of micro-extrusion compression molding and surface modification for real-time wireless detection of liquid leakage. The TCGS utilizes the synergistic effects of Archimedean spiral crack arrays and micropores, which are inspired by the remarkable sensory capabilities of scorpions. This design achieves a sensitivity of 218.13 at a strain of 2%, which is an increase of 4300%. Additionally, it demonstrates exceptional durability by withstanding over 5000 usage cycles. The robust superhydrophobicity of the TCGS significantly enhances sensitivity and stability in detecting small-scale liquid leakage, enabling precise monitoring of liquid leakage across a wide range of sizes, velocities, and compositions while issuing prompt alerts. This provides critical early warnings for both industrial pipelines and potential liquid leakage scenarios in everyday life. The development and utilization of bioinspired ultrasensitive flexible strain sensors offer an innovative and effective solution for the early wireless detection of liquid leakage.

Highlights:
1 Micro-extrusion compression molding and surface modification were proposed for the mass fabrication of a superhydrophobic thermoplastic polyurethane sensor (TCGS).
2 Inspired by scorpions, TCGS features Archimedean spiral crack arrays and micropores, achieving 218.13 sensitivity at 2% strain, a 4300% increase, and over 5000 usage cycles of durability.
3 The robust superhydrophobicity of TCGS improves sensitivity and stability for detecting small-scale liquid leakage, allowing precise monitoring across various sizes and compositions while providing early warnings in various scenarios.

Direct Photolithography of WOx Nanoparticles for High-Resolution Non-Emissive Displays

Thu, 21 Nov 2024 00:00:00 +0000

High-resolution non-emissive displays based on electrochromic tungsten oxides (WO_x) are crucial for future near-eye virtual/augmented reality interactions, given their impressive attributes such as high environmental stability, ideal outdoor readability, and low energy consumption. However, the limited intrinsic structure of inorganic materials has presented a significant challenge in achieving precise patterning/pixelation at the micron scale. Here, we successfully developed the direct photolithography for WO_x nanoparticles based on in situ photo-induced ligand exchange. This strategy enabled us to achieve ultra-high resolution efficiently (line width < 4 µm, the best resolution for reported inorganic electrochromic materials). Additionally, the resulting device exhibited impressive electrochromic performance, such as fast response (< 1 s at 0 V), high coloration efficiency (119.5 cm² C⁻¹), good optical modulation (55.9%), and durability (> 3600 cycles), as well as promising applications in electronic logos, pixelated displays, flexible electronics, etc. The success and advancements presented here are expected to inspire and accelerate research and development (R&D) in high-resolution non-emissive displays and other ultra-fine micro-electronics.

Highlights:
1 Direct photolithography of electrochromic WO_x nanoparticles via in situ photo-induced ligand exchange is proposed and demonstrated.
2 The highest resolution among inorganic electrochromics (< 4 µm) is achieved, which is promising in high-resolution non-emissive displays.
3 The as-prepared device exhibits highly remarkable performance including rapid response, high coloration efficiency and durability.

Exploration of Gas-Dependent Self-Adaptive Reconstruction Behavior of Cu2O for Electrochemical CO2 Conversion to Multi-Carbon Products

Tue, 19 Nov 2024 00:00:00 +0000

Structural reconstruction of electrocatalysts plays a pivotal role in catalytic performances for CO₂ reduction reaction (CO₂RR), whereas the behavior is by far superficially understood. Here, we report that CO₂ accessibility results in a universal self-adaptive structural reconstruction from Cu₂O to Cu@Cu_xO composites, ending with feeding gas-dependent microstructures and catalytic performances. The CO₂-rich atmosphere favors reconstruction for CO₂RR, whereas the CO₂-deficient one prefers that for hydrogen evolution reaction. With the assistance of spectroscopic analysis and theoretical calculations, we uncover a CO₂-induced passivation behavior by identifying a reduction-resistant but catalytic active Cu(I)-rich amorphous layer stabilized by *CO intermediates. Additionally, we find extra CO production is indispensable for the robust production of C₂H₄. An inverse correlation between durability and FE_CO/FE_C2H4 is disclosed, suggesting that the self-stabilization process involving the absorption of *CO intermediates on Cu(I) sites is essential for durable electrolysis. Guided by this insight, we design hollow Cu₂O nanospheres for durable and selective CO₂RR electrolysis in producing C₂H₄. Our work recognizes the previously overlooked passivation reconstruction and self-stabilizing behavior and highlights the critical role of the local atmosphere in modulating reconstruction and catalytic processes.

Highlights:
1 We revealed a universal self-adaptive structural reconstruction from Cu₂O to Cu@Cu_xO composites, ending with feeding gas-dependent microstructures and catalytic performances.
2 We uncovered a CO₂-induced passivation behavior by identifying a reduction-resistant but catalytic active Cu(I)-rich amorphous layer.
3 We designed and fabricated hollow Cu₂O nanospheres, demonstrating durable electrolysis at a partial current density of −200 mA cm⁻² in producing C₂H₄ with an FE of up to 61% at −0.6 V_RHE.

MXene Hybridized Polymer with Enhanced Electromagnetic Energy Harvest for Sensitized Microwave Actuation and Self-Powered Motion Sensing

Mon, 18 Nov 2024 00:00:00 +0000

Polymeric microwave actuators combining tissue-like softness with programmable microwave-responsive deformation hold great promise for mobile intelligent devices and bionic soft robots. However, their application is challenged by restricted electromagnetic sensitivity and intricate sensing coupling. In this study, a sensitized polymeric microwave actuator is fabricated by hybridizing a liquid crystal polymer with Ti₃C₂T_x (MXene). Compared to the initial counterpart, the hybrid polymer exhibits unique space-charge polarization and interfacial polarization, resulting in significant improvements of 230% in the dielectric loss factor and 830% in the apparent efficiency of electromagnetic energy harvest. The sensitized microwave actuation demonstrates as the shortened response time of nearly 10 s, which is merely 13% of that for the initial shape memory polymer. Moreover, the ultra-low content of MXene (up to 0.15 wt%) benefits for maintaining the actuation potential of the hybrid polymer. An innovative self-powered sensing prototype that combines driving and piezoelectric polymers is developed, which generates real-time electric potential feedback (open-circuit potential of ~ 3 mV) during actuation. The polarization-dominant energy conversion mechanism observed in the MXene-polymer hybrid structure furnishes a new approach for developing efficient electromagnetic dissipative structures and shows potential for advancing polymeric electromagnetic intelligent devices.

Highlights:
1 An alternative electromagnetic attenuation pathway is proposed in the MXene-polymer hybrid structure, distinct from conduction loss, for generalizing the results to a wider range of electromagnetic-thermal driven soft materials and devices.
2 By efficiently harvesting and converting electromagnetic energy, the response time of the hybrid polymer to microwave exhibits 87% reduction with merely 0.15 wt% MXene.
3 A new mode of self-powered motion sensing based on deformation-driven piezoelectric effect is developed, enhancing the material’s intelligence.

Flexible Strain Sensors with Ultra-High Sensitivity and Wide Range Enabled by Crack-Modulated Electrical Pathways

Mon, 18 Nov 2024 00:00:00 +0000

This study presents a breakthrough in flexible strain sensor technology with the development of an ultra-high sensitivity and wide-range sensor, addressing the critical challenge of reconciling sensitivity with measurement range. Inspired by the structure of bamboo slips, we introduce a novel approach that utilises liquid metal to modulate the electrical pathways within a cracked platinum fabric electrode. The resulting sensor demonstrates a gauge factor greater than 10⁸ and a strain measurement capability exceeding 100%. The integration of patterned liquid metal enables customisable tuning of the sensor’s response, while the porous fabric structure ensures superior comfort and air permeability for the wearer. Our design not only optimises the sensor’s performance but also enhances the electrical stability that is essential for practical applications. Through systematic investigation, we reveal the intrinsic mechanisms governing the sensor’s response, offering valuable insights for the design of wearable strain sensors. The sensor’s exceptional performance across a spectrum of applications, from micro-strain to large-strain detection, highlights its potential for a wide range of real-world uses, demonstrating a significant advancement in the field of flexible electronics.

Highlights:
1 A method is proposed for the modulation of electrical pathways in the cracks of stretchable electrodes using liquid metals, based on which ultra-high sensitivity (> 108) and large-range (> 100%) strain sensors are realised.
2 A secondary modulation of the response (or performance) of the sensor is proposed, allowing not only electrical modulation by liquid metal patterning during fabrication, but also mechanical modulation by pre-stretching at the time of use.
3 The air permeability and stability of the patterned liquid metal electrode region is optimised to enable air permeability similar to that of conventional fabrics and cycle durability in excess of 2000 cycles.

Low-Temperature Fabrication of Stable Black-Phase CsPbI3 Perovskite Flexible Photodetectors Toward Wearable Health Monitoring

Fri, 15 Nov 2024 00:00:00 +0000

Flexible wearable optoelectronic devices fabricated from organic–inorganic hybrid perovskites significantly accelerate the development of portable energy, biomedicine, and sensing fields, but their poor thermal stability hinders further applications. Conversely, all-inorganic perovskites possess excellent thermal stability, but black-phase all-inorganic perovskite film usually requires high-temperature annealing steps, which increases energy consumption and is not conducive to the fabrication of flexible wearable devices. In this work, an unprecedented low-temperature fabrication of stable black-phase CsPbI₃ perovskite films is demonstrated by the in situ hydrolysis reaction of diphenylphosphinic chloride additive. The released diphenyl phosphate and chloride ions during the hydrolysis reaction significantly lower the phase transition temperature and effectively passivate the defects in the perovskite films, yielding high-performance photodetectors with a responsivity of 42.1 A W⁻¹ and a detectivity of 1.3 × 10¹⁴ Jones. Furthermore, high-fidelity image and photoplethysmography sensors are demonstrated based on the fabricated flexible wearable photodetectors. This work provides a new perspective for the low-temperature fabrication of large-area all-inorganic perovskite flexible optoelectronic devices.

Highlights:
1 Low-temperature fabrication of black-phase CsPbI₃ perovskite films is first demonstrated by using diphenylphosphinic chloride additive under 30–50 °C, arising from the steric effect and chloride insertion engineering.
2 Large-area high-quality all-inorganic perovskite films with fewer defects enhanced crystallographic orientation, and excellent environmental stability is fabricated.
3 The record performances are demonstrated for flexible wearable photodetectors with a responsivity of 42.1 A W⁻¹, a detectivity of 1.3 × 10¹⁴ Jones, high-fidelity image, photoplethysmography sensor functions, and high mechanical stability.

An Artificial Intelligence-Assisted Flexible and Wearable Mechanoluminescent Strain Sensor System

Yan Dong, Wenzheng An, Zihu Wang, Dongzhi Zhang — Fri, 15 Nov 2024 00:00:00 +0000

The complex wiring, bulky data collection devices, and difficulty in fast and on-site data interpretation significantly limit the practical application of flexible strain sensors as wearable devices. To tackle these challenges, this work develops an artificial intelligence-assisted, wireless, flexible, and wearable mechanoluminescent strain sensor system (AIFWMLS) by integration of deep learning neural network-based color data processing system (CDPS) with a sandwich-structured flexible mechanoluminescent sensor (SFLC) film. The SFLC film shows remarkable and robust mechanoluminescent performance with a simple structure for easy fabrication. The CDPS system can rapidly and accurately extract and interpret the color of the SFLC film to strain values with auto-correction of errors caused by the varying color temperature, which significantly improves the accuracy of the predicted strain. A smart glove mechanoluminescent sensor system demonstrates the great potential of the AIFWMLS system in human gesture recognition. Moreover, the versatile SFLC film can also serve as a encryption device. The integration of deep learning neural network-based artificial intelligence and SFLC film provides a promising strategy to break the “color to strain value” bottleneck that hinders the practical application of flexible colorimetric strain sensors, which could promote the development of wearable and flexible strain sensors from laboratory research to consumer markets.

Highlights:
1 The sandwich-structured flexible mechanoluminescent sensor (SFLC) film shows great application potential as wireless wearable strain sensor and encryption device.
2 System-level integration of SFLC film with deep learning-based artificial intelligence enables fast and accurate interpretation of color data to strain values with automatic correction of errors caused by varying color temperatures.
3 The smart glove wearable sensor based on the SFLC film combined with deep learning neural network enables fast and accurate hand gesture recognition.

Ideal Bi-Based Hybrid Anode Material for Ultrafast Charging of Sodium-Ion Batteries at Extremely Low Temperatures

Jie Bai, Jian Hui Jia, Yu Wang, Chun Cheng Yang, Qing Jiang — Wed, 13 Nov 2024 00:00:00 +0000

Sodium-ion batteries have emerged as competitive substitutes for low-temperature applications due to severe capacity loss and safety concerns of lithium-ion batteries at − 20 °C or lower. However, the key capability of ultrafast charging at ultralow temperature for SIBs is rarely reported. Herein, a hybrid of Bi nanoparticles embedded in carbon nanorods is demonstrated as an ideal material to address this issue, which is synthesized via a high temperature shock method. Such a hybrid shows an unprecedented rate performance (237.9 mAh g⁻¹ at 2 A g⁻¹) at − 60 °C, outperforming all reported SIB anode materials. Coupled with a Na₃V₂(PO₄)₃ cathode, the energy density of the full cell can reach to 181.9 Wh kg⁻¹ at − 40 °C. Based on this work, a novel strategy of high-rate activation is proposed to enhance performances of Bi-based materials in cryogenic conditions by creating new active sites for interfacial reaction under large current.

Highlights:
1 Metallic nanoparticles with excellent size controllability and high loading rate are obtained via ultrafast high temperature shock method.
2 The Bi/CNRs-15 electrode exhibits an unprecedented rate performance (237.9 mAh g⁻¹ at 2 A g⁻¹) at − 60 °C, while the energy density of the full cell can reach to 181.9 Wh kg⁻¹ at − 40 °C.
3 A novel strategy of high-rate activation is proposed to obtain high capacity and superior stability at low temperature by creating new active sites for interfacial reaction.

Nanograting-Based Dynamic Structural Colors Using Heterogeneous Materials

Mon, 11 Nov 2024 00:00:00 +0000

Dynamic structural colors can change in response to different environmental stimuli. This ability remains effective even when the size of the species responsible for the structural color is reduced to a few micrometers, providing a promising sensing mechanism for solving microenvironmental sensing problems in micro-robotics and microfluidics. However, the lack of dynamic structural colors that can encode rapidly, easily integrate, and accurately reflect changes in physical quantities hinders their use in microscale sensing applications. Herein, we present a 2.5-dimensional dynamic structural color based on nanogratings of heterogeneous materials, which were obtained by interweaving a pH-responsive hydrogel with an IP-L photoresist. Transverse gratings printed with pH-responsive hydrogels elongated the period of longitudinal grating in the swollen state, resulting in pH-tuned structural colors at a 45° incidence. Moreover, the patterned encoding and array printing of dynamic structural colors were achieved using grayscale stripe images to accurately encode the periods and heights of the nanogrid structures. Overall, dynamic structural color networks exhibit promising potential for applications in information encryption and in situ sensing for microfluidic chips.

Highlights:
1 A 2.5-dimensional dynamic structural color based on nanogratings of heterogeneous materials was proposed by interweaving a pH-responsive hydrogel with IP-L photoresist.
2 The nanogrid structures exhibit brilliant tuneable structural color, high sensitivity, and ultrafast recovery speeds in response to pH.
3 The 4D printing-based grayscale design approach was proposed for the patterned encoding and array printing of dynamic structural colors, promoting their application in patterned printing, information encryption, and microfluidic chip sensing.

Electrode/Electrolyte Optimization-Induced Double-Layered Architecture for High-Performance Aqueous Zinc-(Dual) Halogen Batteries

Thu, 07 Nov 2024 00:00:00 +0000

Aqueous zinc-halogen batteries are promising candidates for large-scale energy storage due to their abundant resources, intrinsic safety, and high theoretical capacity. Nevertheless, the uncontrollable zinc dendrite growth and spontaneous shuttle effect of active species have prohibited their practical implementation. Herein, a double-layered protective film based on zinc-ethylenediamine tetramethylene phosphonic acid (ZEA) artificial film and ZnF₂-rich solid electrolyte interphase (SEI) layer has been successfully fabricated on the zinc metal anode via electrode/electrolyte synergistic optimization. The ZEA-based artificial film shows strong affinity for the ZnF₂-rich SEI layer, therefore effectively suppressing the SEI breakage and facilitating the construction of double-layered protective film on the zinc metal anode. Such double-layered architecture not only modulates Zn²⁺ flux and suppresses the zinc dendrite growth, but also blocks the direct contact between the metal anode and electrolyte, thus mitigating the corrosion from the active species. When employing optimized metal anodes and electrolytes, the as-developed zinc-(dual) halogen batteries present high areal capacity and satisfactory cycling stability. This work provides a new avenue for developing aqueous zinc-(dual) halogen batteries.

Highlights:
1 A double-layered protective film based on zinc-based coordination compound and ZnF₂-rich solid electrolyte interphase layer has been successfully fabricated on the zinc metal anode via electrode/electrolyte synergistic optimization.
2 The double-layered architecture can effectively modulate Zn²⁺ flux and suppress the zinc dendrite growth, thus facilitating the uniform zinc deposition.
3 The as-developed zinc-(dual) halogen batteries based on double-layered protective film can present high areal capacity and satisfactory cycling stability.

Laser-Induced Highly Stable Conductive Hydrogels for Robust Bioelectronics

Yibo Li, Hao Zhou, Huayong Yang, Kaichen Xu — Tue, 05 Nov 2024 00:00:00 +0000

Despite the promising progress in conductive hydrogels made with pure conducting polymer, great challenges remain in the interface adhesion and robustness in long-term monitoring. To address these challenges, Prof. Seung Hwan Ko and Taek-Soo Kim’s team introduced a laser-induced phase separation and adhesion method for fabricating conductive hydrogels consisting of pure poly(3,4-ethylenedioxythiophene):polystyrene sulfonate on polymer substrates. The laser-induced phase separation and adhesion treated conducting polymers can be selectively transformed into conductive hydrogels that exhibit wet conductivities of 101.4 S cm⁻¹ with a spatial resolution down to 5 μm. Moreover, they maintain impedance and charge-storage capacity even after 1 h of sonication. The micropatterned electrode arrays demonstrate their potential in long-term in vivo signal recordings, highlighting their promising role in the field of bioelectronics.

Highlights:
1 Stable adhesion of pure poly(3,4-ethylenedioxythiophene):polystyrene sulfonate hydrogel to polymer substrates was successfully achieved via a laser-induced phase separation and adhesion method.
2 The resulting conductive hydrogel exhibits a superior wet electrical conductivity up to 101.4 S cm⁻¹ and a spatial resolution down to 5 μm.
3 Such hydrogels hold great promise in robust bio-interfacing electrodes suitable for long-term high-fidelity signal monitoring.

Wafer-Scale Vertical 1D GaN Nanorods/2D MoS2/PEDOT:PSS for Piezophototronic Effect-Enhanced Self-Powered Flexible Photodetectors

Xin Tang, Hongsheng Jiang, Zhengliang Lin, Xuan Wang, Wenliang Wang, Guoqiang Li — Tue, 05 Nov 2024 00:00:00 +0000

van der Waals (vdW) heterostructures constructed by low-dimensional (0D, 1D, and 2D) materials are emerging as one of the most appealing systems in next-generation flexible photodetection. Currently, hand-stacked vdW-type photodetectors are not compatible with large-area-array fabrication and show unimpressive performance in self-powered mode. Herein, vertical 1D GaN nanorods arrays (NRAs)/2D MoS₂/PEDOT:PSS in wafer scale have been proposed for self-powered flexible photodetectors arrays firstly. The as-integrated device without external bias under weak UV illumination exhibits a competitive responsivity of 1.47 A W⁻¹ and a high detectivity of 1.2 × 10¹¹ Jones, as well as a fast response speed of 54/71 µs, thanks to the strong light absorption of GaN NRAs and the efficient photogenerated carrier separation in type-II heterojunction. Notably, the strain-tunable photodetection performances of device have been demonstrated. Impressively, the device at − 0.78% strain and zero bias reveals a significantly enhanced photoresponse with a responsivity of 2.47 A W⁻¹, a detectivity of 2.6 × 10¹¹ Jones, and response times of 40/45 µs, which are superior to the state-of-the-art self-powered flexible photodetectors. This work presents a valuable avenue to prepare tunable vdWs heterostructures for self-powered flexible photodetection, which performs well in flexible sensors.

Highlights:
1 Vertical 1D GaN nanorod arrays/2D MoS₂/PEDOT:PSS heterostructures in wafer scale have been fabricated for flexible photodetection firstly.
2 Self-powered flexible photodetector at compressive strain reveals a significantly enhanced photoresponse with a responsivity of 2.47 A W⁻¹ and response times of 40/45 µs, which are superior to the state-of-the-art flexible devices.
3 This work not only provides a valuable strategy for the design and construction of tunable van der Waals heterostructures, but also opens a new opportunity for flexible sensors.

Defect Engineering with Rational Dopants Modulation for High-Temperature Energy Harvesting in Lead-Free Piezoceramics

Kaibiao Xi, Jianzhe Guo, Mupeng Zheng, Mankang Zhu, Yudong Hou — Mon, 04 Nov 2024 00:00:00 +0000

High temperature piezoelectric energy harvester (HT-PEH) is an important solution to replace chemical battery to achieve independent power supply of HT wireless sensors. However, simultaneously excellent performances, including high figure of merit (FOM), insulation resistivity (ρ) and depolarization temperature (T_d) are indispensable but hard to achieve in lead-free piezoceramics, especially operating at 250 °C has not been reported before. Herein, well-balanced performances are achieved in BiFeO₃–BaTiO₃ ceramics via innovative defect engineering with respect to delicate manganese doping. Due to the synergistic effect of enhancing electrostrictive coefficient by polarization configuration optimization, regulating iron ion oxidation state by high valence manganese ion and stabilizing domain orientation by defect dipole, comprehensive excellent electrical performances (T_d = 340 °C, ρ_{250 °C} > 10⁷ Ω cm and FOM_{250 °C} = 4905 × 10^–15 m² N⁻¹) are realized at the solid solubility limit of manganese ions. The HT-PEHs assembled using the rationally designed piezoceramic can allow for fast charging of commercial electrolytic capacitor at 250 °C with high energy conversion efficiency (η = 11.43%). These characteristics demonstrate that defect engineering tailored BF-BT can satisfy high-end HT-PEHs requirements, paving a new way in developing self-powered wireless sensors working in HT environments.

Highlights:
1 The solution limit of manganese ion in BiFeO₃–BaTiO₃ (BF–BT) was determined by combining multiple advanced characterization methods.
2 The defect engineering associated with fine doping can realize the co-modulation of polarization configuration, iron oxidation state and domain orientation.
3 The BF–BT–0.2Mn piezoelectric energy harvester shows excellent power generation capacity at 250 °C, which is an important breakthrough for lead-free piezoelectric devices.

Multifunctional Nacre-Like Nanocomposite Papers for Electromagnetic Interference Shielding via Heterocyclic Aramid/MXene Template-Assisted In-Situ Polypyrrole Assembly

Thu, 31 Oct 2024 00:00:00 +0000

Robust, ultra-flexible, and multifunctional MXene-based electromagnetic interference (EMI) shielding nanocomposite films exhibit enormous potential for applications in artificial intelligence, wireless telecommunication, and portable/wearable electronic equipment. In this work, a nacre-inspired multifunctional heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite paper with large-scale, high strength, super toughness, and excellent tolerance to complex conditions is fabricated through the strategy of HA/MXene hydrogel template-assisted in-situ assembly of PPy. Benefiting from the "brick-and-mortar" layered structure and the strong hydrogen-bonding interactions among MXene, HA, and PPy, the paper exhibits remarkable mechanical performances, including high tensile strength (309.7 MPa), outstanding toughness (57.6 MJ m⁻³), exceptional foldability, and structural stability against ultrasonication. By using the template effect of HA/MXene to guide the assembly of conductive polymers, the synthesized paper obtains excellent electronic conductivity. More importantly, the highly continuous conductive path enables the nanocomposite paper to achieve a splendid EMI shielding effectiveness (EMI SE) of 54.1 dB at an ultra-thin thickness (25.4 μm) and a high specific EMI SE of 17,204.7 dB cm² g⁻¹. In addition, the papers also have excellent applications in electromagnetic protection, electro-/photothermal de-icing, thermal therapy, and fire safety. These findings broaden the ideas for developing high-performance and multifunctional MXene-based films with enormous application potential in EMI shielding and thermal management.

Highlights:
1 The large-scale, high-strength, super-tough, and multifunctional nacre-like heterocyclic aramid (HA)/MXene@polypyrrole (PPy) (HMP) nanocomposite papers were fabricated using the in-situ assembly of PPy onto the HA/MXene hydrogel template.
2 The "brick-and-mortar" layered structure and abundant hydrogen-bonding interactions among MXene, PPy, and HA respond cooperatively to external stress and effectively increase the mechanical properties of HMP nanocomposite papers.
3 The templating effect from HA/MXene was utilized to guide the assembly of conducting polymers, leading to high electrical conductivity and outstanding electromagnetic interference shielding performance.

Inter-Skeleton Conductive Routes Tuning Multifunctional Conductive Foam for Electromagnetic Interference Shielding, Sensing and Thermal Management

Mon, 28 Oct 2024 00:00:00 +0000

Conductive polymer foam (CPF) with excellent compressibility and variable resistance has promising applications in electromagnetic interference (EMI) shielding and other integrated functions for wearable electronics. However, its insufficient change amplitude of resistance with compressive strain generally leads to a degradation of shielding performance during deformation. Here, an innovative loading strategy of conductive materials on polymer foam is proposed to significantly increase the contact probability and contact area of conductive components under compression. Unique inter-skeleton conductive films are constructed by loading alginate-decorated magnetic liquid metal on the polymethacrylate films hanged between the foam skeleton (denoted as AMLM-PM foam). Traditional point contact between conductive skeletons under compression is upgraded to planar contact between conductive films. Therefore, the resistance change of AMLM-PM reaches four orders of magnitude under compression. Moreover, the inter-skeleton conductive films can improve the mechanical strength of foam, prevent the leakage of liquid metal and increase the scattering area of EM wave. AMLM-PM foam has strain-adaptive EMI shielding performance and shows compression-enhanced shielding effectiveness, solving the problem of traditional CPFs upon compression. The upgrade of resistance response also enables foam to achieve sensitive pressure sensing over a wide pressure range and compression-regulated Joule heating function.

Highlights:
1 Unique inter-skeleton conductive films are constructed in polymer foam.
2 The resistance change of the foam can reach four orders of magnitude under compression.
3 This foam exhibits strain-adaptive electromagnetic interference shielding performance, anti-interference pressure sensor with high sensitivity over a wide pressure range and compression-regulated Joule heating function.

Scalable Ir-Doped NiFe2O4/TiO2 Heterojunction Anode for Decentralized Saline Wastewater Treatment and H2 Production

Mon, 28 Oct 2024 00:00:00 +0000

Wastewater electrolysis cells (WECs) for decentralized wastewater treatment/reuse coupled with H₂ production can reduce the carbon footprint associated with transportation of water, waste, and energy carrier. This study reports Ir-doped NiFe₂O₄ (NFI, ~ 5 at% Ir) spinel layer with TiO₂ overlayer (NFI/TiO₂), as a scalable heterojunction anode for direct electrolysis of wastewater with circumneutral pH in a single-compartment cell. In dilute (0.1 M) NaCl solutions, the NFI/TiO₂ marks superior activity and selectivity for chlorine evolution reaction, outperforming the benchmark IrO₂. Robust operation in near-neutral pH was confirmed. Electroanalyses including operando X-ray absorption spectroscopy unveiled crucial roles of TiO₂ which serves both as the primary site for Cl⁻ chemisorption and a protective layer for NFI as an ohmic contact. Galvanostatic electrolysis of NH₄⁺-laden synthetic wastewater demonstrated that NFI/TiO₂ not only achieves quasi-stoichiometric NH₄⁺-to-N₂ conversion, but also enhances H₂ generation efficiency with minimal competing reactions such as reduction of dissolved oxygen and reactive chlorine. The scaled-up WEC with NFI/TiO₂ was demonstrated for electrolysis of toilet wastewater.

Highlights:
1 Ir-doped NiFe₂O₄ (NFI) spinel with TiO₂ heterojunction overlayer brought about outstanding chlorine evolution reaction in circumneutral pH.
2 Electroanalyses including operando X-ray absorption spectroscopy uncovered the active role of TiO₂ for Cl⁻ chemisorption.
3 NFI/TiO₂ anode boosted both NH₄⁺-to-N₂ conversion and H₂ generation in wastewater, and the practical applicability was confirmed with scaled-up anodes and real wastewater.

A Flexible Smart Healthcare Platform Conjugated with Artificial Epidermis Assembled by Three-Dimensionally Conductive MOF Network for Gas and Pressure Sensing

Fri, 25 Oct 2024 00:00:00 +0000

The rising flexible and intelligent electronics greatly facilitate the noninvasive and timely tracking of physiological information in telemedicine healthcare. Meticulously building bionic-sensitive moieties is vital for designing efficient electronic skin with advanced cognitive functionalities to pluralistically capture external stimuli. However, realistic mimesis, both in the skin’s three-dimensional interlocked hierarchical structures and synchronous encoding multistimuli information capacities, remains a challenging yet vital need for simplifying the design of flexible logic circuits. Herein, we construct an artificial epidermal device by in situ growing Cu₃(HHTP)₂ particles onto the hollow spherical Ti₃C₂T_x surface, aiming to concurrently emulate the spinous and granular layers of the skin’s epidermis. The bionic Ti₃C₂T_x@Cu₃(HHTP)₂ exhibits independent NO₂ and pressure response, as well as novel functionalities such as acoustic signature perception and Morse code-encrypted message communication. Ultimately, a wearable alarming system with a mobile application terminal is self-developed by integrating the bimodular senor into flexible printed circuits. This system can assess risk factors related with asthmatic, such as stimulation of external NO₂ gas, abnormal expiratory behavior and exertion degrees of fingers, achieving a recognition accuracy of 97.6% as assisted by a machine learning algorithm. Our work provides a feasible routine to develop intelligent multifunctional healthcare equipment for burgeoning transformative telemedicine diagnosis.

Highlights:
1 A smart wearable alarming system integrated artificial epidermal device for pluralistically identifying asthmatic attack risk factors, achieving a 97.6% classification accuracy as assisted by machine learning algorithm.
2 A meticulous mimicry both in the advanced structural attributes and encoding information abilities of the skin was adopted to design a novel artificial epidermal device by integrating conductive Cu₃(HHTP)₂ coupled with spherical Ti₃C₂T_x.
3 The bioinspired Ti₃C₂T_x@Cu₃(HHTP)₂ sensors can independently perceive NO₂ gas and pressure-triggered stimuli.

Dynamic Regulation of Hydrogen Bonding Networks and Solvation Structures for Synergistic Solar-Thermal Desalination of Seawater and Catalytic Degradation of Organic Pollutants

Ming‑Yuan Yu, Jing Wu, Guang Yin, Fan‑Zhen Jiao, Zhong‑Zhen Yu, Jin Qu — Wed, 23 Oct 2024 00:00:00 +0000

Although solar steam generation strategy is efficient in desalinating seawater, it is still challenging to achieve continuous solar-thermal desalination of seawater and catalytic degradation of organic pollutants. Herein, dynamic regulations of hydrogen bonding networks and solvation structures are realized by designing an asymmetric bilayer membrane consisting of a bacterial cellulose/carbon nanotube/Co₂(OH)₂CO₃ nanorod top layer and a bacterial cellulose/Co₂(OH)₂CO₃ nanorod (BCH) bottom layer. Crucially, the hydrogen bonding networks inside the membrane can be tuned by the rich surface –OH groups of the bacterial cellulose and Co₂(OH)₂CO₃ as well as the ions and radicals in situ generated during the catalysis process. Moreover, both SO₄²⁻ and HSO₅⁻ can regulate the solvation structure of Na⁺ and be adsorbed more preferentially on the evaporation surface than Cl⁻, thus hindering the de-solvation of the solvated Na⁺ and subsequent nucleation/growth of NaCl. Furthermore, the heat generated by the solar-thermal energy conversion can accelerate the reaction kinetics and enhance the catalytic degradation efficiency. This work provides a flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane for synergistic solar thermal desalination of seawater/brine and catalytic degradation of organic pollutants.

Highlights:
1 A flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane is designed for synergistic solar-thermal desalination of seawater/brine and catalytic degradation of organic pollutants.
2 The hydrogen bonding networks can be regulated by the abundant surface –OH groups and the in situ generated ions and radicals during the degradation process for promoting solar-driven steam generation.
3 The de-solvation of solvated Na⁺ and subsequent nucleation/growth of NaCl are effectively inhibited by SO₄²⁻/HSO₅⁻ ions.

Graphene Aerogel Composites with Self-Organized Nanowires-Packed Honeycomb Structure for Highly Efficient Electromagnetic Wave Absorption

Mon, 21 Oct 2024 00:00:00 +0000

With vigorous developments in nanotechnology, the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers. Herein, a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity. The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires (SiC_nws) grown in situ, while boron nitride (BN) interfacial structure is introduced on graphene nanoplates. The unique composite structure forces multiple scattering of incident EMWs, ensuring the combined effects of interfacial polarization, conduction networks, and magnetic-dielectric synergy. Therefore, the as-prepared composites present a minimum reflection loss value of − 37.8 dB and a wide effective absorption bandwidth (EAB) of 9.2 GHz (from 8.8 to 18.0 GHz) at 2.5 mm. Besides, relying on the intrinsic high-temperature resistance of SiC_nws and BN, the EAB also remains above 5.0 GHz after annealing in air environment at 600 °C for 10 h.

Highlights:
1 A new strategy for elaborate regulation of microstructure was successfully introduced by the ice template‑assisted 3D printing and chemical vapor deposition strategy, including graphene nanoplate/silicon carbide nanowires hierarchical porous structure and graphene nanoplate/boron nitride composite heterogeneous interface.
2 The composite exhibits excellent electromagnetic wave absorption performance with an RLmin of -37.8 dB and an EABmax of 9.2 GHz (from 8.8 to 18.0 GHz) at 2.5 mm. And the high-temperature absorption stability makes it a promising absorber candidate under high temperature and oxidizing atmosphere.

Integration of Electrical Properties and Polarization Loss Modulation on Atomic Fe–N-RGO for Boosting Electromagnetic Wave Absorption

Fri, 18 Oct 2024 00:00:00 +0000

Developing effective strategies to regulate graphene's conduction loss and polarization has become a key to expanding its application in the electromagnetic wave absorption (EMWA) field. Based on the unique energy band structure of graphene, regulating its bandgap and electrical properties by introducing heteroatoms is considered a feasible solution. Herein, metal-nitrogen doping reduced graphene oxide (M–N-RGO) was prepared by embedding a series of single metal atoms M–N₄ sites (M = Mn, Fe, Co, Ni, Cu, Zn, Nb, Cd, and Sn) in RGO using an N-coordination atom-assisted strategy. These composites had adjustable conductivity and polarization to optimize dielectric loss and impedance matching for efficient EMWA performance. The results showed that the minimum reflection loss (RL_min) of Fe–N-RGO reaches − 74.05 dB (2.0 mm) and the maximum effective absorption bandwidth (EAB_max) is 7.05 GHz (1.89 mm) even with a low filler loading of only 1 wt%. Combined with X-ray absorption spectra (XAFS), atomic force microscopy, and density functional theory calculation analysis, the Fe–N₄ can be used as the polarization center to increase dipole polarization, interface polarization and defect-induced polarization due to d-p orbital hybridization and structural distortion. Moreover, electron migration within the Fe further leads to conduction loss, thereby synergistically promoting energy attenuation. This study demonstrates the effectiveness of metal-nitrogen doping in regulating the graphene′s dielectric properties, which provides an important basis for further investigation of the loss mechanism.

Highlights:
1 Single-atom Fe–N₄ sites embedded into graphene were successfully synthesized to exert the dielectric properties of graphene.
2 The absorption mechanisms of metal-nitrogen doping reduced graphene oxide mainly include enhanced dipole polarization, interface polarization, conduction loss and defect-induced polarization.
3 Excellent reflection loss of − 74.05 dB (2.0 mm) and broad effective absorption bandwidth of 7.05 GHz (1.89 mm, with filler loading only 1 wt%) were obtained.

Sulfolane-Based Flame-Retardant Electrolyte for High-Voltage Sodium-Ion Batteries

Fri, 18 Oct 2024 00:00:00 +0000

Sodium-ion batteries hold great promise as next-generation energy storage systems. However, the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs. In particular, an unstable cathode–electrolyte interphase (CEI) leads to successive electrolyte side reactions, transition metal leaching and rapid capacity decay, which tends to be exacerbated under high-voltage conditions. Therefore, constructing dense and stable CEIs are crucial for high-performance SIBs. This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H, 1H, 5H-octafluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether, which exhibited excellent oxidative stability and was able to form thin, dense and homogeneous CEI. The excellent CEI enabled the O3-type layered oxide cathode NaNi_1/3Mn_1/3Fe_1/3O₂ (NaNMF) to achieve stable cycling, with a capacity retention of 79.48% after 300 cycles at 1 C and 81.15% after 400 cycles at 2 C with a high charging voltage of 4.2 V. In addition, its nonflammable nature enhances the safety of SIBs. This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.

Highlights:
1 NaTFSI/SUL:OTE:FEC facilitates the formation of S, N-rich, dense and robust cathode–electrolyte interphase on NaNMF cathode, which improves the cycling stability under high voltage.
2 By utilizing NaTFSI/SUL:OTE:FEC, the Na||NaNMF batteries achieved an impressive retention of 81.15% after 400 cycles at 2 C with the cutoff voltage of 4.2 V.
3 The study offers a reference for the utilization of sulfolane-based electrolytes in sodium-ion batteries (SIBs), while the nonflammability of the NaTFSI/SUL:OTE:FEC enhances the safety of SIBs.

Gradient-Layered MXene/Hollow Lignin Nanospheres Architecture Design for Flexible and Stretchable Supercapacitors

Thu, 17 Oct 2024 00:00:00 +0000

With the rapid development of flexible wearable electronics, the demand for stretchable energy storage devices has surged. In this work, a novel gradient-layered architecture was design based on single-pore hollow lignin nanospheres (HLNPs)-intercalated two-dimensional transition metal carbide (Ti₃C₂T_x MXene) for fabricating highly stretchable and durable supercapacitors. By depositing and inserting HLNPs in the MXene layers with a bottom-up decreasing gradient, a multilayered porous MXene structure with smooth ion channels was constructed by reducing the overstacking of MXene lamella. Moreover, the micro-chamber architecture of thin-walled lignin nanospheres effectively extended the contact area between lignin and MXene to improve ion and electron accessibility, thus better utilizing the pseudocapacitive property of lignin. All these strategies effectively enhanced the capacitive performance of the electrodes. In addition, HLNPs, which acted as a protective phase for MXene layer, enhanced mechanical properties of the wrinkled stretchable electrodes by releasing stress through slip and deformation during the stretch-release cycling and greatly improved the structural integrity and capacitive stability of the electrodes. Flexible electrodes and symmetric flexible all-solid-state supercapacitors capable of enduring 600% uniaxial tensile strain were developed with high specific capacitances of 1273 mF cm⁻² (241 F g⁻¹) and 514 mF cm⁻² (95 F g⁻¹), respectively. Moreover, their capacitances were well preserved after 1000 times of 600% stretch-release cycling. This study showcased new possibilities of incorporating biobased lignin nanospheres in energy storage devices to fabricate stretchable devices leveraging synergies among various two-dimensional nanomaterials.

Highlights:
1 A novel gradient-layered architecture based on single-pore hollow lignin nanospheres (HLNPs)-intercalated MXene layers was created to fabricate highly stretchable (600%) and durable (1000 cycling) supercapacitor electrodes.
2 The architecture reduced the overstacking of MXene, and the micro-chamber structure of HLNPs better utilized lignin’s pseudocapacitive property to improve ion and electron accessibility (specific capacitance reached 1273 mF cm⁻²).
3 HLNPs enhanced mechanical durability and capacitive stability of the integrated wrinkled electrodes during the stretch-release cycling.

Ultra-High Sensitivity Anisotropic Piezoelectric Sensors for Structural Health Monitoring and Robotic Perception

Wed, 16 Oct 2024 00:00:00 +0000

Monitoring minuscule mechanical signals, both in magnitude and direction, is imperative in many application scenarios, e.g., structural health monitoring and robotic sensing systems. However, the piezoelectric sensor struggles to satisfy the requirements for directional recognition due to the limited piezoelectric coefficient matrix, and achieving sensitivity for detecting micrometer-scale deformations is also challenging. Herein, we develop a vector sensor composed of lead zirconate titanate-electronic grade glass fiber composite filaments with oriented arrangement, capable of detecting minute anisotropic deformations. The as-prepared vector sensor can identify the deformation directions even when subjected to an unprecedented nominal strain of 0.06%, thereby enabling its utility in accurately discerning the 5 μm-height wrinkles in thin films and in monitoring human pulse waves. The ultra-high sensitivity is attributed to the formation of porous ferroelectret and the efficient load transfer efficiency of continuous lead zirconate titanate phase. Additionally, when integrated with machine learning techniques, the sensor’s capability to recognize multi-signals enables it to differentiate between 10 types of fine textures with 100% accuracy. The structural design in piezoelectric devices enables a more comprehensive perception of mechanical stimuli, offering a novel perspective for enhancing recognition accuracy.

Highlights:
1 A novel anisotropic sensor with oriented piezoelectric filaments was prepared, capable of detecting both the magnitude and direction of micro-deformations.
2 Due to the efficient load transfer of continuous fibers and the formation of porous ferroelectrets, an ultra-low strain detection limit of 0.06% was achieved in the sensor.
3 Given the sensor's ultra-low detection limit and deformation direction sensing capability, we developed the sensor for detecting micron-scale deformations in thin-film structures and for robotic tactile sensing applications.

A Rapid Adaptation Approach for Dynamic Air-Writing Recognition Using Wearable Wristbands with Self-Supervised Contrastive Learning

Wed, 16 Oct 2024 00:00:00 +0000

Wearable wristband systems leverage deep learning to revolutionize hand gesture recognition in daily activities. Unlike existing approaches that often focus on static gestures and require extensive labeled data, the proposed wearable wristband with self-supervised contrastive learning excels at dynamic motion tracking and adapts rapidly across multiple scenarios. It features a four-channel sensing array composed of an ionic hydrogel with hierarchical microcone structures and ultrathin flexible electrodes, resulting in high-sensitivity capacitance output. Through wireless transmission from a Wi-Fi module, the proposed algorithm learns latent features from the unlabeled signals of random wrist movements. Remarkably, only few-shot labeled data are sufficient for fine-tuning the model, enabling rapid adaptation to various tasks. The system achieves a high accuracy of 94.9% in different scenarios, including the prediction of eight-direction commands, and air-writing of all numbers and letters. The proposed method facilitates smooth transitions between multiple tasks without the need for modifying the structure or undergoing extensive task-specific training. Its utility has been further extended to enhance human–machine interaction over digital platforms, such as game controls, calculators, and three-language login systems, offering users a natural and intuitive way of communication.

Highlights:
1 Utilizing self-supervised learning, the proposed wearable wristband with a four-channel sensing array and wireless transmission module is developed for tracking air-writing and dynamic gestures.
2 The model can learn prior features from unlabeled signals of random wrist movements, significantly reducing the dependency on extensive labeled data for training.
3 The wristband system rapidly adapts to multiple scenarios after fine-tuning using few-shot data, enhancing user interaction through natural and intuitive communication.

Magneto-Dielectric Synergy and Multiscale Hierarchical Structure Design Enable Flexible Multipurpose Microwave Absorption and Infrared Stealth Compatibility

Chen Li, Leilei Liang, Baoshan Zhang, Yi Yang, Guangbin Ji — Wed, 16 Oct 2024 00:00:00 +0000

Developing advanced stealth devices to cope with radar-infrared (IR) fusion detection and diverse application scenarios is increasingly demanded, which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations. Here, we propose a multiscale hierarchical structure design, integrating wrinkled MXene IR shielding layer and flexible Fe₃O₄@C/PDMS microwave absorption layer. The top wrinkled MXene layer induces the intensive diffuse reflection effect, shielding IR radiation signals while allowing microwave to pass through. Meanwhile, the permeable microwaves are assimilated into the bottom Fe₃O₄@C/PDMS layer via strong magneto-electric synergy. Through theoretical and experimental optimization, the assembled stealth devices realize a near-perfect stealth capability in both X-band (8–12 GHz) and long-wave infrared (8–14 µm) wavelength ranges. Specifically, it delivers a radar cross-section reduction of − 20 dB m², a large apparent temperature modulation range (ΔT = 70 °C), and a low average IR emissivity of 0.35. Additionally, the optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s). This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments.

Highlights:
1 A multiscale hierarchical structure design, integrating wrinkled MXene radar-infrared shielding layer and flexible Fe₃O₄@C/PDMS microwave absorption layer
2 The assembled stealth devices realize a near-perfect stealth capability in both X-band (8-12 GHz) and long-wave infrared (8-14 µm) wavelength ranges.
3 The optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s).

Efficient and Stable Perovskite Solar Cells and Modules Enabled by Tailoring Additive Distribution According to the Film Growth Dynamics

Tue, 15 Oct 2024 00:00:00 +0000

Gas quenching and vacuum quenching process are widely applied to accelerate solvent volatilization to induce nucleation of perovskites in blade-coating method. In this work, we found these two pre-crystallization processes lead to different order of crystallization dynamics within the perovskite thin film, resulting in the differences of additive distribution. We then tailor-designed an additive molecule named 1,3-bis(4-methoxyphenyl)thiourea to obtain films with fewer defects and holes at the buried interface, and prepared perovskite solar cells with a certified efficiency of 23.75%. Furthermore, this work also demonstrates an efficiency of 20.18% for the large-area perovskite solar module (PSM) with an aperture area of 60.84 cm². The PSM possesses remarkable continuous operation stability for maximum power point tracking of T₉₀ > 1000 h in ambient air.

Highlights:
1 Two pre-crystallization processes of gas quenching and vacuum quenching lead to different order of crystallization dynamics within the perovskite thin film, resulting in the differences of additive distribution.
2 A tailor designed 1,3-bis(4-methoxyphenyl)thiourea was utilized to improve the buried interface, leading to a certified efficiency of 23.75% for blade-coated perovskite solar cell.
3 The perovskite solar module (aperture area: 60.84 cm²) demonstrates an efficiency of 20.18% with excellent operational stability (maximum power point tracking of T90 > 1000 h).

Porous Organic Cage-Based Quasi-Solid-State Electrolyte with Cavity-Induced Anion-Trapping Effect for Long-Life Lithium Metal Batteries

Tue, 15 Oct 2024 00:00:00 +0000

Porous organic cages (POCs) with permanent porosity and excellent host–guest property hold great potentials in regulating ion transport behavior, yet their feasibility as solid-state electrolytes has never been testified in a practical battery. Herein, we design and fabricate a quasi-solid-state electrolyte (QSSE) based on a POC to enable the stable operation of Li-metal batteries (LMBs). Benefiting from the ordered channels and cavity-induced anion-trapping effect of POC, the resulting POC-based QSSE exhibits a high Li⁺ transference number of 0.67 and a high ionic conductivity of 1.25 × 10⁻⁴ S cm⁻¹ with a low activation energy of 0.17 eV. These allow for homogeneous Li deposition and highly reversible Li plating/stripping for over 2000 h. As a proof of concept, the LMB assembled with POC-based QSSE demonstrates extremely stable cycling performance with 85% capacity retention after 1000 cycles. Therefore, our work demonstrates the practical applicability of POC as SSEs for LMBs and could be extended to other energy-storage systems, such as Na and K batteries.

Highlights:
1 A porous organic cage (POC)-based quasi-solid-state electrolyte (QSSE) with cavity-induced anion-trapping effect was rationally designed to enable the stable operation of Li-metal batteries.
2 The POC-based QSSE exhibits a high Li⁺ transference number of 0.67 and a high ionic conductivity of 1.25×10⁻⁴ S cm⁻¹ with a low activation energy of 0.17 eV.
3 The POC-based QSSE demonstrates a highly reversible Li plating/stripping cycling for 2000 h and superior Li||LFePO₄ cycling for thousands of cycles at room temperature.

An Unprecedented Efficiency with Approaching 21% Enabled by Additive-Assisted Layer-by-Layer Processing in Organic Solar Cells

Mon, 14 Oct 2024 00:00:00 +0000

Recently published in Joule, Feng Liu and colleagues from Shanghai Jiaotong University reported a record-breaking 20.8% power conversion efficiency in organic solar cells (OSCs) with an interpenetrating fibril network active layer morphology, featuring a bulk p-i-n structure and proper vertical segregation achieved through additive-assisted layer-by-layer deposition. This optimized hierarchical gradient fibrillar morphology and optical management synergistically facilitates exciton diffusion, reduces recombination losses, and enhances light capture capability. This approach not only offers a solution to achieving high-efficiency devices but also demonstrates the potential for commercial applications of OSCs.

Highlights:
1 Additive-assisted layer-by-layer (LBL) deposition enables organic solar cells to achieve an unprecedented power conversion efficiency of 20.8%, the highest efficiency to date.
2 The gradient fibrillar morphology enabled by additive-assisted LBL processing promotes the formation of bulk p-i-n structure, improving exciton and carrier diffusion, and reducing recombination losses.
3 The wrinkle pattern morphology achieved by additive-assisted LBL processing is constructed to enhance the light capture capability.

MoS2 Lubricate-Toughened MXene/ANF Composites for Multifunctional Electromagnetic Interference Shielding

Fri, 11 Oct 2024 00:00:00 +0000

The design and fabrication of high toughness electromagnetic interference (EMI) shielding composite films with diminished reflection are an imperative task to solve electromagnetic pollution problem. Ternary MXene/ANF (aramid nanofibers)–MoS₂ composite films with nacre-like layered structure here are fabricated after the introduction of MoS₂ into binary MXene/ANF composite system. The introduction of MoS₂ fulfills an impressive “kill three birds with one stone” improvement effect: lubrication toughening mechanical performance, reduction in secondary reflection pollution of electromagnetic wave, and improvement in the performance of photothermal conversion. After the introduction of MoS₂ into binary MXene/ANF (mass ratio of 50:50), the strain to failure and tensile strength increase from 22.1 1.7% and 105.7 6.4 MPa and to 25.8 0.7% and 167.3 9.1 MPa, respectively. The toughness elevates from 13.0 4.1 to 26.3 0.8 MJ m⁻³ (~ 102.3%) simultaneously. And the reflection shielding effectiveness (SE_R) of MXene/ANF (mass ratio of 50:50) decreases ~ 10.8%. EMI shielding effectiveness (EMI SE) elevates to 41.0 dB (8.2–12.4 GHz); After the introduction of MoS₂ into binary MXene/ANF (mass ratio of 60:40), the strain to failure increases from 18.3 1.9% to 28.1 0.7% (~ 53.5%), the SE_R decreases ~ 22.2%, and the corresponding EMI SE is 43.9 dB. The MoS₂ also leads to a more efficient photothermal conversion performance (~ 45 to ~ 55 °C). Additionally, MXene/ANF–MoS₂ composite films exhibit excellent electric heating performance, quick temperature elevation (15 s), excellent cycle stability (2, 2.5, and 3 V), and long-term stability (2520 s). Combining with excellent mechanical performance with high MXene content, electric heating performance, and photothermal conversion performance, EMI shielding ternary MXene/ANF–MoS₂ composite films could be applied in many industrial areas. This work broadens how to achieve a balance between mechanical properties and versatility of composites in the case of high-function fillers.

Highlights:
1 The introduction of MoS₂ generates a “kill three birds with one stone” effect to the original binary MXene/ANF system: lubrication toughening mechanical performance; reduction in secondary reflection pollution of electromagnetic wave; and improvement in the performance of photothermal conversion.
2 After the introduction of MoS₂ into MXene/ANF (60:40), the strain and toughness were increased by 53.5% (from 18.3% to 28.1%) and 61.7% (from 8.9 to 14.5 MJ m⁻³), respectively. Fortunately, the SER decreases by 22.4%, and the photothermal conversion performance was increased by 22.2% from ~ 45 to ~ 55 °C.

High Fe-Loading Single-Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

Fri, 04 Oct 2024 00:00:00 +0000

The current single-atom catalysts (SACs) for medicine still suffer from the limited active site density. Here, we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron. The constructed iron SACs (h³-FNC) with a high metal loading of 6.27 wt% and an optimized adjacent Fe distance of ~ 4 Å exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects. Attractively, a “density effect” has been found at a high-enough metal doping amount, at which individual active sites become close enough to interact with each other and alter the electronic structure, resulting in significantly boosted intrinsic activity of single-atomic iron sites in h³-FNCs by 2.3 times compared to low- and medium-loading SACs. Consequently, the overall catalytic activity of h³-FNC is highly improved, with mass activity and metal mass-specific activity that are, respectively, 66 and 315 times higher than those of commercial Pt/C. In addition, h³-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion (O₂·⁻) and glutathione (GSH) depletion. Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h³-FNCs in promoting wound healing. This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Highlights:
1 Fe single-atom catalysts (h³-FNCs) with high loading, high catalytic activity and high stability were synthesized via a method capable of increasing both the metal loading and mass-specific activity by exchanging zinc with iron.
2 The “density effect,” derived from the sufficiently high density of active sites, has been discovered for the first time, leading to a significant alteration in the intrinsic activity of single-atom metal sites.
3 The superior oxidase-like catalytic performance of h³-FNCs ensures highly effective bacterial eradication.

Aligned Ion Conduction Pathway of Polyrotaxane-Based Electrolyte with Dispersed Hydrophobic Chains for Solid-State Lithium–Oxygen Batteries

Tue, 01 Oct 2024 00:00:00 +0000

A critical challenge hindering the practical application of lithium–oxygen batteries (LOBs) is the inevitable problems associated with liquid electrolytes, such as evaporation and safety problems. Our study addresses these problems by proposing a modified polyrotaxane (mPR)-based solid polymer electrolyte (SPE) design that simultaneously mitigates solvent-related problems and improves conductivity. mPR-SPE exhibits high ion conductivity (2.8 × 10⁻³ S cm⁻¹ at 25 °C) through aligned ion conduction pathways and provides electrode protection ability through hydrophobic chain dispersion. Integrating this mPR-SPE into solid-state LOBs resulted in stable potentials over 300 cycles. In situ Raman spectroscopy reveals the presence of an LiO₂ intermediate alongside Li₂O₂ during oxygen reactions. Ex situ X-ray diffraction confirm the ability of the SPE to hinder the permeation of oxygen and moisture, as demonstrated by the air permeability tests. The present study suggests that maintaining a low residual solvent while achieving high ionic conductivity is crucial for restricting the sub-reactions of solid-state LOBs.

Highlights:
1 Strategic materials design of polyrotaxane-based electrolytes was suggested by aligning the ion conduction pathways and dispersing hydrophobic chains for solid-state Li–O₂ batteries.
2 Owing to intentional design, solid-state Li–O₂ battery resulted in stable potential over 300 cycles at 25 °C.

3D Printing of Tough Hydrogel Scaffolds with Functional Surface Structures for Tissue Regeneration

Sun, 29 Sep 2024 00:00:00 +0000

Hydrogel scaffolds have numerous potential applications in the tissue engineering field. However, tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties. Inspired by Chinese ramen, we propose a universal fabricating method (printing-P, training-T, cross-linking-C, PTC & PCT) for tough hydrogel scaffolds to fill this gap. First, 3D printing fabricates a hydrogel scaffold with desired structures (P). Then, the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance (T). Finally, the training results are fixed by photo-cross-linking processing (C). The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa (622-fold untreated) and have excellent biocompatibility. Furthermore, this scaffold possesses functional surface structures from nanometer to micron to millimeter, which can efficiently induce directional cell growth. Interestingly, this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt, and many hydrogels, such as gelatin and silk, could be improved with PTC or PCT strategies. Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers, blood vessels, and nerves within 4 weeks, prompting the rapid regeneration of large-volume muscle loss injuries.

Highlights:
1 We propose the novel concept of a tough hydrogel scaffold within the realm of tissue engineering. This scaffold combines exceptional strength (6.66 MPa), customization capabilities, and superior biocompatibility in a manner not previously achieved in existing research.
2 These tough hydrogel scaffolds possess functional surface structures and can effectively enhance cell-guided growth and prompt regeneration of muscle tissue in vivo.
3 This is a universal manufacturing method for tough hydrogel scaffolds in tissue engineering.

Locally Enhanced Flow and Electric Fields Through a Tip Effect for Efficient Flow-Electrode Capacitive Deionization

Fri, 27 Sep 2024 00:00:00 +0000

Low-electrode capacitive deionization (FCDI) is an emerging desalination technology with great potential for removal and/or recycling ions from a range of waters. However, it still suffers from inefficient charge transfer and ion transport kinetics due to weak turbulence and low electric intensity in flow electrodes, both restricted by the current collectors. Herein, a new tip-array current collector (designated as T-CC) was developed to replace the conventional planar current collectors, which intensifies both the charge transfer and ion transport significantly. The effects of tip arrays on flow and electric fields were studied by both computational simulations and electrochemical impedance spectroscopy, which revealed the reduction of ion transport barrier, charge transport barrier and internal resistance. With the voltage increased from 1.0 to 1.5 and 2.0 V, the T-CC-based FCDI system (T-FCDI) exhibited average salt removal rates (ASRR) of 0.18, 0.50, and 0.89 μmol cm⁻² min⁻¹, respectively, which are 1.82, 2.65, and 2.48 folds higher than that of the conventional serpentine current collectors, and 1.48, 1.67, and 1.49 folds higher than that of the planar current collectors. Meanwhile, with the solid content in flow electrodes increased from 1 to 5 wt%, the ASRR for T-FCDI increased from 0.29 to 0.50 μmol cm⁻² min⁻¹, which are 1.70 and 1.67 folds higher than that of the planar current collectors. Additionally, a salt removal efficiency of 99.89% was achieved with T-FCDI and the charge efficiency remained above 95% after 24 h of operation, thus showing its superior long-term stability.

Highlights:
1 Steel tip arrays were used as current collectors to replace planar conductors.
2 Optimal flow and electric fields reduced barriers for electron and ion transport.
3 Desalination performance of flow-electrode capacitive deionization is enhanced by the tip-array current collectors.

An Efficient Boron Source Activation Strategy for the Low-Temperature Synthesis of Boron Nitride Nanotubes

Fri, 27 Sep 2024 00:00:00 +0000

Lowering the synthesis temperature of boron nitride nanotubes (BNNTs) is crucial for their development. The primary reason for adopting a high temperature is to enable the effective activation of high-melting-point solid boron. In this study, we developed a novel approach for efficiently activating boron by introducing alkali metal compounds into the conventional MgO–B system. This approach can be adopted to form various low-melting-point AM–Mg–B–O growth systems. These growth systems have improved catalytic capability and reactivity even under low-temperature conditions, facilitating the synthesis of BNNTs at temperatures as low as 850 °C. In addition, molecular dynamics simulations based on density functional theory theoretically demonstrate that the systems maintain a liquid state at low temperatures and interact with N atoms to form BN chains. These findings offer novel insights into the design of boron activation and are expected to facilitate research on the low-temperature synthesis of BNNTs.

Highlights:
1 Developed more efficient boron activation strategies, while establishing various low-melting growth systems.
2 The preparation temperature of boron nitride nanotubes has been reduced to 850 °C.

Defects-Rich Heterostructures Trigger Strong Polarization Coupling in Sulfides/Carbon Composites with Robust Electromagnetic Wave Absorption

Fri, 27 Sep 2024 00:00:00 +0000

Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies, as well as veiled dielectric-responsive character, are instrumental in electromagnetic dissipation. Conventional methods, however, constrain their delicate constructions. Herein, an innovative alternative is proposed: carrageenan-assistant cations-regulated (CACR) strategy, which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix. This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction, benefiting the delicate construction of defects-rich heterostructures in M_xS_y/carbon composites (M-CAs). Impressively, these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and, simultaneously, induct local asymmetry of electronic structure to evoke large dipole moment, ultimately leading to polarization coupling, i.e., defect-type interfacial polarization. Such “Janus effect” (Janus effect means versatility, as in the Greek two-headed Janus) of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time. Consequently, the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm, compared to sulfur vacancies-free CAs without any dielectric response. Harnessing defects-rich heterostructures, this one-pot CACR strategy may steer the design and development of advanced nanomaterials, boosting functionality across diverse application domains beyond electromagnetic response.

Highlights:
1 A series of sulfides/carbon composites with sulfur vacancies-rich sulfides heterointerfaces are well-designed and developed via a simple one-pot carrageenan-assistant cations-regulated strategy.
2“Janus effect” of interfacial sulfur vacancies, which triggers strong defect-type interfacial polarization, are firstly intuitively confirmed by both theoretical and experimental investigations.
3 Optimized Co/Ni-carbon composites (CAs) imbued with sulfur vacancies-rich heterointerfaces displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm, compared to sulfur vacancies-free CAs without any dielectric response.

Multiple Tin Compounds Modified Carbon Fibers to Construct Heterogeneous Interfaces for Corrosion Prevention and Electromagnetic Wave Absorption

Fri, 27 Sep 2024 00:00:00 +0000

Currently, the demand for electromagnetic wave (EMW) absorbing materials with specific functions and capable of withstanding harsh environments is becoming increasingly urgent. Multi-component interface engineering is considered an effective means to achieve high-efficiency EMW absorption. However, interface modulation engineering has not been fully discussed and has great potential in the field of EMW absorption. In this study, multi-component tin compound fiber composites based on carbon fiber (CF) substrate were prepared by electrospinning, hydrothermal synthesis, and high-temperature thermal reduction. By utilizing the different properties of different substances, rich heterogeneous interfaces are constructed. This effectively promotes charge transfer and enhances interfacial polarization and conduction loss. The prepared SnS/SnS₂/SnO₂/CF composites with abundant heterogeneous interfaces have and exhibit excellent EMW absorption properties at a loading of 50 wt% in epoxy resin. The minimum reflection loss (RL) is − 46.74 dB and the maximum effective absorption bandwidth is 5.28 GHz. Moreover, SnS/SnS₂/SnO₂/CF epoxy composite coatings exhibited long-term corrosion resistance on Q235 steel surfaces. Therefore, this study provides an effective strategy for the design of high-efficiency EMW absorbing materials in complex and harsh environments.

Highlights:
1 Excellent impedance matching through component modulation engineering.
2 Rich heterogeneous interfaces are constructed to realize excellent electromagnetic wave (EMW) absorption performance.
3 Long-term corrosion protection and excellent EMW absorption properties.

Constructing Donor–Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li+ Migration in Quasi-Solid-State Battery

Thu, 26 Sep 2024 00:00:00 +0000

Regulation the electronic density of solid-state electrolyte by donor–acceptor (D–A) system can achieve highly-selective Li⁺ transportation and conduction in solid-state Li metal batteries. This study reports a high-performance solid-state electrolyte thorough D–A-linked covalent organic frameworks (COFs) based on intramolecular charge transfer interactions. Unlike other reported COF-based solid-state electrolyte, the developed concept with D–A-linked COFs not only achieves electronic modulation to promote highly-selective Li⁺ migration and inhibit Li dendrite, but also offers a crucial opportunity to understand the role of electronic density in solid-state Li metal batteries. The introduced strong electronegativity F-based ligand in COF electrolyte results in highly-selective Li⁺ (transference number 0.83), high ionic conductivity (6.7 × 10^–4 S cm⁻¹), excellent cyclic ability (1000 h) in Li metal symmetric cell and high-capacity retention in Li/LiFePO₄ cell (90.8% for 300 cycles at 5C) than substituted C- and N-based ligands. This is ascribed to outstanding D–A interaction between donor porphyrin and acceptor F atoms, which effectively expedites electron transferring from porphyrin to F-based ligand and enhances Li⁺ kinetics. Consequently, we anticipate that this work creates insight into the strategy for accelerating Li⁺ conduction in high-performance solid-state Li metal batteries through D–A system.

Highlights:
1 Donor–acceptor-linked covalent organic framework (COF)-based electrolyte can not only fulfill highly-selective Li⁺ conduction, but also offer a crucial opportunity to understand the role of electronic density in quasi-solid-state Li metal batteries.
2 Donor–acceptor-linked COF electrolyte results in Li+ transference number 0.83, high ionic conductivity 6.7 × 10^–4 S cm⁻¹ and excellent cyclic ability in Li metal batteries.
3 In situ characterizations, density functional theory calculation and time-of-flight secondary ion mass spectrometry are adopted to expound the mechanism of the rapid migration of Li⁺ in the “donor–acceptor” electrolyte system.

Designing Electronic Structures of Multiscale Helical Converters for Tailored Ultrabroad Electromagnetic Absorption

Thu, 26 Sep 2024 00:00:00 +0000

Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption (EMWA) materials. However, the relationship between configuration and electromagnetic (EM) loss mechanism has remained elusive. Herein, drawing inspiration from the DNA transcription process, we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability. Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn–N₄–C configuration, along with cross polarization generated by the helical structure, endow the helical converters with enhanced EM loss. As a result, HMC-8 demonstrates outstanding EMWA performance, achieving a minimum reflection loss of −63.13 dB at an ultralow thickness of 1.29 mm. Through precise tuning of the graphite domain size, HMC-7 achieves an effective absorption bandwidth (EAB) of 6.08 GHz at 2.02 mm thickness. Furthermore, constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm, with the maximum radar cross section reduction value reaching 36.4 dB m². This innovative approach not only advances the understanding of metal–nonmetal co-doping but also realizes broadband EMWA, thus contributing to the development of EMWA mechanisms and applications.

Highlights:
1 The energy conversion mechanism is thoroughly analyzed, with a detailed quantitative characterization of the dissipation capacities of polarization, conduction, and magnetic loss.
2 Inspired by DNA transcription, atom and geometry configurations co-modulating multi-scale helical converters achieve the RLmin of −63.13 dB at 1.29 mm, and the maximum RCS reduction value reach 36.4 dB m².
3 Orbital coupling, spin and cross polarization synergize to realize a 6.08 GHz EAB, further expanding to ultrabroad electromagnetic wave absorption of 12.16 GHz through metamaterial design.

Spontaneous Orientation Polarization of Anisotropic Equivalent Dipoles Harnessed by Entropy Engineering for Ultra-Thin Electromagnetic Wave Absorber

Thu, 26 Sep 2024 00:00:00 +0000

The synthesis of carbon supporter/nanoscale high-entropy alloys (HEAs) electromagnetic response composites by carbothermal shock method has been identified as an advanced strategy for the collaborative competition engineering of conductive/dielectric genes. Electron migration modes within HEAs as manipulated by the electronegativity, valence electron configurations and molar proportions of constituent elements determine the steady state and efficiency of equivalent dipoles. Herein, enlightened by skin-like effect, a reformative carbothermal shock method using carbonized cellulose paper (CCP) as carbon supporter is used to preserve the oxygen-containing functional groups (O·) of carbonized cellulose fibers (CCF). Nucleation of HEAs and construction of emblematic shell-core CCF/HEAs heterointerfaces are inextricably linked to carbon metabolism induced by O·. Meanwhile, the electron migration mode of switchable electron-rich sites promotes the orientation polarization of anisotropic equivalent dipoles. By virtue of the reinforcement strategy, CCP/HEAs composite prepared by 35% molar ratio of Mn element (CCP/HEAs-Mn_2.15) achieves efficient electromagnetic wave (EMW) absorption of − 51.35 dB at an ultra-thin thickness of 1.03 mm. The mechanisms of the resulting dielectric properties of HEAs-based EMW absorbing materials are elucidated by combining theoretical calculations with experimental characterizations, which provide theoretical bases and feasible strategies for the simulation and practical application of electromagnetic functional devices (e.g., ultra-wideband bandpass filter).

Highlights:
1 The strengthening mechanism of spontaneous orientation polarization of anisotropic equivalent dipoles within high-entropy alloys (HEAs) is proposed for enhancing dielectric attenuation of HEAs.
2 The source of carbon supporter is expanded to the biomass category, which can construct the shell-core heterointerfaces with HEAs by means of a reformative carbothermal shock method.
3 The sample carbonized cellulose paper/HEAs-Mn_2.15 achieves efficient electromagnetic wave absorption of -51.35 dB at an ultra-thin thickness of 1.03 mm.
4 This work combines theoretical calculations and electromagnetic simulations to propose feasible strategies for the design and application of electromagnetic functional devices such as ultra-wideband bandpass filter.

Molecule-Level Multiscale Design of Nonflammable Gel Polymer Electrolyte to Build Stable SEI/CEI for Lithium Metal Battery

Fri, 27 Sep 2024 00:00:00 +0000

The risk of flammability is an unavoidable issue for gel polymer electrolytes (GPEs). Usually, flame-retardant solvents are necessary to be used, but most of them would react with anode/cathode easily and cause serious interfacial instability, which is a big challenge for design and application of nonflammable GPEs. Here, a nonflammable GPE (SGPE) is developed by in situ polymerizing trifluoroethyl methacrylate (TFMA) monomers with flame-retardant triethyl phosphate (TEP) solvents and LiTFSI–LiDFOB dual lithium salts. TEP is strongly anchored to PTFMA matrix via polarity interaction between -P = O and -CH₂CF₃. It reduces free TEP molecules, which obviously mitigates interfacial reactions, and enhances flame-retardant performance of TEP surprisingly. Anchored TEP molecules are also inhibited in solvation of Li⁺, leading to anion-dominated solvation sheath, which creates inorganic-rich solid electrolyte interface/cathode electrolyte interface layers. Such coordination structure changes Li⁺ transport from sluggish vehicular to fast structural transport, raising ionic conductivity to 1.03 mS cm⁻¹ and transfer number to 0.41 at 30 °C. The Li|SGPE|Li cell presents highly reversible Li stripping/plating performance for over 1000 h at 0.1 mA cm⁻², and 4.2 V LiCoO₂|SGPE|Li battery delivers high average specific capacity > 120 mAh g⁻¹ over 200 cycles. This study paves a new way to make nonflammable GPE that is compatible with Li metal anode.

Highlights:
1 Nonflammable gel polymer electrolyte (SGPE) is developed by in situ polymerizing trifluoroethyl methacrylate (TFMA) monomers with flame-retardant triethyl phosphate (TEP) solvents and LiTFSI–LiDFOB dual lithium salts.
2 Molecular polarity interaction between TEP and PTFMA mitigates interfacial reactions and changes the solvation of Li⁺.
3 SGPE forms stable inorganic-rich solid electrolyte interface/cathode electrolyte interface layer, exhibiting well compatibility with Li anode and LiCoO₂-type high-voltage cathode.

Bioinspired Passive Tactile Sensors Enabled by Reversible Polarization of Conjugated Polymers

Feng He, Sitong Chen, Ruili Zhou, Hanyu Diao, Yangyang Han, Xiaodong Wu — Fri, 27 Sep 2024 00:00:00 +0000

Tactile perception plays a vital role for the human body and is also highly desired for smart prosthesis and advanced robots. Compared to active sensing devices, passive piezoelectric and triboelectric tactile sensors consume less power, but lack the capability to resolve static stimuli. Here, we address this issue by utilizing the unique polarization chemistry of conjugated polymers for the first time and propose a new type of bioinspired, passive, and bio-friendly tactile sensors for resolving both static and dynamic stimuli. Specifically, to emulate the polarization process of natural sensory cells, conjugated polymers (including poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), polyaniline, or polypyrrole) are controllably polarized into two opposite states to create artificial potential differences. The controllable and reversible polarization process of the conjugated polymers is fully in situ characterized. Then, a micro-structured ionic electrolyte is employed to imitate the natural ion channels and to encode external touch stimulations into the variation in potential difference outputs. Compared with the currently existing tactile sensing devices, the developed tactile sensors feature distinct characteristics including fully organic composition, high sensitivity (up to 773 mV N⁻¹), ultralow power consumption (nW), as well as superior bio-friendliness. As demonstrations, both single point tactile perception (surface texture perception and material property perception) and two-dimensional tactile recognitions (shape or profile perception) with high accuracy are successfully realized using self-defined machine learning algorithms. This tactile sensing concept innovation based on the polarization chemistry of conjugated polymers opens up a new path to create robotic tactile sensors and prosthetic electronic skins.

Highlights:
1 Fully organic and passive tactile sensors are developed via mimicking the sensing behavior of natural sensory cells.
2 Controllable polarizability of conjugated polymers is adopted for the first time to construct passive tactile sensors.
3 Machine learning-assisted surface texture detection, material property recognition, as well as shape/profile perception are realized with the tactile sensors.

“Zero-Strain” NiNb2O6 Fibers for All-Climate Lithium Storage

Fri, 27 Sep 2024 00:00:00 +0000

Niobates are promising all-climate Li⁺-storage anode material due to their fast charge transport, large specific capacities, and resistance to electrolyte reaction. However, their moderate unit-cell-volume expansion (generally 5%–10%) during Li⁺ storage causes unsatisfactory long-term cyclability. Here, “zero-strain” NiNb₂O₆ fibers are explored as a new anode material with comprehensively good electrochemical properties. During Li⁺ storage, the expansion of electrochemical inactive NiO₆ octahedra almost fully offsets the shrinkage of active NbO₆ octahedra through reversible O movement. Such superior volume-accommodation capability of the NiO₆ layers guarantees the “zero-strain” behavior of NiNb₂O₆ in a broad temperature range (0.53%//0.51%//0.74% at 25// − 10//60 °C), leading to the excellent cyclability of the NiNb₂O₆ fibers (92.8%//99.2% // 91.1% capacity retention after 1000//2000//1000 cycles at 10C and 25// − 10//60 °C). This NiNb₂O₆ material further exhibits a large reversible capacity (300//184//318 mAh g⁻¹ at 0.1C and 25// − 10//60 °C) and outstanding rate performance (10 to 0.5C capacity percentage of 64.3%//50.0%//65.4% at 25// − 10//60 °C). Therefore, the NiNb₂O₆ fibers are especially suitable for large-capacity, fast-charging, long-life, and all-climate lithium-ion batteries.

Highlights:
1 “Zero-strain” NiNb₂O₆ fibers with nanosized primary particles are explored as an all-climate anode material with comprehensively good Li⁺-storage properties.
2 The almost completely opposite volume changes of electrochemical inactive NiO₆ octahedra and active NbO₆ octahedra are achieved through reversible O movement, leading to the “zero-strain” behavior of NiNb₂O₆ with minor unit-cell-volume change and excellent cyclability in a broad temperature range.
3 The gained insight can provide guide for the exploration of high-performance energy-storage materials working at harsh temperatures.

Smart Cellulose-Based Janus Fabrics with Switchable Liquid Transportation for Personal Moisture and Thermal Management

Thu, 26 Sep 2024 00:00:00 +0000

The Janus fabrics designed for personal moisture/thermal regulation have garnered significant attention for their potential to enhance human comfort. However, the development of smart and dynamic fabrics capable of managing personal moisture/thermal comfort in response to changing external environments remains a challenge. Herein, a smart cellulose-based Janus fabric was designed to dynamically manage personal moisture/heat. The cotton fabric was grafted with N-isopropylacrylamide to construct a temperature-stimulated transport channel. Subsequently, hydrophobic ethyl cellulose and hydrophilic cellulose nanofiber were sprayed on the bottom and top sides of the fabric to obtain wettability gradient. The fabric exhibits anti-gravity directional liquid transportation from hydrophobic side to hydrophilic side, and can dynamically and continuously control the transportation time in a wide range of 3–66 s as the temperature increases from 10 to 40 °C. This smart fabric can quickly dissipate heat at high temperatures, while at low temperatures, it can slow down the heat dissipation rate and prevent the human from becoming too cold. In addition, the fabric has UV shielding and photodynamic antibacterial properties through depositing graphitic carbon nitride nanosheets on the hydrophilic side. This smart fabric offers an innovative approach to maximizing personal comfort in environments with significant temperature variations.

Highlights:
1 A smart all-cellulose Janus fabric was designed for personal moisture/thermal management.
2 The fabric can dynamically and continuously control the liquid transportation time in response to the temperature.
3 The fabric can accelerate the heat dissipation rate at high temperatures, while slow it down at low temperatures.

Alternative Strategy for Development of Dielectric Calcium Copper Titanate-Based Electrolytes for Low-Temperature Solid Oxide Fuel Cells

Thu, 26 Sep 2024 00:00:00 +0000

The development of low-temperature solid oxide fuel cells (LT-SOFCs) is of significant importance for realizing the widespread application of SOFCs. This has stimulated a substantial materials research effort in developing high oxide-ion conductivity in the electrolyte layer of SOFCs. In this context, for the first time, a dielectric material, CaCu₃Ti₄O₁₂ (CCTO) is designed for LT-SOFCs electrolyte application in this study. Both individual CCTO and its heterostructure materials with a p-type Ni_0.8Co_0.15Al_0.05LiO_2−δ (NCAL) semiconductor are evaluated as alternative electrolytes in LT-SOFC at 450–550 °C. The single cell with the individual CCTO electrolyte exhibits a power output of approximately 263 mW cm⁻² and an open-circuit voltage (OCV) of 0.95 V at 550 °C, while the cell with the CCTO–NCAL heterostructure electrolyte capably delivers an improved power output of approximately 605 mW cm⁻² along with a higher OCV over 1.0 V, which indicates the introduction of high hole-conducting NCAL into the CCTO could enhance the cell performance rather than inducing any potential short-circuiting risk. It is found that these promising outcomes are due to the interplay of the dielectric material, its structure, and overall properties that led to improve electrochemical mechanism in CCTO–NCAL. Furthermore, density functional theory calculations provide the detailed information about the electronic and structural properties of the CCTO and NCAL and their heterostructure CCTO–NCAL. Our study thus provides a new approach for developing new advanced electrolytes for LT-SOFCs.

Highlights:
1 Dielectric CaCu₃Ti₄O₁₂ (CCTO) was used as electrolyte in low-temperature solid oxide fuel cells for the first time.
2 A new heterostructure electrolyte was designed based on CCTO and Ni_0.8Co_0.15Al_0.05LiO_2−δ (NCAL). Promising ionic conductivity and high fuel cell performance were achieved
3 CCTO–NCAL realized an electrolyte function due to its good dielectric property and a heterojunction effect.

Ultra-Transparent and Multifunctional IZVO Mesh Electrodes for Next-Generation Flexible Optoelectronics

Thu, 26 Sep 2024 00:00:00 +0000

Mechanically durable transparent electrodes are essential for achieving long-term stability in flexible optoelectronic devices. Furthermore, they are crucial for applications in the fields of energy, display, healthcare, and soft robotics. Conducting meshes represent a promising alternative to traditional, brittle, metal oxide conductors due to their high electrical conductivity, optical transparency, and enhanced mechanical flexibility. In this paper, we present a simple method for fabricating an ultra-transparent conducting metal oxide mesh electrode using self-cracking-assisted templates. Using this method, we produced an electrode with ultra-transparency (97.39%), high conductance (R_s = 21.24 Ω sq⁻¹), elevated work function (5.16 eV), and good mechanical stability. We also evaluated the effectiveness of the fabricated electrodes by integrating them into organic photovoltaics, organic light-emitting diodes, and flexible transparent memristor devices for neuromorphic computing, resulting in exceptional device performance. In addition, the unique porous structure of the vanadium-doped indium zinc oxide mesh electrodes provided excellent flexibility, rendering them a promising option for application in flexible optoelectronics.

Highlights:
1 Ultra-transparent vanadium-doped indium zinc oxide mesh (mIZVO) electrodes are fabricated using a self-cracking template.
2 Fabricated electrodes are employed to realize flexible organic solar cell (OSC), organic light-emitting diode (OLED), and memristor devices. OSC exhibits 14.38% power conversion efficiency and OLED achieves 18.06% external quantum efficiency with mIZVO electrode.
3 Flexible-transparent memristor based on mIZVO mimics various synaptic functions.

Boosting Oxygen Evolution Reaction Performance on NiFe-Based Catalysts Through d-Orbital Hybridization

Xing Wang, Wei Pi, Sheng Hu, Haifeng Bao, Na Yao, Wei. Luo — Thu, 26 Sep 2024 00:00:00 +0000

Anion-exchange membrane water electrolyzers (AEMWEs) for green hydrogen production have received intensive attention due to their feasibility of using earth-abundant NiFe-based catalysts. By introducing a third metal into NiFe-based catalysts to construct asymmetrical M-NiFe units, the d-orbital and electronic structures can be adjusted, which is an important strategy to achieve sufficient oxygen evolution reaction (OER) performance in AEMWEs. Herein, the ternary NiFeM (M: La, Mo) catalysts featured with distinct M-NiFe units and varying d-orbitals are reported in this work. Experimental and theoretical calculation results reveal that the doping of La leads to optimized hybridization between d orbital in NiFeM and 2p in oxygen, resulting in enhanced adsorption strength of oxygen intermediates, and reduced rate-determining step energy barrier, which is responsible for the enhanced OER performance. More critically, the obtained NiFeLa catalyst only requires 1.58 V to reach 1 A cm⁻² in an anion exchange membrane electrolyzer and demonstrates excellent long-term stability of up to 600 h.

Highlights:
1 The NiFeLa catalyst with 3d-5d orbital coupling exhibits remarkable oxygen evolution reaction (OER) activity and stability, enabling an anion-exchange membrane water electrolyzers device to achieve a cell voltage of only 1.58 V at 1 A cm⁻² as well as long-term stability over 600 h.
2 The introduction of La disrupts the symmetry of Ni-Fe units and optimize d band center, which affects the d-p orbital hybridization between the metal sites on the surface of the catalyst and oxygen-containing intermediates during the OER process.
3 The 5d-introduced NiFeLa has enhanced adsorption strength of oxygen intermediates, which can reduce the rate-determining step energy barrier and prevent catalyst dissolution.

Tailoring Light–Matter Interactions in Overcoupled Resonator for Biomolecule Recognition and Detection

Dongxiao Li, Hong Zhou, Zhihao Ren, Cheng Xu, Chengkuo Lee — Thu, 26 Sep 2024 00:00:00 +0000

Plasmonic nanoantennas provide unique opportunities for precise control of light–matter coupling in surface-enhanced infrared absorption (SEIRA) spectroscopy, but most of the resonant systems realized so far suffer from the obstacles of low sensitivity, narrow bandwidth, and asymmetric Fano resonance perturbations. Here, we demonstrated an overcoupled resonator with a high plasmon-molecule coupling coefficient (μ) (OC-Hμ resonator) by precisely controlling the radiation loss channel, the resonator-oscillator coupling channel, and the frequency detuning channel. We observed a strong dependence of the sensing performance on the coupling state, and demonstrated that OC-Hμ resonator has excellent sensing properties of ultra-sensitive (7.25% nm⁻¹), ultra-broadband (3–10 μm), and immune asymmetric Fano lineshapes. These characteristics represent a breakthrough in SEIRA technology and lay the foundation for specific recognition of biomolecules, trace detection, and protein secondary structure analysis using a single array (array size is 100 × 100 µm²). In addition, with the assistance of machine learning, mixture classification, concentration prediction and spectral reconstruction were achieved with the highest accuracy of 100%. Finally, we demonstrated the potential of OC-Hμ resonator for SARS-CoV-2 detection. These findings will promote the wider application of SEIRA technology, while providing new ideas for other enhanced spectroscopy technologies, quantum photonics and studying light–matter interactions.

Highlights:
1 Proposed a new paradigm for nanoantenna design using coupled-mode theory.
2 Designed an OC-Hµ resonator with excellent sensing performance.
3 Using OC-Hµ resonators for biomolecule recognition and detection.

Crystallization Modulation and Holistic Passivation Enables Efficient Two-Terminal Perovskite/CuIn(Ga)Se2 Tandem Solar Cells

Wed, 25 Sep 2024 00:00:00 +0000

Two-terminal (2-T) perovskite (PVK)/CuIn(Ga)Se₂ (CIGS) tandem solar cells (TSCs) have been considered as an ideal tandem cell because of their best bandgap matching regarding to Shockley–Queisser (S–Q) limits. However, the nature of the irregular rough morphology of commercial CIGS prevents people from improving tandem device performances. In this paper, D-homoserine lactone hydrochloride is proven to improve coverage of PVK materials on irregular rough CIGS surfaces and also passivate bulk defects by modulating the growth of PVK crystals. In addition, the minority carriers near the PVK/C60 interface and the incompletely passivated trap states caused interface recombination. A surface reconstruction with 2-thiopheneethylammonium iodide and N,N-dimethylformamide assisted passivates the defect sites located at the surface and grain boundaries. Meanwhile, LiF is used to create this field effect, repelling hole carriers away from the PVK and C60 interface and thus reducing recombination. As a result, a 2-T PVK/CIGS tandem yielded a power conversion efficiency of 24.6% (0.16 cm²), one of the highest results for 2-T PVK/CIGS TSCs to our knowledge. This validation underscores the potential of our methodology in achieving superior performance in PVK/CIGS tandem solar cells.

Highlights:
1 Integrating perovskite solar cells onto irregular rough CuIn(Ga)Se₂ (CIGS) surfaces remains a challenge; new strategy was explored to develop monolithic perovskite/CIGS tandem solar cell by manipulating the crystallization of perovskite.
2 Surface reconstruction and field-effect passivation are developed synergistically to issue complex interface relationship between perovskite and C60.
3 The champion power conversion efficiency （PCE） of 24.6% realized, providing significant commercial opportunities for all thin-film-based perovskite/CIGS tandem cells.

Low-Temperature Oxidation Induced Phase Evolution with Gradient Magnetic Heterointerfaces for Superior Electromagnetic Wave Absorption

Wed, 25 Sep 2024 00:00:00 +0000

Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching, adjusting dielectric/magnetic resonance and promoting electromagnetic (EM) wave absorption, but still exist a significant challenging in regulating local phase evolution. Herein, accordion-shaped Co/Co₃O₄@N-doped carbon nanosheets (Co/Co₃O₄@NC) with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and low-temperature oxidation process. The results indicate that the surface epitaxial growth of crystal Co₃O₄ domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components, which are beneficial for optimizing impedance matching and interfacial polarization. Moreover, gradient magnetic heterointerfaces simultaneously realize magnetic coupling, and long-range magnetic diffraction. Specifically, the synthesized Co/Co₃O₄@NC absorbents display the strong electromagnetic wave attenuation capability of − 53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz, both are superior to those of single magnetic domains embedded in carbon matrix. This design concept provides us an inspiration in optimizing interfacial polarization, regulating magnetic coupling and promoting electromagnetic wave absorption.

Highlights:
1 Co/Co₃O₄@NC nanosheets with gradient magnetic heterointerfaces have been fabricated by the high-temperature carbonization/low-temperature oxidation processes.
2 Experimental and theoretical simulation results indicate that magnetic heterointerfaces engineering is beneficial for optimizing impedance matching and promoting electromagnetic wave absorption.
3 Gradient magnetic heterointerfaces with magnetic-heteroatomic components realize the adjustment of interfacial polarization, magnetic coupling, and long-range magnetic diffraction.

Catalyst–Support Interaction in Polyaniline-Supported Ni3Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn-Air Batteries

Wed, 25 Sep 2024 00:00:00 +0000

Catalyst–support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction (OER). Here we modulate the catalyst–support interaction in polyaniline-supported Ni₃Fe oxide (Ni₃Fe oxide/PANI) with a robust hetero-interface, which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm⁻² and specific activity of 2.08 mA cm_ECSA⁻² at overpotential of 300 mV, 3.84-fold that of Ni₃Fe oxide. It is revealed that the catalyst–support interaction between Ni₃Fe oxide and PANI support enhances the Ni–O covalency via the interfacial Ni–N bond, thus promoting the charge and mass transfer on Ni₃Fe oxide. Considering the excellent activity and stability, rechargeable Zn-air batteries with optimum Ni₃Fe oxide/PANI are assembled, delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm⁻². The regulation of the effect of catalyst–support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

Highlights:
1 Ni₃Fe oxide, with an average size of 3.5 ± 1.5 nm, was successfully deposited onto polyaniline (PANI) support through a solvothermal strategy followed by calcination.
2 The catalyst–support interaction between Ni₃Fe oxide and PANI can enhance the Ni-O covalency via the interfacial Ni-N bond.
3 Ni₃Fe oxide/PANI-assembled Zn-air batteries achieve superior cycling life for over 400 h at 10 mA cm⁻² and a low charge potential of around 1.95 V.

Photo-Energized MoS2/CNT Cathode for High-Performance Li–CO2 Batteries in a Wide-Temperature Range

Tingsong Hu, Wenyi Lian, Kang Hu, Qiuju Li, Xueliang Cui, Tengyu Yao, Laifa Shen — Wed, 25 Sep 2024 00:00:00 +0000

Li–CO₂ batteries are considered promising energy storage systems in extreme environments such as Mars; however, severe performance degradation will occur at a subzero temperature owning to the sluggish reaction kinetics. Herein, a photo-energized strategy adopting sustainable solar energy in wide working temperature range Li–CO₂ battery was achieved with a binder-free MoS₂/carbon nanotube (CNT) photo-electrode as cathode. The unique layered structure and excellent photoelectric properties of MoS₂ facilitate the abundant generation and rapid transfer of photo-excited carriers, which accelerate the CO₂ reduction and Li₂CO₃ decomposition upon illumination. The illuminated battery at room temperature exhibited high discharge voltage of 2.95 V and mitigated charge voltage of 3.27 V, attaining superior energy efficiency of 90.2% and excellent cycling stability of over 120 cycles. Even at an extremely low temperature of − 30 °C, the battery with same electrolyte can still deliver a small polarization of 0.45 V by the photoelectric and photothermal synergistic mechanism of MoS₂/CNT cathode. This work demonstrates the promising potential of the photo-energized wide working temperature range Li–CO₂ battery in addressing the obstacle of charge overpotential and energy efficiency.

Highlights:
1 The unique layered structure and excellent photoelectric properties of MoS₂ facilitate the abundant generation and rapid transfer of photo-excited carriers, which accelerate the CO₂ reduction and Li₂CO₃ decomposition upon illumination.
2 MoS₂-based photo-energized Li–CO₂ battery displays ultra-low charge voltage of 3.27 V, high energy efficiency of 90.2%, superior cycling stability after 120 cycles and high rate capability.
3 The low-temperature Li–CO₂ battery achieves an ultra-low charge voltage of 3.4 V at –30 °C with a round-trip efficiency of 86.6%.