Truly form-factor-free industrially scalable system integration for electronic textile architectures with multifunctional fiber devices.

An integrated textile electronic system is reported here, enabling a truly free form factor system via textile manufacturing integration of fiber-based electronic components. Intelligent and smart systems require freedom of form factor, unrestricted design, and unlimited scale. Initial attempts to develop conductive fibers and textile electronics failed to achieve reliable integration and performance required for industrial-scale manufacturing of technical textiles by standard weaving technologies. Here, we present a textile electronic system with functional one-dimensional devices, including fiber photodetectors (as an input device), fiber supercapacitors (as an energy storage device), fiber field-effect transistors (as an electronic driving device), and fiber quantum dot light-emitting diodes (as an output device). As a proof of concept applicable to smart homes, a textile electronic system composed of multiple functional fiber components is demonstrated, enabling luminance modulation and letter indication depending on sunlight intensity.

Room Temperature Wafer-Scale Synthesis of Highly Transparent, Conductive CuS Nanosheet Films via a Simple Sulfur Adsorption-Corrosion Method.

The development of highly conductive electrodes with robust mechanical durability and clear transmittance in the visible to IR spectral range is of great importance for future wearable/flexible electronic applications. In particular, low resistivity, robust flexibility, and wide spectral transparency have a significant impact on optoelectronic performance. Herein, we introduce a new class of covellite copper monosulfide (CuS) nanosheet films as a promising candidate for soft transparent conductive electrodes (TCEs). An atmospheric sulfur adsorption-corrosion phenomenon represents a key approach in our work for the achievement of wafer-scale CuS nanosheet films through systematic control of the neat Cu layer thickness ranging from 2 to 10 nm multilayers at room temperature. These nanosheet films provide outstanding conductivity (∼25 Ω sq-1) and high transparency (> 80%) in the visible to infrared region as well as distinct flexibility and long stability under air exposure, yielding a high figure-of-merit (∼60) that is comparable to that of conventional rigid metal oxide material-based TCEs. Our unique room temperature synthesis process delivers high quality CuS nanosheets on any arbitrary substrates in a short time (< 1 min) scale, thus guaranteeing the widespread use of highly producible and scalable device fabrication.

Synergistic Effects of Phosphorus and Boron Co-Incorporated Activated Carbon for Ultrafast Zinc-Ion Hybrid Supercapacitors.

The rapid expansion of the development of the electrochemical capacitor appliance and its industry areas has created the need for long cycling stability of over 30 000 cycles along with an ultrafast performance (referred to as ultrafast longevity). In recent years, zinc-ion hybrid supercapacitors (ZICs) are considered to be emerging energy storage applications thanks to their high specific capacity and remarkable cycling stability. However, ZICs still face serious challenges in overcoming the ultrafast performance and lifetime limitations related to the cathode materials, activated carbon (AC), due to inadequate electrical properties and poor wettability between the electrolyte and the electrode, which cause reductions in specific capacity and lifetime rapidly at high current densities during cycling. To address these drawbacks, a novel phosphorus (P) and boron (B) codoped AC (designated P&B-AC) is presented herein with enhanced electrical properties due to B-doping along with improved wettability due to P-doping to provide an ultrafast longevity ZICs. The prepared ZICs display a superior electrochemical performance with an excellent specific capacity of 169.4 mAh g-1 at 0.5 A g-1, a remarkable ultrafast performance of 84.0 mAh g-1 at 10 A g-1, and outstanding ultrafast longevity indicated by an 88% capacity retention for up to 30 000 cycles at 10 A g-1. The excellent energy storage ability is firmly ascribed to the P and B codoping synergistic effect, leading to a superior diffusion capability of Zn ion and charge-transfer process of the AC cathode.

Surface functionalization-induced photoresponse characteristics of monolayer MoS2 for fast flexible photodetectors.

Monolayered, semiconducting molybdenum disulfide (MoS2) is of considerable interest for its potential applications in next-generation flexible, wearable, and transparent photodetectors because it has outstanding physical properties coupled with unique atomically thin dimensions. However, there is still a lack of understanding in terms of the underlying mechanisms responsible for the photoresponse dynamics, which makes it difficult to identify the appropriate device design strategy for achieving a fast photoresponse time in MoS2 photodetectors. In this study, we investigate the importance of surface functionalization on controlling the charge carrier densities in a MoS2 monolayer and in turn the corresponding behavior of the photoresponse in relation to the position of the Fermi-level and the energy band structure. We find that the p-doping and n-doping, which is achieved through the surface functionalization of the MoS2 monolayer, leads to devices with different photoresponse behavior. Specifically, the MoS2 devices with surface functional groups contributing to p-doping exhibited a faster response time as well as higher sensitivity compared to that observed for the MoS2 devices with surface functional groups contributing to n-doping. We attribute this difference to the degree of bending in the energy bands at the metal-semiconductor junction as a result of shifting in the Fermi-level position, which influences the optoelectronic transport properties as well as the recombination dynamics leading to a low dark and thus high detectivity and fast decay time. Based upon these findings, we have also demonstrated the broad applicability of surface functionalization by fabricating a flexible MoS2 photodetector that shows an outstanding decay time of 0.7 s, which is the fastest response time observed in flexible MoS2 detectors ever reported.

Consecutive Junction-Induced Efficient Charge Separation Mechanisms for High-Performance MoS2/Quantum Dot Phototransistors.

Phototransistors that are based on a hybrid vertical heterojunction structure of two-dimensional (2D)/quantum dots (QDs) have recently attracted attention as a promising device architecture for enhancing the quantum efficiency of photodetectors. However, to optimize the device structure to allow for more efficient charge separation and transfer to the electrodes, a better understanding of the photophysical mechanisms that take place in these architectures is required. Here, we employ a novel concept involving the modulation of the built-in potential within the QD layers for creating a new hybrid MoS2/PbS QDs phototransistor with consecutive type II junctions. The effects of the built-in potential across the depletion region near the type II junction interface in the QD layers are found to improve the photoresponse as well as decrease the response times to 950 µs, which is the faster response time (by orders of magnitude) than that recorded for previously reported 2D/QD phototransistors. Also, by implementing an electric-field modulation of the MoS2 channel, our experimental results reveal that the detectivity can be as large as 1 × 1011 jones. This work demonstrates an important pathway toward designing hybrid phototransistors and mixed-dimensional van der Waals heterostructures.

Improved Ionic Diffusion through the Mesoporous Carbon Skin on Silicon Nanoparticles Embedded in Carbon for Ultrafast Lithium Storage.

Because of their combined effects of outstanding mechanical stability, high electrical conductivity, and high theoretical capacity, silicon (Si) nanoparticles embedded in carbon are a promising candidate as electrode material for practical utilization in Li-ion batteries (LIBs) to replace the conventional graphite. However, because of the poor ionic diffusion of electrode materials, the low-grade ultrafast cycling performance at high current densities remains a considerable challenge. In the present study, seeking to improve the ionic diffusion, we propose a novel design of mesoporous carbon skin on the Si nanoparticles embedded in carbon by hydrothermal reaction, poly(methyl methacrylate) coating process, and carbonization. The resultant electrode offers a high specific discharge capacity with excellent cycling stability (1140 mA h g-1 at 100 mA g-1 after 100 cycles), superb high-rate performance (969 mA h g-1 at 2000 mA g-1), and outstanding ultrafast cycling stability (532 mA h g-1 at 2000 mA g-1 after 500 cycles). The battery performances are surpassing the previously reported results for carbon and Si composite-based electrodes on LIBs. Therefore, this novel approach provides multiple benefits in terms of the effective accommodation of large volume expansions of the Si nanoparticles, a shorter Li-ion diffusion pathway, and stable electrochemical conditions from a faster ionic diffusion during cycling.

Tunneled Mesoporous Carbon Nanofibers with Embedded ZnO Nanoparticles for Ultrafast Lithium Storage.

Carbon and metal oxide composites have received considerable attention as anode materials for Li-ion batteries (LIBs) owing to their excellent cycling stability and high specific capacity based on the chemical and physical stability of carbon and the high theoretical specific capacity of metal oxides. However, efforts to obtain ultrafast cycling stability in carbon and metal oxide composites at high current density for practical applications still face important challenges because of the longer Li-ion diffusion pathway, which leads to poor ultrafast performance during cycling. Here, tunneled mesoporous carbon nanofibers with embedded ZnO nanoparticles (TMCNF/ZnO) are synthesized by electrospinning, carbonization, and postcalcination. The optimized TMCNF/ZnO shows improved electrochemical performance, delivering outstanding ultrafast cycling stability, indicating a higher specific capacity than previously reported ZnO-based anode materials in LIBs. Therefore, the unique architecture of TMCNF/ZnO has potential for use as an anode material in ultrafast LIBs.

Ultrafast Lithium Storage Using Antimony-Doped Tin Oxide Nanoparticles Sandwiched between Carbon Nanofibers and a Carbon Skin.

Metal oxides as anode materials for Li-ion batteries (LIBs) are of significant interest to many potential technologies because of their high theoretical capacity value, low price, and environmentally friendly features. In spite of these considerable benefits and ongoing progress in the field, momentous challenges exist, related with structural disintegration due to volume expansion of electrode materials. This leads to rapid capacity decline and must be resolved in order to progress for realistic utilization of LIBs with ultrafast cycling stability. This article proposes a novel architecture of Sb-doped SnO2 nanoparticles sandwiched between carbon nanofiber and carbon skin (CNF/ATO/C) using electrospinning and hydrothermal methods. The CNF/ATO/C exhibits superb electrochemical behavior such as high specific capacity and outstanding cycling stability (705 mA h g-1 after 100 cycles), outstanding high-rate performance (411 mA h g-1 at 2000 mA g-1), and ultrafast cycling stability (347 mA h g-1 at 2000 mA g-1 after 100 cycles), which is high compared to any reported value using SnO2-based anode materials. Thus, this unique architecture furnishes profitable effects, including electroactive sites, structural stability, and electrical conductivity, which can potentially be realizes for ultrafast LIBs.

Carbon-Encapsulated Hollow Porous Vanadium-Oxide Nanofibers for Improved Lithium Storage Properties.

Carbon-encapsulated hollow porous vanadium-oxide (C/HPV2O5) nanofibers have been fabricated using electrospinning and postcalcination. By optimized postcalcination of vanadium-nitride and carbon-nanofiber composites at 400 °C for 30 min, we synthesized a unique architecture electrode with interior void spaces and well-defined pores as well as a uniform carbon layer on the V2O5 nanofiber surface. The optimized C/HPV2O5 electrode postcalcined at 400 °C for 30 min showed improved lithium storage properties with high specific discharge capacities, excellent cycling durability (241 mA h g(-1) at 100 cycles), and improved high-rate performance (155 mA h g(-1) at 1000 mA g(-1)), which is the highest performance in comparison with previously reported V2O5-based cathode materials. The improved electrochemical feature is due to the attractive properties of the carbon-encapsulated hollow porous structure: (I) excellent cycling durability with high specific capacity relative to the adoption of carbon encapsulation as a physical buffer layer and the effective accommodation of volume changes due to the hollow porous structure, (II) improved high-rate performance because of a shorter Li-ion diffusion pathway resulting from interior void spaces and well-defined pores at the surface. This unique electrode structure can potentially provide new cathode materials for high-performance lithium-ion batteries.

Synergistic Effects of a Multifunctional Graphene Based Interlayer on Electrochemical Behavior and Structural Stability.

The ability to rationally design and manipulate the interfacial structure in lithium ion batteries (LIBs) is of utmost technological importance for achieving desired performance requirements as it provides synergistic effects to the electrochemical properties and cycling stability of electrode materials. However, despite considerable efforts and progress made in recent years through the interface engineering based on active electrode materials, relatively little attention has been devoted to address the physical aspects of the interface and interfacial layer between the anode materials layer and the current collector. Here, we propose and successfully grow unique graphene directly on a Cu current collector as an ideal interfacial layer using the modified chemical vapor deposition (CVD). The anode with an engineered graphene interlayer exhibits remarkably improved electrochemical performances, such as large reversible specific capacity (921.4 mAh g(-1) at current density of 200 mA g(-1)), excellent Coulombic efficiency (close to approximately 96%), and superior cycling capacity retention and rate properties compared to the bare Cu. These excellent electrochemical features are discussed in terms of multiple beneficial effects of graphene on interfacial stability and adhesion between the anode and the collector, oxidation or corrosion resistance of the graphene grown Cu current collector, and electrical contact conductance during the charge/discharge process.

Ruthenium and ruthenium oxide nanofiber supports for enhanced activity of platinum electrocatalysts in the methanol oxidation reaction.

Novel supports for the dispersion of Pt electrocatalysts in fuel cells are constantly being developed in order to improve the electrochemical performance and reduce the cost. The electrocatalytic activity and stability in fuel cells largely depend on the surface morphology and structure of the support. In this study, Ru and RuO2 nanofibers prepared by electrospinning and post-calcination have been considered as Pt-catalyst supports. The composite material loaded with 20 wt% Pt catalyst exhibited a high anodic current density of 641.7 mA mgPt(-1), a high IF/IB ratio of 1.9, and excellent electrocatalytic stability compared to commercial Pt/C. The improved anodic current density of the composite is attributed to the high dispersion of the Pt catalyst over the large surface area of the nanosized support grains, while its low onset potential, high IF/IB ratio, and excellent electrocatalytic stability are ascribed to a bifunctional effect resulting from the existence of Ru atoms on the support surface. Finally, the efficient electron transfer and a rapid diffusion rate of the electrolyte are due to the unique network structure of the supports. Thus, the Ru and RuO2 nanofiber composites act as promising Pt-catalyst supports for the methanol oxidation reaction.

Activated mesoporous carbon nanofibers fabricated using water etching-assisted templating for high-performance electrochemical capacitors.

Activated mesoporous carbon nanofibers (AMCNFs) are synthesized by a sequential process of electrospinning, water etching-assisted templating, and acid treatment. Their morphologies, crystal structures, melting behavior, chemical bonding states, surface properties, and electrochemical performance are investigated for three different polyacrylonitrile (PAN) to polyvinylpyrrolidone (PVP) weight ratios - PAN : PVP = 8 : 2, 7 : 3, and 6 : 4. Compared to other samples, the AMCNFs with an optimum weight ratio of 6 : 4 show the highest specific surface area of 692 m(2) g(-1), a high volume percentage of mesopores of 43.9%, and an increased amount of carboxyl groups (10.5%). This results in a high specific capacitance of 207 F g(-1), a high-rate capability with a capacitance retention of 93%, a high energy density of 24.8-23.1 W h kg(-1), and an excellent cycling durability of up to 3000 cycles. The electrochemical performance improvement can be explained by the combined effect of the high surface area relative to the increased electrical double-layers, the high volume fraction of mesopores relative to shorter diffusion routes and low resistance pathways for ions, and the increased amount of carboxyl groups on the CNF surface relative to enhanced wettability.

Comparison of Electrodes for High-Performance Electrochemical Capacitors: Multi-Layer MnO2/Pt and Composite MnO2/Pt on Carbon Nanofibres.

Four different types of electrodes for high-performance electrochemical capacitors were prepared using electrospinning method and/or impregnation methods: (1) conventional carbon nanofibres (CNF) supports, and CNFs decorated with (2) MnO2 nanophases, (3) multi-layer MnO2/Pt nanophases, and (4) composite MnO2 and Pt nanophases. Their morphological, structural, chemical, and electrochemical properties were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and galvanostatic charge/discharge measurements. Composite MnO2 and Pt nanophases decorated on the CNFs exhibited superior capacitance (-252.3 F/g at 10 mV/s), excellent capacitance retention (-93.5% after 300 cycles), and high energy densities (13.53-18.06 Wh/kg). The enhanced electrochemical performances can be explained by the composite structure, presenting well-dispersed MnO2 nanophases leading to high capacitance, and well-dispersed Pt nanophases leading to improved electrical conductivity.