Growth of 1D Carbon Nanotube@Perovskite Core-Shell van der Waals Heterostructures through Chemical Vapor Deposition.

Perovskite is an emerging material with immense potential in the field of optoelectronics. 1D perovskite nanowires are crucial building blocks for the development of optoelectronic devices. However, producing perovskite nanowires with high quality and controlled alignment is challenging. In this study, the direct epitaxial growth of perovskite on oriented carbon nanotube (CNT) templates is presented through a chemical vapor deposition method. The deposition process of lead iodide and methylammonium iodide is systematically investigated, and a layer plus island growth mechanism is proposed to interpret the experimental observations. The aligned long CNTs serve as 1D templates and allow the growth of CNT@perovskite core-shell heterostructure with a high aspect ratio to withstand large deformation. The obtained 1D perovskite materials can be easily manipulated and transferred, enabling the facile preparation of microscale flexible devices. For proof of concept, a photodetector based on an individual CNT@methylammonium lead iodide heterostructure is fabricated. This work provides a new approach to prepare 1D hetero-nanostructure and may inspire the design of novel flexible nanophotodetectors.

Experimental Study and Mechanism Analysis of Paraffin/Sisal Composite Phase Change Energy Storage Fiber Prepared by Vacuum Adsorption Method.

Sisal fiber exhibits a fibrous and porous structure with significant surface roughness, making it highly suitable for storing phase change materials (PCMs). Its intricate morphology further aids in mitigating the risk of PCM leakage. This research successfully employs vacuum adsorption to encapsulate paraffin within sisal fiber, yielding a potentially cost-effective, durable, and environmentally friendly phase change energy storage medium. A systematic investigation was carried out to evaluate the effects of sisal-to-paraffin mass ratio, fiber length, vacuum level, and negative pressure duration on the loading rate of paraffin. The experimental results demonstrate that a paraffin loading rate of 8 wt% can be achieved by subjecting a 3 mm sisal fiber to vacuum adsorption with 16 wt% paraffin for 1 h at -0.1 MPa. Through the utilization of nano-CT imaging enhancement technology, along with petrographic microscopy, this study elucidates the mechanism underlying paraffin storage within sisal fiber during vacuum adsorption. The observations reveal that a substantial portion of paraffin is primarily stored within the pores of the fiber, while a smaller quantity is firmly adsorbed onto its surface, thus yielding a durable phase change energy storage medium. The research findings contribute to both the theoretical foundations and the available practical guidance for the fabrication and implementation of paraffin/sisal fiber composite phase change energy storage mediums.

Monitoring blood pressure and cardiac function without positioning via a deep learning-assisted strain sensor array.

Continuous and reliable monitoring of blood pressure and cardiac function is of great importance for diagnosing and preventing cardiovascular diseases. However, existing cardiovascular monitoring approaches are bulky and costly, limiting their wide applications for early diagnosis. Here, we developed an intelligent blood pressure and cardiac function monitoring system based on a conformal and flexible strain sensor array and deep learning neural networks. The sensor has a variety of advantages, including high sensitivity, high linearity, fast response and recovery, and high isotropy. Experiments and simulation synergistically verified that the sensor array can acquire high-precise and feature-rich pulse waves from the wrist without precise positioning. By combining high-quality pulse waves with a well-trained deep learning model, we can monitor blood pressure and cardiac function parameters. As a proof of concept, we further constructed an intelligent wearable system for real-time and long-term monitoring of blood pressure and cardiac function, which may contribute to personalized health management, precise and early diagnosis, and remote treatment.

Inter-Shell Sliding in Individual Few-Walled Carbon Nanotubes for Flexible Electronics.

Few-walled carbon nanotube (FWCNT) is composed of a few coaxial shells of CNTs with different diameters. The shells in one tube can slide relatively to each other under external forces, potentially leading to regulated electrical properties, which are never explored due to experimental difficulties. In this work, the electromechanical response induced by inter-shell sliding of individual CNTs is studied and revealed the linear electrical current variation for the first time. Based on centimeter-long FWCNTs grown through chemical vapor deposition, controllable and reversible inter-shell sliding is realized while simultaneously recording the electrical current. Reversible and linear current variation with inter-shell sliding is observed, which is consistent with the proposed inter-shell tunneling model. Further, a silk fibroin-assisted transfer technique is developed for long CNTs and realized the fabrication of FWCNT-based flexible devices. Tensile stress can be applied on the FWCNTs@silk film encapsulated in elastic silicone to induce inter-shell sliding and thus controls electrical current, which is demonstrated to serve as a new human-machine interface with high reliability. Besides, it is foreseen that the electromechanical behaviors induced by inter-layer sliding in 1D nanotubes may also be extended to 2D layered materials, shedding new light on the fabrication of novel electronics.

The Effect of Seawater on Mortar Matrix Coated with Hybrid Nano-Silica-Modified Surface Protection Materials.

Surface treatment technology is an effective method to reinforce the durability of concrete. In this study, cement-based materials containing industrial solid wastes were modified by hybrid nano-silica (HN), then applied as a novel surface protection material (SPM-HN). The effect of SPM-HN on surface hardness of mortar matrix exposed to seawater was investigated. Further, the microstructure was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and mercury intrusion porosimetry (MIP). The results show SPM-HN could significantly enhance the surface hardness of matrix in seawater curing, and the rebound number is increased by 94%.The microstructure analysis demonstrates that the incorporation of HN inhibits the formation of ettringite, thaumasite, and Friedel's salt. In addition, thermodynamic modeling shows the incorporation of hybrid nano-silica could generate more C-S-H, and decrease the maximum volume of Friedel's salt when SPM is exposed to seawater. This research indicates SPM-HN can be applied as a concrete protective layer in the marine environment.

Mechanically Reinforced Silkworm Silk Fiber by Hot Stretching.

Silkworm silk, which is obtained from domesticated Bombyx mori (B. mori), can be produced in a large scale. However, the mechanical properties of silkworm silk are inferior to its counterpart, spider dragline silk. Therefore, researchers are continuously exploring approaches to reinforce silkworm silk. Herein, we report a facile and scalable hot stretching process to reinforce natural silk fibers obtained from silkworm cocoons. Experimental results show that the obtained hot-stretched silk fibers (HSSFs) retain the chemical components of the original silk fibers while being endowed with increased ß-sheet nanocrystal content and crystalline orientation, leading to enhanced mechanical properties. Significantly, the average modulus of the HSSFs reaches 21.6 ± 2.8 GPa, which is about twice that of pristine silkworm silk fibers (11.0 ± 1.7 GPa). Besides, the tensile strength of the HSSFs reaches 0.77 ± 0.13 GPa, which is also obviously higher than that of the pristine silk (0.56 ± 0.08 GPa). The results show that the hot stretching treatment is effective and efficient for producing superstiff, strong, and tough silkworm silk fibers. We anticipate this approach may be also effective for reinforcing other natural or artificial polymer fibers or films containing abundant hydrogen bonds.

Sustainable Silk-Derived Multimode Carbon Dots.

Carbon dots (CDs) are widely studied for years due to their unique luminescent properties and potential applications in many fields. However, aggregation-caused quenching, monotonous emission modes, and unsustainable preparation impose restrictions on their performance and practical applications. Here, this work reports the facile synthesis of sustainable silk-derived multimode emitting CDs with dispersed-state fluorescence (DSF), aggregation-induced fluorescence (AIF), and aggregation-induced room temperature phosphorescence (AIRTP) through radiating sericin proteins in a household microwave oven (800 W, 2.5 min). The structure, luminescent properties, and the mechanism are investigated and discussed. The sericin-derived CDs have graphitized cores and heteroatom-cluster-rich surfaces. The DSF corresponds to the graphitized cores and the AIF origins from the aggregation-induced abundant orbital energy levels on the heteroatom-cluster-rich surfaces. The presence of abundant hydrogen bonds and small gap between the lowest singlet and triplet excited states induces AIRTP. Finally, based on the unique multimode emission of the prepared CDs, their applications in high-performance white-light-emitting diode, information encryption, anti-counterfeiting, and visual humidity sensors are demonstrated.

Biomass-Derived Carbon Materials: Controllable Preparation and Versatile Applications.

Biomass-derived carbon materials (BCMs) are encountering the most flourishing moment because of their versatile properties and wide potential applications. Numerous BCMs, including 0D carbon spheres and dots, 1D carbon fibers and tubes, 2D carbon sheets, 3D carbon aerogel, and hierarchical carbon materials have been prepared. At the same time, their structure-property relationship and applications have been widely studied. This paper aims to present a review on the recent advances in the controllable preparation and potential applications of BCMs, providing a reference for future work. First, the chemical compositions of typical biomass and their thermal degradation mechanisms are presented. Then, the typical preparation methods of BCMs are summarized and the relevant structural management rules are discussed. Besides, the strategies for improving the structural diversity of BCMs are also presented and discussed. Furthermore, the applications of BCMs in energy, sensing, environment, and other areas are reviewed. Finally, the remaining challenges and opportunities in the field of BCMs are discussed.

Microribbons composed of directionally self-assembled nanoflakes as highly stretchable ionic neural electrodes.

Many natural materials possess built-in structural variation, endowing them with superior performance. However, it is challenging to realize programmable structural variation in self-assembled synthetic materials since self-assembly processes usually generate uniform and ordered structures. Here, we report the formation of asymmetric microribbons composed of directionally self-assembled two-dimensional nanoflakes in a polymeric matrix during three-dimensional direct-ink printing. The printed ribbons with embedded structural variations show site-specific variance in their mechanical properties. Remarkably, the ribbons can spontaneously transform into ultrastretchable springs with controllable helical architecture upon stimulation. Such springs also exhibit superior nanoscale transport behavior as nanofluidic ionic conductors under even ultralarge tensile strains (>1,000%). Furthermore, to show possible real-world uses of such materials, we demonstrate in vivo neural recording and stimulation using such springs in a bullfrog animal model. Thus, such springs can be used as neural electrodes compatible with soft and dynamic biological tissues.

Electricity-Triggered Self-Healing of Conductive and Thermostable Vitrimer Enabled by Paving Aligned Carbon Nanotubes.

Electrically conducting films are important for the development of modern electronics. However, most of these conducting films become susceptible to structure fractures under complex deformations or accidental damages, causing the devices to fail to work. Inspired by the self-healing capability of creatures, we developed a self-healing, thermostable, and electrically conducting film that can be healed by electricity by paving aligned carbon nanotube (CNT) sheets onto the surface of liquid crystal elastomer composite films. The aligned CNT sheets make the composites conductive, so the composites can be healed not only by light but also by electricity after breaking. The scratches on the self-healing film can be healed easily under a voltage of 1.18 V/mm because of the electro-thermal effect of aligned CNT sheets. The healed film has almost the same mechanical properties compared to the pristine sample. The electrical and mechanical self-healing of the film is derived from the electrical reconnection of carbon nanotubes and transesterification-induced topology change of the network, respectively. We further demonstrated soft actuators and high-performance supercapacitors based on the prepared self-healing conducting films. This method for preparing self-healing conducting films enables the development of self-healing electronics.

Laser Writing of Janus Graphene/Kevlar Textile for Intelligent Protective Clothing.

Protective clothing plays a vital role in safety and security. Traditional protective clothing can protect the human body from physical injury. It is highly desirable to integrate modern wearable electronics into a traditional protection suit to endow it with versatile smart functions. However, it is still challenging to integrate electronics into clothing through a practical approach while keeping the intrinsic flexibility and breathability of textiles. In this work, we realized the direct writing of laser-induced graphene (LIG) on a Kevlar textile in air and demonstrated the applications of the as-prepared Janus graphene/Kevlar textile in intelligent protective clothing. The C═O and N-C bonds in Kevlar were broken, and the remaining carbon atoms were reorganized into graphene, which can be ascribed to a photothermal effect induced by the laser irradiation. Proof-of-concept devices based on the prepared graphene/Kevlar textile, including flexible Zn-air batteries, electrocardiogram electrodes, and NO2 sensors, were demonstrated. Further, we fabricated self-powered and intelligent protective clothing based on the graphene/Kevlar textile. The laser-induced direct writing of graphene from commercial textiles in air conditions provides a versatile and rapid route for the fabrication of textile electronics.

CVD growth of perovskite/graphene films for high-performance flexible image sensor.

Hybrid perovskite possesses excellent photoelectric properties, including large light-absorption capacity and high carrier mobility, and is an ideal light-absorbing material for photoelectric devices. The grain size and compactness of hybrid perovskite are key factors affecting the performance of photoelectric devices. The photocurrent and photoresponsivity of these devices are relatively low because of the rapidly recombined photoexcited electron-hole pairs in hybrid perovskite. Herein, we develop a facile two-step chemical vapor deposition (CVD) method to synthesize a high-quality van der Waals (vdWs) MAPbI3/graphene heterostructure for high-performance image sensor. We introduced inorganic sources (PbI2) to vdWs epitaxially grown PbI2 film on a seamless graphene monolayer film template through CVD. Methylammonium iodide (MAI) was then reintroduced to prepare the vdWs MAPbI3/graphene heterostructure. The MAPbI3 layer is composed of densely packed, large-size grains and displays a smooth surface. High photoresponsivity of 107 A/W is achieved in the corresponding photodetector. Inspired by the human visual system, we designed a flexible photodetector array containing (24 × 24) pixels, achieving perfect image recognition and color discrimination. Our study may greatly facilitate the construction of high-performance optoelectronic devices in artificial retina, biomedical imaging, remote sensing, and optical communication.

Catalytically Active Oil-Based Lubricant Additives Enabled by Calcining Ni-Al Layered Double Hydroxides.

Layered double hydroxides (LDHs) have lately been hailed as robust lubricant additives for improving tribological properties and as ideal catalysts for synthesizing carbon-based nanomaterials. In this paper, in situ analytical tools are used to track the evolution of the crystal structure and chemical composition of LDHs during calcination. Nickel oxide and elemental nickel can be produced by calcining NiAl-LDH in air (LDH-C-Air) and argon (LDH-C-Ar), respectively. For the base oil with 1 wt % LDH-C-Air, negligible wear can be detected even after a 2 h friction test under a severe contact pressure (∼637 MPa). A relatively thick tribofilm (∼60 nm) with a better mechanical property is formed, which protects the solid surface from severe wear. In addition, the possible formed carbon debris may also prevent the direct collision of asperities and effectively improve the wear resistance. This work provides a unique vision for the application of calcined LDHs with the combination of catalysis and tribology.

Silk-Based Advanced Materials for Soft Electronics.

Soft bioelectronics that could be integrated with soft and curvilinear biological tissues/organs have attracted multidisciplinary research interest from material scientists, electronic engineers, and biomedical scientists. Because of their potential human health-related applications, soft bioelectronics require stringent demands for biocompatible components. Silk, as a kind of well-known ancient natural biopolymer, shows unique combined merits such as good biocompatibility, programmable biodegradability, processability into various material formats, and large-scale sustainable production. Such unique merits have made silk popular for intensive design and study in soft bioelectronics over the past decade. Due to the development of fabrication techniques in material processing and progress in research, silk has been engineered into a variety of advanced materials including silk fibers/textiles, nanofibers, films, hydrogels, and aerogels. Natural and regenerated silk materials can also be transformed into intrinsically nitrogen-doped and electrically conductive carbon materials, due to their unique molecular structure and high nitrogen content. The rich morphologies and varied processing options for silk materials can furnish transformed carbon materials with well-designed structures and properties. The favorable and unique material merits of silk materials and silk-derived carbon materials offer potential applications in soft electronics. Based on commercial silk fibers/textiles and the availability of re-engineered silk materials with versatile technological formats, functional soft electronics have been explored with silk as flexible biosupports/biomatrixes or active components. These soft systems include bioresorbable electronics, ultraconformal bioelectronics, transient electronics, epidermal electronics, textile electronics, conformal biosensors, flexible transistors, and resistive switching memory devices. Silk-derived carbon materials with rationally designed morphologies and structures have also been developed as active components for wearable sensors, electronic skins, and flexible energy devices, which provide novel concepts and opportunities for soft electronics. In this Account, we highlight the unique hierarchical and chemical structure of natural silk fibers, the fabrication strategies for processing silk into materials with versatile morphologies and into electrically conductive carbon materials, as well as recent progress in the development of silk-based advanced materials (silk materials and silk-derived carbon materials) for soft bioelectronics. The design and functionality of soft electronics developed with commercial silk fibers/textiles, re-engineered silk materials, and silk-derived carbon materials as biosubstrate/matrix and active components is introduced in detail. We further discuss future challenges and prospects for developing silk-based soft bioelectronics for wearable healthcare systems. By leveraging the unique advantages of silk-based advanced materials, the design and construction strategy for flexible electronics, as well as the potential of flexible electronics for conformable and intimate association with human tissues/organs, silk-based soft bioelectronics should have a significant impact on diverse healthcare fields.

Hollow core-sheath nanocarbon spheres grown on carbonized silk fabrics for self-supported and nonenzymatic glucose sensing.

Flexible enzymatic glucose sensors have been investigated extensively for health monitoring systems. However, enzymatic glucose sensors have some problems, such as poor stability and complicated immobilization procedures. Rational and controllable design of nanomaterials with a unique structure, high activity and good electrochemical performance for nonenzymatic glucose sensors is desired critically. In this paper, we synthesize cuprous oxide nanoparticles embedded in carbon spheres directly on carbonized silk fabrics (Cu2O NPs@CSs/CSF), which is further used for the fabrication of a flexible and self-supported non-enzymatic glucose sensor. The Cu2O NPs@CSs/CSF shows good electrical conductivity due to the large contact area and the stable connection between the carbonized silk fabrics and carbon spheres. We demonstrate that the as-obtained non-enzymatic glucose sensor possesses high sensitivity and good stability, indicating its potential for practical applications. This strategy diversifies the toolbox available to the field of nonenzymatic glucose sensors and holds promise for flexible electronic devices.

Calcium Gluconate Derived Carbon Nanosheet Intrinsically Decorated with Nanopapillae for Multifunctional Printed Flexible Electronics.

With the blooming of wearable technology, developing active materials that can be printed on a large scale has been attracting great attention. Particularly, there are abundant genius structure designs in nature that are endowed with superior performance, inspiring the design of materials for high-performance wearables. Herein, we report the controllable preparation of bionic carbon nanosheets decorated with in situ formed nanoparticles (NP-CNS) through the pyrolysis of calcium gluconate (CG), which are further used for printing high-performance humidity/pressure/strain sensors. The transformation from CG to NP-CNS had been studied in detail. Interestingly, papillae-like CaO NPs are formed on the carbon nanosheets, endowing NP-CNS with good dispersion in inks and rapid response to external stimuli. Particularly, the printed humidity sensor possesses a fast response time (1.7 s) and a broad detection range (0-96% RH), increasing from the high hydroscopicity of the CaO NPs and the thus induced expansion of the NP-CNS. Besides, the strain sensor and pressure sensor also show high sensitivity and broad detection range, which is derived from the unique bionic structure of the NP-CNS. We further showed their excellent performance in monitoring of pulse wave, breath, and human motion, indicating the wide potential applications of the bionic NP-CNS in smart wearables.

Silk-Derived 2D Porous Carbon Nanosheets with Atomically-Dispersed Fe-Nx -C Sites for Highly Efficient Oxygen Reaction Catalysts.

Controlled synthesis of highly efficient, stable, and cost-effective oxygen reaction electrocatalysts with atomically-dispersed Me-Nx -C active sites through an effective strategy is highly desired for high-performance energy devices. Herein, based on regenerated silk fibroin dissolved in ferric chloride and zinc chloride aqueous solution, 2D porous carbon nanosheets with atomically-dispersed Fe-Nx -C active sites and very large specific surface area (≈2105 m2 g-1 ) are prepared through a simple thermal treatment process. Owing to the 2D porous structure with large surface area and atomic dispersion of Fe-Nx -C active sites, the as-prepared silk-derived carbon nanosheets show superior electrochemical activity toward the oxygen reduction reaction with a half-wave potential (E1/2 ) of 0.853 V, remarkable stability with only 11 mV loss in E1/2 after 30 000 cycles, as well as good catalytic activity toward the oxygen evolution reaction. This work provides a practical and effective approach for the synthesis of high-performance oxygen reaction catalysts towards advanced energy materials.

Advanced Carbon for Flexible and Wearable Electronics.

Flexible and wearable electronics are attracting wide attention due to their potential applications in wearable human health monitoring and care systems. Carbon materials have combined superiorities such as good electrical conductivity, intrinsic and structural flexibility, light weight, high chemical and thermal stability, ease of chemical functionalization, as well as potential mass production, enabling them to be promising candidate materials for flexible and wearable electronics. Consequently, great efforts are devoted to the controlled fabrication of carbon materials with rationally designed structures for applications in next-generation electronics. Herein, the latest advances in the rational design and controlled fabrication of carbon materials toward applications in flexible and wearable electronics are reviewed. Various carbon materials (carbon nanotubes, graphene, natural-biomaterial-derived carbon, etc.) with controlled micro/nanostructures and designed macroscopic morphologies for high-performance flexible electronics are introduced. The fabrication strategies, working mechanism, performance, and applications of carbon-based flexible devices are reviewed and discussed, including strain/pressure sensors, temperature/humidity sensors, electrochemical sensors, flexible conductive electrodes/wires, and flexible power devices. Furthermore, the integration of multiple devices toward multifunctional wearable systems is briefly reviewed. Finally, the existing challenges and future opportunities in this field are summarized.

Splash-Resistant and Light-Weight Silk-Sheathed Wires for Textile Electronics.

Silk has outstanding mechanical properties and biocompatibility. It has been used to fabricate traditional textiles for thousands of years and can be produced in large scale. Silk materials are potentially attractive in modern textile electronics. However, silk is not electrically conductive, thus limiting its applications in electronics. Moreover, regenerated silk is generally rigid and brittle, which hinder post processing. Here we report the fabrication of conductive silk wire in which carbon nanotube (CNT) yarns are wrapped with fluffy and flexible silk nanofiber films. The silk nanofiber film was prepared by electrospinning and then wrapped around a rotating CNT yarn in situ. The obtained silk-sheathed CNT (CNT@Silk) wire has an insulating sheath, which protects the body against electrical shock. In addition, the fabricated wires exhibit a high electrical conductivity (3.1 × 104 S/m), good mechanical strength (16 cN/tex), excellent flexibility, and high durability. More importantly, the wires have an extremely low density (2.0-7.8 × 104 g/m3), which is 2 orders of magnitude lower than that of the traditional metal wire (for example, Cu). Moreover, the wires display a good resistance to humidity, and a simple post treatment can make the wires splash-resistant, thereby expanding its applications. On the basis of these features, we demonstrate the use of the lightweight CNT@Silk wires in smart clothes, including electrochromism and near-field communication.