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(vd Ws)MAPb I3/graphene heterostructure for high-performance image sensor.We introduced inorganic sources(PbI2)to vd Ws epitaxially grown Pb I2 film on a seamless graphene monolayer film template through CVD.Methylammonium iodide(MAI)was then reintroduced to prepare the vd Ws MAPb I3/graphene heterostructure.The MAPb I3 layer is composed of densely packed,large-size grains and displays a smooth surface.High photoresponsivity of 107A/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.

Superelastic wire-shaped supercapacitor sustaining 850% tensile strain based on carbon nanotube@graphene fiber

Stretchable and flexible supercapacitors are highly desired due to their many potential applications in wearable devices. However, it is challenging to fabricate supercapacitors that can withstand large tensile strain while maintaining high performance. Herein, we report an ultra-stretchable wire-shaped supercapacitor based on carbon nanotube@graphene@MnO2 fibers wound around a superelastic core fiber. The supercapacitor can sustain tensile strain up to 850%, which is the highest value reported for this type of device to date, while maintaining stable electrochemical performance. The energy density of the supercapacitor is 3.37 mWh·cm^-3 at a power density of 54.0 mW·cm^-3. The results show that 82% of the specific capacitance is retained after 1,000 stretch-release cycles with strains of 700%, demonstrating the superior durability of the elastic supercapacitor and showcasing its potential application in ultra-stretchable flexible electronics.

Physical sensors for skin-inspired electronics

Skin,the largest organ in the human body,is sensitive to external stimuli.In recent years,an increasing number of skin-inspired electronics,including wearable electronics,implantable electronics,and electronic skin,have been developed because of their broad applications in healthcare and robotics.Physical sensors are one of the key building blocks of skin-inspired electronics.Typical physical sensors include mechanical sensors,temperature sensors,humidity sensors,electrophysiological sensors,and so on.In this review,we systematically review the latest advances of skin-inspired mechanical sensors,temperature sensors,and humidity sensors.The working mechanisms,key materials,device structures,and performance of various physical sensors are summarized and discussed in detail.Their applications in health monitoring,human disease diagnosis and treatment,and intelligent robots are reviewed.In addition,several novel properties of skin-inspired physical sensors such as versatility,self-healability,and implantability are introduced.Finally,the existing challenges and future perspectives of physical sensors for practical applications are discussed and proposed.

Growth of large-area aligned pentagonal graphene domains on high-index copper surfaces

Single-crystal graphene domains grown by chemical vapor deposition （CVD） intrinsically tend to have a six-fold symmetry; however, several factors can influence the growth kinetics, which can in turn lead to the formation of graphene with different shapes. Here we report the growth of oriented large-area pentagonal single-crystal graphene domains on Cu foils by CVD. We found that high-index Cu planes contributed selectively to the formation of pentagonal graphene. Our results indicated that lattice steps present on the crystalline surface of the underlying Cu promoted graphene growth in the direction perpendicular to the steps and finally led to the disappearance of one of the edges forming a pentagon. In addition, hydrogen promoted the formation of pentagonal domains. This work provides new insights into the mechanism of graphene growth.

Silkworm Silk Fibers with Multiple Reinforced Properties Obtained through Feeding Ag Nanowires

Silkworm silk fbers have been woven into textiles for thousands of years,because of their attractive luster,good mechanical properties,excellent biocompatibility,and large-scale production.With the development of human society,preparation of silk fbers with modifed or enhanced properties are highly desirable for potential applications in structural materials and smart textiles.Herein,we realized the reinforcement of multiple properties of silk fbers by feeding silkworms with Ag nanowire(Ag NW)modifed diets.The obtained silk fbers show obviously enhanced comprehensive mechanical properties,including improved tensile strength,elongation at break,tensile modulus,and toughness,which are increased by 37.2%,37.6%,68.3%,and 69.8%,respectively.Furthermore,compared with unmodifed silk,the electrical conductivity and thermal conductivity of modifed silk fbers are improved by 246.4%and 32.1%,respectively.The analysis on the components and structure shows that the incorporated Ag NWs lead to increased content of random coil/α-helix,improved orientation of crystallites,and increased content of Ag compared to pristine silk fbers,which may contribute to the enhanced mechanical,electrical,and thermal properties.

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 increasedβ-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.

Carbothermal shock enabled facile and fast growth of carbon nanotubes in a second

Carbon nanotubes(CNTs)hold great promise in many fields because of their unique structures and properties.However,the preparation of CNTs generally involves cumbersome equipment and time-consuming processes.Here,we report an ultra-fast carbothermal shock(CTS)approach for synthesizing CNTs with a simple homemade setup by employing Joule heating of a carbon substrate.Carbonized silk fabric(CSF)loaded with transition metal salts in ethanol solution was used as the substrate,which was treated with a pulse voltage of 40 V for only 50 ms and then covered with uniform CNTs grown with bimetallic alloy catalyst nanoparticles(diameter:~9 nm).The temperature ramp rate is as high as 105 K/s.The as-obtained sample has a unique fluffy structure similar to the trichobothrium of spiders,endowing it versatile applications such as airflow sensors or air filters.The CTS technique presents an easy-accessible and highly efficient approach for synthesizing CNTs,which may be also applied in synthesizing other nanomaterials.