Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,i...Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,is very challenging.Two‐dimensional sheets are known to be excellent units for assembling fiber entities,particularly when sheets are oriented in a stacking manner,which helps integrate their intrinsic in‐plane advantages,especially those related with mechanical and electronic performances.In this study,we developed a flexible macroscopic and continuous fiber in an unusual ribbon shape composed solely of Ti3C2 sheets,a typical member of the MXene family.The ribbon morphology was realized through highly ordered stacking of Ti3C2,which imparts fibers with favorable mechanical characteristics.Based on the intrinsic metallic conductivity of Ti3C2 sheets and the oriented stacking structure,the developed macroscopic ribbon exhibited excellent conductivity for both electrons(up to 2458 S/cm)and ions.A fiber‐shaped asymmetric supercapacitor using the developed macroscopic ribbon as a cathode coupled with reduced graphene oxide fibers as an anode delivered a competitive maximum volumetric energy density of 58.4mWh/cm3(20.0Wh/kg)while maintaining a power level of 1679.0mW/cm3(581.0 W/kg)and excellent cycling stability(92.4%retention after 10000 cycles at 10 A/g).This study highlights the excellent potential of MXene as a platform for macroscopic assembly and definitely broadens the applications of MXene materials in wearable electronics.展开更多
Heteroatom nitrogen doping in two-dimensional transition metal carbides,known as MXenes,has been considered as a promising strategy for modulating their electronic structure and electrochemical reactivity.While highte...Heteroatom nitrogen doping in two-dimensional transition metal carbides,known as MXenes,has been considered as a promising strategy for modulating their electronic structure and electrochemical reactivity.While hightemperature annealing in the presence of a nitrogen source has been one popular method to introduce nitrogen,annealing exfoliated multilayered MXenes typically brings about incomplete delamination and the treatment of delaminated monolayer MXenes often leads to irreversible restacking.Here,starting from the typical carbide precursor,we developed an aqueous colloid containing monolayered nitrogen-doped titanium carbide sheets with excellent dispersity and stability.This achievement is critically dependent on the retaining of the hydrophilic surface of host layers during annealing treatment.The successful realization of nitrogen doping into individual MXene monolayers resulted in enhanced electrical conductivity and redox reactivity,for which the sample exhibited excellent capacitive electrochemical performance(586 F/g at a scan rate of 5mV/s)and cycling stability(capacitance retention of 96.2%after 104 cycles at 5 A/g).This paper presents a feasible and simple strategy for designing nitrogen-doped MXenes colloid,the realization of which promises its facile uses in liquid phase engineering techniques toward versatile applications.展开更多
Macroscopic films assembled from graphene sheets could be ideal for lightweight and flexible electromagnetic interference shielding applications if the excellent mechanical strength and electrical conductivity of indi...Macroscopic films assembled from graphene sheets could be ideal for lightweight and flexible electromagnetic interference shielding applications if the excellent mechanical strength and electrical conductivity of individual graphene can be replicated on the macroscale.However,in practice,a large performance gap remains between individual graphene and graphene-based macroscopic films.In this work,we report macroscopic graphene-based films with high mechanical strength and electrical conductivity(1.70±0.05 GPa and 1170±60 S cm^(-1))obtained by introducing a covalent conjugating aromatic amide group to bridge graphene edges.The bridging was achieved by reacting a doctor-bladed GO film with 1,2,4,5-benzenetetraamine hydrochloride followed by chemical reduction.Impact load tests demonstrated efficient stress transfer in these films,with stress spread uniformly well beyond the impact area.This is in sharp contrast to previously reported films,which showed the immediate initiation of cracks followed by crack extension in random directions.Our conducting films achieved a shielding effectiveness of 114.1 dB for a 120μm thick film,and the specific shielding effectiveness was calculated to be 67.9 dB cm^(3) g^(-1),which significantly exceeds those of currently known shielding materials as well as graphene films synthesized under similar conditions without thermal annealing.Owing to the graphene films’mechanical robustness,the shielding performance was maintained even after repeated folding.展开更多
A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet(UV)irradiation-assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tu...A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet(UV)irradiation-assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tungstate nanosheets.By this process,a hierarchical porous network structure was finely constructed while showing ultrahigh flexibility.More importantly,the newly prepared hydrogel retained the photochromic properties of the cesium tungstate nanosheets.The color transitions could be readily controlled by UV laser irradiation and were completely reversible via laser exposure or dark treatment.The nanocomposite hydrogel with its excellent photochromic properties and ultrahigh flexibility will have great applications in flexible photochromic devices.The synthetic procedure is simple and has promises to be extended to developing other hydrogels with various new functionalities.展开更多
基金This study was supported by the National Natural Science Foundation of China(Grant no.51772201)Jiangsu Specially‐Appointed Professor Programand a project funded by the Priority Academic Program Developmentof Jiangsu Higher Education Institutions.
文摘Flexible and wearable fiber electrodes with high conductivity and acceptable electrochemical behavior are crucial for extending the application of nextgeneration portable electronics,the development of which,however,is very challenging.Two‐dimensional sheets are known to be excellent units for assembling fiber entities,particularly when sheets are oriented in a stacking manner,which helps integrate their intrinsic in‐plane advantages,especially those related with mechanical and electronic performances.In this study,we developed a flexible macroscopic and continuous fiber in an unusual ribbon shape composed solely of Ti3C2 sheets,a typical member of the MXene family.The ribbon morphology was realized through highly ordered stacking of Ti3C2,which imparts fibers with favorable mechanical characteristics.Based on the intrinsic metallic conductivity of Ti3C2 sheets and the oriented stacking structure,the developed macroscopic ribbon exhibited excellent conductivity for both electrons(up to 2458 S/cm)and ions.A fiber‐shaped asymmetric supercapacitor using the developed macroscopic ribbon as a cathode coupled with reduced graphene oxide fibers as an anode delivered a competitive maximum volumetric energy density of 58.4mWh/cm3(20.0Wh/kg)while maintaining a power level of 1679.0mW/cm3(581.0 W/kg)and excellent cycling stability(92.4%retention after 10000 cycles at 10 A/g).This study highlights the excellent potential of MXene as a platform for macroscopic assembly and definitely broadens the applications of MXene materials in wearable electronics.
基金The authors acknowledge the financial support from the National Natural Science Foundation of China(Grant no.51772201)Jiangsu Specially-Appointed Professor Programa project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Heteroatom nitrogen doping in two-dimensional transition metal carbides,known as MXenes,has been considered as a promising strategy for modulating their electronic structure and electrochemical reactivity.While hightemperature annealing in the presence of a nitrogen source has been one popular method to introduce nitrogen,annealing exfoliated multilayered MXenes typically brings about incomplete delamination and the treatment of delaminated monolayer MXenes often leads to irreversible restacking.Here,starting from the typical carbide precursor,we developed an aqueous colloid containing monolayered nitrogen-doped titanium carbide sheets with excellent dispersity and stability.This achievement is critically dependent on the retaining of the hydrophilic surface of host layers during annealing treatment.The successful realization of nitrogen doping into individual MXene monolayers resulted in enhanced electrical conductivity and redox reactivity,for which the sample exhibited excellent capacitive electrochemical performance(586 F/g at a scan rate of 5mV/s)and cycling stability(capacitance retention of 96.2%after 104 cycles at 5 A/g).This paper presents a feasible and simple strategy for designing nitrogen-doped MXenes colloid,the realization of which promises its facile uses in liquid phase engineering techniques toward versatile applications.
基金support from the National Science Fund for Distinguished Young Scholars(52425310)the National Natural Science Foundation of China(52173288).
文摘Macroscopic films assembled from graphene sheets could be ideal for lightweight and flexible electromagnetic interference shielding applications if the excellent mechanical strength and electrical conductivity of individual graphene can be replicated on the macroscale.However,in practice,a large performance gap remains between individual graphene and graphene-based macroscopic films.In this work,we report macroscopic graphene-based films with high mechanical strength and electrical conductivity(1.70±0.05 GPa and 1170±60 S cm^(-1))obtained by introducing a covalent conjugating aromatic amide group to bridge graphene edges.The bridging was achieved by reacting a doctor-bladed GO film with 1,2,4,5-benzenetetraamine hydrochloride followed by chemical reduction.Impact load tests demonstrated efficient stress transfer in these films,with stress spread uniformly well beyond the impact area.This is in sharp contrast to previously reported films,which showed the immediate initiation of cracks followed by crack extension in random directions.Our conducting films achieved a shielding effectiveness of 114.1 dB for a 120μm thick film,and the specific shielding effectiveness was calculated to be 67.9 dB cm^(3) g^(-1),which significantly exceeds those of currently known shielding materials as well as graphene films synthesized under similar conditions without thermal annealing.Owing to the graphene films’mechanical robustness,the shielding performance was maintained even after repeated folding.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(51402204 and 51772201)Thousand Young Talents Program,Jiangsu Specially-Appointed Professor Program,and a project funded by the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet(UV)irradiation-assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tungstate nanosheets.By this process,a hierarchical porous network structure was finely constructed while showing ultrahigh flexibility.More importantly,the newly prepared hydrogel retained the photochromic properties of the cesium tungstate nanosheets.The color transitions could be readily controlled by UV laser irradiation and were completely reversible via laser exposure or dark treatment.The nanocomposite hydrogel with its excellent photochromic properties and ultrahigh flexibility will have great applications in flexible photochromic devices.The synthetic procedure is simple and has promises to be extended to developing other hydrogels with various new functionalities.
