Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology r...Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.展开更多
Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono...Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono-layer WS2, the monolayer WS2 in the equilibrium WS2/graphene heterojunctionis characterized by indirect band gap due to the weak van der Waals interaction. The height of the schottky barrier for the WS2/graphene heterojunction is 0.13 eV, which is lower than the conventional metal/MoS2 contact. Moreover, the band properties and height of schottky barrier for WS2/graphene heterojunction can be tuned by strain. It is found that the height of the schottky barrier can be tuned to be near zero under an in-plane compressive strain, and the band gap of the WS2 in the heterojunction is turned into a direct band gap from the indirect band gap with the increasing schottky barrier height under an in-plane tensile strain. Our calculation results may provide a potential guidance for designing and fabricating the WS2-based field effect transistors.展开更多
Constructing nanocomposites that combine the advantages of composite materials,nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO2.In this study,2D‐2...Constructing nanocomposites that combine the advantages of composite materials,nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO2.In this study,2D‐2D TiO2 nanosheet/layered WS2(TNS/WS2)heterojunctions were prepared via a hydrothermal method.The structure and morphology of the photocatalysts were systematically characterized.Layered WS2(~4 layers)was wrapped on the surface of TiO2 nanosheets with a plate‐to‐plate stacked structure and connected with each other by W=O bonds.The as‐prepared TNS/WS2 heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible‐light irradiation,than pristine TiO2 nanosheets and layered WS2.The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency,which originated from the perfect 2D‐2D nanointerfaces and intimate interfacial contacts between TiO2 nanosheets and layered WS2.Based on experimental results,a double‐transfer photocatalytic mechanism for the TNS/WS2 heterojunctions was proposed and discussed.This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.展开更多
In this work,the 2D nanostructured h-BN/WS2 heterojunction was successfully prepared by the hydrothermal method-assisted exfoliation of bulk h-BN and WS2.The morphology and structure of the as-prepared heterojunction ...In this work,the 2D nanostructured h-BN/WS2 heterojunction was successfully prepared by the hydrothermal method-assisted exfoliation of bulk h-BN and WS2.The morphology and structure of the as-prepared heterojunction were determined by a series of characterization techniques.The mechanism for the formation of the as-prepared heterojunction was proposed.The friction coefficient and wear rate of the as-prepared h-BN/WS2 heterojunction-grease was decreased by 33.9%and 45.9%,respectively,as compared to those of the neat grease.展开更多
Graphene monolayer has been extensively applied as a transparency electrode material in photoelectronic devices due to its high transmittance,high carrier mobility,and ultrafast carrier dynamics.In this study,a high-p...Graphene monolayer has been extensively applied as a transparency electrode material in photoelectronic devices due to its high transmittance,high carrier mobility,and ultrafast carrier dynamics.In this study,a high-performance self-powered photodetector,which is made of a SnO_(2)microwire,p-type GaN film,and monolayer graphene transparent electrode,was proposed and fabricated.The detector is sensitive to ultraviolet light signals and illustrates pronounced detection performances,including a peak respon-sivity∼223.7 mA W^(-1),a detectivity∼6.9×10^(12)Jones,fast response speed(rising/decaying times∼18/580μs),and excellent external quantum efficiency∼77%at 360 nm light illumination without exter-nal power supply.Compared with the pristine SnO_(2)/GaN photodetector using ITO electrode,the device performances of responsivity and detectivity are significantly increased over 6×10^(3)%and 3×10^(3)%,respectively.The performance-enhanced characteristics are mainly attributed to the high-quality het-erointerface of n-SnO_(2)/p-GaN,the highly conductive capacity,and the unique transparency of graphene electrodes.Particularly,the built-in potential formed at the SnO_(2)/GaN heterojunction interface could be strengthened by the Schottky potential barrier derived from the graphene electrode and SnO_(2)wire,en-hancing the carrier collection efficiency through graphene as a charge collection medium.This work is of great importance and significance to developing excellent-performance ultraviolet photodetectors for photovoltaic and optoelectronic applications in a self-powered operation manner.展开更多
Bi_(2)O_(2)CO_(3)(BOC)/Bi_(4)O_5Br_(2)(BOB)/reduced graphene oxide(rGO)Z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method.Ultra-thin nanosheet...Bi_(2)O_(2)CO_(3)(BOC)/Bi_(4)O_5Br_(2)(BOB)/reduced graphene oxide(rGO)Z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method.Ultra-thin nanosheets of BOC and BOB were grown in situ on r GO.The formed 2D/2D direct Z-scheme heterojunction of BOC/BOB with oxygen vacancies(OVs)effectively leads to lower negative electron reduction potential of BOB as well as higher positive hole oxidation potential of BOC,showing improved reduction/oxidation ability.Particularly,rGO is an acceptor of the electrons from the conduction band of BOC.Its dual roles significantly improve the transfer performance of photo-induced charge carriers and accelerate their separation.With layered nanosheet structure,rich OVs,high specific surface area,and increased utilization efficiency of visible light,the multiple synergistic effects of BOC/BOB/rGO can achieve effective generation and separation of the electron-holes,thereby generating more·O_(2)^(-)and h^(+).The photocatalytic reduction efficiency of CO_(2)to CO(12.91μmol/(g·hr))is three times higher than that of BOC(4.18μmol/(g·hr)).Moreover,it also achieved almost 100%removal of Rhodamine B and cyanobacterial cells within 2 hours.展开更多
Two-dimensional(2D)nanomaterials are categorized as a new class of microwave absorption(MA)materials owing to their high specific surface area and peculiar electronic properties.In this study,2D WS2-reduced graphene o...Two-dimensional(2D)nanomaterials are categorized as a new class of microwave absorption(MA)materials owing to their high specific surface area and peculiar electronic properties.In this study,2D WS2-reduced graphene oxide(WS2-rGO)heterostructure nanosheets were synthesized via a facile hydrothermal process;moreover,their dielectric and MA properties were reported for the first time.Remarkably,the maximum reflection loss(RL)of the sample-wax composites containing 40 wt% WS2-rGO was-41.5 dB at a thickness of 2.7 mm;furthermore,the bandwidth where RL<-10 dB can reach up to 13.62 GHz(4.38-18 GHz).Synergistic mechanisms derived from the interfacial dielectric coupling and multiple-interface scattering after hybridization of WS2 with rGO were discussed to explain the drastically enhanced microwave absorption performance.The results indicate these lightweight WS2-rGO nanosheets to be potential materials for practical electromagnetic wave-absorbing applications.展开更多
Recently,the issue of bacterial resistance has gotten worse because of the overuse of antibiotics.The newborn superbacteria,such as vancomycin-resistant bacteria,were hard to kill,inspiring researchers to find new way...Recently,the issue of bacterial resistance has gotten worse because of the overuse of antibiotics.The newborn superbacteria,such as vancomycin-resistant bacteria,were hard to kill,inspiring researchers to find new ways to kill the bacteria efficiently.TiO_(2) was used as an efficient photocatalyst for water split-ting and pollutant degradation.However,the weak efficiency limited the application to solve the drug-resistance problem.Consequently,the incorpora-tion of low-cost 0D carbon quantum dots(CQDs)and 2D graphene oxide(GO)was pursued to amplify the visible light absorption capabilities of TiO_(2) and thereby elevate its photocatalytic activity.After forming the heterogeneous interface of CQDs and TiO_(2),CQDs converted part of visible light into wave-length less than 400 nm using the up-conversion property.The modification of CQDs enabled electrons to be easily transferred from the conduction band of CQDs to the conduction band of TiO_(2).Meanwhile,GO can act as an electron acceptor,reduce the recombination efficiency of holes and electrons,and transfer the photogenerated electrons in the redox reaction in the heterogeneous interface.Because of the excellent absorption of GO,TiO_(2)/CQDs/GO reached 57.8℃after 20 min irradiation under 1.5 times sunlight,which provided a prerequisite for photodynamic antibacterial therapy/photothermal antibacterial therapy synergistic antibacterial potential.TiO_(2)/CQDs/GO possessed an anti-bacterial efficiency as high as 99.3%toward Staphylococcus aureus which has a bright future in disinfection in vivo and medical devices as well as water sterilization.展开更多
The formation of heterojunction within solid-state devices enables them with eventually high performances,but provides a challenge for material synthesis and device fabrication because strict conditions such as lattic...The formation of heterojunction within solid-state devices enables them with eventually high performances,but provides a challenge for material synthesis and device fabrication because strict conditions such as lattice match are needed.Herein,we show a facile method to fabricate a van der Waals(vdW)heterojunction between two-dimensional(2D)bismuth oxyselenide(Bi2O2Se)and graphene,during which the graphene is directly transferred to the Bi2O2Se and served as a lowcontract-resistant electrode with small work function mismatch(~50 meV).As an optoelectronic device,the Bi2O2Se/graphene vdW heterojunction allows for the efficient sensing toward 1200-nm incident laser.Regarding the application of fieldeffect transistors(FETs),the short-channel(50 nm)sample can be synthesized by utilizing these two 2D materials(ie,channel:Bi2O2Se;drain/source terminal:graphene)and the n-type characteristic can be observed with the accordant field modulation.It is confirmed that we show a simple way to prepare the vdW heterojunction which is aiming to the high-performance applications among optoelectronics and FETs.展开更多
Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exh...Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exhibit picosecond photoresponse speed.However,2D materials naturally have low absorption,and when increasing thickness to gain higher responsivity,the response time usually slows to nanoseconds,limiting their photodetection performance.Here,by taking time-resolved photocurrent measurements,we demonstrated that graphene/MoTe_(2) van der Waals heterojunctions realize a fast 10 ps photoresponse time owing to the reduced average photocurrent drift time in the heterojunction,which is fundamentally distinct from traditional Dirac semimetal photodetectors such as graphene or Cd_(3)As_(2) and implies a photodetection bandwidth as wide as 100 GHz.Furthermore,we found that an additional charge carrier transport channel provided by graphene can ef-fectively decrease the photocurrent recombination loss to the entire device,preserving a high responsivity in the near-infrared region.Our study provides a deeper understanding of the ultrafast electrical response in van der Waals heterojunctions and offers a promising approach for the realization of photodetectors with both high responsivity and ultrafast electrical response.展开更多
The heterojunction integration of two-dimensional(2D)materials via van der Waals(vdW)forces,unencumbered by lattice and processing constraints,constitutes an efficacious approach to enhance the overall optoelectronic ...The heterojunction integration of two-dimensional(2D)materials via van der Waals(vdW)forces,unencumbered by lattice and processing constraints,constitutes an efficacious approach to enhance the overall optoelectronic performance of photodetectors,due to an assortment of distinctive light-matter interactions.Nonetheless,vdW heterojunction photodetectors based on transition metal dichalcogenides(TMDs)face an inevitable trade-off between low dark currents and high responsivity,curtailing the application potential of myriad novel optoelectronic components in sensing,spectral,and communication systems.In this study,we present the successful actualization of a highly sensitive,self-powered,and gate-tunable bipolar response photodetector.The mechanisms underlying photocurrent generation were scrutinized via bias-,power-,and position-dependent mapping photoresponse measurements,identifying the photovoltaic effect,which is attributable to the Schottky junction’s built-in electric field,as the predominant mechanism.The prototype Au-WS2-graphene photodetector exhibits a remarkable light on/off ratio of 1.2×10^(6),a specific detectivity of 6.12×10^(11)cm H^(z1/2)W^(-1)with 20μs response time at 638 nm.The wide gate-tunable responsivity provides an adjustability scope,ranging from 0.9 to 3.1 A W^(-1).Notably,the device demonstrates an exceptional linear photocurrent response,with a linear dynamic range(LDR)value approximating 130 dB,which significantly surpasses that of other photodetectors based on TMDs.展开更多
A high-performance heterojunction photodetector is formed by combining an n-type Si substrate with p-type monolayer WSe2 obtained using physical vapor deposition. The high quality of the WSe2/Si heterojunction is demo...A high-performance heterojunction photodetector is formed by combining an n-type Si substrate with p-type monolayer WSe2 obtained using physical vapor deposition. The high quality of the WSe2/Si heterojunction is demonstrated by the suppressed dark current of I nA and the extremely high rectification ratio of 107. Under illumination, the heterojunction exhibits a wide photoresponse range from ultraviolet to near-infrared radiation. The introduction of graphene quantum dots (GQDs) greatly elevates the photodetective capabilities of the heterojunction with strong light absorption and long carrier lifetimes. The GQDs/WSe2/Si heterojunction exhibits a high responsivity of -707 mA·W^-1, short response time of 0.2 ms, and good specific detectivity of -4.51×10^9 Jones. These properties suggest that the GQDs/WSe2/Si heterojunction holds great potential for application in future high- performance photodetectors.展开更多
We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding wavegui...We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 m W and slope efficiency of 37%. In comparison with the systems based on single WS_2 or graphene SA, the lasing Q-switched by a graphene∕WS_2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promisingapplications of van der Waals heterostructures for ultrafast photonic devices.展开更多
Most resistance-type humidity sensors exhibit negative humidity sensitivity,i.e.,their resistance decreases with a corresponding increase in humidity.This is primarily attributed to the dominant role of ionic conducti...Most resistance-type humidity sensors exhibit negative humidity sensitivity,i.e.,their resistance decreases with a corresponding increase in humidity.This is primarily attributed to the dominant role of ionic conduction in adsorbed water.In this work,a humidity sensor based on a p-type reduced graphene oxide(p-rGO)with positive humidity sensitivity is proposed.Moreover,its positive humidity sensing response is further enhanced by n-type WS_(2) nanoparticles modification.The results show that both rGO and r GO/WS_(2) humidity sensors have good linear response in the relative humidity(RH)range of0%-91.5%.The sensitivity of the rGO/WS_(2) humidity sensor is 1.87 times that of rGO humidity sensor,which is mainly attributed to p-n heterojunction between rGO and WS_(2).Besides,the r GO/WS_(2) humidity sensor has small humidity hysteresis(-3%RH)and good repeatability.This work demonstrates a humidity sensor based on rGO/WS_(2) composite film and provides a facile route for fabricating humidity sensor with positive humidity sensing properties.展开更多
Constructing two-dimensional(2D)layered materials with traditional three-dimensional(3D)semiconductors into complex heterostructures has opened a new platform for the development of optoelectronic devices.Herein,large...Constructing two-dimensional(2D)layered materials with traditional three-dimensional(3D)semiconductors into complex heterostructures has opened a new platform for the development of optoelectronic devices.Herein,large-area high performance self-driven photodetectors based on monolayer WS2∕GaAs heterostructures were successfully fabricated with a wide response spectrum band ranging from the ultraviolet to near-infrared region.The detector exhibits an overall high performance,including high photoresponsivity of 65.58 A/W at 365 nm and 28.50 A/W at 880 nm,low noise equivalent power of 1.97×10^−15 W∕Hz1∕2,high detectivity of 4.47×10^12 Jones,and fast response speed of 30/10 ms.This work suggests that the WS2∕GaAs heterostructure is promising in future novel optoelectronic device applications,and also provides a low-cost,easy-to-process method for the preparation of 2D/3D heterojunction-based devices.展开更多
Carbon dioxide(CO_(2))can be reduced to high-value fuels using the photocatalysis(PC)technique,which holds immense potential for tackling environmental issues and energy crises.The construction of metalfree photocatal...Carbon dioxide(CO_(2))can be reduced to high-value fuels using the photocatalysis(PC)technique,which holds immense potential for tackling environmental issues and energy crises.The construction of metalfree photocatalyst capable of utilizing infrared light to execute thermal-assisted photocatalysis(TPC)remains a challenge.In this study,reduced graphene oxide(RGO)with full-spectrum absorption was used as a thermal-assisted photocatalyst in CO_(2) reduction.It exhibited higher CO_(2) reduction efficiency under the visible and infrared irradiation than the sole visible irradiation.RGO-5(GO treated at 120℃ for 5 h)presented the highest defect density and C-OH/C-O-C content,leading to the best PC and TPC efficiencies.RGO was further engineered with HCl protonated g-C_(3)N_(4)(H-CN)to obtain two-dimensional heterojunction RGO/H-CN,which demonstrated the S-scheme charge transfer process.Owing to the synergistic effect of heterojunction and thermal assistance,RGO/H-CN exhibited better CO_(2) reduction efficiencies in both PC and TPC than RGO.The largest yields of CO and CH4 were achieved in 15%RGO/H-CN.This research provides new insights for applying RGO as thermal-assisted heterojunction photocatalyst for efficient CO_(2) reduction.展开更多
Two-dimensional (2D) crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals (vdW) heterostruc...Two-dimensional (2D) crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals (vdW) heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride (hBN) and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio (〉103) between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.U2002212,52102058,52204414,52204413,and 52204412)the National Key R&D Program of China (Nos.2021YFC1910504,2019YFC1907101,2019YFC1907103,and 2017YFB0702304)+7 种基金the Key R&D Program of Ningxia Hui Autonomous Region,China (Nos.2021BEG01003 and2020BCE01001)the Xijiang Innovation and Entrepreneurship Team,China (No.2017A0109004)the Macao Young Scholars Program (No.AM2022024),Chinathe Beijing Natural Science Foundation (Nos.L212020 and 2214073),Chinathe Guangdong Basic and Applied Basic Research Foundation,China (Nos.2021A1515110998 and 2020A1515110408)the China Postdoctoral Science Foundation (No.2022M710349)the Fundamental Research Funds for the Central Universities,China (Nos.FRF-BD-20-24A,FRF-TP-20-031A1,FRF-IC-19-017Z,and 06500141)the Integration of Green Key Process Systems MIIT and Scientific and Technological Innovation Foundation of Foshan,China(Nos.BK22BE001 and BK21BE002)。
文摘Exclusive responsiveness to ultraviolet light (~3.2 eV) and high photogenerated charge recombination rate are the two primary drawbacks of pure TiO_(2). We combined N-doped graphene quantum dots (N-GQDs), morphology regulation, and heterojunction construction strategies to synthesize N-GQD/N-doped TiO_(2)/P-doped porous hollow g-C_(3)N_(4) nanotube (PCN) composite photocatalysts (denoted as G-TPCN). The optimal sample (G-TPCN doped with 0.1wt% N-GQD, denoted as 0.1% G-TPCN) exhibits significantly enhanced photoabsorption, which is attributed to the change in bandgap caused by elemental doping (P and N), the improved light-harvesting resulting from the tube structure, and the upconversion effect of N-GQDs. In addition, the internal charge separation and transfer capability of0.1% G-TPCN are dramatically boosted, and its carrier concentration is 3.7, 2.3, and 1.9 times that of N-TiO_(2), PCN, and N-TiO_(2)/PCN(TPCN-1), respectively. This phenomenon is attributed to the formation of Z-scheme heterojunction between N-TiO_(2) and PCNs, the excellent electron conduction ability of N-GQDs, and the short transfer distance caused by the porous nanotube structure. Compared with those of N-TiO_(2), PCNs, and TPCN-1, the H2 production activity of 0.1%G-TPCN under visible light is enhanced by 12.4, 2.3, and 1.4times, respectively, and its ciprofloxacin (CIP) degradation rate is increased by 7.9, 5.7, and 2.9 times, respectively. The optimized performance benefits from excellent photoresponsiveness and improved carrier separation and migration efficiencies. Finally, the photocatalytic mechanism of 0.1% G-TPCN and five possible degradation pathways of CIP are proposed. This study clarifies the mechanism of multiple modification strategies to synergistically improve the photocatalytic performance of 0.1% G-TPCN and provides a potential strategy for rationally designing novel photocatalysts for environmental remediation and solar energy conversion.
基金Project supported by the National Natural Science Foundation of China(Grant No.11202178)
文摘Based on the density functional calculations, the structural and electronic properties of the WS2/graphene heterojunction under different strains are investigated. The calculated results show that unlike the free mono-layer WS2, the monolayer WS2 in the equilibrium WS2/graphene heterojunctionis characterized by indirect band gap due to the weak van der Waals interaction. The height of the schottky barrier for the WS2/graphene heterojunction is 0.13 eV, which is lower than the conventional metal/MoS2 contact. Moreover, the band properties and height of schottky barrier for WS2/graphene heterojunction can be tuned by strain. It is found that the height of the schottky barrier can be tuned to be near zero under an in-plane compressive strain, and the band gap of the WS2 in the heterojunction is turned into a direct band gap from the indirect band gap with the increasing schottky barrier height under an in-plane tensile strain. Our calculation results may provide a potential guidance for designing and fabricating the WS2-based field effect transistors.
基金supported by the National High Technology Research and Development Program of China(863 Program,2012AA063504)the National Natural Science Foundation of China(U1407116,21511130020,21276193)the Tianjin Municipal Natural Science Foundation(13JCZDJC35600)~~
文摘Constructing nanocomposites that combine the advantages of composite materials,nanomaterials,and interfaces has been regarded as an important strategy to improve the photocatalytic activity of TiO2.In this study,2D‐2D TiO2 nanosheet/layered WS2(TNS/WS2)heterojunctions were prepared via a hydrothermal method.The structure and morphology of the photocatalysts were systematically characterized.Layered WS2(~4 layers)was wrapped on the surface of TiO2 nanosheets with a plate‐to‐plate stacked structure and connected with each other by W=O bonds.The as‐prepared TNS/WS2 heterojunctions showed higher photocatalytic activity for the degradation of RhB under visible‐light irradiation,than pristine TiO2 nanosheets and layered WS2.The improvement of photocatalytic activity was primarily attributed to enhanced charge separation efficiency,which originated from the perfect 2D‐2D nanointerfaces and intimate interfacial contacts between TiO2 nanosheets and layered WS2.Based on experimental results,a double‐transfer photocatalytic mechanism for the TNS/WS2 heterojunctions was proposed and discussed.This work provides new insights for synthesizing highly efficient and environmentally stable photocatalysts by engineering the surface heterojunctions.
基金This work was funded by the Zhenjiang High Technology Research Institute of Yangzhou University(2017),the Yangzhou Social Development Project(YZ2016072)the Jiangsu Province Six Talent Peaks Project(2014-XCL-013)the Jiangsu Industrial-Academic-Research Prospective Joint Project(BY2016069-02).
文摘In this work,the 2D nanostructured h-BN/WS2 heterojunction was successfully prepared by the hydrothermal method-assisted exfoliation of bulk h-BN and WS2.The morphology and structure of the as-prepared heterojunction were determined by a series of characterization techniques.The mechanism for the formation of the as-prepared heterojunction was proposed.The friction coefficient and wear rate of the as-prepared h-BN/WS2 heterojunction-grease was decreased by 33.9%and 45.9%,respectively,as compared to those of the neat grease.
基金This work was financially supported by the National Natural Science Foundation of China(NSFC)(Nos.11974182 and 11874220)Fundamental Research Funds for the Central Universities(No.NC2022008)Funding for Outstanding Doctoral Dissertation in NUAA(No.BCXJ22-14).
文摘Graphene monolayer has been extensively applied as a transparency electrode material in photoelectronic devices due to its high transmittance,high carrier mobility,and ultrafast carrier dynamics.In this study,a high-performance self-powered photodetector,which is made of a SnO_(2)microwire,p-type GaN film,and monolayer graphene transparent electrode,was proposed and fabricated.The detector is sensitive to ultraviolet light signals and illustrates pronounced detection performances,including a peak respon-sivity∼223.7 mA W^(-1),a detectivity∼6.9×10^(12)Jones,fast response speed(rising/decaying times∼18/580μs),and excellent external quantum efficiency∼77%at 360 nm light illumination without exter-nal power supply.Compared with the pristine SnO_(2)/GaN photodetector using ITO electrode,the device performances of responsivity and detectivity are significantly increased over 6×10^(3)%and 3×10^(3)%,respectively.The performance-enhanced characteristics are mainly attributed to the high-quality het-erointerface of n-SnO_(2)/p-GaN,the highly conductive capacity,and the unique transparency of graphene electrodes.Particularly,the built-in potential formed at the SnO_(2)/GaN heterojunction interface could be strengthened by the Schottky potential barrier derived from the graphene electrode and SnO_(2)wire,en-hancing the carrier collection efficiency through graphene as a charge collection medium.This work is of great importance and significance to developing excellent-performance ultraviolet photodetectors for photovoltaic and optoelectronic applications in a self-powered operation manner.
基金supported by the National Natural Science Foundation of China(Nos.51602281 and 52100014)the Natural Science Foundation of Jiangsu Province(No.BK20180938)the Yangzhou University High-end Talent Support Program and the“Qinglan Project”of Jiangsu Universities。
文摘Bi_(2)O_(2)CO_(3)(BOC)/Bi_(4)O_5Br_(2)(BOB)/reduced graphene oxide(rGO)Z-scheme heterojunction with promising photocatalytic properties was synthesized via a facile one-pot room-temperature method.Ultra-thin nanosheets of BOC and BOB were grown in situ on r GO.The formed 2D/2D direct Z-scheme heterojunction of BOC/BOB with oxygen vacancies(OVs)effectively leads to lower negative electron reduction potential of BOB as well as higher positive hole oxidation potential of BOC,showing improved reduction/oxidation ability.Particularly,rGO is an acceptor of the electrons from the conduction band of BOC.Its dual roles significantly improve the transfer performance of photo-induced charge carriers and accelerate their separation.With layered nanosheet structure,rich OVs,high specific surface area,and increased utilization efficiency of visible light,the multiple synergistic effects of BOC/BOB/rGO can achieve effective generation and separation of the electron-holes,thereby generating more·O_(2)^(-)and h^(+).The photocatalytic reduction efficiency of CO_(2)to CO(12.91μmol/(g·hr))is three times higher than that of BOC(4.18μmol/(g·hr)).Moreover,it also achieved almost 100%removal of Rhodamine B and cyanobacterial cells within 2 hours.
基金financially supported by the National Natural Science Foundation of China (Nos. 51272110, 51772160, and 51771123)the Shenzhen Peacock Innovation Project (No. KQJSCX20170327151307811)+1 种基金the support of China Scholarship Council (No. 201506100018)the START project of Japan Science and Technology Agency (JST)
文摘Two-dimensional(2D)nanomaterials are categorized as a new class of microwave absorption(MA)materials owing to their high specific surface area and peculiar electronic properties.In this study,2D WS2-reduced graphene oxide(WS2-rGO)heterostructure nanosheets were synthesized via a facile hydrothermal process;moreover,their dielectric and MA properties were reported for the first time.Remarkably,the maximum reflection loss(RL)of the sample-wax composites containing 40 wt% WS2-rGO was-41.5 dB at a thickness of 2.7 mm;furthermore,the bandwidth where RL<-10 dB can reach up to 13.62 GHz(4.38-18 GHz).Synergistic mechanisms derived from the interfacial dielectric coupling and multiple-interface scattering after hybridization of WS2 with rGO were discussed to explain the drastically enhanced microwave absorption performance.The results indicate these lightweight WS2-rGO nanosheets to be potential materials for practical electromagnetic wave-absorbing applications.
基金supported by the China National Funds for Distinguished Young Scientists(No.51925104)the National Natural Science Foundation of China(NSFC)(No.52173251)+3 种基金NSFC-Guangdong Province Joint Program(Key program No.U21A2084)Yanzhao Young Scientist Project(No.C2023202018)Beijing Natural Science Foundation(No.7232338)the Central Guidance on Local Science and Technology Development Fund of Hebei Province(No.226Z1303G).
文摘Recently,the issue of bacterial resistance has gotten worse because of the overuse of antibiotics.The newborn superbacteria,such as vancomycin-resistant bacteria,were hard to kill,inspiring researchers to find new ways to kill the bacteria efficiently.TiO_(2) was used as an efficient photocatalyst for water split-ting and pollutant degradation.However,the weak efficiency limited the application to solve the drug-resistance problem.Consequently,the incorpora-tion of low-cost 0D carbon quantum dots(CQDs)and 2D graphene oxide(GO)was pursued to amplify the visible light absorption capabilities of TiO_(2) and thereby elevate its photocatalytic activity.After forming the heterogeneous interface of CQDs and TiO_(2),CQDs converted part of visible light into wave-length less than 400 nm using the up-conversion property.The modification of CQDs enabled electrons to be easily transferred from the conduction band of CQDs to the conduction band of TiO_(2).Meanwhile,GO can act as an electron acceptor,reduce the recombination efficiency of holes and electrons,and transfer the photogenerated electrons in the redox reaction in the heterogeneous interface.Because of the excellent absorption of GO,TiO_(2)/CQDs/GO reached 57.8℃after 20 min irradiation under 1.5 times sunlight,which provided a prerequisite for photodynamic antibacterial therapy/photothermal antibacterial therapy synergistic antibacterial potential.TiO_(2)/CQDs/GO possessed an anti-bacterial efficiency as high as 99.3%toward Staphylococcus aureus which has a bright future in disinfection in vivo and medical devices as well as water sterilization.
基金support from the National Basic Research Program of China(No.2016YFA0200101)the National Natural Science Foundation of China(Nos.21733001 and 21525310)Boya Postdoctoral Fellowship.
文摘The formation of heterojunction within solid-state devices enables them with eventually high performances,but provides a challenge for material synthesis and device fabrication because strict conditions such as lattice match are needed.Herein,we show a facile method to fabricate a van der Waals(vdW)heterojunction between two-dimensional(2D)bismuth oxyselenide(Bi2O2Se)and graphene,during which the graphene is directly transferred to the Bi2O2Se and served as a lowcontract-resistant electrode with small work function mismatch(~50 meV).As an optoelectronic device,the Bi2O2Se/graphene vdW heterojunction allows for the efficient sensing toward 1200-nm incident laser.Regarding the application of fieldeffect transistors(FETs),the short-channel(50 nm)sample can be synthesized by utilizing these two 2D materials(ie,channel:Bi2O2Se;drain/source terminal:graphene)and the n-type characteristic can be observed with the accordant field modulation.It is confirmed that we show a simple way to prepare the vdW heterojunction which is aiming to the high-performance applications among optoelectronics and FETs.
基金This work was supported by the National Natural Science Foundation of China(Grants No.52022029,91850116,51772084,and U19A2090)the Sino-German Center for Research Promotion(Grant No.GZ1390)the Hunan Provincial Natural Science Foundation of China(Grants No.2018RS3051 and 2019XK2001)。
文摘Understanding the fundamental charge carrier dynamics is of great significance for photodetectors with both high speed and high responsivity.Devices based on two-dimensional(2D)transition metal dichalcogenides can exhibit picosecond photoresponse speed.However,2D materials naturally have low absorption,and when increasing thickness to gain higher responsivity,the response time usually slows to nanoseconds,limiting their photodetection performance.Here,by taking time-resolved photocurrent measurements,we demonstrated that graphene/MoTe_(2) van der Waals heterojunctions realize a fast 10 ps photoresponse time owing to the reduced average photocurrent drift time in the heterojunction,which is fundamentally distinct from traditional Dirac semimetal photodetectors such as graphene or Cd_(3)As_(2) and implies a photodetection bandwidth as wide as 100 GHz.Furthermore,we found that an additional charge carrier transport channel provided by graphene can ef-fectively decrease the photocurrent recombination loss to the entire device,preserving a high responsivity in the near-infrared region.Our study provides a deeper understanding of the ultrafast electrical response in van der Waals heterojunctions and offers a promising approach for the realization of photodetectors with both high responsivity and ultrafast electrical response.
基金supported by the National Natural Science Foundation of China(Grant Nos.62305077,62222514,61991440,and 62005249)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y2021070)+8 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB43010200)Shanghai Rising-Star Program(Grant No.20QA1410400)Shanghai Science and Technology Committee(Grant Nos.23ZR1482000,20JC1416000,and 22JC1402900)the Natural Science Foundation of Zhejiang Province(Grant No.LR22F050004)Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Hangzhou West Science and Technology Innovation Corridor Youth ProjectExcellent Postdoctoral Research Projects of Zhejiang Province(Grant No.ZJ2021019)the Open Fund of State Key Laboratory of Infrared Physics(Grant No.SITP-NLIST-YB-2023-13)Zhejiang Provincial Natural Science Foundation(Grant No.LQ20F050005)。
文摘The heterojunction integration of two-dimensional(2D)materials via van der Waals(vdW)forces,unencumbered by lattice and processing constraints,constitutes an efficacious approach to enhance the overall optoelectronic performance of photodetectors,due to an assortment of distinctive light-matter interactions.Nonetheless,vdW heterojunction photodetectors based on transition metal dichalcogenides(TMDs)face an inevitable trade-off between low dark currents and high responsivity,curtailing the application potential of myriad novel optoelectronic components in sensing,spectral,and communication systems.In this study,we present the successful actualization of a highly sensitive,self-powered,and gate-tunable bipolar response photodetector.The mechanisms underlying photocurrent generation were scrutinized via bias-,power-,and position-dependent mapping photoresponse measurements,identifying the photovoltaic effect,which is attributable to the Schottky junction’s built-in electric field,as the predominant mechanism.The prototype Au-WS2-graphene photodetector exhibits a remarkable light on/off ratio of 1.2×10^(6),a specific detectivity of 6.12×10^(11)cm H^(z1/2)W^(-1)with 20μs response time at 638 nm.The wide gate-tunable responsivity provides an adjustability scope,ranging from 0.9 to 3.1 A W^(-1).Notably,the device demonstrates an exceptional linear photocurrent response,with a linear dynamic range(LDR)value approximating 130 dB,which significantly surpasses that of other photodetectors based on TMDs.
文摘A high-performance heterojunction photodetector is formed by combining an n-type Si substrate with p-type monolayer WSe2 obtained using physical vapor deposition. The high quality of the WSe2/Si heterojunction is demonstrated by the suppressed dark current of I nA and the extremely high rectification ratio of 107. Under illumination, the heterojunction exhibits a wide photoresponse range from ultraviolet to near-infrared radiation. The introduction of graphene quantum dots (GQDs) greatly elevates the photodetective capabilities of the heterojunction with strong light absorption and long carrier lifetimes. The GQDs/WSe2/Si heterojunction exhibits a high responsivity of -707 mA·W^-1, short response time of 0.2 ms, and good specific detectivity of -4.51×10^9 Jones. These properties suggest that the GQDs/WSe2/Si heterojunction holds great potential for application in future high- performance photodetectors.
基金111 Project of China(B13029)Strategic Priority Research Program of CAS(XDB16030700)+2 种基金Key Research Program of Frontier Science of CAS(QYZDB-SSWJSC041)National Natural Science Foundation of China(NSFC)(11274203,61522510)STCSM Excellent Academic Leader of Shanghai(17XD1403900)
文摘We report on the operation of passively Q-switched waveguide lasers at 1 μm wavelength based on a graphene∕WS_2 heterostructure as a saturable absorber(SA). The gain medium is a crystalline Nd:YVO_4 cladding waveguide produced by femtosecond laser writing. The nanosecond waveguide laser operation at 1064 nm has been realized with the maximum average output power of 275 m W and slope efficiency of 37%. In comparison with the systems based on single WS_2 or graphene SA, the lasing Q-switched by a graphene∕WS_2 heterostructure SA possesses advantages of a higher pulse energy and enhanced slope efficiency, indicating the promisingapplications of van der Waals heterostructures for ultrafast photonic devices.
基金the National Science Funds for Excellent Young Scholars of China(No.61822106)the National Science Funds for Creative Research Groups of China(No.61421002)the National Natural Science Foundation of China(No.61671115)。
文摘Most resistance-type humidity sensors exhibit negative humidity sensitivity,i.e.,their resistance decreases with a corresponding increase in humidity.This is primarily attributed to the dominant role of ionic conduction in adsorbed water.In this work,a humidity sensor based on a p-type reduced graphene oxide(p-rGO)with positive humidity sensitivity is proposed.Moreover,its positive humidity sensing response is further enhanced by n-type WS_(2) nanoparticles modification.The results show that both rGO and r GO/WS_(2) humidity sensors have good linear response in the relative humidity(RH)range of0%-91.5%.The sensitivity of the rGO/WS_(2) humidity sensor is 1.87 times that of rGO humidity sensor,which is mainly attributed to p-n heterojunction between rGO and WS_(2).Besides,the r GO/WS_(2) humidity sensor has small humidity hysteresis(-3%RH)and good repeatability.This work demonstrates a humidity sensor based on rGO/WS_(2) composite film and provides a facile route for fabricating humidity sensor with positive humidity sensing properties.
基金National Natural Science Foundation of China(61804086)Natural Science Foundation of Shandong Province(ZR2019PF002)+1 种基金Jiangsu Province Science Foundation for Youths(BK20170431)Changzhou Science and Technology Project(CJ20190010).
文摘Constructing two-dimensional(2D)layered materials with traditional three-dimensional(3D)semiconductors into complex heterostructures has opened a new platform for the development of optoelectronic devices.Herein,large-area high performance self-driven photodetectors based on monolayer WS2∕GaAs heterostructures were successfully fabricated with a wide response spectrum band ranging from the ultraviolet to near-infrared region.The detector exhibits an overall high performance,including high photoresponsivity of 65.58 A/W at 365 nm and 28.50 A/W at 880 nm,low noise equivalent power of 1.97×10^−15 W∕Hz1∕2,high detectivity of 4.47×10^12 Jones,and fast response speed of 30/10 ms.This work suggests that the WS2∕GaAs heterostructure is promising in future novel optoelectronic device applications,and also provides a low-cost,easy-to-process method for the preparation of 2D/3D heterojunction-based devices.
基金financial support provided by the National Natural Science Foundation of China(Nos.41961134034,42293324,and 21876003)the National Key Research and Development Program of China(No.2022YFC3701104)the Second Tibetan Plateau Scientific Expedition and Research(No.2019QZKK0607).
文摘Carbon dioxide(CO_(2))can be reduced to high-value fuels using the photocatalysis(PC)technique,which holds immense potential for tackling environmental issues and energy crises.The construction of metalfree photocatalyst capable of utilizing infrared light to execute thermal-assisted photocatalysis(TPC)remains a challenge.In this study,reduced graphene oxide(RGO)with full-spectrum absorption was used as a thermal-assisted photocatalyst in CO_(2) reduction.It exhibited higher CO_(2) reduction efficiency under the visible and infrared irradiation than the sole visible irradiation.RGO-5(GO treated at 120℃ for 5 h)presented the highest defect density and C-OH/C-O-C content,leading to the best PC and TPC efficiencies.RGO was further engineered with HCl protonated g-C_(3)N_(4)(H-CN)to obtain two-dimensional heterojunction RGO/H-CN,which demonstrated the S-scheme charge transfer process.Owing to the synergistic effect of heterojunction and thermal assistance,RGO/H-CN exhibited better CO_(2) reduction efficiencies in both PC and TPC than RGO.The largest yields of CO and CH4 were achieved in 15%RGO/H-CN.This research provides new insights for applying RGO as thermal-assisted heterojunction photocatalyst for efficient CO_(2) reduction.
文摘Two-dimensional (2D) crystals have a multitude of forms, including semi-metals, semiconductors, and insulators, which are ideal for assembling isolated 2D atomic materials to create van der Waals (vdW) heterostructures. Recently, artificially-stacked materials have been considered promising candidates for nanoelectronic and optoelectronic applications. In this study, we report the vertical integration of layered structures for the fabrication of prototype non-volatile memory devices. A semiconducting-tungsten-disulfide-channel-based memory device is created by sandwiching high-density-of-states multi-layered graphene as a carrier-confining layer between tunnel barriers of hexagonal boron nitride (hBN) and silicon dioxide. The results reveal that a memory window of up to 20 V is opened, leading to a high current ratio (〉103) between programming and erasing states. The proposed design combination produced layered materials that allow devices to attain perfect retention at 13% charge loss after 10 years, offering new possibilities for the integration of transparent, flexible electronic systems.