Three methods including the atomic resolved density of state, charge difference density, and the transition density matrix are used to visualize metal to ligand charge transfer （MLCT） in ruthenium（II） ammine compl...Three methods including the atomic resolved density of state, charge difference density, and the transition density matrix are used to visualize metal to ligand charge transfer （MLCT） in ruthenium（II） ammine complex. The atomic resolved density of state shows that there is density of Ru on the HOMOs. All the density is localized on the ammine, which reveals that the excited electrons in the Ru complex are delocalized over the ammine ligand. The charge difference density shows that all the holes are localized on the Ru and the electrons on the ammine. The localization explains the MLCT on excitation. The transition density matrix shows that there is electron-hole coherence between Ru and ammine. These methods are also used to examine the MLCT in Os（bpy）2（p0p）Cl （＂Osp0p＂： bpy=2,2-bipyrldyl; p0p=4,4＇- bipyridyl） and the ligand-to-ligand charge transfer （LLCT） in Alq3. The calculated results show that these methods are powerful to examine MLCT and LLCT in the metal-ligand system.展开更多
In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, s...In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, second and third generation （G1, G2 and G3, respectively） are investigated by semi-empirical methods. The calculated results show that the nonlinear optical （NLO） properties of these organic dendrimers are mainly determined by the azobenzene chromospheres. Additionally, the values oft and y increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers （core-hybrid and branch-end hybrid according to the sites combined with transition metals） are simulated and discussed in detail in the framework of time-dependent density functional theory （TDDFT）. The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.展开更多
This paper is to report the temperature dependent electrical conductivity of single crystals of radical ion salt (RIS) potassium-TCNQ (K-tetracyanoquino- dimethane) in a wide range of temperatures from 30 to 500 K. Th...This paper is to report the temperature dependent electrical conductivity of single crystals of radical ion salt (RIS) potassium-TCNQ (K-tetracyanoquino- dimethane) in a wide range of temperatures from 30 to 500 K. This RIS is quasi-one-dimensional in nature. These single crystals of K-TCNQ are grown by different methods like electrochemical, solution growth and diffusion method. Activation energy is determined for the sample in different temperature regions and found different values. More than one semiconductor to metal phase transition is observed in the studied samples during electrical measurements below and above room temperature. All the features observed in the studied samples are analyzed in the framework of their molecular structure as well as under different effects like disorder, impurity, Coulomb interaction, charge density wave (CDW), scattering and 3-D effects etc.展开更多
Exposure to oxygen alters the physical and chemical properties of two-dimensional(2D)transition metal dichalcogenides(TMDs).In particular,oxygen in the ambient may influence the device stability of 2D TMDs over time.E...Exposure to oxygen alters the physical and chemical properties of two-dimensional(2D)transition metal dichalcogenides(TMDs).In particular,oxygen in the ambient may influence the device stability of 2D TMDs over time.Engineering the doping of 2D TMDs,especially hole doping is highly desirable towards their device function.Herein,controllable oxygen-induced p-type doping in a range of hexagonal(MoTe2,WSe2,MoSe2 and PtSe2)and pentagonal(PdSe2)2D TMDs are demonstrated.Scanning tunneling microscopy,electrical transport and X-ray photoelectron spectroscopy are used to probe the origin of oxygen-derived hole doping.Three mechanisms are postulated that contribute to the hole doping in 2D TMDs,namely charge transfer from absorbed oxygen molecules,surface oxides,and chalcogen atom substitution.This work provides insights into the doping effects of oxygen,enabling the engineering of 2D TMDs properties for nanoelectronic applications.展开更多
The random movement and easy recombination of photoinduced charges lead to a low conversion efficiency for photocatalytic hydrogen evolution.The cocatalyst design is a promising route to address such problem through i...The random movement and easy recombination of photoinduced charges lead to a low conversion efficiency for photocatalytic hydrogen evolution.The cocatalyst design is a promising route to address such problem through introducing an appropriate cocatalyst on the semiconductor photocatalysts to construct the high-efficiency heterojunctions.Herein,novel CoS/Nb_(2)O_(5) heterojunctions were constructed via in-situ loading CoS cocatalyst on the surface of Nb_(2)O_(5) nanosheets.Through the femtosecond-resolved transient absorption spectroscopy,the average lifetime of charge carriers for 10 wt% CoS/Nb_(2)O_(5)(159.6 ps)is drastically shortened by contrast with that of Nb_(2)O_(5)(5531.9 ps),strongly suggesting the rapid charge transfer from Nb_(2)O_(5) to CoS.The significantly improved charge-transfer capacity contributes to a high photocatalytic hydrogen evolution rate of 355µmol/h,up to 17.5 times compared with pristine Nb_(2)O_(5).This work would provide a new design platform in the construction of photocatalytic heterojunctions with high charge-transfer efficiency.展开更多
Recently,two dimensional transition metal dichalcogenides MX_2(M = Mo,W,etc; X = S,Se,Te) have ignited immense interests because of their unique structural and physical properties for the potential applications in the...Recently,two dimensional transition metal dichalcogenides MX_2(M = Mo,W,etc; X = S,Se,Te) have ignited immense interests because of their unique structural and physical properties for the potential applications in the nano-optoelectronics,valley-spintronics etc. In terms of the structural compatibility and van der Waals interaction,two dimensional(2D) MX_2 layers can be fabricated into various lateral and vertical hetero-structures. The atomically-thin hetero-structures comprising different layered MX_2 provide a new platform for exploring fundamental physics and device technologies with unprecedented phenomenon and extraordinary functionalities. In this review,we report the recent progress about the fabrication,properties and applications of 2D hetero-structures based on transition metal dichalcogenides.展开更多
As a direct-bandgap semiconductor,single-layer MoS_(2) has gained great attention in optoelectronics,especially wearable photodetectors.However,MoS_(2) exhibits poor photoresponsivity on a stretchable substrate due to...As a direct-bandgap semiconductor,single-layer MoS_(2) has gained great attention in optoelectronics,especially wearable photodetectors.However,MoS_(2) exhibits poor photoresponsivity on a stretchable substrate due to intrinsic low carrier density and a large number of scattering centers on polymer substrates.Few air-stable yet strong dopants on MoS_(2) has been reported.In addition,the roughness,hydrophobicity and susceptibility to organic solvents of polymer surface are critical roadblocks in the development of stretchable high-performance MoS_(2) photodetectors.Here,we realize a stretchable and stable photodetector with high photoresponsivity by combining n-type dopant((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine,N-DMBI)with MoS_(2) and assembly transfer technique.It is found electron tends to transfer from N-DMBI to MoS_(2) and the effect is maintained after the integrable photodetector transferred directly by elastic substrate styrene-ethylene-butylene-styrene(SEBS),even after being exposed to the air for 20 days,which benifits greatly from the encapsulation of SEBS.The increased carrier density greatly promotes carrier injection efficiency and photogenerated electron–hole separation efficiency at the metal–semiconductor interface,thus offering a significantly improved photoresponsivity in MoS_(2) photodetectors.Moreover,such photodetector shows great durability to stretch,which can remain functional after stretched 100 cycles within its stretch limit.Our strategy opens a new avenue to fabricate high-photoresponsivity stretchable electronics or optoelectronics of two-dimensional(2D)materials.展开更多
基金This work was supported by National Natural Science Foundation of China （No.10505001, No.10875055, and No.10874234） and the Educational Department of Liaoning Province （No.2008228）.
文摘Three methods including the atomic resolved density of state, charge difference density, and the transition density matrix are used to visualize metal to ligand charge transfer （MLCT） in ruthenium（II） ammine complex. The atomic resolved density of state shows that there is density of Ru on the HOMOs. All the density is localized on the ammine, which reveals that the excited electrons in the Ru complex are delocalized over the ammine ligand. The charge difference density shows that all the holes are localized on the Ru and the electrons on the ammine. The localization explains the MLCT on excitation. The transition density matrix shows that there is electron-hole coherence between Ru and ammine. These methods are also used to examine the MLCT in Os（bpy）2（p0p）Cl （＂Osp0p＂： bpy=2,2-bipyrldyl; p0p=4,4＇- bipyridyl） and the ligand-to-ligand charge transfer （LLCT） in Alq3. The calculated results show that these methods are powerful to examine MLCT and LLCT in the metal-ligand system.
基金This work was supported by the National Natural Science Foundation of China (No. 20573114 and 90203017)the MOST Projects of 2004CB720605 and 2006DFA43020
文摘In this work, we report a theoretical exploration of the responses of organic azobenzene dendrimers. The polarizabilities, the first and second hyperpolarizabilities of the azobenzene monomers （GO）, and the first, second and third generation （G1, G2 and G3, respectively） are investigated by semi-empirical methods. The calculated results show that the nonlinear optical （NLO） properties of these organic dendrimers are mainly determined by the azobenzene chromospheres. Additionally, the values oft and y increase almost in proportion to the number of chromophores. On the other hand, two types of transition metal hybrid azobenzene dendrimers （core-hybrid and branch-end hybrid according to the sites combined with transition metals） are simulated and discussed in detail in the framework of time-dependent density functional theory （TDDFT）. The calculated results reveal that the NLO responses of these metal dendrimers distinctly varied as a result of altering the charge transfer transition scale and the excitation energies.
文摘This paper is to report the temperature dependent electrical conductivity of single crystals of radical ion salt (RIS) potassium-TCNQ (K-tetracyanoquino- dimethane) in a wide range of temperatures from 30 to 500 K. This RIS is quasi-one-dimensional in nature. These single crystals of K-TCNQ are grown by different methods like electrochemical, solution growth and diffusion method. Activation energy is determined for the sample in different temperature regions and found different values. More than one semiconductor to metal phase transition is observed in the studied samples during electrical measurements below and above room temperature. All the features observed in the studied samples are analyzed in the framework of their molecular structure as well as under different effects like disorder, impurity, Coulomb interaction, charge density wave (CDW), scattering and 3-D effects etc.
基金This work was financially supported by the National Natural Science Foundation of China(No.51472164)Shenzhen Peacock Plan(No.KQTD2016053112042971)+3 种基金the Educational Commission of Guangdong Province(Nos.2015KGJHZ006 and 2016KCXTD006)the Science and Technology Planning Project of Guangdong Province(No.2016B050501005)A.T.S.W.acknowledges funding support from MOE Tier 2 grant R 144-000-382-112,A*STAR Pharos Program(No.1527300025)facility support from the NUS Centre for Advanced 2D Materials(CA2DM).
文摘Exposure to oxygen alters the physical and chemical properties of two-dimensional(2D)transition metal dichalcogenides(TMDs).In particular,oxygen in the ambient may influence the device stability of 2D TMDs over time.Engineering the doping of 2D TMDs,especially hole doping is highly desirable towards their device function.Herein,controllable oxygen-induced p-type doping in a range of hexagonal(MoTe2,WSe2,MoSe2 and PtSe2)and pentagonal(PdSe2)2D TMDs are demonstrated.Scanning tunneling microscopy,electrical transport and X-ray photoelectron spectroscopy are used to probe the origin of oxygen-derived hole doping.Three mechanisms are postulated that contribute to the hole doping in 2D TMDs,namely charge transfer from absorbed oxygen molecules,surface oxides,and chalcogen atom substitution.This work provides insights into the doping effects of oxygen,enabling the engineering of 2D TMDs properties for nanoelectronic applications.
基金funded by the National Natural Science Foundation of China(No.22002014)Applied Basic Research Program of Sichuan Province(No.2020YJ0068)+3 种基金“Young Talent Support Plan”of Xi'an Jiaotong UniversityNational Key Research and Development Program of China(No.2020YFC2005500)Key Research and Sichuan Province(No.2019YFS0514)Development Program of Science and Technology Department of financial support from the National Natural Science Foundation of China(No.22102152).
文摘The random movement and easy recombination of photoinduced charges lead to a low conversion efficiency for photocatalytic hydrogen evolution.The cocatalyst design is a promising route to address such problem through introducing an appropriate cocatalyst on the semiconductor photocatalysts to construct the high-efficiency heterojunctions.Herein,novel CoS/Nb_(2)O_(5) heterojunctions were constructed via in-situ loading CoS cocatalyst on the surface of Nb_(2)O_(5) nanosheets.Through the femtosecond-resolved transient absorption spectroscopy,the average lifetime of charge carriers for 10 wt% CoS/Nb_(2)O_(5)(159.6 ps)is drastically shortened by contrast with that of Nb_(2)O_(5)(5531.9 ps),strongly suggesting the rapid charge transfer from Nb_(2)O_(5) to CoS.The significantly improved charge-transfer capacity contributes to a high photocatalytic hydrogen evolution rate of 355µmol/h,up to 17.5 times compared with pristine Nb_(2)O_(5).This work would provide a new design platform in the construction of photocatalytic heterojunctions with high charge-transfer efficiency.
基金supported by the joint fund of the National Natural Science Foundation Committee of China Academy of Engineering Physics(U1630108)the National Natural Science Foundation of China(21373196,11434009)
文摘Recently,two dimensional transition metal dichalcogenides MX_2(M = Mo,W,etc; X = S,Se,Te) have ignited immense interests because of their unique structural and physical properties for the potential applications in the nano-optoelectronics,valley-spintronics etc. In terms of the structural compatibility and van der Waals interaction,two dimensional(2D) MX_2 layers can be fabricated into various lateral and vertical hetero-structures. The atomically-thin hetero-structures comprising different layered MX_2 provide a new platform for exploring fundamental physics and device technologies with unprecedented phenomenon and extraordinary functionalities. In this review,we report the recent progress about the fabrication,properties and applications of 2D hetero-structures based on transition metal dichalcogenides.
基金supported by the National Natural Science Foundation of China(Nos.21903007 and 22072006)Young Thousand Talents Program(No.110532103)+2 种基金Beijing Normal University Startup funding(No.312232102)Beijing Municipal Science&Technology Commission(No.Z191100000819002)the Fundamental Research Funds for the Central Universities(No.310421109)。
文摘As a direct-bandgap semiconductor,single-layer MoS_(2) has gained great attention in optoelectronics,especially wearable photodetectors.However,MoS_(2) exhibits poor photoresponsivity on a stretchable substrate due to intrinsic low carrier density and a large number of scattering centers on polymer substrates.Few air-stable yet strong dopants on MoS_(2) has been reported.In addition,the roughness,hydrophobicity and susceptibility to organic solvents of polymer surface are critical roadblocks in the development of stretchable high-performance MoS_(2) photodetectors.Here,we realize a stretchable and stable photodetector with high photoresponsivity by combining n-type dopant((4-(1,3-dimethyl-2,3-dihydro-1H-benzoimidazol-2-yl)phenyl)dimethylamine,N-DMBI)with MoS_(2) and assembly transfer technique.It is found electron tends to transfer from N-DMBI to MoS_(2) and the effect is maintained after the integrable photodetector transferred directly by elastic substrate styrene-ethylene-butylene-styrene(SEBS),even after being exposed to the air for 20 days,which benifits greatly from the encapsulation of SEBS.The increased carrier density greatly promotes carrier injection efficiency and photogenerated electron–hole separation efficiency at the metal–semiconductor interface,thus offering a significantly improved photoresponsivity in MoS_(2) photodetectors.Moreover,such photodetector shows great durability to stretch,which can remain functional after stretched 100 cycles within its stretch limit.Our strategy opens a new avenue to fabricate high-photoresponsivity stretchable electronics or optoelectronics of two-dimensional(2D)materials.
