A fundamental understanding of the charge transport mechanism in two-dimensional semiconductors(e.g., MoS2) is crucial for fully exploring their potential in electronic and optoelectronic devices. By using monolayer g...A fundamental understanding of the charge transport mechanism in two-dimensional semiconductors(e.g., MoS2) is crucial for fully exploring their potential in electronic and optoelectronic devices. By using monolayer graphene as the barrier-free contact to MoS2, we show that the field-modulated conductivity can be used to probe the electronic structure of the localized states. A series of regularly distributed plateaus were observed in the gate-dependent transfer curves. Calculations based on the variable-range hopping theory indicate that such plateaus can be attributed to the discrete localized states near mobility edge. This method provides an effective approach to directly profiling the localized states in conduction channel with an ultrahigh resolution up to 1 meV.展开更多
Van der Waals(vdW)integration affords semiconductor heterostructures without constrains of lattice matching and opens up a new realm of functional devices by design.A particularly interesting approach is the electroch...Van der Waals(vdW)integration affords semiconductor heterostructures without constrains of lattice matching and opens up a new realm of functional devices by design.A particularly interesting approach is the electrochemical intercalation of two-dimensional(2D)atomic crystal and formation of superlattices,which can provide scalable production of novel vdW heterostructures.However,this approach has been limited to the use of organic cations with non-functional aliphatic chains,therefore failed to take the advantage of the vast potentials in molecular functionalities(electronic,photonic,magnetic,etc.).Here we report the integration of 2D crystal(MoS_(2),WS_(2),highly oriented pyrolytic graphite(HOPG),WSe_(2) as model systems)with electrochemically inert organic molecules that possess semiconducting characteristics(including perylene-3,4,9,10-tetracarboxylic dianhydride(PTCDA),pentacene and fullerene),through on-chip electrochemical intercalation.An unprecedented long-range spatial feature of intercalation has been achieved,which allowed facile assembly of a vertical MoS_(2)-PTCDA-Si junction.The intercalated heterostructure shows significant modulation of the lateral transport,and leads to a molecular tunneling characteristic at the vertical direction.The general intercalation of charge neutral and functional molecules defines a versatile platform of inorganic/organic hybrid vdW heterostructures with significantly extended molecular functional building blocks,holding great promise in future design of nano/quantum devices.展开更多
Solid-state ionic conductor is a vital part in all electrochemical energy conversion devices. As a widely-applied protonconducting polymer and stabilizer for electrode preparation, Nafion has key applications in elect...Solid-state ionic conductor is a vital part in all electrochemical energy conversion devices. As a widely-applied protonconducting polymer and stabilizer for electrode preparation, Nafion has key applications in electrochemical devices operated under acidic conditions. Specific adsorption of Nafion on the catalyst surface is considered to result in partial loss of intrinsic activity in reactions such as oxygen reduction reaction(ORR), due to its comprehensive occupation of active sites. Many in situ characterization methods such as voltammetric fingerprinting and spectroscopic approaches have been used to explore the dynamic adsorption of Nafion on the electrode surface. However, most of current efforts have been focused on the behaviors of Nafion itself, with little attention paid to its effects on the adsorption of surface intermediates. Here, we employed the in situ electrical transport spectroscopy(ETS) to investigate Nafion adsorption on Pt catalysts and its effects on the ORR intermediates.Our findings suggest that specific adsorption of Nafion results in the increased coverage of oxygen intermediates with weaker adsorption strength, which in turn plays a critical role in the reaction selectivity. The successful application of ETS on the dynamic characterization of reaction intermediates provides a novel perspective for catalyst design in ORR-related applications in future sustainable chemistry.展开更多
Direct far-field visualization and characterization of surface plasmon polaritons(SPPs)are of great importance for fundamental studies and technological applications.To probe the evanescently confined plasmon fields,o...Direct far-field visualization and characterization of surface plasmon polaritons(SPPs)are of great importance for fundamental studies and technological applications.To probe the evanescently confined plasmon fields,one usually requires advanced near-field techniques,which is typically not applicable for real-time,high-throughput detecting or mapping of SPPs in complicated environments.Here,we report the utilization of rare-earth-doped nanoparticles to quantitatively upconvert invisible,evanescently confined SPPs into visible photoluminescence emissions for direct far-field visualization of SPPs in a complicated environment.The observed interference fringes between the SPPs and the coherent incident light at the metal surface provide a quantitative measurement of the SPP wavelength and the SPP propagating length and the local dielectric environments.It thus creates a new signaling pathway to sensitively transduce the local dielectric environment change into interference periodicity variation,enabling a new design of directly measurable,spectrometer-free optical rulers for rapid,ultrasensitive label-free detection of various biomolecules,including streptavidin and prostate-specific antigen,down to the femtomolar level.展开更多
Theπ-πstacking is a well-recognized intermolecular interaction that is responsible for the construction of electron hopping channels in numerous conducting frameworks/aggregates.However,the exact role ofπ-to-πchan...Theπ-πstacking is a well-recognized intermolecular interaction that is responsible for the construction of electron hopping channels in numerous conducting frameworks/aggregates.However,the exact role ofπ-to-πchannels within typical single crystalline organic semiconductors remains unclear as the orientations of these molecules are diverse,and their control usually requires additional side chain groups that misrepresent the intrinsic properties of the original semiconducting molecules.Therefore,the construction of conduction channels with intrinsicπ-πstacking in the molecule-based device is crucial for the utilization of their unique transport characteristics and understanding of the transport mechanism.To this end,we present a molecular intercalation strategy that integrates two-dimensional layered materials with functional organic semiconductor molecules for functional molecule-based electronics.Various organic semiconductor molecules can be effectively intercalated into the van der Waals gaps of semi-metallic TaS_(2) withπ-πstacking configuration and controlled intercalant content.Our results show that the vertical charge transport in the stacking direction shows a tunneling-dominated mechanism that strongly depends on the molecular structures.Furthermore,we demonstrated a new type of molecule-based vertical transistor in which TaS_(2) andπ-πstacked organic molecules function as the electrical contact and the active channel,respectively.On/off ratios as high as 447 are achieved under electrostatic modulation in ionic liquid,comparable to the current state-of-the-art molecular transistors.Our study provides an ideal platform for probing intrinsic charge transport acrossπ-πstacked conjugated molecules and also a feasible approach for the construction of high-performance molecule-based electronic devices.展开更多
基金the support by the National Science Foundation(DMR1508144)the financial support from the National Science Foundation(EFRI-1433541)
文摘A fundamental understanding of the charge transport mechanism in two-dimensional semiconductors(e.g., MoS2) is crucial for fully exploring their potential in electronic and optoelectronic devices. By using monolayer graphene as the barrier-free contact to MoS2, we show that the field-modulated conductivity can be used to probe the electronic structure of the localized states. A series of regularly distributed plateaus were observed in the gate-dependent transfer curves. Calculations based on the variable-range hopping theory indicate that such plateaus can be attributed to the discrete localized states near mobility edge. This method provides an effective approach to directly profiling the localized states in conduction channel with an ultrahigh resolution up to 1 meV.
基金support by the Fundamental Research Funds for the Central Universities in China(No.020514380224)Natural Science Foundation of Jiangsu Province(No.BK20180321)+5 种基金instrument/technical support from State Key Lab of Analytical Chemistry for Life Science,and State Key Lab of Coordination Chemistry.P.W.and S.C acknowledge funding from the National Natural Science Foundation of China(No.11874199)the National Basic Research Program of China,(No.2015CB654901)support by the National Natural Science Foundation of China(Nos.61734003,61521001,51861145202,61861166001,and 61851401)the National Key Basic Research Program of China(No.2015CB921600)Strategic Priority Research Program of Chinese Academy of Sciences XDB 30000000,Key Laboratory of Advanced Photonic and Electronic Materials,Collaborative Innovation Center of Solid-State Lighting and Energy-Saving Electronics,and the Fundamental Research Funds for the Central Universities,China.S.H.C.acknowledges the support by the Program A for Outstanding PhD candidate of Nanjing University(No.201801A013)Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX18_0045).
文摘Van der Waals(vdW)integration affords semiconductor heterostructures without constrains of lattice matching and opens up a new realm of functional devices by design.A particularly interesting approach is the electrochemical intercalation of two-dimensional(2D)atomic crystal and formation of superlattices,which can provide scalable production of novel vdW heterostructures.However,this approach has been limited to the use of organic cations with non-functional aliphatic chains,therefore failed to take the advantage of the vast potentials in molecular functionalities(electronic,photonic,magnetic,etc.).Here we report the integration of 2D crystal(MoS_(2),WS_(2),highly oriented pyrolytic graphite(HOPG),WSe_(2) as model systems)with electrochemically inert organic molecules that possess semiconducting characteristics(including perylene-3,4,9,10-tetracarboxylic dianhydride(PTCDA),pentacene and fullerene),through on-chip electrochemical intercalation.An unprecedented long-range spatial feature of intercalation has been achieved,which allowed facile assembly of a vertical MoS_(2)-PTCDA-Si junction.The intercalated heterostructure shows significant modulation of the lateral transport,and leads to a molecular tunneling characteristic at the vertical direction.The general intercalation of charge neutral and functional molecules defines a versatile platform of inorganic/organic hybrid vdW heterostructures with significantly extended molecular functional building blocks,holding great promise in future design of nano/quantum devices.
基金supported by the Natural Science Foundation of China(22172075 and 92156024)the Fundamental Research Funds for the Central Universities in China(14380273)+2 种基金Natural Science Foundation of Jiangsu Province(BK20220069)Beijing National Laboratory for Molecular Sciences(BNLMS202107)the Thousand Talents Plan of Jiangxi Province(jxsq2019102002)。
文摘Solid-state ionic conductor is a vital part in all electrochemical energy conversion devices. As a widely-applied protonconducting polymer and stabilizer for electrode preparation, Nafion has key applications in electrochemical devices operated under acidic conditions. Specific adsorption of Nafion on the catalyst surface is considered to result in partial loss of intrinsic activity in reactions such as oxygen reduction reaction(ORR), due to its comprehensive occupation of active sites. Many in situ characterization methods such as voltammetric fingerprinting and spectroscopic approaches have been used to explore the dynamic adsorption of Nafion on the electrode surface. However, most of current efforts have been focused on the behaviors of Nafion itself, with little attention paid to its effects on the adsorption of surface intermediates. Here, we employed the in situ electrical transport spectroscopy(ETS) to investigate Nafion adsorption on Pt catalysts and its effects on the ORR intermediates.Our findings suggest that specific adsorption of Nafion results in the increased coverage of oxygen intermediates with weaker adsorption strength, which in turn plays a critical role in the reaction selectivity. The successful application of ETS on the dynamic characterization of reaction intermediates provides a novel perspective for catalyst design in ORR-related applications in future sustainable chemistry.
基金X.D.acknowledge the financial support from the National Science Foundation through grant No.1610361.
文摘Direct far-field visualization and characterization of surface plasmon polaritons(SPPs)are of great importance for fundamental studies and technological applications.To probe the evanescently confined plasmon fields,one usually requires advanced near-field techniques,which is typically not applicable for real-time,high-throughput detecting or mapping of SPPs in complicated environments.Here,we report the utilization of rare-earth-doped nanoparticles to quantitatively upconvert invisible,evanescently confined SPPs into visible photoluminescence emissions for direct far-field visualization of SPPs in a complicated environment.The observed interference fringes between the SPPs and the coherent incident light at the metal surface provide a quantitative measurement of the SPP wavelength and the SPP propagating length and the local dielectric environments.It thus creates a new signaling pathway to sensitively transduce the local dielectric environment change into interference periodicity variation,enabling a new design of directly measurable,spectrometer-free optical rulers for rapid,ultrasensitive label-free detection of various biomolecules,including streptavidin and prostate-specific antigen,down to the femtomolar level.
基金support by the National Natural Science Foundation of China(Nos.22172075,92156024)the Fundamental Research Funds for the Central Universities in China(Nos.0210/14380174,14380273)+4 种基金Beijing National Laboratory for Molecular Sciences(No.BNLMS202107)Thousand Talents Plan of Jiangxi Province(No.jxsq2019102002)support by the National Natural Science Foundation of China(No.22033004)support from Early Career Scheme Project(No.21302821)General Research Fund Project(No.11314322)from the University Grants Committee of Hong Kong.
文摘Theπ-πstacking is a well-recognized intermolecular interaction that is responsible for the construction of electron hopping channels in numerous conducting frameworks/aggregates.However,the exact role ofπ-to-πchannels within typical single crystalline organic semiconductors remains unclear as the orientations of these molecules are diverse,and their control usually requires additional side chain groups that misrepresent the intrinsic properties of the original semiconducting molecules.Therefore,the construction of conduction channels with intrinsicπ-πstacking in the molecule-based device is crucial for the utilization of their unique transport characteristics and understanding of the transport mechanism.To this end,we present a molecular intercalation strategy that integrates two-dimensional layered materials with functional organic semiconductor molecules for functional molecule-based electronics.Various organic semiconductor molecules can be effectively intercalated into the van der Waals gaps of semi-metallic TaS_(2) withπ-πstacking configuration and controlled intercalant content.Our results show that the vertical charge transport in the stacking direction shows a tunneling-dominated mechanism that strongly depends on the molecular structures.Furthermore,we demonstrated a new type of molecule-based vertical transistor in which TaS_(2) andπ-πstacked organic molecules function as the electrical contact and the active channel,respectively.On/off ratios as high as 447 are achieved under electrostatic modulation in ionic liquid,comparable to the current state-of-the-art molecular transistors.Our study provides an ideal platform for probing intrinsic charge transport acrossπ-πstacked conjugated molecules and also a feasible approach for the construction of high-performance molecule-based electronic devices.
