Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllab...Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllable doping of TMDs remains a challenging issue due to the natural doping of these materials.Here,we demonstrate the controllable growth of indium-doped p-type WS_(2) monolayers with various doping concentrations via chemical vapor deposition(CVD)of a host tungsten(W)source and indium(In)dopant.Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS_(2) lattice.Intriguingly,the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration,which first increases remarkably with an enhancement factor up to~35 and then decreases gradually when further increasing the doping concentration.Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples.The assignment was further verified by the electric behavior of the fabricated In-doped WS_(2) field effect transistors,which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration.The successful growth of p-type monolayer WS_(2) and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.展开更多
The recently reported Rh(Ⅱ)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an attractive strategy to prepare coumarin derivatives with novel chemoselectivity.Motivated by the mechani...The recently reported Rh(Ⅱ)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an attractive strategy to prepare coumarin derivatives with novel chemoselectivity.Motivated by the mechanistic ambiguity(on the origin of the chemoselectivity and the details for lactonization etc.),we conducted a detailed mechanistic study for the rhodium-catalyzed lactonization of 2-arylphenols with density functional theory(DFT)calculations.The results suggest that the reaction occurs via the coordination exchange,C-H bond activation,carboxylation,protonation and lactonization steps.The rate-determining step is the carboxylation,in which CO_(2) favorably inserts into the Rh-C bond(instead of the more nucleophilic Rh-O bond).The protonation step after carboxylation is critical,which makes the subsequent CO_(2)-assisted lactonization feasible.Interestingly,the corresponding pK_(a) value of the base can reasonably predict the reaction energy barrier of the C-H bond activation step.The calculations will provide insights and suggestions for developing and advancing the subsequent C-H bond activation carboxylation reaction.展开更多
基金supported by the National Natural Science Foundation of China(21732006,51821006,21927814)the CAS Collaborative Innovation Program of Hefei Science Center(2021HSC-CIP004)the University Synergy Innovation Program of Anhui Province(GXXT-2021-023)。
基金supported by the National Natural Science Foundation of China(62375079,52072117,62375081,52221001,51972105,62090035,U19A2090,and 61905071)the National Key R&D Program of China(2022YFA1204300)+4 种基金the Key Program of Science and Technology Department of Hunan Province(2019XK2001 and 2020XK2001)the Key Research and Development Plan of Hunan Province(2023GK2012)the Open Project Program of Key Laboratory of Nanodevices and Applications,Suzhou Institute of Nano-Tech and Nano-Bionics,Chinese Academy of Sciences(22ZS01)the Hunan Provincial Natural Science Foundation of China(2021JJ30132)the China Scholarship Council.
基金financially supported by the National Natural Science Foundation of China (51525202, 61635001, 52072117 and 21703059)the Key Program of the Hunan Provincial Science and Technology Department (2019XK2001)the International Science and Technology Innovation Cooperation Base of Hunan Province (2018WK4004)
文摘Substitutional doping of two-dimensional(2D)transition metal dichalcogenides(TMDs)has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications.However,controllable doping of TMDs remains a challenging issue due to the natural doping of these materials.Here,we demonstrate the controllable growth of indium-doped p-type WS_(2) monolayers with various doping concentrations via chemical vapor deposition(CVD)of a host tungsten(W)source and indium(In)dopant.Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS_(2) lattice.Intriguingly,the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration,which first increases remarkably with an enhancement factor up to~35 and then decreases gradually when further increasing the doping concentration.Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples.The assignment was further verified by the electric behavior of the fabricated In-doped WS_(2) field effect transistors,which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration.The successful growth of p-type monolayer WS_(2) and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.
基金supported by the National Natural Science Foundation of China(51961135104,21732006,51821006)the National Key R&D Program of China(2017YFA0303502).
文摘The recently reported Rh(Ⅱ)-catalyzed direct C-H bond activation and lactonization of 2-arylphenols uncovers an attractive strategy to prepare coumarin derivatives with novel chemoselectivity.Motivated by the mechanistic ambiguity(on the origin of the chemoselectivity and the details for lactonization etc.),we conducted a detailed mechanistic study for the rhodium-catalyzed lactonization of 2-arylphenols with density functional theory(DFT)calculations.The results suggest that the reaction occurs via the coordination exchange,C-H bond activation,carboxylation,protonation and lactonization steps.The rate-determining step is the carboxylation,in which CO_(2) favorably inserts into the Rh-C bond(instead of the more nucleophilic Rh-O bond).The protonation step after carboxylation is critical,which makes the subsequent CO_(2)-assisted lactonization feasible.Interestingly,the corresponding pK_(a) value of the base can reasonably predict the reaction energy barrier of the C-H bond activation step.The calculations will provide insights and suggestions for developing and advancing the subsequent C-H bond activation carboxylation reaction.
