Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,...Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,and this severely limits their potential for being designed as multi-functional heterostructures.Recently,thermal annealing has been reported as an easy means of p-doping TMDs,but the mechanism remains ambiguous,thereby preventing reliable outcomes and it becoming a mature doping technology for TMDs.Here,the mechanism of thermal annealing for p-doping a 2D selenide is investigated thoroughly,revealing the key role of the catalytic effect of nano-thick gold electrodes in achieving p-doping.As an example,2D SnSe_(2)with a fairly high electron density of∼10^(18)cm^(−3)is used,and its electrical performance is greatly enhanced after thermal annealing when 30-nm-thick gold electrodes are deposited.The results of performing XPS and Auger electron spectroscopy on samples before and after annealing show that the p-doping effect is due to the oxidation of selenide atoms,during which the gold acts as a critical catalytic element.This method is also shown to be valid for other 2D selenides including WSe_(2)and MoSe_(2),and the present findings offer new avenues for enriching the electrical properties of 2D selenides by means of annealing.展开更多
An intramolecular selenocyclizations of olefins mediated by a commercially available hypervalent iodine(Ⅲ) reagent,PhIO,was developed.This method provided access to a wide range of selenenylated heterocycles under am...An intramolecular selenocyclizations of olefins mediated by a commercially available hypervalent iodine(Ⅲ) reagent,PhIO,was developed.This method provided access to a wide range of selenenylated heterocycles under ambient conditions.The striking advantages of this protocol over all previous methods include mild reaction conditions,easy operation,good yields,high levels of functional group compatibility,large-scale application and suitability for the late-stage functionalization of complex molecules of biological importance.展开更多
A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethyls...A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethylsilyl chloride under mild conditions. Presumably, the diselenides are cleaved by Sm/TMSCI system to form selemde anions, which then undergo SN2＇ substitution of Baylis-Hillman adducts to produce the （Z）-allyl selenides.展开更多
A facile and efficient electrochemical method for sustainable constructing both selanyl phenanthrenes and selanyl polycyclic heteroaromatics(32 examples,71%-97%yields)through the radical annulation of 2-alkynyl biaryl...A facile and efficient electrochemical method for sustainable constructing both selanyl phenanthrenes and selanyl polycyclic heteroaromatics(32 examples,71%-97%yields)through the radical annulation of 2-alkynyl biaryls and 2-heteroaryl-substituted alkynyl benzenes with diselenides at ambient temperature under additive-,chemical oxidant-,catalyst-free and mild conditions was established.展开更多
The Se-Se bond in diaryl diselenides was reduced by Zn/ZrCl4 system to produce selenide anions, which react with acyl chlorides or acid anhydrides to afford selenoesters in THF under mild and neutral conditions.
The reduction of diacyl diselenides by samarium diiodide led to the production ofsamarium acylselenolates, which reacted with a,β-unsaturated esters or nitriles to give β-selenoesters or selenonitriles under mild an...The reduction of diacyl diselenides by samarium diiodide led to the production ofsamarium acylselenolates, which reacted with a,β-unsaturated esters or nitriles to give β-selenoesters or selenonitriles under mild and neutral conditions.展开更多
KBr or NaCl is found to be a good catalyst in Se-Se bond cleavage of diselenides in the present of the oxidant mCPBA.The electrophilic addition of the in situ generated reactive electrophilic selenium species PhSeX（X...KBr or NaCl is found to be a good catalyst in Se-Se bond cleavage of diselenides in the present of the oxidant mCPBA.The electrophilic addition of the in situ generated reactive electrophilic selenium species PhSeX（X = Br,Cl） to alkenes in AcOH provides a convenient access to 2-acetoxy-1-selenides.Compared with other catalysts,KBr or NaCl is less expensive and more environment-friendly.展开更多
The two-dimensional MoSe_(2)possesses a large interlayer spacing(0.65 nm)and a narrow bandgap(1.1 eV),showing potential in sodium-ion storage.However,it faces slow kinetics and volume stress during Na^(+)(de)intercala...The two-dimensional MoSe_(2)possesses a large interlayer spacing(0.65 nm)and a narrow bandgap(1.1 eV),showing potential in sodium-ion storage.However,it faces slow kinetics and volume stress during Na^(+)(de)intercalation process,thereby affecting the cycling stability and lifespan of sodium-ion batteries(SIBs).In this work,a novel approach involving anionic doping and structural design has been proposed,wherein a two-step in-situ selenization and surface thermal annealing doping process is applied to fabricate a novel configuration material of fluorine-doped MoSe_(2)@nitrogen-doped carbon nanosheets(F-MoSe_(2)@FNC).The obtained F-MoSe_(2)@FNC,benefiting from the dual advantages of structure and F-doping,synergistically promotes and accelerates the stable(de)intercalation of Na^(+).Henceforth,F-MoSe_(2)@FNC demonstrates notable characteristics in terms of reversible specific capacity,boasting a high initial coulombic efficiency of 76.97%,alongside remarkable rate capabilities and cyclic stability.The constructed F-MoSe_(2)@FNC anode-based half cell manifests exceptional longevity,enduring up to 2550 cycles at 10 A·g^(-1)with a specific capacity of 322.04 mAh·g^(-1).Its electrochemical performance surpasses that of MoSe_(2)@NC and Pure MoSe_(2),underscoring the significance of the proposed synergistic modulation.Through comprehensive kinetic analyses,encompassing in-situ electrochemical impedance spectroscopy(EIS),it is elucidated that the F-MoSe_(2)@FNC electrode showcases elevated pseudo-capacitance and rapid diffusion attributes during charge and discharge processes.Furthermore,the assembled full-cell(F-MoSe_(2)@FNC//Na_(3)V_(2)(PO_(4))_(3))attains a notable energy density of 166.94 Wh·kg^(-1).This design provides insights for the optimization of MoSe_(2)electrodes and their applications in SIBs.展开更多
The transport properties of two-dimensional(2D)molybdenum diselenide(MoSe_(2))were comprehensively investigated.To understand experimental data,a detailed transport theory was developed by considering charged impurity...The transport properties of two-dimensional(2D)molybdenum diselenide(MoSe_(2))were comprehensively investigated.To understand experimental data,a detailed transport theory was developed by considering charged impurity,acoustic phonon,and optical phonon scatterings,and excellent quantitative agreements were obtained between theory and experiment.The observed metal-insulator transition(MIT)in MoSe_(2)is attributed to the screened Coulombic disorder arising from the random distribution of charged impurities in the semiconductor structures,indicating that MoSe_(2)2D MIT is a finite-temperature density-inhomogeneity-driven effective transition.We argue that the critical carrier density(nc)is sensitive to impurity density(ni)as a result of the competition with intrinsic phonons.Due to low impurity density,our devices show linear ohmic contact between the channel and electrodes.Furthermore,high performance MoSe_(2)all-2D photodetectors are fabricated by using a transparent electrode on a hexagonal boron nitride(hBN)substrate.The fabricated all-2D MoSe_(2)photodetectors demonstrate a substantial enhancement of photocurrent due to multiple reflections at the hBN and MoSe_(2)interface.Additionally,they exhibit a high photo-to-dark current ratio(1.1×10^(4)),high responsivity(3500 A/W),and high detectivity(5.8×10^(10)Jones).展开更多
Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can prov...Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.展开更多
In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence ...In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence band offsets(VBO)of the three heterojunctions were measured by x-ray photoelectron spectroscopy(XPS),while the PtSe_(2)/n-GaN is 3.70±0.15 eV,PtSe_(2)/p-GaN is 0.264±0.15 eV,and PtSe_(2)/u-GaN is 3.02±0.15 eV.The conduction band offset(CBO)of the three heterojunctions was calculated from the material bandgap and VBO,while the PtSe_(2)/n-GaN is 0.61±0.15 eV,PtSe_(2)/p-GaN is 2.83±0.15 eV,and PtSe_(2)/u-GaN is 0.07±0.15 eV.This signifies that both PtSe_(2)/u-GaN and PtSe_(2)/p-GaN exhibit type-Ⅰband alignment,but the PtSe_(2)/n-GaN heterojunction has type-Ⅲband alignment.This signifies that the band engineering of PtSe_(2)/GaN heterojunction can be achieved by manipulating the concentration and type of doping,which is significantly relevant for the advancement of related devices through the realization of band alignment and the modulation of the material properties of the PtSe_(2)/GaN heterojunction.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMDs),which allow atomic-scale manipulation,have supe-rior electrical and optical properties that challenge the limits of traditional bulk semiconductors like silico...Two-dimensional(2D)transition metal dichalcogenides(TMDs),which allow atomic-scale manipulation,have supe-rior electrical and optical properties that challenge the limits of traditional bulk semiconductors like silicon^([1,2]).As a repre-sentative TMD and a promising 2D channel material for high-performance,scalable p-type transistors,tungsten diselenide(WSe_(2))has attracted considerable academic and industrial interest for its potential in advanced complementary metal−oxide−semiconductor(CMOS)logic technology and in extending Moore’s Law^([3−7]).展开更多
Stereoselective Michael addition and Michael-aldol tandem reaction of diorganyl diselenides and disulfides with conjugated alkynones mediated by samarium diiodide were studied. The reaction temperature was critical fo...Stereoselective Michael addition and Michael-aldol tandem reaction of diorganyl diselenides and disulfides with conjugated alkynones mediated by samarium diiodide were studied. The reaction temperature was critical for the stereoselectivity. -Organylselenoalkenones or -organylthioalkenones and ?-organylselenoallylic alcohols or ?-organylthioallylic alcohols were prepared in good yields.展开更多
The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(...The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(2)-based photodetection faces obstacles,including slow response speed and low normalized detectivity.In this work,photodetectors based on SnS/SnSe_(2)and SnSe/SnSe_(2)p−n heterostructures have been implemented through a polydimethylsiloxane(PDMS)−assisted transfer method.These photodetectors demonstrate broad-spectrum photoresponse within the 405 to 850 nm wavelength range.The photodetector based on the SnS/SnSe_(2)heterostructure exhibits a significant responsivity of 4.99×10^(3)A∙W^(−1),normalized detectivity of 5.80×10^(12)cm∙Hz^(1/2)∙W^(−1),and fast response time of 3.13 ms,respectively,owing to the built-in electric field.Meanwhile,the highest values of responsivity,normalized detectivity,and response time for the photodetector based on the SnSe/SnSe_(2)heterostructure are 5.91×10^(3)A∙W^(−1),7.03×10^(12)cm∙Hz^(1/2)∙W−1,and 4.74 ms,respectively.And their photodetection performances transcend those of photodetectors based on individual SnSe_(2),SnS,SnSe,and other commonly used 2D materials.Our work has demonstrated an effective strategy to improve the performance of SnSe_(2)-based photodetectors and paves the way for their future commercialization.展开更多
Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides in the presence of potassium t-butoxide. The advantages of this protocol include the use of...Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides in the presence of potassium t-butoxide. The advantages of this protocol include the use of readily available substrates and reagent and good yield of the products.展开更多
An eco-friendly,sustainable and practical method for the efficient preparation of 5-organylselanyl uracils through the electrochemical selenylation of uracils and dio rganyl diselenides at room temperature under oxida...An eco-friendly,sustainable and practical method for the efficient preparation of 5-organylselanyl uracils through the electrochemical selenylation of uracils and dio rganyl diselenides at room temperature under oxidant-and external electrolvte-free conditions was developed.展开更多
Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)...Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)Tx(PVA/MXene)nanofibers film and monolayer molybdenum diselenide(MoSe2)piezoelectric nanogenerator(PENG)was reported for the first time.The monolayer MoSe_(2)-based PENG was fabricated by atmospheric pressure chemical vapor deposition techniques,which can generate a peak output of 35 mV and a power density of42 mW m^(-2).The flexible PENG integrated on polyethylene terephthalate(PET)substrate can harvest energy generated by different parts of human body and exhibit great application prospects in wearable devices.The electrospinned PVA/MXene nanofiber-based humidity sensor with flexible PET substrate under the driven of monolayer MoSe_(2) PENG,shows high response of~40,fast response/recovery time of 0.9/6.3 s,low hysteresis of 1.8%and excellent repeatability.The self-powered flexible humidity sensor yields the capability of detecting human skin moisture and ambient humidity.This work provides a pathway to explore the high-performance humidity sensor integrated with PENG for the self-powered flexible electronic devices.展开更多
Rhenium diselenide(ReSe2) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability.In this study,ReS...Rhenium diselenide(ReSe2) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability.In this study,ReSe2 nanoparticles encapsulated in carbon nanofibers were synthesized successfully with simple electrospinning and heat treatment.It was found that graphene modifications could affect considerably the microstructure and electrochemical properties of ReSe2–carbon nanofibers.Accordingly,the modified compound maintained a capacity of 227 mAhg-1 after 500cycles at 200 mAg-1 for Na+storage,230 mAh g-1 after 200 cycles at 200 mAg-1,212 mAh g-1 after 150 cycles at 500 mAg-1 for K+ storage,which corresponded to the capacity retention ratios of 89%,97%,and 86%,respectively.Even in Na+full cells,its capacity was maintained to 82% after 200 cycles at 1 C(117 mAg-1).The superior stability of ReSe2–carbon nanofibers benefitted from the extremely weak van der Waals interactions and large interlayer spacing of ReSe2,in association with the role of graphene-modified carbon nanofibers,in terms of the shortening of electron/ion transport paths and the improvement of structural support.This study may provide a new route for a broadened range of applications of other rhenium-based compounds.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52075385 and 12034001)the National Key R&D Program(Grant No.2018YFA0307200)the 111 Project(Grant No.B07014).
文摘Two-dimensional transition metal dichalcogenides(TMDs)show great promise for developing the next generation of electronic and optoelectronic devices.However,most TMDs have n-type or n-dominant bipolar characteristics,and this severely limits their potential for being designed as multi-functional heterostructures.Recently,thermal annealing has been reported as an easy means of p-doping TMDs,but the mechanism remains ambiguous,thereby preventing reliable outcomes and it becoming a mature doping technology for TMDs.Here,the mechanism of thermal annealing for p-doping a 2D selenide is investigated thoroughly,revealing the key role of the catalytic effect of nano-thick gold electrodes in achieving p-doping.As an example,2D SnSe_(2)with a fairly high electron density of∼10^(18)cm^(−3)is used,and its electrical performance is greatly enhanced after thermal annealing when 30-nm-thick gold electrodes are deposited.The results of performing XPS and Auger electron spectroscopy on samples before and after annealing show that the p-doping effect is due to the oxidation of selenide atoms,during which the gold acts as a critical catalytic element.This method is also shown to be valid for other 2D selenides including WSe_(2)and MoSe_(2),and the present findings offer new avenues for enriching the electrical properties of 2D selenides by means of annealing.
基金supported by the Natural Science Foundation of Jiangsu Province (No.BK20170439)Science and Technology Plan Projects of Nantong (Nos.JC2019102 and JC2020072)。
文摘An intramolecular selenocyclizations of olefins mediated by a commercially available hypervalent iodine(Ⅲ) reagent,PhIO,was developed.This method provided access to a wide range of selenenylated heterocycles under ambient conditions.The striking advantages of this protocol over all previous methods include mild reaction conditions,easy operation,good yields,high levels of functional group compatibility,large-scale application and suitability for the late-stage functionalization of complex molecules of biological importance.
基金Project (No. 2004C21032) supported by the Key Technologies R &D Program of Zhejiang Province, China
文摘A simple and convenient procedure for stercoselective synthesis of （Z）-allyl selenides has been developed by a one-pot reaction of diselenides with Baylis-Hillman adducts in the presence of samarium metal-trimethylsilyl chloride under mild conditions. Presumably, the diselenides are cleaved by Sm/TMSCI system to form selemde anions, which then undergo SN2＇ substitution of Baylis-Hillman adducts to produce the （Z）-allyl selenides.
基金funded by the Scientific Research Fund of Hunan Provincial Education Department(No.22B0435).
文摘A facile and efficient electrochemical method for sustainable constructing both selanyl phenanthrenes and selanyl polycyclic heteroaromatics(32 examples,71%-97%yields)through the radical annulation of 2-alkynyl biaryls and 2-heteroaryl-substituted alkynyl benzenes with diselenides at ambient temperature under additive-,chemical oxidant-,catalyst-free and mild conditions was established.
文摘The Se-Se bond in diaryl diselenides was reduced by Zn/ZrCl4 system to produce selenide anions, which react with acyl chlorides or acid anhydrides to afford selenoesters in THF under mild and neutral conditions.
文摘The reduction of diacyl diselenides by samarium diiodide led to the production ofsamarium acylselenolates, which reacted with a,β-unsaturated esters or nitriles to give β-selenoesters or selenonitriles under mild and neutral conditions.
文摘KBr or NaCl is found to be a good catalyst in Se-Se bond cleavage of diselenides in the present of the oxidant mCPBA.The electrophilic addition of the in situ generated reactive electrophilic selenium species PhSeX（X = Br,Cl） to alkenes in AcOH provides a convenient access to 2-acetoxy-1-selenides.Compared with other catalysts,KBr or NaCl is less expensive and more environment-friendly.
基金supported by the National Natural Science Foundation of China(No.52301260)the National Science Foundation of Jiangsu Province(No.BK20230712)China Postdoctoral Science Foundation(No.2022M711686).
文摘The two-dimensional MoSe_(2)possesses a large interlayer spacing(0.65 nm)and a narrow bandgap(1.1 eV),showing potential in sodium-ion storage.However,it faces slow kinetics and volume stress during Na^(+)(de)intercalation process,thereby affecting the cycling stability and lifespan of sodium-ion batteries(SIBs).In this work,a novel approach involving anionic doping and structural design has been proposed,wherein a two-step in-situ selenization and surface thermal annealing doping process is applied to fabricate a novel configuration material of fluorine-doped MoSe_(2)@nitrogen-doped carbon nanosheets(F-MoSe_(2)@FNC).The obtained F-MoSe_(2)@FNC,benefiting from the dual advantages of structure and F-doping,synergistically promotes and accelerates the stable(de)intercalation of Na^(+).Henceforth,F-MoSe_(2)@FNC demonstrates notable characteristics in terms of reversible specific capacity,boasting a high initial coulombic efficiency of 76.97%,alongside remarkable rate capabilities and cyclic stability.The constructed F-MoSe_(2)@FNC anode-based half cell manifests exceptional longevity,enduring up to 2550 cycles at 10 A·g^(-1)with a specific capacity of 322.04 mAh·g^(-1).Its electrochemical performance surpasses that of MoSe_(2)@NC and Pure MoSe_(2),underscoring the significance of the proposed synergistic modulation.Through comprehensive kinetic analyses,encompassing in-situ electrochemical impedance spectroscopy(EIS),it is elucidated that the F-MoSe_(2)@FNC electrode showcases elevated pseudo-capacitance and rapid diffusion attributes during charge and discharge processes.Furthermore,the assembled full-cell(F-MoSe_(2)@FNC//Na_(3)V_(2)(PO_(4))_(3))attains a notable energy density of 166.94 Wh·kg^(-1).This design provides insights for the optimization of MoSe_(2)electrodes and their applications in SIBs.
基金supported by the National Research Foundation of Korea(NRF)(No.2021R1A2C1012176)support from the National Natural Science Foundation of China(No.62105018 and 61975007)+1 种基金the Fundamental Research Funds for the Central Universities 2021RC212Beijing Natural Science Foundation of China(Nos.Z190006 and 4222073).
文摘The transport properties of two-dimensional(2D)molybdenum diselenide(MoSe_(2))were comprehensively investigated.To understand experimental data,a detailed transport theory was developed by considering charged impurity,acoustic phonon,and optical phonon scatterings,and excellent quantitative agreements were obtained between theory and experiment.The observed metal-insulator transition(MIT)in MoSe_(2)is attributed to the screened Coulombic disorder arising from the random distribution of charged impurities in the semiconductor structures,indicating that MoSe_(2)2D MIT is a finite-temperature density-inhomogeneity-driven effective transition.We argue that the critical carrier density(nc)is sensitive to impurity density(ni)as a result of the competition with intrinsic phonons.Due to low impurity density,our devices show linear ohmic contact between the channel and electrodes.Furthermore,high performance MoSe_(2)all-2D photodetectors are fabricated by using a transparent electrode on a hexagonal boron nitride(hBN)substrate.The fabricated all-2D MoSe_(2)photodetectors demonstrate a substantial enhancement of photocurrent due to multiple reflections at the hBN and MoSe_(2)interface.Additionally,they exhibit a high photo-to-dark current ratio(1.1×10^(4)),high responsivity(3500 A/W),and high detectivity(5.8×10^(10)Jones).
基金supported by the National Natural Sci-ence Foundation of China(No.22174135,No.21790352)the National Key R&D Program of China(No.2021YFA1500500,No.2016YFA0200600)+4 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies(No.AHY090100)CAS Project for Young Scientists in Basic Research(No.YSBR-054)Innovation Program for Quantum Science and Technology(No.2021ZD0303301)the Fundamental Research Funds for the Central Universities.
文摘Double-resonance Raman(DRR)scattering in two-di-mensional(2D)materials describes the intravalley or intervalley scattering of an electron or a hole excited by incident photons.Although the presence of defects can provide additional momentum and influence the scat-tering process involving one or two phonons,only the idealized defects without any structural details are considered in tra-ditional DRR theory.Here,the second-order DRR spectra of WSe_(2) monolayer with different types of defects are calculated involving the combinations of acoustic and optical phonons in the vicinity of K(K')and M points of the Brillouin zone.The electronic band structures are modified due to the presence of defects,and the band unfolding method is adopted to show the bending of valence and conduction bands for the defective WSe_(2) monolayers.The associ-ated phononic band structures also exhibit different changes in phonon dispersion curves,re-sulting in different DRR spectra corresponding to the different types of defects in the WSe_(2) monolayers.For example,the existence of W vacancy in the WSe_(2) monolayer would result in downshifts in vibrational frequencies and asymmetrical broadenings in linewidths for most combination modes due to the dramatic changes in contour shape of electronic valleys at K and K'.Moreover,the scattering from K to Q is found to be forbidden for the two Se vacan-cies because of the elevation of conduction band at the Q point.Our work highlights the role of defect structures in the intervalley scattering and may provide better understanding in the underlying physics of DRR process in 2D materials.
基金Project supported by the National Natural Science Foundation of China(Grant No.61874108)the Fundamental Research Funds for the Central Universities(Grant No.lzujbky-2024-04)the Gansu Provincial Scientific and Technologic Planning Program(Grant No.22ZD6GE016).
文摘In order to investigate the effect of different doping types on the band alignment of heterojunctions,we prepared PtSe_(2)/n-GaN,PtSe_(2)/p-GaN,and PtSe_(2)/u-GaN heterojunctions by wet transfer technique.The valence band offsets(VBO)of the three heterojunctions were measured by x-ray photoelectron spectroscopy(XPS),while the PtSe_(2)/n-GaN is 3.70±0.15 eV,PtSe_(2)/p-GaN is 0.264±0.15 eV,and PtSe_(2)/u-GaN is 3.02±0.15 eV.The conduction band offset(CBO)of the three heterojunctions was calculated from the material bandgap and VBO,while the PtSe_(2)/n-GaN is 0.61±0.15 eV,PtSe_(2)/p-GaN is 2.83±0.15 eV,and PtSe_(2)/u-GaN is 0.07±0.15 eV.This signifies that both PtSe_(2)/u-GaN and PtSe_(2)/p-GaN exhibit type-Ⅰband alignment,but the PtSe_(2)/n-GaN heterojunction has type-Ⅲband alignment.This signifies that the band engineering of PtSe_(2)/GaN heterojunction can be achieved by manipulating the concentration and type of doping,which is significantly relevant for the advancement of related devices through the realization of band alignment and the modulation of the material properties of the PtSe_(2)/GaN heterojunction.
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs),which allow atomic-scale manipulation,have supe-rior electrical and optical properties that challenge the limits of traditional bulk semiconductors like silicon^([1,2]).As a repre-sentative TMD and a promising 2D channel material for high-performance,scalable p-type transistors,tungsten diselenide(WSe_(2))has attracted considerable academic and industrial interest for its potential in advanced complementary metal−oxide−semiconductor(CMOS)logic technology and in extending Moore’s Law^([3−7]).
基金the National Natural Science Foundation of China (No. 20072033) and the Specialized Research Fund for the Doctoral Program of Higher Education of China.
文摘Stereoselective Michael addition and Michael-aldol tandem reaction of diorganyl diselenides and disulfides with conjugated alkynones mediated by samarium diiodide were studied. The reaction temperature was critical for the stereoselectivity. -Organylselenoalkenones or -organylthioalkenones and ?-organylselenoallylic alcohols or ?-organylthioallylic alcohols were prepared in good yields.
基金supported by the Jilin Scientific and Technological Development Program(Grant No.20230101286JC)National Natural Science Foundation of China(Grant Nos.61975051,6227503,and 52002110)Hebei Provincial Department of Education Innovation Ability Training Funding Project for graduate students.
文摘The emergent two-dimensional(2D)material,tin diselenide(SnSe_(2)),has garnered significant consideration for its potential in image capturing systems,optical communication,and optoelectronic memory.Nevertheless,SnSe_(2)-based photodetection faces obstacles,including slow response speed and low normalized detectivity.In this work,photodetectors based on SnS/SnSe_(2)and SnSe/SnSe_(2)p−n heterostructures have been implemented through a polydimethylsiloxane(PDMS)−assisted transfer method.These photodetectors demonstrate broad-spectrum photoresponse within the 405 to 850 nm wavelength range.The photodetector based on the SnS/SnSe_(2)heterostructure exhibits a significant responsivity of 4.99×10^(3)A∙W^(−1),normalized detectivity of 5.80×10^(12)cm∙Hz^(1/2)∙W^(−1),and fast response time of 3.13 ms,respectively,owing to the built-in electric field.Meanwhile,the highest values of responsivity,normalized detectivity,and response time for the photodetector based on the SnSe/SnSe_(2)heterostructure are 5.91×10^(3)A∙W^(−1),7.03×10^(12)cm∙Hz^(1/2)∙W−1,and 4.74 ms,respectively.And their photodetection performances transcend those of photodetectors based on individual SnSe_(2),SnS,SnSe,and other commonly used 2D materials.Our work has demonstrated an effective strategy to improve the performance of SnSe_(2)-based photodetectors and paves the way for their future commercialization.
基金the K.N.Toosi University of Technology Research Council for financial assistance
文摘Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides in the presence of potassium t-butoxide. The advantages of this protocol include the use of readily available substrates and reagent and good yield of the products.
基金financial support from the National Natural Science Foundation of China(No.21902014)the Basic Frontier Research Project of Chongqing(No.Cstc2018jcyjAX0051)Hunan Provincial Natural Science Foundation of China(No.2019JJ20008)。
文摘An eco-friendly,sustainable and practical method for the efficient preparation of 5-organylselanyl uracils through the electrochemical selenylation of uracils and dio rganyl diselenides at room temperature under oxidant-and external electrolvte-free conditions was developed.
基金supported by the National Natural Science Foundation of China(51777215)National Natural Science Foundation of China(51775306)+1 种基金Beijing Municipal Natural Science Foundation(4192027)the Graduate Innovation Fund of China University of Petroleum(YCX2020097)。
文摘Two-dimensional material has been widely investigated for potential applications in sensor and flexible electronics.In this work,a self-powered flexible humidity sensing device based on poly(vinyl alcohol)/Ti_(3)C_(2)Tx(PVA/MXene)nanofibers film and monolayer molybdenum diselenide(MoSe2)piezoelectric nanogenerator(PENG)was reported for the first time.The monolayer MoSe_(2)-based PENG was fabricated by atmospheric pressure chemical vapor deposition techniques,which can generate a peak output of 35 mV and a power density of42 mW m^(-2).The flexible PENG integrated on polyethylene terephthalate(PET)substrate can harvest energy generated by different parts of human body and exhibit great application prospects in wearable devices.The electrospinned PVA/MXene nanofiber-based humidity sensor with flexible PET substrate under the driven of monolayer MoSe_(2) PENG,shows high response of~40,fast response/recovery time of 0.9/6.3 s,low hysteresis of 1.8%and excellent repeatability.The self-powered flexible humidity sensor yields the capability of detecting human skin moisture and ambient humidity.This work provides a pathway to explore the high-performance humidity sensor integrated with PENG for the self-powered flexible electronic devices.
基金supported by the National Natural Science Foundation of China(Grants51772082,51574117,and 51804106)the Research Projects of Degree and Graduate Education Teaching Reformation in Hunan Province(JG2018B031,JG2018A007)+1 种基金the Natural Science Foundation of Hunan Province(2019JJ30002,2019JJ50061)project funded by the China Postdoctoral Science Foundation(2017M610495,2018T110822)
文摘Rhenium diselenide(ReSe2) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability.In this study,ReSe2 nanoparticles encapsulated in carbon nanofibers were synthesized successfully with simple electrospinning and heat treatment.It was found that graphene modifications could affect considerably the microstructure and electrochemical properties of ReSe2–carbon nanofibers.Accordingly,the modified compound maintained a capacity of 227 mAhg-1 after 500cycles at 200 mAg-1 for Na+storage,230 mAh g-1 after 200 cycles at 200 mAg-1,212 mAh g-1 after 150 cycles at 500 mAg-1 for K+ storage,which corresponded to the capacity retention ratios of 89%,97%,and 86%,respectively.Even in Na+full cells,its capacity was maintained to 82% after 200 cycles at 1 C(117 mAg-1).The superior stability of ReSe2–carbon nanofibers benefitted from the extremely weak van der Waals interactions and large interlayer spacing of ReSe2,in association with the role of graphene-modified carbon nanofibers,in terms of the shortening of electron/ion transport paths and the improvement of structural support.This study may provide a new route for a broadened range of applications of other rhenium-based compounds.
