Comprehensive Summary Carbohelicenes have garnered considerable attention for their inherent chirality and structural flexibility.Increasing multi-helicity and incorporating non-six-membered rings to substitute benzen...Comprehensive Summary Carbohelicenes have garnered considerable attention for their inherent chirality and structural flexibility.Increasing multi-helicity and incorporating non-six-membered rings to substitute benzenoid rings within helicenes are effective strategies for introducing unique photoelectric properties.Despite the disclosure of numerous helicenes,the inaccessible precursors and the lack of synthetic routes pose a challenge in achieving desired helicene structures fused with non-benzenoid rings.Herein,we report the synthesis of multiple non-benzenoid carbohelicenes fused with fluorene unit(s)through intramolecular cyclodehydrogenation of 9,10-di(naphthalen-1-yl)anthracene on Au(111)surface.Two potential cyclodehydrogenation manners between naphthyl and anthracene lead to the formation of fluorene-fused[5]helicene and[4]helicene moiety.Consequently,a total of four stable products were observed.The atomic topographies of products are characterized by bond-resolving scanning tunneling microscopy.The chiral helicity of targeted products can be switched by tip manipulation.Density-functional-theory calculations unveils the reaction pathway of four products.The comparative analysis of their respective energy barriers exhibits a correlation with the experimentally determined yields.Furthermore,we synthesize the polymer chains incorporating non-benzenoid carbohelicenes via the Ullmann reaction of 2,6-dibromo-9,10-di(1-naphthyl)anthracene precursors.Our work proposes a synthetic methodology for several novel helicene-like structures fused with fluorene units and the polymer bearing helicene subunits,thus highlighting the immense potential of these compounds in the application fields of luminescent electronic devices.展开更多
Strain engineering is a vital way to manipulate the electronic properties of two-dimensional(2D)materials.As a typical representative of transition metal mono-chalcogenides(TMMs),a honeycomb CuSe monolayer features wi...Strain engineering is a vital way to manipulate the electronic properties of two-dimensional(2D)materials.As a typical representative of transition metal mono-chalcogenides(TMMs),a honeycomb CuSe monolayer features with one-dimensional(1D)moirépatterns owing to the uniaxial strain along one of three equivalent orientations of Cu(111)substrates.Here,by combining low-temperature scanning tunneling microscopy/spectroscopy(STM/S)experiments and density functional theory(DFT)calculations,we systematically investigate the electronic properties of the strained CuSe monolayer on the Cu(111)substrate.Our results show the semiconducting feature of CuSe monolayer with a band gap of 1.28 eV and the 1D periodical modulation of electronic properties by the 1D moirépatterns.Except for the uniaxially strained CuSe monolayer,we observed domain boundary and line defects in the CuSe monolayer,where the biaxial-strain and strain-free conditions can be investigated respectively.STS measurements for the three different strain regions show that the first peak in conduction band will move downward with the increasing strain.DFT calculations based on the three CuSe atomic models with different strain inside reproduced the peak movement.The present findings not only enrich the fundamental comprehension toward the influence of strain on electronic properties at 2D limit,but also offer the benchmark for the development of 2D semiconductor materials.展开更多
Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of ...Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.展开更多
Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-...Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-dibromochrysene(DBCh),we successfully constructed and characterized the large-area two-dimensional chiral networks on Au(111)and one-dimensional metal-liganded chiral chains on Cu(111)respectively.The reasons and processes of chiral transformation of chiral networks on Au(111)were analyzed.We used scanning tunneling spectroscopy(STS)to analyze the electronic state information of this chiral structure.This work combines scanning tunneling microscopy(STM)with non-contact atomic force microscopy(nc-AFM)techniques to achieve ultra-high-resolution characterization of chiral structures on low-dimensional surfaces,which may be applied to the bond analysis of functional nanofilms.Density functional theory(DFT)was used to simulate the adsorption behavior of the molecular and energy analysis in order to verify the experimental results.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62271238,22372074,62301240)Yunnan Fundamental Research Projects(Nos.202201AT070078,202201BE070001-009 and 202301AW070017)+3 种基金the Major Basic Research Project of Science and Technology of Yunnan(202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(202305AS350017)Graphene Application and Engineering Research Centre of Education Department of Yunnan Providence(KKPP202351001)the Analysis and Testing Foundation of KUST(2021T20170056).
文摘Comprehensive Summary Carbohelicenes have garnered considerable attention for their inherent chirality and structural flexibility.Increasing multi-helicity and incorporating non-six-membered rings to substitute benzenoid rings within helicenes are effective strategies for introducing unique photoelectric properties.Despite the disclosure of numerous helicenes,the inaccessible precursors and the lack of synthetic routes pose a challenge in achieving desired helicene structures fused with non-benzenoid rings.Herein,we report the synthesis of multiple non-benzenoid carbohelicenes fused with fluorene unit(s)through intramolecular cyclodehydrogenation of 9,10-di(naphthalen-1-yl)anthracene on Au(111)surface.Two potential cyclodehydrogenation manners between naphthyl and anthracene lead to the formation of fluorene-fused[5]helicene and[4]helicene moiety.Consequently,a total of four stable products were observed.The atomic topographies of products are characterized by bond-resolving scanning tunneling microscopy.The chiral helicity of targeted products can be switched by tip manipulation.Density-functional-theory calculations unveils the reaction pathway of four products.The comparative analysis of their respective energy barriers exhibits a correlation with the experimentally determined yields.Furthermore,we synthesize the polymer chains incorporating non-benzenoid carbohelicenes via the Ullmann reaction of 2,6-dibromo-9,10-di(1-naphthyl)anthracene precursors.Our work proposes a synthetic methodology for several novel helicene-like structures fused with fluorene units and the polymer bearing helicene subunits,thus highlighting the immense potential of these compounds in the application fields of luminescent electronic devices.
基金the National Natural Science Foundation of China(Nos.62271238 and 61901200)the Yunnan Fundamental Research Projects(Nos.202201AT070078,202101AV070008,202101AW070010,and 202101AU070043)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(XDB30000000)the Analysis and Testing Foundation of KUST(2021T20170056)the Dongguan Innovation Research Team Program.Numerical computations were performed on Hefei advanced computing center.
文摘Strain engineering is a vital way to manipulate the electronic properties of two-dimensional(2D)materials.As a typical representative of transition metal mono-chalcogenides(TMMs),a honeycomb CuSe monolayer features with one-dimensional(1D)moirépatterns owing to the uniaxial strain along one of three equivalent orientations of Cu(111)substrates.Here,by combining low-temperature scanning tunneling microscopy/spectroscopy(STM/S)experiments and density functional theory(DFT)calculations,we systematically investigate the electronic properties of the strained CuSe monolayer on the Cu(111)substrate.Our results show the semiconducting feature of CuSe monolayer with a band gap of 1.28 eV and the 1D periodical modulation of electronic properties by the 1D moirépatterns.Except for the uniaxially strained CuSe monolayer,we observed domain boundary and line defects in the CuSe monolayer,where the biaxial-strain and strain-free conditions can be investigated respectively.STS measurements for the three different strain regions show that the first peak in conduction band will move downward with the increasing strain.DFT calculations based on the three CuSe atomic models with different strain inside reproduced the peak movement.The present findings not only enrich the fundamental comprehension toward the influence of strain on electronic properties at 2D limit,but also offer the benchmark for the development of 2D semiconductor materials.
基金supported by the National Natural Science Foundation of China(Nos.62271238,22372074,62301240)Yunnan Fundamental Research Projects(Nos.202201AT070078,202201BE070001-009 and 202301AW070017)+2 种基金the Major Basic Research Project of Science and Technology of Yunnan(202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(202305AS350017)Graphene Application and Engineering Research Centre of Education Department of Yunnan Providence(KKPP202351001).
文摘Comprehensive Summary Kagome lattices have garnered significant attention due to their promising applications in catalysis,electronics,and magnetics.Although many efforts have been paid to the design and synthesis of Kagome lattices,there is a limited focus on constructing this lattice by multiple interaction forces.In this work,we employ 2,7-dibromo-carbazole as precursors to successfully fabricate the two-dimensional self-assembly Kagome lattices stabled by multiple interaction forces on Au(111)substrate.Using low-temperature scanning tunneling microscopy,non-contact atomic force microscopy and density functional theory calculation,we visualize and identify the four interaction forces within Kagome lattices:Au—N coordination bonds,Au—H hydrogen bonds,Br—Br halogen bonds,and Br—H hydrogen bonds,respectively.This study provides a basic understanding for designing and constructing more complex Kagome lattices.
基金supported by the National Natural Science Foundation of China(Nos.51861020,61901200 and 12064020)the National Recruitment Program for Young Professionals(No.132310976002)+4 种基金the Yunnan Province Science and Technology Plan Project(No.2019FD041)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB30010000)the Reserve Talents for Yunnan Young and Middle Aged Academic and Technical Leaders(No.2017HB010)the Yunnan Province for Recruiting High-Caliber Technological Talents(No.1097816002)Yunnan Fundamental Research Projects(No.202101AU070043).
文摘Nanoscale low-dimensional chiral architectures are increasingly receiving scientific interest,because of their potential applications in many fields such as chiral recognition,separation and transformation.Using 6,12-dibromochrysene(DBCh),we successfully constructed and characterized the large-area two-dimensional chiral networks on Au(111)and one-dimensional metal-liganded chiral chains on Cu(111)respectively.The reasons and processes of chiral transformation of chiral networks on Au(111)were analyzed.We used scanning tunneling spectroscopy(STS)to analyze the electronic state information of this chiral structure.This work combines scanning tunneling microscopy(STM)with non-contact atomic force microscopy(nc-AFM)techniques to achieve ultra-high-resolution characterization of chiral structures on low-dimensional surfaces,which may be applied to the bond analysis of functional nanofilms.Density functional theory(DFT)was used to simulate the adsorption behavior of the molecular and energy analysis in order to verify the experimental results.
