Despite the great success in the synthesis of binary covalent organic frameworks(COFs)in the past decade,the fabrication of structurally ordered ternary COFs remains a big challenge,due to the inevitable competition a...Despite the great success in the synthesis of binary covalent organic frameworks(COFs)in the past decade,the fabrication of structurally ordered ternary COFs remains a big challenge,due to the inevitable competition and exchange of monomers.Herein,two ternary ordered COFs(2Me-OMe-COF and Me-2OMe-COF)are successfully synthesized by two-step polymerization based on irreversible covalent bonds.In contrast to the ternary random COFs synthesized by one-pot method,ternary ordered COFs possess definite structures at the molecular level.Accordingly,we systematically compare the performance of the two ternary ordered COFs in photocatalytic H_(2)production with two corresponding binary COFs as controlled comparison.Significantly,they exhibit very different photocatalytic performance,highlighting the importance of component and structural order for their properties.This work provides a unique strategy to the targeted polymerization and synthesis of ternary ordered,or even multivariate ordered COFs.展开更多
The precise generation and harnessing of carbon magnetism at the single-molecule level have been captivating areas of research in chemistry and nanotechnology.However,the realization of magnetic nanographenes,also kno...The precise generation and harnessing of carbon magnetism at the single-molecule level have been captivating areas of research in chemistry and nanotechnology.However,the realization of magnetic nanographenes,also known as single-moleculeπ-magnets,through solution-based synthesis has proven challenging because of their high reactivity and insolubility tendency.Recent advancements in on-surface chemistry and scanning probe techniques have significantly propelled the fabrication of carbon-based magnetic nanostructures to offer a rich platform to probe quantumπ-magnetism at the single-molecule level.Atomic manipulation,also referred to as probe chemistry,stands as an exciting and essential approach in the toolbox of on-surface chemistry.This approach enables site-selective chemical reactions,thereby allowing for the atomically precise imprinting and tailoringπ-magnetism in a variety of nanographenes.This review highlights the recent achievements in the precise synthesis of single-moleculeπ-magnets using atomic manipulation.Furthermore,we also provide an outlook on the future of probe chemistry in the fabrication of this intriguing class of magnetic nanographenes,featuring designer quantum magnetism.展开更多
The scanning interference field exposure technique is an effective method to fabricate holographic diffraction grating with meter-level size and nano-level precision.The main problems of fabricating large-aperture and...The scanning interference field exposure technique is an effective method to fabricate holographic diffraction grating with meter-level size and nano-level precision.The main problems of fabricating large-aperture and high-precision grating by this technique are the high-precision displacement measurement of the stage,the high-precision control of the interference fringe and the real time compensation of the grating phase error.In this paper,the influence of grating groove error on the wavefront aberration is analyzed.In order to improve the precision of the stage with displacement range more than one meter,an integrated displacement measurement combining grating sensing and laser interferometry is proposed,which suppresses the influence of environment on measurement precision under long displacement range.An interference fringe measurement method is proposed,which combines the diffraction characteristics of the measuring grating with the phase-shifting algorithm.By controlling the direction,period and phase nonlinear errors of the interference fringe,high quality interference fringe can be obtained.Further,a dynamic phase-locking model is established by using heterodyne interferometry to compensate grating phase error caused by stage motion error in real time.A grating with the aperture of 1500mm×420mm is fabricated.The wavefront aberration reaches 0.327λ@632.8 nm and the wavefront gradient reaches 16.444 nm/cm.This research presents a novel technique for the fabrication of meter-level size and nano-level precision holographic grating,which would further promote the development of chirped pulse amplification systems,high-energy laser and ultra-high precision displacement measurement.展开更多
基金supported by the National Key Research and Development Program of China(2021YFA1500400)the National Natural Science Foundation of China(21725101,22205224,22205225,22161142001)+1 种基金China Postdoctoral Science Foundation(BX2021281,2021M703064)the Fundamental Research Funds for the Central Universities(WK3450000007,WK2060000038,WK2060000041,WK2060000045)。
文摘Despite the great success in the synthesis of binary covalent organic frameworks(COFs)in the past decade,the fabrication of structurally ordered ternary COFs remains a big challenge,due to the inevitable competition and exchange of monomers.Herein,two ternary ordered COFs(2Me-OMe-COF and Me-2OMe-COF)are successfully synthesized by two-step polymerization based on irreversible covalent bonds.In contrast to the ternary random COFs synthesized by one-pot method,ternary ordered COFs possess definite structures at the molecular level.Accordingly,we systematically compare the performance of the two ternary ordered COFs in photocatalytic H_(2)production with two corresponding binary COFs as controlled comparison.Significantly,they exhibit very different photocatalytic performance,highlighting the importance of component and structural order for their properties.This work provides a unique strategy to the targeted polymerization and synthesis of ternary ordered,or even multivariate ordered COFs.
基金support from MOE Tier 2 grants(MOE2019-T2-2-044 and MOE-T2EP10221-0005)Agency for Science,Technology and Research(A*STAR)under MTC Individual Research Grants(Project ID:M21K2c0113)the support from Agency for Science,Technology and Research(A*STAR)Advanced Manufacturing&Engineering(AME)Young Individual Research Grant(YIRG)A2084c0171.
文摘The precise generation and harnessing of carbon magnetism at the single-molecule level have been captivating areas of research in chemistry and nanotechnology.However,the realization of magnetic nanographenes,also known as single-moleculeπ-magnets,through solution-based synthesis has proven challenging because of their high reactivity and insolubility tendency.Recent advancements in on-surface chemistry and scanning probe techniques have significantly propelled the fabrication of carbon-based magnetic nanostructures to offer a rich platform to probe quantumπ-magnetism at the single-molecule level.Atomic manipulation,also referred to as probe chemistry,stands as an exciting and essential approach in the toolbox of on-surface chemistry.This approach enables site-selective chemical reactions,thereby allowing for the atomically precise imprinting and tailoringπ-magnetism in a variety of nanographenes.This review highlights the recent achievements in the precise synthesis of single-moleculeπ-magnets using atomic manipulation.Furthermore,we also provide an outlook on the future of probe chemistry in the fabrication of this intriguing class of magnetic nanographenes,featuring designer quantum magnetism.
基金supported by National Key R&D Program of China(2022YFB3606100)the National Natural Science Foundation of(62435019,52275554,U21A20509,61227901)+1 种基金CAS Project for Young Scientists in Basic Research(YSBR-103)Chinese Academy of Sciences Youth Innovation Promotion Association grant(2021220).
文摘The scanning interference field exposure technique is an effective method to fabricate holographic diffraction grating with meter-level size and nano-level precision.The main problems of fabricating large-aperture and high-precision grating by this technique are the high-precision displacement measurement of the stage,the high-precision control of the interference fringe and the real time compensation of the grating phase error.In this paper,the influence of grating groove error on the wavefront aberration is analyzed.In order to improve the precision of the stage with displacement range more than one meter,an integrated displacement measurement combining grating sensing and laser interferometry is proposed,which suppresses the influence of environment on measurement precision under long displacement range.An interference fringe measurement method is proposed,which combines the diffraction characteristics of the measuring grating with the phase-shifting algorithm.By controlling the direction,period and phase nonlinear errors of the interference fringe,high quality interference fringe can be obtained.Further,a dynamic phase-locking model is established by using heterodyne interferometry to compensate grating phase error caused by stage motion error in real time.A grating with the aperture of 1500mm×420mm is fabricated.The wavefront aberration reaches 0.327λ@632.8 nm and the wavefront gradient reaches 16.444 nm/cm.This research presents a novel technique for the fabrication of meter-level size and nano-level precision holographic grating,which would further promote the development of chirped pulse amplification systems,high-energy laser and ultra-high precision displacement measurement.
