检索结果-南通市图书馆

Energy band engineering via“Bite”defect located on N=8 armchair graphene nanoribbons

在线全文

学校读者我要写书评

暂无评论

Nano Research 2022年第1期15卷 653-658页

作者： Shijie Sun Yurou Guan Zhenliang Hao Zilin Ruan Hui Zhang jianchen lu Lei Gao Xiaoqing Zuo Jinming Cai Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650000China Faculty of Science Kunming University of Science and TechnologyKunming 650000China

Graphene nanoribbons(GNRs)not only share many superlative properties of graphene but also display an exceptional degree of tunability of their electronic properties.The bandgaps of GNRs depend greatly on their widths,edges,etc.Herein,we report the synthesis path and the physical properties of atomic accuracy staggered narrow N=8 armchair graphene nanoribbons(sn-8AGNR)with alternating"Bite"defects on the opposite side.The intermediate structures in the surface physicochemical reactions from the precursors to the sn-8AGNR are characterized by scanning tunneling microscopy.The electronic properties of the sn-8AGNR are characterized by scanning tunneling spectroscopies and 6//6V mappings.Compared with the perfect N=8 armchair graphene nanoribbons(8AGNR),the sn-8AGNR has a larger bandgap,indicating that the liB\Xen edges can effectively regulate the electronic structures of GNRs.

关键词： graphene nanoribbons(GNRs) scanning tunneling spectroscopy(STS) non-contact atomic force microscopy(NC-AFM) density functional theory(DFT) energy band regulation

Magnetism engineering of nanographene:An enrichment strategy by co-depositing diverse precursors on Au(111)

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2023年第1期34卷 206-210页

作者： Hui Zhang jianchen lu Yong Zhang Lei Gao Xin-Jing Zhao Yuan-Zhi Tan Jinming Cai School of Pharmacy China Pharmaceutical UniversityNanjing 211198China Jiangsu Aosaikang Pharmaceutical Co. Ltd.Nanjing 211112China Key Laboratory of Modern Preparation of TCM Ministry of EducationJiangxi University of Chinese MedicineNanchang 330004China

The magnetism of nanographene is dominated by the structure of its carbon skeleton.However,the magnetism engineering of nanographene is hindered due to finite precursors.Here,we demonstrate an ingenious synthetic strategy to engineer the magnetism of nanographene through hetero-coupling two precursors on Au(111)surface.Bond-resolved scanning tunneling microscopy and spectroscopy results show that two homo-coupled products host a closed-shell structure,while the products with five membered ring defects perform as an open-shell one with the total spin number of 1/2,confirmed by spin-polarized density functional theory calculations.While two hetero precursors on Au(111)substrate,the heterocoupled products both perform as the magnetic structure with total spin quantum numbers of 1/2 and 1,resulting from carbon skeleton transformations.Our work provides an effective way to engineer the magnetism of nanographene by enriching the magnetic products simultaneous,which could be extended into other controllable magnetic nanographene instruction.

关键词： Nanographene Magnetism enrichment Co-deposition Scanning tunneling microscope

Intrinsically patterned corrals in monolayer Ag_(5)Se_(2) and selective molecular co-adsorption

在线全文

学校读者我要写书评

暂无评论

Nano Research 2022年第7期15卷 6730-6735页

作者： jianchen lu Shiru Song Shuai Zhang Yang Song Yun Cao Zhenyu Wang Li Huang Hongliang lu Yu-Yang Zhang Sokrates T.Pantelides Shixuan Du Xiao Lin Hong-Jun Gao Institute of Physics&University of Chinese Academy of Sciences Chinese Academy of SciencesBeijing 100190China Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science Vanderbilt UniversityNashvilleTN 37235USA CAS Center for Excellence in Topological Quantum Computation Chinese Academy of SciencesBeijing 100190China Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunmingYunnan 650093China

Functionalized two-dimensional(2D)materials play an important role in both fundamental sciences and practical applications.The construction and precise control of patterns at the atomic-scale are necessary for selective and multiple functionalization.Here we report the fabrication of monolayer pentasilver diselenide(Ag_(5)Se_(2)),a new type of intrinsically patterned 2D material,by direct selenization of a Ag(111)surface.The atomic arrangement is determined by a combination of scanning tunneling microscopy(STM),low-energy electron diffraction(LEED),and density-functional-theory(DFT)calculations.Large-scale STM images exhibit a quasi-periodic pattern of stoichiometric triangular domains with a side length of~15 nm and apical offsets.The boundaries between triangular domains are sub-stoichiometric.Deposition of different molecules on the patterned Ag_(5)Se_(2) exhibits selective adsorption behavior.Pentacene molecules preferentially adsorb on the boundaries,while tetracyanoquinodimethane(TCNQ)molecules adsorb both on the boundaries and the triangular domains.By co-depositing pentacene and TCNQ molecules,we successfully construct molecular corrals with pentacene on the boundaries encircling TCNQ molecules on the triangular domains.The realization of epitaxial large-scale and high-quality,monolayer Ag_(5)Se_(2) extends the family of intrinsically patterned 2D materials and provides a paradigm for dual functionalization of 2D materials.

关键词： two-dimensional materials dual functionalization scanning tunneling microscope epitaxial growth Ag_(5)Se_(2)monolayer

Electronic properties of monolayer copper selenide with one-dimensional moirépatterns

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of physics 2023年第1期18卷 133-139页

作者： Gefei Niu jianchen lu Jianqun Geng Shicheng Li Hui Zhang Wei Xiong Zilin Ruan Yong Zhang Boyu Fu Lei Gao Jinming Cai Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650093China Faculty of Science Kunming University of Science and TechnologyKunming 650500China

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.

关键词： CuSe monolayer scanning tunneling microscopy strain electronic bandgap electronic property

Chiral structures of 6,12-dibromochrysene on Au(111)and Cu(111)surfaces

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Chemical Letters 2022年第12期33卷 5142-5146页

作者： Shijie Sun Baijin Li Boyu Fu Zilin Ruan Hui Zhang Wei Xiong Yong Zhang Gefei Niu jianchen lu Xiaoqing Zuo Lei Gao Jinming Cai Faculty of Materials Science and Engineering Kunming University of Science and TechnologyKunming 650000China Faculty of Science Kunming University of Science and TechnologyKunming 650000China

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.

关键词： Scanning tunneling microscope Scanning tunneling spectroscopy Non-contact atomic force microscope Surface chirality Chiral transition

Sulfur-doped graphene nanoribbons with a sequence of distinct band gaps

在线全文

学校读者我要写书评

暂无评论

Nano Research 2017年第10期10卷 3377-3384页

作者： Yan-Fang Zhang Yi Zhang Geng Li jianchen lu Yande Que Hui Chen Reinhard Berger Xinliang Feng Klaus Müllen Xiao Lin Yu-Yang Zhang Shixuan Du Sokrates T. Pantelides Hong-Jun Gao Institute of Physics & University of Chinese Academy of Sciences Chinese Academy of Sciences Beijing 100190 China Max Planck Institute for Polymer Research Ackermannweg 10 D-55128 Mainz Germany Center for Advancing Electronics Dresden (cfaed) & Department of Chemistry and Food Chemistry Technische Universitat Dresden D-01069 Dresden Germany School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science Vanderbilt University Nashville Tennessee 37235 USA

Unlike graphene sheets, graphene nanoribbons （GNRs） can exhibit semiconducting band gap characteristics that can be tuned by controlling impurity doping and the GNR widths and edge structures. However, achieving such control is a major challenge in the fabrication of GNRs. Chevron-type GNRs were recently synthesized via surface-assisted polymerization of pristine or N-substituted oligophenylene monomers. In principle, GNR heterojunctions can be fabricated by mixing two different monomers. In this paper, we report the fabrication and characterization of chevron-type GNRs using sulfur-substituted oligophenylene monomers to produce GNRs and related heterostructures for the first time. First-principles calculations show that the GNR gaps can be tailored by applying different sulfur configurations from cyclodehydrogenated isomers via debromination and intramolecular cyclodehydrogenation. This feature should enable a new approach for the creation of multiple GNR heterojunctions by engineering their sulfur configurations. These predictions have been confirmed via scanning tunneling microscopy and scanning tunneling spectroscopy. For example, we have found that the S-containing GNRs contain segments with distinct band gaps, i.e., a sequence of multiple heterojunctions that results in a sequence of quantum dots. This unusual intraribbon heterojunction sequence may be useful in nanoscale optoelectronic applications that use quantum dots.

关键词： bottom-up fabrication chevron-type graphene nanoribbons nanoscale quantum dots scanning tunneling microscopy density functional theory

气候变暖背景下陕西猕猴桃温度适宜度变化特征分析

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

中国农学通报 2024年第11期40卷 103-111页

作者：刘建辰屈振江黄俊芳张勇刘璐梁轶陕西省气象干部培训学院西安710016 陕西省农业遥感与经济作物气象服务中心西安710016

为分析气候变暖背景下陕西猕猴桃温度适宜度的变化特征,为陕西猕猴桃产业适应气候变化提供科学依据和参考,提升陕西猕猴桃产业可持续发展能力。根据陕西猕猴桃全生育期温度适宜度函数,分析评价华县、眉县、城固3个代表县1961—2010年的... 详细信息

为分析气候变暖背景下陕西猕猴桃温度适宜度的变化特征,为陕西猕猴桃产业适应气候变化提供科学依据和参考,提升陕西猕猴桃产业可持续发展能力。根据陕西猕猴桃全生育期温度适宜度函数,分析评价华县、眉县、城固3个代表县1961—2010年的猕猴桃温度适宜度,并利用RCPs排放情景下的气候变化预估数据对2016—2060年的陕西猕猴桃温度适宜度进行预估。研究表明:1961—2010年陕西猕猴桃温度适宜度呈2—3年缓慢波动变化趋势,1992年后猕猴桃温度适宜度呈升高的趋势;未来在中等和高排放情景下,陕西猕猴桃温度适宜度呈缓慢波动上升趋势,且高排放情景下猕猴桃温度适宜度的趋势强度要强于中等排放情景;中等和高排放情景下陕西猕猴桃温度适宜度分布较1961—2010年均有不同程度北移,除渭北东部地区猕猴桃温度适宜度升高较为明显外,关中和陕南的猕猴桃温度适宜度均有所下降,原有的适宜区范围缩小较为明显,且高排放情景下更为显著。未来陕西猕猴桃产业发展可考虑种植适度北移,同时考虑未来增温对猕猴桃产业造成的威胁,尤其是关中和陕南猕猴桃产区猕猴桃温度适宜度存在下降风险,高温热害对猕猴桃的威胁可能逐步上升。研究结果可为今后陕西猕猴桃产业的布局调整提供一定参考。

关键词：气候变化猕猴桃温度适宜度预估

在线全文

学校读者我要写书评

暂无评论

结合轻量化骨干与多尺度融合的单阶段检测器

中国图象图形学报 2022年第12期27卷 3596-3607页

作者：黄健宸王晗卢昊北京林业大学信息学院北京100083 国家林业和草原局林业智能信息处理工程技术研究中心北京100083

目的基于卷积神经网络的单阶段目标检测网络具有高实时性与高检测精度,但其通常存在两个问题:1)模型中存在大量冗余的卷积计算;2)多尺度特征融合结构导致额外的计算开销。这导致单阶段检测器需要大量的计算资源,难以在计算资源不足的设... 详细信息

目的基于卷积神经网络的单阶段目标检测网络具有高实时性与高检测精度,但其通常存在两个问题:1)模型中存在大量冗余的卷积计算;2)多尺度特征融合结构导致额外的计算开销。这导致单阶段检测器需要大量的计算资源,难以在计算资源不足的设备上应用。针对上述问题,本文在YOLOv5(you only look once version 5)的结构基础上,提出一种轻量化单阶段目标检测网络架构,称为E-YOLO(efficient-YOLO)。方法利用E-YOLO架构构建了E-YOLOm(efficient-YOLO medium)与E-YOLOs(efficient-YOLO small)两种不同大小的模型。首先,设计了多种更加高效的特征提取模块以减少冗余的卷积计算,对模型中开销较大的特征图通过下采样、特征提取、通道升降维与金字塔池化进行了轻量化设计。其次,为解决多尺度特征融合带来的冗余开销,提出了一种高效多尺度特征融合结构,使用多尺度特征加权融合方案减少通道降维开销,设计中层特征长跳连接缓解特征流失。结果实验表明,E-YOLOm、E-YOLOs与YOLOv5m、YOLOv5s相比,参数量分别下降了71.5%和61.6%,运算量下降了67.3%和49.7%。在VOC(visual object classes)数据集上的平均精度(average precision,AP),E-YOLOm比YOLOv5m仅下降了2.3%,E-YOLOs比YOLOv5s提升了3.4%。同时,E-YOLOm的参数量和运算量相比YOLOv5s分别低15.5%与1.7%,mAP@0.5和AP比其高3.9%和11.1%,具有更小的计算开销与更高的检测效率。结论本文提出的E-YOLO架构显著降低了单阶段目标检测网络中冗余的卷积计算与多尺度融合开销,且具有良好的鲁棒性,并优于对比网络轻量化方案,在低运算性能的环境中具有重要的实用意义。

关键词：卷积神经网络(CNN) 目标检测模型轻量化注意力模块多尺度融合

在线全文

学校读者我要写书评

暂无评论

超高真空下纳米石墨烯磁性及调控

化学进展 2022年第3期34卷 557-567页

作者：张辉熊玮卢建臣蔡金明昆明理工大学材料科学与工程学院昆明650093

纳米石墨烯在磁学上的优异表现开始获得了更多的关注和研究。由于不饱和电子的存在,磁性纳米石墨烯的湿法化学法合成难度提高,借助超高真空下的表面催化,可以精确地实现将设计好的前驱体分子向磁性纳米石墨烯转变。相较于过渡金属的磁性... 详细信息

纳米石墨烯在磁学上的优异表现开始获得了更多的关注和研究。由于不饱和电子的存在,磁性纳米石墨烯的湿法化学法合成难度提高,借助超高真空下的表面催化,可以精确地实现将设计好的前驱体分子向磁性纳米石墨烯转变。相较于过渡金属的磁性,纳米石墨烯拥有更高的自旋波刚度、更弱的自旋-轨道耦合作用、更为精细的耦合作用、更长的自旋寿命,使其在自旋电子器件以及基础研究领域拥有很高的研究潜力。由于不饱和电子的存在,提高了湿法化学法合成出磁性纳米石墨烯的难度。近年来,借助超高真空下的表面催化,可以精确地实现将设计好的前驱体分子制备成磁性纳米石墨烯。进一步地,可以利用通过针尖操纵以及将磁性纳米石墨烯进行连接形成二聚体或者磁性链来进行磁性调控和研究。本综述结合近几年超高真空下纳米石墨烯的磁性研究,介绍了纳米石墨磁性的产生和利用超高真空扫描隧道显微技术对其结构和磁性的表征,以及在此基础上对纳米石墨烯磁性的磁序调控。

关键词：纳米石墨烯磁性调控扫描隧道显微镜