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Chinese Physics Letters 2012年第6期29卷 238-241页

作者： MAO Han-qing LI Na CHEN Xi xue qi-kun State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Tsinghua UniversityBeijing 100084

Using a home-made Q-plus sensor,simultaneous scanning tunneling microscopy (STM) and atomic force microscopy (AFM) measurements were performed on the wedge-shaped Pb islands grown on Si(111)-7 × *** resolved AFM images were *** contrast of AFM topography shows no dependence on the sample bias (tip is grounded),while the simultaneously obtained tunneling current image exhibits strong bias dependence due to quantum well states (QWS).Furthermore,In the AFM mode,neighboring Pb films with one monolayer (ML) thickness difference within the same Pb island show the same apparent height,which means that the apparent step heights of Pb films oscillate with a bilayer periodicity,being consistent with previous observations by helium atom scattering,x-ray diffraction,and *** possible reasons underlying the oscillation of apparent step heights in AFM topography are discussed.

关键词： apparent tunneling neighboring

Modifying Quantum Well States of Pb Thin Films via Interface Engineering

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Chinese Physics Letters 2010年第6期27卷 160-163页

作者： FU Ying-Shuang JI Shuai-Hua ZHANG Tong CHEN Xi JIA Jin-Feng xue qi-kun MA Xu-Cun Institute of Physics Chinese Academy of Sciences Beijing 100190 Department of Physics Tsinghua University Beijing 100084

We demonstrate the importance of interface modification on improving electron confinement by preparing Pb quantum islands on Si（111） substrates with two different surface reconstructions, i.e., Si（111）-7 ×7 and Si（111）- Root3×Root3-Pb （hereafter, 7 ×7 and R3）. Characterization with scanning tunneling microscopy/spectroscopy shows that growing Pb films directly on a 7 × 7 surface will generate many interface defects, which makes the lifetime of quantum well states （QWSs） strongly dependent on surface locations. On the other hand, QWSs in Pb films on an R3 surface are well defined with small variations in linewidth on different surface locations and are much sharper than those on the 7 × 7 surface. We show that the enhancement in quantum confinement is primarily due to the reduced electron-defect scattering at the interface.

关键词： QUANTUM wells ENERGY levels (Quantum mechanics) METALLIC films INTERFACES (Physical sciences) QUARK confinement SILICA SCANNING tunneling microscopy SCATTERING (Physics)

X-Ray Photoelectron Spectroscopy Study of the Metal/Cermet Interface

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Chinese Physics Letters 2001年第1期18卷 94-96页

作者： LU Hua SHEN Dian-Hong xue qi-kun M.Polak N.Froumin Department of Materials Engineering Ben-Gurion University of the NegevIsrael

Interfacial reactions between aluminium and polycrystalline cermet TiC_(0.6) were investigated using x-ray photoelectron spectroscopy,Auger electron spectroscopy and x-ray *** was found that titanium exists in two chemical *** carbide and oxide of titanium can be detected simultaneously,and the atomic ratio of Ti:C:O is 5:3:*** suggests that TiC^(0.6) is a Ti-oxycarbide or oxygenated TiC composite:Ti_(5)C_(3)O_(2)(TiO_(2)+4TiC_(0.75)).When Al is deposited in vacuum on the Ti-oxycarbide surface,the active Al atoms react chemically only with TiO_(2) at room temperature,but not with Tico.75 in *** reaction products are Al2O3 and theintermetallic compound Als *** the Al/TiC_(0.6) interface at 750℃,Al reacts also with TiC_(0.75) to form a brittle Al_(4)C_(3) phase.

关键词： carbide diffraction. intermetallic

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基础研究突破与杰出人才培养

清华大学教育研究 2021年第3期42卷 1-6页

作者：薛其坤南方科技大学广东深圳518055 清华大学物理系北京100084

当今全球正处于百年未有之大变局,新科技革命、国家发展战略与高等教育变革等多因素历史地交汇在一起,各国科技竞争的新态势呼啸而至,使我国面临前所未有的机遇与挑战。本文旨在通过几个科学突破的例子,阐释加强基础研究人才培养的重要... 详细信息

当今全球正处于百年未有之大变局,新科技革命、国家发展战略与高等教育变革等多因素历史地交汇在一起,各国科技竞争的新态势呼啸而至,使我国面临前所未有的机遇与挑战。本文旨在通过几个科学突破的例子,阐释加强基础研究人才培养的重要性和战略意义,强调培养杰出人才需高度重视科学精神的塑造和学科规划等。

关键词：基础研究杰出人才强基计划学科规划

FeSe/SrTiO_(3)高温超导体中的电子条纹相

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物理学报 2022年第12期71卷 244-258页

作者：袁永浩薛其坤李渭清华大学低维量子物理国家重点实验室北京100084 清华大学量子信息前沿科学中心北京100084 北京量子信息科学研究院北京100193 南方科技大学深圳518055

单层FeSe/SrTiO_(3)中的界面超导增强是近年来高温超导领域的重要发现.该体系中SrTiO_(3)衬底对FeSe的超导增强机制已被广泛研究,其调控作用主要表现为两个方面:电荷掺杂和界面电声耦合.然而,关于FeSe薄膜本身的电子特性研究还不够充分... 详细信息

单层FeSe/SrTiO_(3)中的界面超导增强是近年来高温超导领域的重要发现.该体系中SrTiO_(3)衬底对FeSe的超导增强机制已被广泛研究,其调控作用主要表现为两个方面:电荷掺杂和界面电声耦合.然而,关于FeSe薄膜本身的电子特性研究还不够充分.本文介绍该体系超导增强机制的新进展:FeSe薄膜中的电子条纹相及其与超导的关联.通过扫描隧道显微镜结合分子束外延生长技术,对不同厚度的FeSe薄膜进行了系统研究.我们发现FeSe薄膜中电子倾向于排成条纹状结构,并观测到该条纹相随层厚变化显现出从短程到长程的演化.条纹相是一种电子液晶态,它源于薄层FeSe中被增强的电子关联作用.表面电子掺杂一方面会减弱FeSe薄膜中的电子关联作用,逐渐抑制条纹相;另一方面会诱导超导相变,而剩余的条纹相涨落会对超导电性带来额外增强.我们的结果加深了对低维界面超导体系的认识,也揭示了FeSe薄膜本征的特异性,完善了对FeSe/SrTiO_(3)超导增强机制的理解.

关键词：条纹相超导增强电子液晶态扫描隧道显微镜

3D-printable Boron Nitride/Polyacrylic Hydrogel Composites with High Thermal Conductivities

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Journal of Wuhan University of Technology(Materials Science) 2024年第5期39卷 1303-1310页

作者： DAI Jialei xue Bingyu qiAN qi HE Wenhao ZHU Chenglong LEI Liwen WANG kun XIE Jingjing Hubei Longzhong Laboratory Xiangyang 441000China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China

Polyacrylic acid(PAA)hydrogel composites with different hexagonal boron nitride(h-BN)fillers were synthesized and successfully 3D-printed while their thermal conductivity was systematically *** the content of h-BN increasing from 0.1 wt%to 0.3 wt%,the thermal conductivity of the 3D-printed composites has been ***,through the shear force given by the 3D printer,a complete thermal conductivity path is obtained inside the hydrogel,which significantly improves the thermal conductivity of the h-BN hydrogel *** maximum thermal conductivity is 0.8808 W/(m·K),leading to a thermal conductive enhancement of 1000%,compared with the thermal conductivity of pure PAA *** study shows that using h-BN fillers can effectively and significantly improve the thermal conductivity of hydrogelbased materials while its 3D-printable ability has been maintained.

关键词： hydrogel composites boron nitride 3D printing thermal conductivity

Manipulating guest-responsive spin transition to achieve switchable fluorescence in a Hofmann-type framework

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Science China Chemistry 2024年第10期67卷 3339-3346页

作者： xue-Ru Wu Shu-qi Wu Zhi-kun Liu Ming-Xing Chen Jun Tao Osamu Sato Hui-Zhong Kou Engineering Research Center of Advanced Rare Earth Materials (Ministry of Education) Department of ChemistryTsinghua University Institute for Materials Chemistry and Engineering & IRCCS Kyushu University Key Laboratory of Cluster Science of Ministry of Education School of Chemistry and Chemical EngineeringLiangxiang CampusBeijing Institute of Technology Analytical Instrumentation Center College of Chemistry and Molecular EngineeringPeking University

The change of fluorescence emission manipulated by spin state transition attracts considerable attention owing to its potential applications in magneto-optical switching ***,we report two two-dimensional（2D） Hofmann-type spin crossover（SCO） metal-organic frameworks（MOFs）[FeⅡ（PNI）2{AgⅠ（CN）2}2]·CHCl3（3Ag·CHCl3） and[FeⅡ（PNI）2{AuⅠ（CN）2}2]·CHCl3（3Au·CHCl3） based on the fluorescent ligand N-（4-pyridylmethyl）-1,8-naphthalimide（PNI）.Both complexes exhibit interesting SCO behaviors switched by guest solvent molecules,namely three-step transitions for the solvated complexes and complete onestep hysteretic SCO for the desolvated ones,verified by temperature-dependent magnetic susceptibility measurements,Mossbauer spectra,structural analyses,and differential scanning calorimetry ***,temperature-dependent fluorescence spectra exhibit double peaks（monomer and excimer emission） with both emission peaks change consistent with the change in SCO properties during the solvent molecule *** this study,we integrated guest-responsive SCO behavior into MOFs to manipulate the multistability of spin state and fluorescence switching,providing a rational strategy for the development of stimuli-responsive multifunctional materials.

关键词： spin crossover fluorescence multifunctional materials metal-organic frameworks Hofmann-type

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原子力显微镜中化学成键对力的贡献(英文)

物理化学学报 2014年第2期30卷 205-209页

作者：李娜陈曦薛其坤清华大学物理系低维量子物理国家重点实验室北京100084

迄今非接触原子力显微镜已经成为一个非常强大的工具.它不仅能够得到表面的原子周期结构,还能给出分子内部的化学键信息.针尖和样品之间的相互作用是原子力显微镜的有效信号,主要包括三种,即范德瓦尔斯相互作用、静电相互作用和化学键... 详细信息

迄今非接触原子力显微镜已经成为一个非常强大的工具.它不仅能够得到表面的原子周期结构,还能给出分子内部的化学键信息.针尖和样品之间的相互作用是原子力显微镜的有效信号,主要包括三种,即范德瓦尔斯相互作用、静电相互作用和化学键相互作用.本文在生长于Si(111)-7×7的铅薄膜上测量了针尖和样品之间的化学键相互作用.通过获取该相互作用随偏压的变化,并且利用抛物线拟合有效局域接触势的位置,我们发现它是随着针尖和样品之间距离的增大而减小的.这种趋势来自于针尖和样品之间波函数的交叠.从而可以得到电子的衰减长度.我们还测量到了该衰减长度随着铅薄膜厚度的变化会发生振荡,这种振荡归因于平顶楔形铅岛内电子的量子尺寸效应.

关键词：原子力显微镜 Q-plus传感器局域接触势化学键量子尺寸效应

An unprecedented synthesis of axially chiral biaryls by rearrangement and aromatization of carbocations with central-to-axial conversion of chirality

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Science China Chemistry 2024年第9期67卷 2998-3003页

作者： qi Liu xue-Dong Li Liang Cheng Li Liu Beijing National Laboratory for Molecular Sciences(BNLMS) CAS Key Laboratory of Molecular Recognition and FunctionCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

The central-to-axial chirality conversion represents a fascinating class of chemical processes consisting of the destruction of stereogenic centers and the simultaneous installation of axial chiral elements,which provides efficient methods for the preparation of axially chiral ***,developing catalytic asymmetric approaches for constructing these central chirality precursors and the efficient central-to-axial chirality conversion remains a challenge due to the requirement of aromatization or elimination *** this work,we have developed an unprecedented enantioselective intramolecular FriedelCrafts alkylation with unactivated-ketone carbonyls from which a chiral tertiary alcohol was generated with high efficiency and excellent *** addition,the central-to-axial chirality conversion strategy has been successfully applied to the synthesis of enantioenriched biaryls via a less-explored carbocation-initiated rearrangement and aromatization under the promotion of Lewis *** methodology provided a straightforward and sustainable access to a broad range of biaryl-2-carboxylic acid and in excellent yields(up to 92%)and excellent central-to-axial chirality conversion(up to 99%conversion percentage).This work could be a great model for developing new methods for synthesizing axially chiral biaryls and a general protocol for the rearrangement and aromatization of carbocations for further functionalization.

关键词： br?nsted acid catalysis desymmetrization phosphoric acid axially chiral biaryls central-to-axial conversion

Tendencies of alloyed engineering in BiOX-based photocatalysts:a state-of-the-art review

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Rare Metals 2024年第4期43卷 1488-1512页

作者： Yan-Dong Sun Chao Zeng xue Zhang Zi-qi Zhang Bo Yang Sheng-qi Guo Tianjin Key Laboratory of Clean Energy and Pollutant Control School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China State-Province Joint Engineering Laboratory of Zeolite Membrane Materials Institute of Advanced MaterialsCollege of Chemistry and Chemical EngineeringJiangxi Normal UniversityNanchang330022China Anhui Province Key Laboratory of Pollutant Sensitive Materials and Environmental Remediation School of Physics and Electronic InformationAnhui Province Industrial Generic Technology Research Center for Alumics MaterialsHuaibei Normal UniversityHuaibei235000China

Energy-saving and environmentally friendly photocatalysis has emerged as a popular research area in response to issues with energy scarcity and environmental *** to the unique layer-like structure,BiOX(Cl,Br,I)is frequently used in ***,inherent flaws in BiOX,such as an inappropriate band gap and low carrier separation efficiency,restrict its capacity for *** to the tunable grouping layer,alloying engineering is employed to optimize the intrinsic properties of BiOX and alloyed BiOX becomes a promising photocatalytic *** review describes the structure of BiOX,where tunable halogen layers provide favorable conditions for the implementation of alloying engineering to improve intrinsic *** article compares the effects and mechanisms of alloying engineering on the optimization of the energy band structure and carrier behavior of BiOX,and lists various modification methods used to improve the optimization of the intrinsic properties by alloying engineering,including defect engineering,morphology control as well as the synergy between alloying and other modification methods(bismuth-rich strategies,cation doping,construction of heterojunctions and plasma resonance effects).Subsequently,applications of alloyed BiOX in energy and environmental fields are summarized,including contaminant degradation,antibacterial,CO_(2)reduction,nitrogen fixation and organic ***,we summarize the current challenges and future directions of alloyed *** is expected that this work will provide guidance and assistance for an in-depth study and understanding of the mechanisms of alloying engineering to optimize intrinsic properties and design alloyed BiOX with higher photocatalytic activity.

关键词： Bismuth oxyhalide Photocatalytic Alloyed engineering Microstructural regulation Application