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Advances in electrokinetics revealed in graphene

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National Science Review 2015年第1期2卷 17-18页

作者： zhongfan liu College of Chemistry and Molecular Engineering Peking University

Since the early 19th century,electrokinetic phenomena such as electrophoresis,electroosmosis and streaming potential have been observed and have played important roles in modern industry from

关键词： Advances in electrokinetics revealed in graphene Nature

Movement of Dirac points and band gaps in graphyne under rotating strain

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Nano Research 2017年第6期10卷 2005-2020页

作者： Zhenzhu Li zhongfan liu Zhirong liu College of Chemistry and Molecular Engineering Center for Nanochemistry State Key Laboratory for Structure Chemistry of Unstableand Stable Species and Beijing National Laboratory for Molecular Sciences (BNLMS) Peking University Beijing 100871 China

The introduction of lattice anisotropy causes Dirac cones to shift in response to the applied strain, leaving a pseudogap at the original Dirac points. Here, a group-theory analysis is combined with first-principles calculations to reveal the movement characteristics of Dirac points and band gaps in various graphynes under rotating uniaxial and shear strains. Graphene, where linear effects dominate, is different from α-,β-, and γ-graphynes, which generate strong nonlinear responses due to their bendable acetylenic linkages. However, the linear components of the electronic response, which are essential in determining material performance such as intrinsic carrier mobility due to electron-phonon coupling, can be readily separated, and are well described by a unified theory. The movement of the Dirac points in α-graphyne is circular under a rotating strain, and the pseudogap opening is isotropic with a magnitude of only 2% that in graphene. In comparison, the movement in β-graphyne is elliptical and the center is displaced from the origin. For γ-graphyne, three branches of gaps change with the applied strains with a sine/cosine dependence on the strain angle. The developed methodology is useful in determining the electronic response to various strains of Dirac materials and two-dimensional semiconductors,

关键词： graphene graphyne Dirac point band gap first-principles strain effect

Natural Biopolymers for Flexible Sensing and Energy Devices

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Chinese Journal of Polymer Science 2020年第5期38卷 459-490,I0006页

作者： Muqiang Jian Yingying Zhang zhongfan liu Center for Nanochemistry Beijing Science and Engineering Center for NanocarbonsBeijing National Laboratory for Molecular SciencesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Beijing Graphene Institute Beijing 100095China Key Laboratory of Organic Optoelectronics and Molecular Engineering of the Ministry of Education Department of ChemistryTsinghua UniversityBeijing 100084China

Natural biopolymers feature natural abundance,diverse chemical compositions,tunable properties,easy processability,excellent biocompatibility and biodegradability,as well as nontoxicity,providing new opportunities for the development of flexible sensing and energy ***,biopolymers are utilized as the passive and active building blocks to endow the flexible devices with mechanical robustness and good *** review aims to provide a comprehensive review on natural biopolymer-based sensing and energy *** diverse structures and fabrication processes of three typical biopolymers,including silk,cellulose,and chitin/chitosan,are *** review their utilities as the supporting substrates/matrix,active middle layers,separators,electrolytes,and active components of flexible sensing devices(sensors,actuators,transistors)and energy devices(batteries,supercapacitors,triboelectric nanogenerators).Finally,the remaining challenges and future research opportunities are discussed.

关键词： Biopolymers Silk Cellulose Electronics Energy devices

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The rare two-dimensional materials with Dirac cones

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National Science Review 2015年第1期2卷 22-39页

作者： Jinying Wang Shibin Deng zhongfan liu Zhirong liu Center for Nanochemstry Colledge of Chemistry and Molecular EngineeringPeking University

Inspired by the great development of graphene, more and more research has been conducted to seek new two-dimensional(2D) materials with Dirac cones. Although 2D Dirac materials possess many novel properties and physics, they are rare compared with the numerous 2D materials. To provide explanation for the rarity of 2D Dirac materials as well as clues in searching for new Dirac systems, here we review the recent theoretical aspects of various 2D Dirac materials, including graphene, silicene, germanene,graphynes, several boron and carbon sheets, transition-metal oxides(VO2)n/(TiO2)m and(CrO2)n/(TiO2)m, organic and organometallic crystals, so-MoS2, and artiicial latices(electron gases and ultracold atoms). heir structural and electronic properties are summarized. We also investigate how Dirac points emerge, move, and merge in these systems. he von Neumann–Wigner theorem is used to explain the scarcity of Dirac cones in 2D systems, which leads to rigorous requirements on the symmetry,parameters, Fermi level, and band overlap of materials to achieve Dirac cones. Connections between existence of Dirac cones and the structural features are also discussed.

关键词： graphene silicene graphyne two-dimensional Dirac cone Dirac materials

Step-Directed Deposition of Au Nanostructures By Electron Beam Evaporation

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Journal of Rare Earths 2004年第Z2期22卷 141-144页

作者： Xu Xiangdong liu Zhihong Wang Yinchuan liu zhongfan Institute of Microelectronics Tsinghua UniversityBeijing 100084China Institute of MicroelectronicsTsinghua UniversityBeijing 100084China Center for Nanoscale Science & TechnologyCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China Center for Nanoscale Science & TechnologyCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

Au atoms were vaporized by electron beam evaporation, and their subsequent growths on Si (111 ) and highly ordered pyrolytic graphite (HOPG) substrates were studied using atomic force microscopy. Results show that Au nanoparticles tend to nucleate and grow regularly along the step edges of HOPG, however, nanoparticles are distributed homogeneously over the whole Si substrate. The possibility of controlled growth of Au in ultrahigh vacuum with peculiar surface structures was preseuted.

关键词： electron beam evaporation HOPG Au controlled growth ultrahigh vacuum

Laser irradiation induced spectral evolution of the surface-enhanced Raman scattering(SERS) of 4-tert-butylbenzylmercaptan on gold nanoparticles assembly

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Science China Chemistry 2007年第4期50卷 520-525页

作者： TONG LianMing ZHU Tao liu zhongfan Center for Nanoscale Science and Technology College of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

The spectral evolution of the surface-enhanced Raman scattering (SERS) of 4-tert-butylbenzylmer-captan (4-tBBM) on gold nanoparticles assembly under laser irradiation is reported. The relative intensities of typical peaks in the spectrum of 4-tBBM gradually change with irradiation time. Comparison of the rate of spectral changes under several experimental conditions indicates that the surface plasmon resonance (SPR) induced heat in the gold nanoparticles assembly is the origin of the spectral evolution. During the process of self-assembly, 4-tBBM molecules do not form a compact ordered monolayer because of the spatial hindrance of the 4-tert-butyl end group. The heat induced by laser irradiation drives the 4-tBBM molecules to rearrange to a more stable orientation.

关键词： surface-enhanced Raman scattering(SERS) spectral evolution surface plasmon resonance(SRP) thermal effect

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Strain Effects in Graphene and Graphene Nanoribbons:The Underlying Mechanism

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Nano Research 2010年第8期3卷 545-556页

作者： Yang Li Xiaowei Jiang zhongfan liu Zhirong liu College of Chemistry and Molecular Engineering State Key Laboratory for Structural Chemistry of Unstable and Stable Speciesand Beijing National Laboratory for Molecular SciencesPeking UniversityBeijing 100871China School of Physics Peking UniversityBeijing 100871China

A tight-binding analytic framework is combined with first-principles calculations to reveal the mechanism underlying the strain effects on electronic structures of graphene and graphene nanoribbons(GNRs).It provides a unified and precise formulation of the strain effects under various circumstances-including the shift of the Fermi(Dirac)points,the change in band gap of armchair GNRs with uniaxial strain in a zigzag pattern and its insensitivity to shear strain,and the variation of the k-range of edge states in zigzag GNRs under uniaxial and shear strains which determine the gap behavior via the spin polarization interaction.

关键词： Graphene graphene nanoribbons(GNRs) band gap strain first-principles calculations tight-binding model

Spatially-Resolved Crystallization of Amorphous Silicon Films on the Glass Substrate by Multi-beam Laser Interference

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Journal of Materials Science & Technology 2007年第4期23卷 465-467页

作者： zhongfan liu Xuede YUAN Xue HAO F.Muecklich College of Physical Science and Technology Dalian University Dalian 116622 China Institute of Functional Materials University of Saarland Saarbruecken 66123 Germany

Laser interference induced crystallization of amorphous silicon （a-Si） on the glass substrate was performed using a Q-switched Nd：YAG （yttrium aluminum garnet） laser. White light interferometer （WLI） and atomic force microscope （AFM） were used to characterize the morphology of the structured films, while X-ray diffraction （XRD）, combined with the AFM, was used to analyse the crystalline structure of the film. The experimental results show that the laser energy density above a certain threshold, in the range of 400-500 mJ/cm2,triggers the patterned crystallizations which take the form similar to the laser intensity distribution. For the patterned crystallization under multipulse exposure, a definite polycrystalline structure with individual phases was observed by XRD. The difference in feature form, e.g., deepened craters or heightened lines, is related to the laser energy density relative to the threshold of evaporation of the material.

关键词： Pulsed laser Laser interference Amorphous silicon Crystallization

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Nanobarrier-Terminated Growth of Single-Walled Carbon Nanotubes on Quartz Surfaces

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Nano Research 2009年第10期2卷 768-773页

作者： Chaoqun Feng Yagang Yao Jin Zhang zhongfan liu Beijing National Laboratory for Molecular Sciences(BNLMS) Key Laboratory for the Physics and Chemistry of NanodevicesState Key Laboratory for Structural Chemistry of Unstable and Stable SpeciesCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China

Using carbon nanotubes as nanobarriers,the growth of single-walled carbon nanotubes(SWNTs)on a quartz surface can be ***,carbon nanotube nanobarriers were grown on a quartz surface by the gas ow-directed growth ***,the SWNTs were grown on the quartz surface via the lattice-oriented growth mode,in which growth of SWNTs can be terminated by hitting the nanotube ***,using the carbon nanotube nanobarrier as a marker,the mechanism of the growth of SWNTs on the quartz surface can be studied;a base-growth mechanism is *** on this termination process and the base-growth mechanism,SWNT arrays with controlled lengths can be grown on a quartz surface by xing the sites of bothcatalysts and nanobarriers.

关键词： Single-walled carbon nanotubes terminated growth carbon nanotube nanobarrier length control of carbon nanotubes