Our Publications

  • Strain Loading Mode Dependent Bandgap Deformation Potential in ZnO Micro/Nanowires. ACS Nano (2015)

    ACS Nano
    Xuewen Fu, Zhi-Min Liao, Ren Liu, Fang Lin, Jun Xu, Rui Zhu, Wei Zhong, Yingkai Liu, Wanlin Guo,and Dapeng Yu
    DOI 10.1021/acsnano.5b04617
    State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871, P. R. China, ‡Collaborative Innovation Center of Quantum
    Matter,Beijing100871,P.R.China, KeyLaboratoryofYunnanHigherEducationInstitutesforOptoelectricInformation&Technology,Kunming650500,P.R.China, and State Key Laboratory of Mechanics and Control of Mechanical Structures and Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, 29 Yudao Street, Nanjing 210016, P. R. China
    Strain Loading Mode Dependent Bandgap Deformation Potential in ZnO Micro/Nanowires.

    ABSTRACT
    The electronic-mechanical coupling in semiconductor nanostructures under different strain loading modes can modulate their photoelectric properties in different manners. Here, we report the systematic investigation on the strain mode dependent bandgap deformation potential of ZnO micro/nanowires under both uniaxial tensile and bending strains at room temperature. Uniaxial stretching-photoluminescence results show that the deformation potential of the smaller ZnO nanowire (with diameter d = 260 nm) is 30.6 meV/%, and is close to the bulk value, whereas it deviates the bulk value and becomes to be 10.6 meV/% when the wire diameter is increased to d = 2 μm. This unconventional size dependence stems from surface effect induced inhomogeneous strain in the surface layer and the core of the ZnO micro/nanowires under uniaxial tension. Forbendingloadmode, the in situhigh-resolution transmission electron microscope analysis reveals that the local strain distributes linearly in the bending crosssection.Further cathodoluminescence measurements on a bending ZnO microwire(d=1.8 μm)demonstrate that the deformation potentialis 27meV/%,whose absolute value is much larger than that of the ZnO microwire under uniaxial tension. Further analysis reveals that the distinct deformation potentials originate from the different deforming modes in ZnO micro/nanowires under bending or uniaxial tensile strains. Our results should facilitate the design of flexible optoelectronic nanodevices.

    http://pubs.acs.org/doi/abs/10.1021/acsnano.5b04617

  • Phonon Trapping in Pearl-Necklace-Shaped Silicon Nanowires. Small (2015)

    Small
    Chunyang Miao , Guoan Tai , Jianxin Zhou , and Wanlin Guo
    DOI: 10.1002/smll.201501956
    C. Miao, Dr. G. Tai, Dr. J. Zhou, Prof. W. Guo
    Key Laboratory of Intelligent Nano Materials and Devices of MOE
    State Key Laboratory of Mechanics and Control of Mechanical Structures
    Institute of Nano Science of Nanjing University of Aeronautics and Astronautics
    Nanjing 210016 , China
    E-mail: wlguo@nuaa.edu.cn
    Phonon Trapping in Pearl-Necklace-Shaped SiliconNanowires

    Abstract

    A pearl-necklace-shaped silicon nanowire, in contrast to a smooth nanowire, presents a much lower thermal conductivity due to the phonon trapping effect. By precisely controlling the pearl size and density, this reduction can be more than 70% for the structures designed in the study, which provides a unique approach for designing high-performance nanoscale thermoelectric devices.

    http://onlinelibrary.wiley.com/doi/10.1002/smll.201501956/full

  • Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons (ACS Nano)

    ACS Nano
    Water in Inhomogeneous Nanoconfinement: Coexistence of Multilayered Liquid and Transition to Ice Nanoribbons
    Hu Qiu, Xiao Cheng Zeng, and Wanlin Guo
    DOI: 10.1021/acsnano.5b04947
    Key Laboratory for Intelligent Nano Materials and Devices of MOE and State Key Laboratory of Mechanics and Control of Mechanical Structures, Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
    Department of Chemistry and Nebraska Center for Materials and Nanoscience, University of Nebraska−Lincoln, Lincoln, Nebraska 68588, United States
    qiuhu@nuaa.edu.cn, xzeng1@unl.edu, wlguo@nuaa.edu.cn.

    Abstract
    Phase behavior and the associated phase transition of water within inhomogeneous nanoconfinement are investigated using molecular dynamics simulations. The nanoconfinement is constructed by a flat bottom plate and a convex top plate. At 300 K, the confined water can be viewed as a coexistence of monolayer, bilayer, and trilayer liquid domains to accommodate the inhomogeneous confinement. With increasing liquid density, the confined water with uneven layers transforms separately into two-dimensional ice crystals with unchanged layer number and rhombic in-plane symmetry for oxygen atoms. The monolayer water undergoes the transition first into a puckered ice nanoribbon, and the bilayer water transforms into a rhombic ice nanoribbon next, followed by the transition of trilayer water into a trilayer ice nanoribbon. The sequential localized liquid-to-solid transition within the inhomogeneous confinement can also be achieved by gradually decreasing the temperature at low liquid densities. These findings of phase behaviors of water under the inhomogeneous nanoconfinement not only extend the phase diagram of confined water but also have implications for realistic nanofluidic systems and microporous materials.

    ARTICLE LINK

  • Aligned Growth of Hexagonal Boron Nitride Monolayer Germanium (Small)

    Small
    Jun Yin,Xiaofei Liu,Wanglin Lu,Jidong Li,Yuanzhi Cao,Yao Li,Ying Xu,Xuemei Li,Jun Zhou,Chuanhong Jin,Wanlin Guo
    DOI: 10.1002/smll.201501439
    Aligned Growth of Hexagonal Boron Nitride Monolayer Germanium

    State Key Laboratory of Mechanicsand Control of Mechanical StructuresKey Laboratory for Intelligent Nano Materials and Devices of the Ministry of Educationand Institute of Nanoscience
    Nanjing University of Aeronautics and Astronautics
    Nanjing 210016 , China
    E-mail: wlguo@nuaa.edu.cn

    Abstract
    A hexagonal boron nitride monolayer with aligned orientations is grown on reusable semiconducting germanium. The number of primary orientations of the h-BN domains depends on the symmetry of the underlying crystal face, and Ge (110) gives rise to only two opposite orientations. The structures and electrical properties of grain boundaries between h-BN domains with opposite orientations are also systematically analyzed.

    ARTICLE LINK

  • Large-Area, Periodic, Hexagonal Wrinkles on Nanocrystalline Graphitic Film (Adv. Funct. Mater)

    Adv. Funct. Mater
    Yanpeng Liu, Kenry, Yufeng Guo, Surabhi Sonam, Seul Ki Hong, Mui Hoon Nai,
    Chang Tai Nai, Libo Gao, Jianyi Chen, Byung Jin Cho, Chwee Teck Lim,
    Wanlin Guo, and Kian Ping Loh
    DOI: 10.1002/adfm.201502010
    Large-Area, Periodic, Hexagonal Wrinkles on Nanocrystalline Graphitic Film
    Department of Chemistry and Graphene Research Center National University of Singapore
    3 Science Drive 3 , Singapore 117543 , Singapore
    State Key Laboratory of Mechanics and Control of Mechanical Structures and MOE
    Key Laboratory for Intelligent Nano Materials and Devices, Institute of Nanoscience,
    Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
    E-mail: yfguo@nuaa.edu.cn; Fax:+ 86-25-84895827; Tel: + 86-25-84890513

    Abstract
    Sinusoidal wrinkles develop in compressively stressed film as a means to release stored elastic energy. Here, a simple way to fabricate large-area, periodic, hexagonal wrinkled pattern on nanocrystalline graphitic films grown on c-plane sapphire (<50 nm thick) by the spontaneous delamination–buckling of the as-grown film during cooling is reported. According to the continuum mechanics calculation, strain-relief pattern adopting the hexagonal wrinkled pattern has a lower elastic energy than that of the telephone cord wrinkle at thickness regime below 50 nm. A high-fidelity transfer method is developed to transfer the hexagonal wrinkled films onto arbitrary substrates. Nanoindentation studies show that hexagonal wrinkle film engineered this way may act as shock absorber. The hexagonal wrinkled carbon film is able to selectively promote the differentiation of human mesenchymal stem cell toward the osteogenic lineage in the absence of osteogenic inducing medium.

    ARTICLE LINK

  • Yufeng Guo and Wanlin Guo. Hydroxylation of a metal-supported hexagonal boron nitride monolayer by oxygen induced water dissociation. Phys. Chem. Chem. Phys.(2015)

    Phys. Chem. Chem. Phys
    Yufeng Guo and Wanlin Guo
    DOI: 10.1039/c5cp02494c
    Hydroxylation of a metal-supported hexagonal boron nitride monolayer by oxygen induced water dissociation
    State Key Laboratory of Mechanics and Control of Mechanical Structures and MOE
    Key Laboratory for Intelligent Nano Materials and Devices, Institute of Nanoscience,
    Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China.
    E-mail: yfguo@nuaa.edu.cn; Fax:+ 86-25-84895827; Tel: + 86-25-84890513

    Received 29th April 2015,
    Accepted 19th May 2015

    Abstract
    Hydroxylated hexagonal boron nitride (h-BN) nanosheets exhibit potential application in nanocomposites and functional surface coating. Our first-principles calculations reveal possible hydroxylation of a h-BN monolayer on a Ni substrate by surface O adatom induced spontaneo us dissociation of water molecules. Here one H atom is
    split from a water molecule by bonding with the O adatom on the B atom and the resulting O–H radical then bonds with an adjacent B atom, which leads to two hydroxyl groups formed on h-BN/Ni. Hydroxylation slightly influences the electronic properties of a Ni-supported h- BN layer. Similar water dissociation and hydroxylation
    can occur on the surface of O functionalized h-BN/Cu depending on the O adsorption configuration. Metal substrates play an important catalytic role in enhancing the chemical reactivity of O adatoms on h-BN with water molecules through transferring additional charges to them.

    ARTICLE LINK

  • Yan Li, Xinsheng Liu, Jens Christian Claussen and Wanlin Guo . Evolutionary dynamics for persistent cooperation in structured populations. PHYSICAL REVIEW E(2015)(2015)

    PHYSICAL REVIEW E
    Yan Li, Xinsheng Liu, Jens Christian Claussen and Wanlin Guo
    PHYSICAL REVIEW E(2015)(2015)
    DOI:10.1103/PhysRevE.91.062802
    Evolutionary dynamics for persistent cooperation in structured populations

    Institute of Nano Science, State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education, and Department of Mathematics, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
    Jacobs University Bremen, Computational Systems Biology Lab, Research 2, Campus Ring 1, D-28759 Bremen, Germany

    Received 14 November 2014; published 5 June 2015

    Abstract

    The emergence and maintenance of cooperative behavior is a fascinating topic in evolutionary biology and social science. The public goods game (PGG) is a paradigm for exploring cooperative behavior. In PGG, the total resulting payoff is divided equally among all participants. This feature still leads to the dominance of defection
    without substantially magnifying the public good by a multiplying factor. Much effort has been made to explain the evolution of cooperative strategies, including a recent model in which only a portion of the total benefit is shared by all the players through introducing a new strategy named persistent cooperation. A persistent cooperator is a contributor who is willing to pay a second cost to retrieve the remaining portion of the payoff contributed by themselves. In a previous study, this model was analyzed in the framework of well-mixed populations. This paper focuses on discussing the persistent cooperation in lattice-structured populations. The evolutionary dynamics of the structured populations consisting of three types of competing players (pure cooperators, defectors, and persistent cooperators) are revealed by theoretical analysis and numerical simulations. In particular, the
    approximate expressions of fixation probabilities for strategies are derived on one-dimensional lattices. The phase diagrams of stationary states, and the evolution of frequencies and spatial patterns for strategies are illustrated on both one-dimensional and square lattices by simulations. Our results are consistent with the general observation that, at least in most situations, a structured population facilitates the evolution of cooperation. Specifically, here we find that the existence of persistent cooperators greatly suppresses the spreading of defectors under more relaxed conditions in structured populations compared to that obtained in well-mixed populations.

    ARTICLE LINK

  • Jun Yin, Jin Yu, Xuemei Li, Jidong Li, Jianxin Zhou, Zhuhua Zhang, and Wanlin Guo. Large Single-Crystal Hexagonal Boron Nitride Monolayer Domains with Controlled Morphology and Straight Merging Boundaries. Small (2015)

    Small
    Jun Yin, Jin Yu, Xuemei Li, Jidong Li, Jianxin Zhou, Zhuhua Zhang, and Wanlin Guo Small(2015) DOI: 10.1002/smll.201500210
    Large Single-Crystal Hexagonal Boron Nitride Monolayer Domains with Controlled Morphology and Straight Merging Boundaries

    wlguo@nuaa.edu.cn
    State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China

    Article first published online: 3 JUN 2015

    Abstract

    Hexagonal boron nitride monolayers with domain sizes up to 700 μm2 and geometry from triangle to hexagon are fabricated through a refined control over the precursor and morphology of the copper substrate. Hydrogen etching is shown to tailor the h-BN monolayers precisely along the grain boundaries, providing their morphology over micro­meter scale and a new avenue toward fabricating nanoribbons.

    ARTICLE LINK

  • Jin Yu and Wanlin Guo.Strain tunable electronic and magnetic properties of pristine and semihydrogenated hexagonal boron phosphide. Appl. Phys. Lett. 106, 043107 (2015)

    Appl. Phys. Lett.
    Jin Yu and Wanlin Guo Appl. Phys. Lett. 106, 043107 (2015) DOI:10.1063/1.4906998
    Strain tunable electronic and magnetic properties of pristine and semihydrogenated hexagonal boron phosphide

    wlguo@nuaa.edu.cn
    State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China

    Received 24 November 2014; accepted 19 January 2015; published online 30 January 2015

    Abstract

    Tunable electromagnetic properties of pristine two-dimensional boron phosphide (h-BP) nanosheet and its semihydrogenated structure were studied by density functional theory computations. In sharp contrast to previously reported tensile strain-induced red shift in two-dimensional semiconductors, the direct gap of h-BP undergoes blue shift under biaxial tensile strain. Once semihydrogenated, the h-BP not only transform from the nonmagnetic semiconductor into metal which is spin-resolved but
    also exhibits linear response between the magnetic moment and biaxial strain with a slope up to 0.005lB/1%. These findings provide a simple and effective route to tune the electronic and mag-netic properties of h-BP nanostructures in a wide range and should inspire experimental enthusiasm.

  • Yufeng Guo and Wanlin Guo. Magnetism in Oxygen-Functionalized Hexagonal Boron Nitride Nanosheet on Copper Substrate. J. Phys. Chem. C 119, 873 (2015)

    J. Phys. Chem. C
    Yufeng Guo and Wanlin Guo J. Phys. Chem. C 119, 873 (2015) DOI: 10.1021/jp5122799
    Magnetism in Oxygen-Functionalized Hexagonal Boron Nitride Nanosheet on Copper Substrate

    wlguo@nuaa.edu.cn
    State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China

    Abstract

    Wide-bandgap hexagonal boro n nitride (h-BN) nanosheets, white graphene, can be uniformly grown on conducting Cu foils with high quality. Here, we show that h-BN monolayers on Cu substrates exhibit ferromagnetic, antiferromagnetic, or ferrimagnetic properties with ozone (O3) molecules or oxygen−hydrogen (O−H2)groups
    bonded on its B atoms, depending on the adsorption density and configuration of these
    functional groups. The magnetisms in the O3- and O−H2-functionalized h-BN sheets
    originate from unpaired electrons in the ozone molecule and electrons transferred from
    the H2 molecule to the O atom, respectively. The Cu substrate plays an essential role in stabilizing the chemisorption of O3or O−H2 on the h-BN sheets. Magnetic composite
    structures composed of Cu, h-BN, and oxygen provide a feasible route to facilitate the
    design of two-dimensional h-BN-based spin devices.

  • Wenwen Fei, Jianxin Zhou, and Wanlin Guo.Low-voltage Driven Graphene Foam Thermoacoustic Speaker. Small 19,2252 (2015)

    Small
    Wenwen Fei, Jianxin Zhou, and Wanlin Guo Small 19,2252 (2015) DOI:10.1002/smll.201402982
    Low-voltage Driven Graphene Foam Thermoacoustic Speaker

    wlguo@nuaa.edu.cn
    State Key Laboratory of Mechanics and Control of Mechanical Structures, Key Laboratory for Intelligent Nano Materials and Devices of the Ministry of Education and Institute of Nanoscience, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China

    Article first published online: 13 MAY 2015

    Abstract

    A low-voltage-driven thermoacoustic speaker is fabricated by W. Guo and co-workers using graphene foams synthesized by a chemical vapor deposition method. When an audio signal is applied to the speaker, sound waves are produced due to the periodicity of air vibrations induced by Joule heating. On page 2252, with the feasible tunability in structure and thermoacoustic performance, the graphene foam-based thermoacoustic speaker is shown to be promising for applications requiring flexible or ultrasonic acoustic devices.

    ARTICLE LINK