报告题目：Mechanical-electric-magnetic coupling and energy conversion in
two-dimensional materials
报告人： 郭万林 教授
南京航空航天大学航空宇航学院
时间： 1月18日（周一) 下午4:00
地点： 卢嘉锡楼报告厅（202）
以下是报告的摘要部分：
Abstract:
It is widely known that when the spatial scale goes down from macroscale to nanoscale, temporal scale will reduce to nano to femtosecond. It is more important that the related energy scale of an externally applied field will drop for eighteen orders from joule (1 Newton times 1 meter) to attojoule (1 nanoNewton times 1 nanometer = 6.42 eV), falling into the energy scale of the local fields of matter which consist of electronic structures, charge, molecular orbital and spin states. Therefore, at nanoscale, matters will show distinctly different performances from their bulk materials mainly due to the strong coupling between the local fields of matter and external applied fields. Such nanoscalemultifield couplings can turn very common materials such as carbon, even insulating boron nitride, into functional nanomaterials with fantastic properties we expected for nanoelectronics, spintronics as well as high efficient energy conversion devices.
It will also be demonstrated by our recent findings that exceptional functional properties in the intrinsically insulating h-BN nanostructures (Nano Lett. 10, 5049,2010;13, 3232, 2013;JACS 133, 14831, 2011, Small 2015) and exotic properties of transition metal dichalcogenide (ACS Nano7, 7126-7131, 2013; Phys. Rev. Lett.112, 205502, 2014).
Recently we also found that an induced ‘waving electronic potential’ can be observed in graphene as it is dipped - ‘waved’ - in and out of seawater1. We also found that drawing a droplet of ionic solutions over the surface of graphene can induce “drawing electric potential” in the graphene2. The potentials are found to be raised by the moving boundary of the electric double layer formed at the interface of the droplet and graphene surface, or the solid-air-liquid boundary of a graphene sheet across a liquid surface. The findings extend centuries’ old theories of electrokinetic effects and help understand the behaviour of carbon nanomaterials in liquids, which has been subject to conflicting reports for over a decade. The novel effects have been used to demonstrate energy harvest from dropping droplets, sensing the handwriting on graphene and stimulating a sciatic nerve of a frog.The waving potential, which is proportional to both the speed and the size of the graphene, can also be scaled up by connecting in series or parallel for possible applications in self-powered functional sensors such as tsunami monitors to wave energy harvest, monitors and remote ocean devices.
It is more interesting that the coupling promising us to break the 10 nanometer limitation of energy beam fabrication down to subnanometre scale3,4. Such extraordinary mechanical-electric-magnetic coupling effects in nano systems open up new vistas in functional nanodevices compatible with the concurrent technology for efficient energy conversion, self-powering flexible devices and novel functional systems.
References:
[1] Jun Yin, Zhuhua Zhang, Xuemei Li, Jin Yu, Jianxin Zhou, Yaqing Chen & Wanlin Guo*, Waving potential in graphene. Nature Communications5, 3582 (2014).
[2] Jun Yin, Xuemei Li, Jin Yu, Zhuhua Zhang, Jianxin Zhou &Wanlin Guo*, Generating electricity by moving a droplet of ionic liquid along graphene. Nature Nanotechnology9 (5), 378-383 (2014).
[3] Xiaofei Liu, Tao Xu, Xing Wu, Zhuhua Zhang, Jin Yu, Hao Qiu, Jinhua Hong, Chuanhong Jin, Jixue Li, Xinran Wang, Litao Sun*, Wanlin Guo*, Top-down fabrication of sub-nanometre semiconducting nanoribbons derived from molybdenum disulfide sheets, Nature Communications4, 1776 (2013).
[4] Wanlin Guo*, Xiaofei Liu, 2D materials: Metallic when narrow. Nature Nanotech. 9, 413 (2014).
