题目：Mechanical-electric-magnetic coupling in two-dimensional nanomaterials

报告人：郭万林  教授（南京航天航空大学）

时间：2014年8月26日（周二）10:15-11:45

地点：李薰楼468会议室

摘要:

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 eighteenth 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 nanoscale multifield 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.

Recently we 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 results 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 decade³. 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 will also be demonstrated by our recent findings that the magnetism in graphene nanoribbons on silicon substrates can be tuned linearly by applied bias voltage (Phys.Rev.Lett, 103, 187204, 2009), graphene can sense gas flow⁴, but cannot sense ionic liquid flow when immersed in the liquid⁵, strain gradient induced exciton energy shift, the flexoelectronic effect, in semiconductors (Adv. Mater. 21, 1, 2009; 24, 4707, 2012; 26, 2572, 2014; ACS Nano 8, 3412, 2014) , and exceptional functional properties in the intrinsically insulating h-BN nanostructures⁶ (Nano Lett. 10, 5049,2010; JACS 133, 14831, 2011) and exotic properties of transition metal dichalcogenide (ACS Nano 7, 7126-7131, 2013; Phys. Rev. Lett. 112, 205502, 2014).

It is more interesting that the coupling promising us to break the 10 nanometer limitation of energy beam fabrication down to subnanometre scale^7,8. 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 Communications 5, 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 Nanotechnology 9 (5), 378-383 (2014).

[3] http://nanotechweb.org/cws/article/tech/57149, 科技日报5月15日1版等。

[4] Wanlin Guo* et al. Applied Physics Letters 99, 073103 (2011)；100, 183108 (2012).

[5] J. Yin, Z. H. Zhang, X. M. Li, J. X. Zhou, W.L. Guo*, Harvesting Energy from Water Flow over Graphene? Nano Lett., 2012, 12 (3), 1736–1741.

[6] Jun Yin, Xuemei Li, Jianxin Zhou, Wanlin Guo*, Ultralight Three-Dimensional Boron Nitride Foam with Ultralow Permittivity and Superelasticity, Nano Letters 13 (7), 3232-3236 (2013).

[7] 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 Communications 4, 1776 (2013).

[8] Wanlin Guo*, Xiaofei Liu, 2D materials: Metallic when narrow. Nature Nanotech. 9, 413 (2014).

报告人简历：

Wanlin GUO, Ph.D. Professor in Mechanics and Nanomaterials

Director of Institute of Nano Science in Nanjing University of Aeronautics and Astronautics (NUAA);

Director of Key Laboratory of Intelligent Nano Materials and Devices of MoE in NUAA;

Deputy Director of State Key Laboratory of Mechanics and Control of Mechanical Structures in NUAA;

In 1981-1991, He studied Aerospace Engineering and solid mechanics in Northwestern Ploytechnical University and obtained his Master and PhD degrees in solids mechanics with the best academic records. From 1991-2002 he has worked as Post-D, associated professor and professor in Xian Jiaotong University. In 1995-1998, he worked at the Center-of-Expertise of Australian Defence Science and Technology Organization at Monash University. He obtained the Outstanding Young Scientist Award (Premier Fund) of China in 1996 and the honor of Cheung Kong Scholars in 1999 and worked as Chair Professor in Nanjing University of Aeronautics and Astronautics since 2000. In 2005, he leaded a team in Nano-scale Physical Mechanics enters the Cheung Kong Scholars Excellent Team Programme of the Ministry of Education of China. In 2010, he founded the Key Laboratory of Intelligent Nano Materials and Devices of the Ministry of Education of China.

His current research interests cover intelligent nano materials and devices, high efficient energy conversion nanotechnology, three dimensional fatigue fracture and damage tolerance and durability of mechanical structures. He has published 300+ refereed papers in mechanics-related journals such as Nature Nanotech, Nature Comm. Phys. Rev. Lett., Nano Lett., J. Am. Chem. Soc., Adv. Mater., Small, Nanoscale, J. Mech. Phys. Solids et al. with SCI citation by other over 2600 and was awarded the National Prize in Nature Science in 2012 and Xu Zhilun Mechanical Prize in 2013 fro his outstanding academic contribution.

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