学术报告

题目：Characterizing Localized Surface Plasmons using Electron Energy-Loss Spectroscopy

报告人：李国梁博士（Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, United States）

时间：2016年3月9日(星期三)下午15:00-16:00

地点：中南大学南校区双超所211报告室

简历：

李国梁博士，于2005考入中南大学物理教学改革试验班，主修材料科学与工程并辅修应用物理，于2009年毕业获得学士学位；同年进入美国田纳西大学材料科学与工程系攻读博士并于2013年获得博士学位；2013-2014转入田纳西大学化学系从事博士后研究；2014至今在美国圣母大学化学与生物化学系从事博士后研究；在美期间长年保持与橡树岭国家实验室扫描透射电镜组的密切合作。主要研究:扫描透射电镜显微学（Scanning Transmission Electron Microscopy）,电子能量损失谱学（Electron Energy-loss Spectroscopy），表面等离子体光子学（Plasmonics），半导体薄膜材料界面分析（Interfaces in Thin-Film Semiconductor Materials）。在Annual Review of Physical Chemistry, Nano Letters, ACS Nano, JPC Letters等刊物发表论文8篇。

Abstract:Localized surface plasmon resonances (LSPRs) are the coherent and collective oscillations of conduction band electrons at the surface of metallic nanoparticles. LSPRs are known to localize far-field light to a sub-diffraction-limited length scale, yielding an intense electric field at the particle surface. This effect has been harnessed to dramatically enhance light-matter interactions, leading to a variety of applications such as surface-enhanced Raman spectroscopy (SERS),¹photothermal cancer therapy²and solar energy harvesting.³Though a variety of near- and far-field optical methods are used to probe LSPRs, the spatial resolution of these methods is on the order of tens of nanometers,⁴limiting their effectiveness. In contrast, electron energy loss spectroscopy (EELS) performed in a scanning transmission electron microscope (STEM)combines sub-nanometer resolving power with the capability to excite both optical-accessible and –inaccessible plasmon modes and thereforehas emerged as one of the leading techniques used in characterizing LSPRs.In this presentation, I will first briefly introduce (1) the basics of LSPRs and (2) the STEM/EELS technique and then demonstrate (3) the power of STEM/EELS in the characterization of LSPRs based upon my previous work. Finally I will (4) highlight recent research interests of the plasmonics community and what possibilities I pursue to make impact. Figure 1 is a schematic of the working principle of STEM/EELS. Figure 2 shows selected STEM/EELS results.

Figure 1.Schematic of the working principle of STEM/EELS

Figure 2.STEM/EELS results demonstration. (a) Mapping plasmon modes of Au nanoparism (150 nm in edge length). (b) Imaging plasmon bonding of a Ag nanoparticle dimer (165 nm in diameter).

References

(1). Nie, S.; Emory, S. R. Science 1997, 275, (5303), 1102-1106.

(2). Morton, J.; Day, E.; Halas, N.; West, J., Nanoshells for Photothermal Cancer Therapy. In Cancer Nanotechnology, Grobmyer, S. R.; Moudgil, B. M., Eds. Humana Press: 2010; Vol. 624, pp 101-117.

(3). Clavero, C. Nature Photonics 2014, 8, (2), 95-103.

(4). Ringe, E.; Sharma, B.; Henry, A.-I.; Marks, L. D.; Van Duyne, R. P. Physical Chemistry Chemical Physics 2013, 15, (12), 4110-4129.