CAREER: Development of Novel-scheme Nano-optical Chemical Imaging Spectroscopy

在化学系化学测量和成像计划的支持下，加州大学河滨分校的严教授将开发一种显微成像技术，以纳米级分辨率和高灵敏度研究表面的化学成分。传统的光学显微镜只能将光聚焦到数百纳米。在这个长度的尺度上，数千个分子被一起研究。然而，在许多情况下，了解电池中的一个小缺陷或动物体内一个沉默的DNA分子的行为是至关重要的。严教授的技术能够从只有几个纳米的区域监测分子，她可以在那里研究化学键，并获得涉及的一个或几个分子的化学信息。这一新的化学成像技术的结果将对许多有兴趣解开表面复杂化学相互作用的研究人员有用，这些相互作用涉及材料、催化和生命科学研究。例如，她正在使用她的技术对单个神经细胞的DNA进行测序，以精确定位基因突变，这可能有助于揭示包括自闭症或精神分裂症在内的大脑疾病。严教授还对通过为加利福尼亚州河滨和圣贝纳迪诺县的高中生提供早期接触科学研究的机会来增加美国科技劳动力的多样性感兴趣。她还计划开发一个中美学生交流项目，为美国STEM学生为全球市场和充满活力的科学界做好准备。该项目旨在开发一种基于纳米纤维的方法，以提高尖端增强拉曼光谱(TERS)的性能和可靠性，并简化其在纳米级复杂和非均质表面的化学成像中的操作。TERS是一种独特的无标记化学表征工具，具有纳米级的空间分辨率。然而，传统的TERS仍然是一种深奥的技术，因为它的光学对准困难以及灵敏度和分辨率的限制，这两者都源于分子长度尺度上的光学聚焦不良。严教授致力于建立一个高性能、无对准的TERS平台，具有低于10 nm的空间分辨率、低分子灵敏度和高对比度、无背景成像能力。她的方法基于绝热等离子体纳米聚焦机制，将光集中到纳米限制的拉曼传感体积，并从其中提取信号，具有高效率和能量吞吐量。该项目的关键部分是：(1)新型TERS平台的可行性的模拟演示和实验验证；(2)TERS系统与商用AFM和STM系统的集成，并开发协议来评估和优化其性能；以及(3)新型TERS平台的应用，以解决材料、催化、电子和生物系统中复杂表面的化学分析中的实际问题。除了通过产业合作将开发的技术转化为商业化外，严教授还计划通过(1)夏令营和研究实习项目，为当地高中生提供现代光学和化学研究的实践经验，以及(2)国际学生交流项目(与中国)，为华中大学STEM本科生和研究生提供国际研究接触，积极吸引学生参加研究培训并建立STEM管道。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Yan at University of California, Riverside, will be developing a microscopic imaging technique to study the chemical compositions of a surface with nanometer scale resolution and high sensitivity. Conventional optical microscopes can only focus light down to hundreds of nanometers. At this length scale, thousands of molecules are studied together. However, in many cases, understanding how one small defect in a battery or one muted DNA molecule in an animal behaves is vitally important. Professor Yan's technique is able to monitor molecules from an area of only a few nanometers cross where she can study chemical bonds and obtain chemical information of one or a few molecules involved. The results of this new chemical imaging technique will be useful to many researchers who are interested in untangling complex chemical interactions on a surface, related to materials, catalysis, and life science research. For example, she is using her technique to sequence DNAs from a single neural cell to pinpoint gene mutations, which may shed light on brain disorders including autism or schizophrenia. Professor Yan is also interested in increasing the diversity of the US science and technology workforce by providing early exposure to scientific research to high school students in Riverside and San Bernardino counties in California. She also plans to develop a Sino-US student-exchange program to prepare US STEM students for a global marketplace and dynamic scientific communities.This project seeks to develop a nanofiber-based method to improve the performance and reliability of tip-enhanced Raman spectroscopy (TERS) and to simplify its operation in chemical imaging of nanoscale complex and heterogeneous surfaces. TERS is a unique tool for label-free chemical characterization with the spatial resolution at nanometer scale. However, conventional TERS remains an esoteric technique due to its difficult optical alignment and limitations in sensitivity and resolution, both stemming from the poor optical focusing at the molecular length scale. Professor Yan is working on establishing a high-performance and alignment-free TERS platform with sub-10 nm spatial resolution, few-molecule sensitivity and high-contrast, background-free imaging capacity. Her approach is based on a adiabatic plasmonic nanofocusing mechanism to concentrate light to, and extract signal from, a nano-confined Raman sensing volume with high efficiency and energy throughput. The key components of this project are: (1) simulation demonstration and experimental verification of the feasibility of the novel TERS platform; (2) integration of the TERS system with commercial AFM and STM systems, and develop protocols to evaluate and optimize its performance; and (3) application of the novel TERS platform to address practical issues in chemical analysis of complex surfaces in materials, catalytic, electronic and biological systems. In addition to bringing the developed technique to commercialization through industrial collaboration, Professor Yan also plans to actively engage students in research training and build STEM pipeline through (1) summer camps and research internship programs that provide local high school students with hands-on experience with modern optics and chemical research, and (2) an international student exchange program (with China) to provide UCR STEM undergraduates and graduate students with international research exposure.