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.
