Plasmon-Enhanced Scanning Probe Spectroscopy for Chemical Mapping of Nanoscale Interfaces

在化学系化学测量和成像项目的支持下，加州大学圣地亚哥分校的陶教授研究和开发了用于表面分析的新工具。虽然表面和界面在决定关键化学过程中起着关键作用，但缺乏足够的纳米级表面分析工具。陶教授正在研究和创建能够将光聚焦到纳米尺度体积（人类头发的直径）的光学探针，这些探针可用于生物成像，催化，等离子体和固态表面科学等应用。该项目为本科生，研究生和高中生提供了独特的研究机会，以了解光学和纳米材料。 陶教授与一家纳米材料初创公司合作，为她的学生提供了对企业家路线图的直接和个人见解。 陶教授也有兴趣提高工程社区在加州大学圣地亚哥分校的多样性。 该研究通过确保产品质量以及通过减少缺陷来帮助改进合成方法来为化学工业做出贡献。该项目集成了原子力显微镜（AFM）和尖端增强拉曼光谱（TERS），用于对表面的化学和机械性质以及表面结合事件进行多模态测量。AFM-TERS通过使用金属光学天线对入射光和拉曼散射光进行近场放大，逐点采集化学信息丰富的拉曼光谱。本工作研究了胶体AFM-TERS探针的化学和物理性质，该探针是通过将成形的金属纳米晶体组装到AFM针尖上而制成的。银纳米立方体探针作为一个模型系统，以了解光-物质的相互作用，这是实现大的拉曼增强和低背景信号的关键。这些研究提供了新的基本洞察近场光学探针如何与分子和表面分析物相互作用，澄清近场光学限制是如何支持在尖端衬底结，并调查如何增强其他光学过程（如非弹性散射，多光子吸收）影响TERS读出。实验和模型都被用来确定和开发设计规则的拉曼光学天线，以最大限度地提高拉曼灵敏度和成像分辨率。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Tao at University of California, San Diego, studies and develops new tools for surface analysis. Although surfaces and interfaces play a critical role in dictating key chemical processes, adequate tools for nanoscale surface analysis are lacking. Professor Tao is studying and creating optical probes that are capable of focusing light down to nanoscale volumes (the diameter of a human hair) that could be used in applications such as bioimaging, catalysis, plasmonics, and solid-state surface science. This project provides unique research opportunities for undergraduates, graduates, and high school students to learn about optics and nanomaterials. Professor Tao collaborates with a nanomaterials start-up company, which provides her students with direct and personal insight into the entrepreneur roadmap. Professor Tao is also interested in enhancing the diversity of the engineering community at UC San Diego. This research contributes to chemical industry by ensuring product quality as well as helping to improve synthetic methods by reducing defects. This project integrates atomic force microscopy (AFM) and tip-enhanced Raman spectroscopy (TERS) for carrying out multi-modal measurement of both the chemical and mechanical properties of surfaces and surface binding events. AFM-TERS carries out point-by-point acquisition of chemical information-rich Raman spectra by using a metallic optical antenna to facilitate near-field amplification of both the incident and Raman-scattered light. This work investigates the chemical and physical properties of colloidal AFM-TERS probes that are fabricated by the assembly of shaped metal nanocrystals onto AFM tips. Silver nanocube probes serve as a model system to understand the light-matter interactions that are critical for achieving large Raman enhancements and low background signals. These studies provide new fundamental insight into how near-field optical probes interact with molecular and surface analytes, clarify how near-field optical confinement is supported at the tip-substrate junction, and investigate how the enhancement of other optical processes (e.g. inelastic scattering, multiphoton absorbance) affect TERS readouts. Both experiments and models are used to identify and develop design rules for nanocrystal optical antennas to maximize Raman sensitivities and imaging resolution. The resulting nanocrystal-based AFM-TERS platform are applied toward the chemical and force imaging of nanomaterials and biological surfaces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.