Development of Novel-Scheme Tip-Enhanced Raman Spectroscopy and Its Application in Realistic Conditions -- Photochemistry of MoS2

提供物体表面化学图谱的扫描探针显微镜方法有望揭示有助于提高化学反应效率和开发更快的电子和光学设备的信息。扫描探针显微镜可能有一天会在各种环境中产生单个分子的化学图像，但由于与有效和简单地将探针元件集成到显微镜系统中相关的限制，这种可视化这种小物体的潜力一直受到阻碍。在化学测量和成像计划的支持下，以及化学系大分子，超分子和纳米化学计划的部分共同资助下，贝勒大学的Zhenrong Zhang和霍华德Lee教授正在开发尖端增强拉曼光谱技术，该技术允许在其自然环境中对单个纳米大小的物体进行成像，由于新颖的，集成光纤探针尖端由复杂的微加工方法制成。这种构建化学成像系统的新方法大大简化了显微镜操作，并产生了一种可视化微量样品的方法。 Baylor团队很容易研究气体和液体环境中催化剂表面的化学反应。由于新的纳米级化学成像工具的实用性和可访问性，该研究可能会影响材料，生物医学和光电科学的研究。张教授和李教授为本科生和技术学院的学生提供了光学和扫描探针显微镜的新学习和研究机会。 这样的学生技能对学生未来的职业生涯很有价值。贝勒团队还提供广泛的，公共教育和推广到韦科社区通过频繁的动手光学和光谱学活动在梅伯恩博物馆。本计画发展一种使用者友好的、尖端增强的、拉曼光谱奈米化学成像系统，此系统是基于一种无光学干扰的设计，也就是一个整合的电浆子光纤尖端组件。光纤尖端组件可以很容易地集成到现有的扫描探针显微镜设计中。这种独特的方法提供了一种简单的路径，用于将激发光独立地传递到样品并从样品收集光，这提供了高的光耦合效率和几乎不存在的远场背景干扰。因此，样品信号是高度敏感的，并提供接近单分子的检测限。等离子体纳米结构光纤合并了等离子体和光纤的领域，从而使得尖端增强的拉曼光谱成像应用在许多气体和液体环境中成为可能。本提案的具体目标是使用光纤尖端增强的拉曼光谱成像演示纳米级映射，并在受控的环境压力环境中研究纳米级硫化钼（MoS2）的光化学。 该团队还试图通过使用场可调谐等离子体材料来展示液体环境中的光纤尖端增强拉曼光谱成像。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。

Scanning probe microscopy methods that provide chemical maps of the surface of objects hold promise for revealing information that is useful for making chemical reactions more efficient and developing faster electronic and optical devices. Scanning probe microscopes may one day yield chemical images of individual molecules in a variety of environments, but this potential to visualize such small objects has been stymied due to limitations associated with effectively and simply integrating the probe element into the microscope system. With support from the Chemical Measurement and Imaging Program and partial co-funding from the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Zhenrong Zhang and Howard Lee at Baylor University are developing tip-enhanced Raman spectroscopy techniques that allow for imaging of individual nanometer-sized objects in their native environments, as a result of novel, integrated fiber optic probe tips made by sophisticated microfabrication methods. This new approach to building chemical imaging systems significantly simplifies microscope operation and yields a method for visualizing tiny amounts of sample. The Baylor team readily investigates chemical reactions on catalyst surfaces in gas and liquid environments. Due to the practical and accessible nature of the new nanoscale chemical imaging tool, the research may impact research in materials, biomedical, and optoelectronic sciences. Professors Zhang and Lee are providing undergraduate and technical college students new learning and research opportunities in optics and scanning probe microscopy. Such student skill sets are valuable for the students' future careers. The Baylor team is also providing broad, public education and outreach to the Waco community through frequent hands-on optics and spectroscopy events at the Mayborn Museum. This project develops a user-friendly, tip-enhanced, Raman spectroscopy nanoscale chemical imaging system that is based on an optical alignment-free design, namely, an integrated plasmonic fiber-tip assembly. The fiber-tip assembly can be easily integrated into existing scanning probe microscope designs. This unique approach provides a simple path for independent delivery of excitation light to and collection of light from a sample, which offers high light coupling efficiency and virtually nonexistent far-field background interference. As a result, sample signals are highly sensitive and provide detection limits approaching that of single molecules. The plasmonic nanostructured optical fibers merge the fields of plasmonics and fiber optics, thereby enabling tip-enhanced Raman spectroscopy imaging applications in numerous gaseous and liquid environments. The specific objectives of this proposal are to demonstrate nanoscale mapping using fiber-tip-enhanced Raman spectroscopy imaging and study the photochemistry of molybdenum sulfide (MoS2) at the nanometer scale in a controlled ambient pressure environment. The team also seeks to demonstrate fiber-tip-enhanced Raman spectroscopy imaging in a liquid environment via the use of field-tunable plasmonic materials.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.