Combined Single-Molecule Raman and Conductance Spectroscopies for Understanding Electric Field-Controlled Chemistry

在化学测量和成像(CMI)计划的支持下，以及化学系化学结构、动力学和机制B(CSDM-B)计划的部分共同资助下，加州大学戴维斯分校的Joshua Hihath和他的研究团队旨在了解外加电场对分子开关过程的影响。随着电场成为可以选择性催化反应的“智能试剂”，理解它们在化学反应中的作用是至关重要的。希哈斯团队正致力于开发一种新颖而强大的方法，用于同时施加电场，并在化学过程之前、期间和之后定量测量该电场的影响。他们的方法利用了最近开发的同时进行单分子拉曼光谱和电导测量的系统。跟踪电场和光场、电荷转移和加热对单个分子的影响的能力将影响到控制化学过程很重要的广泛领域。该项目为研究生和本科生研究人员提供研究机会，包括从STEM(科学、技术、工程和数学)代表性较低的群体中积极招募的个人。将拉曼光谱与单分子电学测量相结合，可以提供关于两个电极之间的单个分子中的构型、结合能、机械应变、振动模式和局部有效温度的详细信息。这种多维信息可以解析分子内发生的电场、机械、电荷转移和加热对化学过程的影响。这个项目开始探索两个不同的单分子光开关在一个应用领域中经历构象变化的机制。这项研究将提供有关电场如何绕过轨道对称性选择规则的信息，以及这些过程与光化学转换过程的不同之处。具体目标包括：i)从结合到两个电极上的分子的拉曼信号原位识别单分子系统中的电控异构化过程；ii)提高对电场方向和大小对电子异构化过程中键重组和过渡态的影响的理解；iii)确定外加电场和机械应变对异构化过程的相互作用；以及iv)澄清电流驱动和场驱动异构化过程之间的歧义。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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 (CMI) program and partial co-funding from the Chemical Structure, Dynamics, and Mechanisms - B (CSDM-B) program in the Division of Chemistry, Joshua Hihath and his research team at the University of California, Davis aim to understand the effects of applied external electric fields on molecular switching processes. As electric fields are emerging as “smart reagents” that can selectively catalyze reactions, understanding their role in chemical reactions is critical. The Hihath group is working to develop a novel and powerful approach for simultaneously applying an electric field and quantitatively measuring the effect of this field before, during, and after a chemical process. Their approach leverages a recently developed system for performing single-molecule Raman spectroscopy and conductance measurements simultaneously. The ability to track the effects of electrical and optical fields, charge transfer, and heating on individual molecules will impact a broad range of fields where controlling chemical processes is important. The project is providing research opportunities for graduate and undergraduate researchers, including individuals actively recruited from groups underrepresented in STEM (science, technology, engineering and mathematics).The combination of Raman spectroscopy with single-molecule electrical measurements provides detailed information about the configuration, binding energy, mechanical strain, vibrational modes, and local effective temperature in a single molecule bound between two electrodes. This multidimensional information allows resolution of electric field, mechanical, charge transfer, and heating effects on chemical processes occurring within the molecule. This project sets out to probe the mechanisms by which two distinctive single-molecule photoswitches undergo conformational changes in an applied field. The study will provide information about how the electrical field enables bypassing orbital symmetry selection rules, and how these processes differ from photochemical switching processes. Specific objectives include i) in situ identification of electrically controlled isomerization processes in single-molecule systems from the Raman signature of a molecule bound to two electrodes; ii) improved understanding of the effects of electric field orientation and magnitude on bond reorganization and transition states during electrical isomerization processes; iii) determination of the interplay between applied field and mechanical strain on isomerization processes; and iv) disambiguation between current-driven and field-driven isomerization processes.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.