CAREER: Time-Resolved Multi-Pulse Spectroscopy of Solvated Aza-Aromatics

能够吸收光并利用能量来驱动化学反应的分子对于能量储存，水处理和工业化学品生产的新技术具有潜在的意义。然而，理解和控制这些过程是具有挑战性的，因为能量通常消耗迅速，但储存缓慢。例如，拍摄一颗高速飞行的子弹（能量流）与拍摄一朵花的生长（能量储存）面临着不同的挑战。本研究由化学系化学结构动力学与机理（CSDM-A）项目资助。华盛顿大学（UW）的Schlenker正在使用先进的激光技术来提供对光吸收如何驱动化学反应的基本理解，这两个过程的速率就像高速子弹的速度和花朵的生长一样不同。从这个项目中收集到的科学知识有可能改善阳光到燃料的转化，太阳能水净化，甚至可能是光驱动工业化学品生产的新途径。教授Schlenker的研究综合科学教育（上升）计划的重点是帮助装备低收入和潜在的第一代大学生所需的工具，申请大学，在干专业取得成功，并进入干劳动力。该小组整合了研究和教育，以开发新的同龄人生成的科学教程，由来自华盛顿州最具种族和文化多样性的公立高中的学生提供（例如，通过与华盛顿大学的数学科学向上结合计划合作，在西南部西雅图的Chief Sealth高中）。RISE计划的一个例子产品：逐步的，同伴引导的学习视频科学实验在RISE专用的YouTube频道上免费分发。该研究小组还利用现有的UW资源，例如，通过与UW清洁能源研究所的伙伴关系。有机光化学可能为太阳能水分解领域的新研究奠定概念基础。廉价和可扩展的太阳能氢可以积极影响能源和粮食可持续性，因为氨肥料生产是资源密集型的。该项目的科学目标是了解分子间激发态在氢键分子复合物光化学中的作用。这项研究的重点是了解被称为氮杂芳烃的含氮分子如何通过从水和醇中去除氢原子进行光化学反应。为了实现这一目标，研究小组使用了与瞬态，光生，激发态和自由基相关的光谱和电化学信号。这些物种的人口监测作为一个功能的初始超快可见光激光脉冲（泵）和随后的红外脉冲（推）之间的时间延迟，使用瞬态吸收，光致发光，和电流检测。这种方法值得注意，因为它有可能从慢得多的化学反应的相对产率中提取超快时间信息。氮杂芳烃在光合组装、DNA光保护、工业色素光稳定等方面发挥着重要作用，是质子耦合电子转移（PCET）等可再生能源研究中常见的发色团。在这些能力中，氮杂芳烃可以与羟基基团形成氢键。这些氢键相互作用经常以看似不直观的方式改变发色团的光物理学和光化学反应性。超快光化学物理途径之间的分支比与氮杂芳烃分子的慢得多的后续光化学反应之间的关键机制联系可能构成向前迈出的一步。这项工作的更广泛的影响包括澄清分子间电子激发态是否由氢键相互作用产生的潜在社会效益作为光子引发反应的化学网关。此外，该项目还为研究生和本科生提供培训机会，将研究概念融入科学推广的公众参与活动中。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。

Molecules that can absorb light and use the energy to drive chemical reactions are potentially interesting for new technologies in energy storage, water treatment, and industrial chemical production. However, understanding and controlling these processes is challenging because energy is generally expended quickly but stored slowly. For example, filming a speeding bullet (energy flow) poses different challenges than filming a flower growing (energy storage). In this project, funded by the Chemical Structure Dynamics and Mechanisms (CSDM-A) program of the Chemistry Division, Professor Cody W. Schlenker of the University of Washington (UW) is using advanced laser techniques to provide fundamental understanding of how light absorption drives chemical reactions, two processes with rates as different as the velocity of a speeding bullet and the growth of a flower. The scientific knowledge gleaned from this project has the potential to improve sunlight-to-fuel conversions, solar water decontamination, and possibly even new avenues for light-driven industrial chemical production. Professor Schlenker's Research-Integrated Science Education (RISE) Program focusses on helping to equip low-income and potential first-generation college students with the tools needed to apply to college, succeed in STEM majors, and enter the STEM workforce. The group integrates research and education to develop new peer-generated science tutorials presented by students from the most ethnically and culturally diverse public high-schools in Washington State (e.g. Chief Sealth High School in Southern West Seattle through a partnership with the UW's Math & Science Upward Bound program). One example product of the RISE Program: Step-by-step, peer-led-learning video science experiments are distributed freely on a RISE-dedicated YouTube channel. The research group also leverages existing UW resources, for example, through a partnership with the UW Clean Energy Institute. Organic photochemistry may lay the conceptual groundwork for new research in the field of solar water splitting. Cheap and scalable solar hydrogen could positively impact energy and food sustainability, since ammonia fertilizer production is resource intensive.The scientific objective of this project is to understand the role of inter-molecular excited states in the photochemistry of hydrogen-bonded molecular complexes. This research is focused particularly on understanding how nitrogen-containing molecules known as azaarenes photochemically react by removing hydrogen atoms from water and alcohols. To achieve this goal, the research team uses spectroscopic and electrochemical signals associated with transient, photogenerated, excited-states and free radicals. The population of these species are monitored as a function of the temporal delay between an initial ultrafast visible laser pulse (pump) and a subsequent infrared pulse (push) using transient absorption, photoluminescence, and electrical current detection. This approach is notable because it has the potential to extract ultrafast time information from the relative yields of much slower chemical reactions. Azaarenes play critical roles in photosynthetic assemblies, DNA photo-protection, photo-stabilization of industrial pigments, and they are common chromophores in renewable energy research focused on proton-coupled electron transfer (PCET). In these capacities, azaarenes can hydrogen-bond with hydroxyl groups. These hydrogen bonding interactions often alter the chromophore's photophysics and photochemical reactivity in seemingly unintuitive ways. The critical mechanistic links between the branching ratio among ultrafast photophysical pathways and the much slower subsequent photochemical reactions of azaarene molecules may constitute a step forward. Broader impacts of this work include potential societal benefits resulting from clarifying whether inter-molecular electronic excited-states that arise from hydrogen bonding interactions serve as a chemical gateway to photon-initiated reactions. Additionally, this project provides training opportunities for graduate and undergraduate students, integrating research concepts into public engagement activities for science outreach.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.