CAS: Elucidating How Nanocrystal Structure Controls Electron Flow in Nanocrystal-Enzyme Complexes

在化学系大分子、超分子和纳米化学（MSN）项目的支持下，科罗拉多大学博尔德分校的Gordana Dukovic教授将合成、先进的激光技术和高分辨率显微镜结合起来，跟踪纳米晶体酶复合物中能够产生光驱动氢的电子流动。为了制造氢，纳米晶体首先被光激发，增加其电子的能量。这些被激发的电子必须从纳米晶体跳到酶那里，然后从一个位置跳到另一个位置，到达酶的反应中心，就像从一块石头跳到另一块石头一样。每一种电子跳都对氢的产生很重要，但它们很难观察和控制。Dukovic教授和她的学生将测量关键电子跳跃事件的时间，以及它们如何依赖于纳米晶体结构、表面性质和与酶的结合。他们的发现可能会带来利用阳光制造化学物质的新方法，包括太阳能燃料。此外，该项目通过支持初级教师和科学家的职业发展，以及来自不同背景的学生的本科教育，帮助培养国家的科学、技术、工程和数学（STEM）劳动力。该项目将阐明光化学H2生成的电子途径，当光激发半导体纳米晶体将电子转移到吸附的氢酶上，氢酶催化质子还原为H2。该项目将研究纳米晶体量子点（QDs）的性质（如组成、直径和表面化学）如何影响QD与酶的结合、光激发电子的转移，以及H2生成的其他关键过程，如空穴清除和酶的反向电子转移。该项目的结果将是提高对纳米晶体如何驱动酶催化的理解。反过来，这将导致设计原则，如何利用纳米晶体结构和性质的巨大可调性来适应它们来驱动复杂的，多步骤的光驱动化学。该奖项反映了美国国家科学基金会的法定使命，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 Macromolecular, Supramolecular, and Nanochemistry (MSN) program in the Division of Chemistry, Professor Gordana Dukovic of University of Colorado Boulder is combining synthesis, advanced laser techniques, and high-resolution microscopy to follow the flow of electrons in nanocrystal-enzyme complexes capable of light-driven hydrogen production. To make hydrogen, the nanocrystal is first excited by light, increasing the energy of its electrons. These excited electrons must then hop from the nanocrystal to the enzyme, and then make their way to the enzyme's reaction center by hopping from one site to another, like crossing a stream by jumping from stone to stone. Each of these electron hops is important for hydrogen production, but they are difficult to observe and control. Professor Dukovic and her students will measure the times of the critical electron hopping events, and how they depend on nanocrystal structure, surface properties, and binding to the enzyme. Their discoveries could lead to new ways to use sunlight to make chemicals, including solar fuels. Additionally, the project is helping to foster the Nation's science, technology, engineering, and mathematics (STEM) workforce by supporting career development of junior faculty and scientists, as well as the undergraduate education of students from a variety of backgrounds. This project will elucidate the electron pathways involved in photochemical H2 generation that occurs when photoexcited semiconductor nanocrystals transfer electrons to the adsorbed enzyme hydrogenase, which catalyzes proton reduction to H2. The project will examine how properties of nanocrystalline quantum dots (QDs) such as composition, diameter, and surface chemistry impact the QD binding with the enzyme, the transfer of photoexcited electrons, and other critical processes for H2 production, such as hole scavenging and back-electron transfer from the enzyme. The outcome of the project will be an improved understanding of how nanocrystals drive enzyme catalysis. This, in turn, will lead to design principles for how to use the immense tunability of nanocrystal structure and properties to adapt them to drive complex, multi-step light-driven chemistry.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.