Spectroelectrochemistry of Redox-Active Colloidal Nanocrystals

现在，从许多不同的半导体中生长晶体是可能的，这些半导体的大小只有几个纳米，或者说大约是一缕头发的10万倍。在这些非常小的尺寸下，半导体纳米晶体具有新颖的物理和化学性质，可以通过改变其大小、形状和化学成分来调整，使其在许多下一代光子和能源技术中具有吸引力。尽管这些纳米晶体前景看好，但它们也带来了独特的挑战。例如，当人们通过添加电子给纳米晶体充电时，它可以改变颜色，并在其表面发生新的化学反应。在化学系大分子、超分子和纳米化学项目的支持下，华盛顿大学的丹尼尔·甘梅林教授正在研究电子进入(和离开)半导体纳米晶体是如何改变其物理性质和化学反应活性的。甘默林教授正在与他的学生们合作，开发新的实验方法，使他们能够精确地改变纳米晶体的电荷，同时监测它们的物理化学性质的变化。他们的发现可能会对能源转换、能源储存和高效能源利用方面的新技术产生重要影响。该项目还为学生提供高级跨学科教育和培训，为他们未来成为科学、工程、技术创新和教育领域的领导者做好准备。通过让本科生参与该项目，将项目概念纳入华盛顿大学本科实验室课程，以及在西雅图K-12学校和社区STEM活动中开展推广活动，强调研究和教育的一体化。尽管近年来在控制高质量胶体还原或氧化半导体纳米晶的形成方面进行了广泛的研究和进展，但胶体纳米晶的氧化还原特性仍然知之甚少，特别是在与电荷可调等离子、高密度电荷存储或多电子催化相关的多载流子体系中。该项目的目标是开发和应用新的方法来测量、控制和了解氧化还原活性胶体半导体纳米晶的性质，重点是纳米级化学转变的光谱电化学探针。我们的目标是阐明这种纳米晶体的氧化还原反应性和相关的物理化学性质，这些纳米晶体拥有过多的离域电子或空穴。纳米晶体的研究重点包括：与电荷可调等离子体有关的金属耦合电子转移反应、与储能有关的可溶性超级电容器、与光化学和电子转移有关的纳米结构的带边电势。所有这些都有望在未来的纳米晶体技术中发挥核心作用。光谱电化学电位法被认为是一种对独立胶体半导体NC氧化还原性能的特别强大和定量的探针，它能够实现对纳米晶体氧化还原操作和成分转变的独特在线监测。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。

It is now possible to grow crystals from many different semiconductors that are just a few nanometers in size, or about 100,000 times smaller than a strand of hair. At these very small sizes, semiconductor nanocrystals take on novel physical and chemical properties that can be adjusted by changing their size, shape, and chemical composition, making them attractive for use in many next-generation photonic and energy technologies. Although they hold great promise, these nanocrystals also present unique challenges. For example, as one charges a nanocrystal up by adding electrons, it can change color and new chemical reactions can take place at its surface. With support from the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Daniel Gamelin of the University of Washington is studying how electrons that are transferred into (and out of) semiconductor nanocrystals alter their physical properties and chemical reactivity. Working with his students, Professor Gamelin is developing new experimental methods that enable them to precisely alter the nanocrystal charge while monitoring changes in their physico-chemical properties. Their discoveries could have important implications for new technologies in energy conversion, energy storage, and efficient energy usage. The project is also providing advanced interdisciplinary education and training for students, preparing them to be future leaders in science, engineering, technology innovation, and education. Integration of research and education is emphasized through involvement of undergraduates in the project, incorporation of project concepts into the UW undergraduate laboratory curriculum, and outreach activities at Seattle K-12 schools and community STEM events.Despite extensive studies and progress in controlling the formation of high-quality colloidal reduced or oxidized semiconductor nanocrystals over recent years, the redox properties of colloidal nanocrystals remain poorly understood, particularly in the multiple-carrier regime relevant to charge-tunable plasmonics, high-density charge storage, or multi-electron catalysis. This project targets the development and application of new methods for measuring, controlling, and understanding the properties of redox-active colloidal semiconductor nanocrystals emphasizing spectroelectrochemical probes of nanoscale chemical transformations. The goal is to elucidate the redox reactivities and associated physico-chemical properties of such nanocrystals that possess excess delocalized electrons or holes. Specific nanocrystal research foci include: metal-coupled electron-transfer reactions relevant to charge-tunable plasmonics, soluble supercapacitors relevant to energy storage, and band-edge potentials of nanostructures relevant to photochemistry and electron transfer. All of these are anticipated to play central roles in future nanocrystal technologies. Spectroelectrochemical potentiometry has been identified as a particularly powerful and quantitative probe of the redox properties of free-standing colloidal semiconductor NCs, and it is enabling unique in situ monitoring of nanocrystal redox manipulations and composition transformations.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.