Electrochemical Stability and Reactivity of Atomically Precise Single Metal and Alloy Clusters

化学学部的大分子、超分子和纳米化学项目支持路易斯维尔大学的Francis Zamborini教授和他的团队利用电化学技术创建和研究原子精度的金属纳米团簇。金属纳米团簇是直径小于2纳米（比人类头发直径小5万倍）的微小金属块。它们具有有趣的热、化学和光学特性，这些特性强烈地依赖于它们的大小和原子组成。一些纳米团簇具有有趣的发光特性。另一些可以加速化学反应，这在化学工业和可再生能源（如催化和燃料电池）的努力中很重要。这项研究创造了原子精度的金纳米团簇，并以弱键连接将它们附着在电极上。然后，研究人员使用一种叫做阳极溶出伏安法的电化学技术来研究它们的性质。这种电化学表征工具比其他广泛用于金属纳米簇分析的技术（如电子显微镜、x射线方法或质谱）更快、更便宜。除了获得关于这类材料的反应性和稳定性的新知识外，本研究还为本科生和研究生提供了最前沿的研究培训。该研究还通过课堂、海报会议和专题讨论会向高中和初中学生宣传科学。该项目获得了大分子、超分子和纳米化学项目的奖励，旨在用弱稳定剂合成原子精度的金属/合金纳米团簇（APMNCs/ APANCs），并通过阳极溶出伏安法（ASV）分析它们的尺寸、组成和反应性。新的合成方法和纯化策略现在允许科学家制备具有单一均匀尺寸和非常高纯度的金属纳米团簇，即APMNCs。通过添加第二种金属来制备apanc，可以微调APMNCs的光学和催化性能。具有第二种金属单原子的apac具有独特的性质和反应性。一个问题是，APMNCs和APANCs通常是用强稳定分子合成的，这改变了裸金属或合金的化学反应性，阻碍了阳极溶出伏安法（ASV）对其尺寸和金属成分的分析。ASV比电子显微镜、x射线法和质谱法更快、更便宜。本项目的重点是通过一种称为反电替换（AGR）的方法合成它们，并通过简单，低成本的ASV方法分析APANCs中的单金属原子。研究小组计划在Au APMNCs的电极上直接合成APANCs，并在上述其他方法的支持下，通过ASV在单原子掺杂水平上研究AGR反应的尺寸依赖性，以便更好地了解机理。该团队还旨在测量单原子（Ag, Cu, Pd， Hg和Cd）合金到Au APMNCs的氧化电位，作为簇大小和掺杂位置的函数，并监测AGR反应的动力学。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。

The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Francis Zamborini and his group at University of Louisville to create and study atomically precise metal nanoclusters using electrochemistry. Metal nanoclusters are tiny metal pieces of less than 2 nanometers in diameter (~50,000 times smaller than the diameter of human hair). They have interesting thermal, chemical, and optical properties that strongly depend on their size and atomic composition. Some nanoclusters have interesting light emitting properties. Others can speed up chemical reactions that are important in chemical industry and renewable energy efforts such as catalysis and fuel cells. This research creates atomically precise gold nanoclusters and attaches them to electrodes with weakly bound linkages. The researchers then study their properties using an electrochemical technique called anodic stripping voltammetry. This electrochemical characterization tool is much faster and cheaper than other techniques that are widely used for metal nanocluster analysis such as electron microscopy, x-ray methods, or mass spectrometry. In addition to the new knowledge gained about the reactivity and stability of this class of materials, this research provides cutting edge research training to undergraduate and graduate students. This research also promotes science to high school and middle school students through classes, poster sessions, and symposia. With this award from the Macromolecular, Supramolecular, and Nanochemistry Program, this project aims to synthesize atomically precise metal/alloy nanoclusters (APMNCs/ APANCs) with weak stabilizers and analyze their size, composition, and reactivity by anodic stripping voltammetry (ASV). New synthesis methods and purification strategies now allow scientists to prepare metal nanoclusters with a single uniform size with very high purity, i.e. APMNCs. The optical and catalytic properties of APMNCs can be fine-tuned by adding a second metal to make APANCs. APANCs with single atoms of a second metal have unique properties and reactivity. One problem is that APMNCs and APANCs are usually synthesized with strong stabilizing molecules that alter the bare metal or alloy chemical reactivity and prevent their size and metal composition analysis by anodic stripping voltammetry (ASV). ASV is much faster and cheaper than electron microscopy, x-ray methods, and mass spectrometry. This project focuses on their synthesis by a method called antigalvanic replacement (AGR) and the analysis of the single metal atoms in the APANCs by the simple, low cost ASV method. The research team plans to synthesize the APANCs directly on electrodes from Au APMNCs and study the size-dependence of the AGR reaction at the single atom doping level by ASV with support from other above mentioned methods in order to better understand the mechanism. The team also aims to measure the oxidation potential of single atoms (Ag, Cu, Pd, Hg, and Cd) alloyed to Au APMNCs as a function of cluster size and dopant location and monitor the kinetics of the AGR reactions.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.