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

化学系的大分子、超分子和纳米化学项目支持路易斯维尔大学的弗朗西斯·赞博里尼教授和他的团队使用电化学创建和研究原子级精确的金属纳米团簇。 金属纳米团簇是直径小于2纳米的微小金属片（比人类头发直径小约50，000倍）。 它们具有有趣的热，化学和光学性质，这些性质在很大程度上取决于它们的大小和原子组成。 一些纳米团簇具有有趣的发光性质。 另一些可以加速化学反应，这在化学工业和可再生能源的努力中很重要，如催化和燃料电池。 这项研究创造了原子级精确的金纳米团簇，并将它们连接到具有弱结合键的电极上。 然后研究人员使用一种称为阳极溶出伏安法的电化学技术来研究它们的特性。 这种电化学表征工具比广泛用于金属纳米团簇分析的其他技术（如电子显微镜，X射线方法或质谱法）更快，更便宜。 除了获得有关这类材料的反应性和稳定性的新知识外，这项研究还为本科生和研究生提供了前沿的研究培训。 这项研究还通过课程，海报会议和研讨会向高中和初中学生推广科学。凭借大分子，超分子和纳米化学计划的这一奖项，该项目旨在合成具有弱稳定剂的原子级精确金属/合金纳米团簇（APMNC/ APANCs），并通过阳极溶出伏安法（ASV）分析其尺寸，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非常高纯度的单一均匀尺寸的金属纳米团簇，即APMNC。 APMNC的光学和催化性质可以通过添加第二种金属来微调以制备APANC。 具有第二金属的单个原子的APANC具有独特的性质和反应性。 一个问题是APMNC和APANC通常用强稳定分子合成，所述强稳定分子改变裸金属或合金的化学反应性并阻止通过阳极溶出伏安法（ASV）进行的它们的尺寸和金属组成分析。 ASV比电子显微镜，X射线方法和质谱法更快，更便宜。 该项目的重点是通过一种称为反电流置换（AGR）的方法合成它们，并通过简单，低成本的ASV方法分析APANCs中的单个金属原子。 研究小组计划直接在电极上从Au APMNC合成APANC，并在上述其他方法的支持下，通过ASV研究单原子掺杂水平下AGR反应的尺寸依赖性，以便更好地理解机制。 该团队还旨在测量与Au APMNC合金化的单个原子（Ag、Cu、Pd、Hg和Cd）的氧化电位，作为簇大小和掺杂剂位置的函数，并监测AGR反应的动力学。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。

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.