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.
