Scanning Electrochemical Microscopy Investigations of Monolayer-protected Gold Nanoparticles and Shewanella oneidensis

Abstract

As climate change and population growth increase the demand for energy and clean water, research must be to alleviate the increased pressure on the energy-water nexus. In this work, two potential solutions to this problem were investigated: gold nanoparticles and Shewanella oneidensis. Monolayer protected gold nanoparticles have recently been proposed as possible components of improved photovoltaics as nanocapacitors. In order to effectively implement nanoparticles in this field, it is important to understand the electron transfer properties of a variety of protecting ligands. In this research, we determined the forward heterogeneous electron-transfer rate constant of wired organic-soluble and water-soluble monolayer protected gold NPs using the scanning electrochemical microscope (SECM). Using SECM approach curves, we were able to determine the electron transfer rates of nanoparticles protected with a variety of ligands. By altering the monolayer composition through place exchange as well as changing the ligand charge by adjusting solution pH, we demonstrate effective means of modulating electron transfer rates. Shewanella oneidensis bacteria have been noted for potential use in clean energy production and water purification due to its capability to metabolize a variety of species, including insoluble metal oxides and toxic metal species. Again using SECM, we investigated these dissimilarity metal reduction pathways and spatially determine flavin production and consumption of S. oneidensis biofilms. This understanding of the DMR mechanisms is necessary in the optimization for use of S. oneidensis in bioenergy and bioremediation applications.