Electron Transfer at Biologically Modified Electrodes

Abstract

Electron transfer between biomolecules and electrode surfaces is greatly important in the development and understanding of bioelectrochemical systems. This dissertation studies two bioelectrochemical systems: Photosystem I (PSI) bioelectrodes and carbon paper electrodes for NAD+ reduction. A common focus is the improvement of our understanding of mediated electron transfer (MET). Porous, translucent, and highly conductive inverse-opal indium tin oxide (ITO) electrodes were developed and used as cathodes for PSI bioelectrodes, highlighting the importance of electrode geometry and surface area. PSI monolayers (~8 nm in thickness) were studied by deposition of chemically modified PSI onto gold electrodes and, later, by deposition of many individual PSI layers between PEDOT:PSS through a layer-by-layer deposition scheme. PSI-PEDOT:PSS layer-by-layer films were highly reproducible and achieved electron turnover numbers an order of magnitude higher than drop-casted PSI films. Lastly, the stability of NAD+/NADH in aqueous buffers was investigated and platinum monolayer modified carbon paper electrodes were developed to promote the reduction of NAD+ by providing adsorbed protons on the electrode surface. In all, the study of the electron transfer mechanisms from biomolecules to electrodes can provide insight and opportunities for improvement of the performance of many bioelectrochemical systems.