Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Abstract

Boron dipyrromethene (BODIPY) molecules with donor-acceptor configurations are of great interests for harvesting and converting solar energy in a solar cell. Au nanoparticles have been applied to enhance solar energy harvesting and conversion efficiency of organic solar cells because of their surface plasmon properties for increasing light absorption cross-section of an organic dye. Electrochemical properties of single BODIPY dyes and plasmonic Au nanoparticles (NPs) are studied using combined optical and electrochemical methods to reveal their structure-function relationship at the nanometer scale. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-doped tin oxide (ITO) surfaces. Dark field scattering (DFS), photoluminescence (PL), and electrogenerated chemiluminescence (ECL) are used to probe local redox reactions of single Au nanoparticles at transparent planar and micro-sized electrode. Our study shows that these optical responses at individual plasmonic NPs are strongly dependent on particle size, and are affected by the local chemical and charge transfer environment of the NPs.