Photothermally enhanced catalytic activity of partially aggregated gold nanoparticles

This report describes the catalytic reduction of 4-nitrophenol (4-NP) using gold nanoparticles (GNPs) in aqueous solution upon exposure to a solar-simulated light. As monodispersed GNPs possess a strong but narrow absorption band in the visible areas, anisotropic/partially aggregated GNPs are designed to have a strong and wide absorption band across visible to near-infrared wavelengths of light. Given their strong and broad absorption properties, these partially aggregated GNPs exhibited slightly superior photothermally induced heating of the reaction medium (i.e., water) when compared to the monodispersed GNPs upon exposure to a solar-simulated light. Subsequently, the catalytic reduction of 4-NP to 4-aminophenol was examined in the presence of various GNPs with and without the irradiation of light. While the monodispersed GNPs exhibited a moderate increase in the reaction rates of 4-NP with the light irradiation, the partially aggregated GNPs afforded the notable enhancement of the reaction rate, presumably due to their higher photon-to-heat conversion efficiency.