Enhancing Photochemical Activity of Semiconductor Nanoparticles with Optically Active Ag Nanostructures: Photochemistry Mediated by Ag Surface Plasmons

Composite materials composed of optically active Ag nanostructures and TiO2 photocatalysts show enhanced photoactivity compared to the pure TiO2 in the decomposition of methylene blue. The enhanced photochemical activity is attributed to radiative transfer of energy, mediated by surface plasmons, from Ag particles to the semiconductor leading to higher concentrations of charge carriers (e(-)/h(+) pairs) in the semiconductor and therefore to higher photochemical activity. We demonstrate that the performance of the composite photocatalysts is a strong function of the size and shape of Ag nanostructures. This can be explained by the size- and shape-specific optical activity of Ag nanostructures. We show that by rationally changing the size and shape of Ag nanostructures it is possible to maximize photochemical activity of a semiconductor at a given excitation wavelength.