Site-selective deposition of gold nanoparticles using non-adiabatic reaction induced by optical near-fields

In this paper, we report on site-selective deposition of metal nanoparticles using a non-adiabatic photochemical reaction. Photoreduction of gold was performed in a silica gel membrane containing tetrachloroaurate (AuCl(4)( - )) ions, using ZnO nanorods as the sources of optical near-field light, resulting in deposition of gold nanoparticles with an average diameter of 17.7 nm. The distribution of distances between the gold nanoparticles and nanorod traces revealed that the gold nanoparticles were deposited adjacent to the ZnO nanorods, reflecting the attenuation of the optical near-fields in the vicinity of the ZnO nanorods. We found that the emission wavelength from the ZnO nanorods was longer than the absorption edge wavelength of the tetrachloroaurate. Additionally, from the intensity distribution obtained by a finite-difference time-domain method, the gold deposited around the ZnO nanorods was found to be due to a non-adiabatic photochemical reaction.