Effects of thiol capping agents on the laser-induced deposition of gold nanoparticles

Gold particles were deposited on a cover glass by pulsed-laser irradiation of thiol-capped gold nanoparticles in cyclohexane. Dodecanethiol (DT) was used as the capping agent to stabilize colloidal dispersion of the gold nanoparticles in cyclohexane (DT-capped gold nanoparticles: DTAu). The DT molecules adsorbed on the DTAu were partially replaced with 1,6-hexanedithiol (HD) to obtain photoreactive gold nanoparticles (HDAu). A hydrophilic cover glass was immersed into the cyclohexane solution of HDAu or DTAu, and irradiated by the pulsed 532 nm light (10 Hz, 33 mJ/pulse) of a Nd: YAG laser, resulting the deposition of gold nanoparticles on the cover glass. The degree of deposition was traced by absorption spectroscopy. The amount of deposited gold particles was evaluated from ICP-MS after dissolving them into aqua regia. More than 2 min of irradiation was necessary for the deposition of DTAu, while only 1 min of irradiation resulted in the deposition (∼3 μg) of HDAu. It was found that partial replacement of DT with HD accelerated the laser-induced deposition of the gold nanoparticels as well as their size growth.