Dissociation and aggregation of gold nanoparticles under laser irradiation

Gold nanoparticles having an average diameter of similar to8 nm were prepar ed in an aqueous solution of sodium dodecyl sulfate by laser ablation at 10 64 nm of a gold metal plate and were irradiated by a laser at 532 nm for si ze-reduction of the gold nanoparticles produced by laser ablation. The diam eters of the gold nanoparticles thus produced were measured directly by ele ctron microscopy, while the average diameter was estimated from the optical absorption spectrum of the solution containing the nanoparticles with the aid of the Drude theory of a conducting droplet. The average diameter of th e nanoparticles was found to decrease toward the smallest possible diameter as the laser shot increases: in this condition, the resulting nanoparticle s have comparable diameters. In addition, the smallest possible diameter wa s found to decrease with the laser fluence. It was also shown that aggregat ion of the nanoparticles is not negligible when the laser fluence is high. In conclusion, nanoparticles with an average diameter was pulverized into s maller nanoparticles with a desired average diameter and a narrow distribut ion by a proper selection of the laser fluence and the laser shots. The mec hanism of the particle pulverization was proposed.