Platinum nanoparticles with 6 nm in average diameter were prepared in an aqueous solution of sodium dodecyl sulfate (SIDS) at a given SDS concentration. The solution was irradiated with an intense pulsed laser at 355 nm. The nanoparticles were fragmented under. irradiation into smaller ones with 1.5 nm average diameter above the critical micelle concentration of SDS, whereas they formed nano-scale networks below it. The small nanoparticles and the networks were found to be fabricated selectively by controlling the dynamics of photo-fragments formed by laser excitation of the interband transition of the nanoparticles. (C) 2003 Elsevier B.V. All rights reserved.