ABSTRACTFemtosecond near IR laser irradiation is explored as a general methodology to produce metal nanoparticles from metal precursor solutions. Initial studies of the formation and transformations of gold nanoparticles in aqueous solution are used as model processes to evaluate the effects of laser parameters, reaction medium and surfactants in controlling metal nanoparticle formation. The addition of polymer surfactants such as poly(ethylene glycol) (PEG) was found to significantly accelerate Au(III) reduction as compared to surfactant-free systems. Photo-reduction for aqueous solutions of Au(III) in the presence of PEG results in relatively small narrowly dispersed spherical gold nanoparticles compared to relatively large well-formed crystalline nanoparticles that are observed in the absence of surfactants. Varying the concentration of PEG is an effective approach to tune the diameter and size distribution from 3.9±0.7 nm to 11±2.4 nm for Au nanoparticles produced by laser processing.