Silver nanoparticles (Ag NPs) were prepared by different chemical methods possessing different sizes 3 +/- 2, 8 +/- 2, and 20 +/- 5 nm. The influence the size of Ag NPs was demonstrated by the absorption and fluorescence spectra, the maximum absorption of Ag NPs increases as the particle size increases. When Ag NPs irradiated with 308 nm excimer laser; the maximum absorption and the full width at half maximum decreased as the number of pulses increased up to 100,000 pulse; due to the size reduction. The fluorescence spectra of Ag NPs and irradiated Ag NPs with 308 nm excimer laser were recorded after excitation at 441.5 nm He-Cd laser, showing a red shift increasing as the particle size is increased. (c) 2006 Elsevier B.V. All rights reserved.