Preparation of gold and silver nanoparticles by pulsed laser ablation of solid target in water

Colloidal solutions of gold and silver nanoparticles (NPs) were prepared using a method pulsed laser ablation of target in liquid media. A gold and silver targets immersed in double distilled water are irradiated for 20 min by laser pulses with duration of 15 ns and repetition rate of 10 Hz. In order to investigate influences of laser wavelength and fluence on the particle size, shape and optical properties the experiments were preformed by using two different wavelength - the fundamental and the second harmonic (SH) (lambda = 1064 and 532 nm, respectively) of a Nd:YAG laser system. Two different values of the laser fluence for each wavelength at the experimental conditions chosen were used and thus it was changed from several J/cm(2) to tens of J/cm(2). For characterization of the NPs shape and size distribution were used transmission electron microscope (TEM) and optical transmission spectroscopy in the near UV and in the visible region. Spherical shape of the nanoparticles at the low laser fluence and appearance of aggregation and building of nanowires at the SH and high laser fluence is seen. Dependence of the mean particle size at the SH on the laser fluence was established. The mean diameter of gold NPs became smaller with decrease in laser wavelength.