Effect of nanoparticle sizes on the extinction spectrum of colloidal solutions produced by laser ablation of gold in water

We have measured the extinction spectra of colloidal solutions of gold nanoparticles synthesised by nanosecond laser ablation in water for the conditions of a bimodal particle size distribution. The extinction spectra are analysed by using the Mie theory and the contribution of particles of different sizes to the radiation attenuation is established. A method is proposed for determining the concentrations of individual populations of particles in a solution on the basis of the spectral dependence of the extinction coefficient. Mechanisms of the nanoparticle formation during laser ablation of metals in liquids are discussed.