Size and shape approximation of gold nanoparticles using theoretical modelling

Gold nanoparticles were prepared by citrate reduction of chloroauric acid. Different samples were prepared by varying the concentration of reducing agent. The surface plasmon resonance peak position depends on size and shape of metal nanoparticles. The dependence of the optical properties of spherical gold nanoparticles on particle size and wavelength were analyzed theoretically. It is shown that the average size of gold nanoparticles can be estimated based on the fitting of their UV-vis spectra with the Mie model by comparing the peak positions. Mie theory gives good results and accounts for the presences of spherical nanoparticles in the solution. So the better fitted experimental data with theoretical results also gives the idea of shape of gold nanoparticles.