UV-visible spectra character of larger diameter of gold nanoparticles (AuNPs)

The dependence of the optical properties of spherical gold nanoparticles (AuNPs) on particle size and wavelength were analyzed theoretically using Mie theory, where the complex refractive index of gold was corrected for the effect of a reduced mean free path of the conduction electrons in small particles. The simulation results indicated that larger diameter AuNPs have high sensitivity and the resolution compared to the small diameter AuNPs. Two different fabricated methods for synthesis larger diameter AuNPs have been proposed. One is the directly synthesis 50nm AuNPs, the other method is separated to two steps (prepared 13nm AuNPs seeds, then synthesis 50nm AuNPs). Comparing the UV-vis spectra and SEM image of the AuNPs synthesized by these two method, we find that the symmetry of the directly synthesis method is better than the other method. The experiment results show that the synthesis AuNPs are uniform. The major aim of this work is to provide a simple and fast method to synthesis larger diameter AuNPs and research the optical properties of the nanoparticles.