A systematic growth of Gold nanoseeds on Silica for Silica@Gold core-shell nanoparticles and investigation of optical properties

Metal nanoshells consists of a dielectric core surrounded by a thin noble metal shell, possess unique optical properties, which render nanoshells attractive for use in different technologies. This paper reports a facile method for growth of small gold nanoparticles on the functionalized surface of larger silica nanoparticles. Mono-dispersed silica particles and gold nanoparticles were prepared by the chemical reduction method. The size of the shell nanoseeds could be altered by repeating the stage of reducing HAuCl4 on Au/APTES/silica particles, and the time for which they react. The nanocore-shell particles prepared were studied using transmission electron microscopy (TEM), UV-vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and PL spectrophotometer. The TEM images indicated that by growing gold nanoseeds over the silica cores a red shift in the maximum absorbance of UV-Visible spectroscopy is observed. Furthermore, a remarkable intensification happens in the PL spectra of silica@Au NPs in comparison with that of bare silica NPs. But, the existence of gold nanoseeds on the silica particles surfaces does not change the PL spectra peaks of these nanoparticles.