In this paper, a facile method for the synthesis of gold nanoseeds on the functionalized surface of silica nanoparticles has been investigated. Mono-dispersed silica particles and gold nanoparticles were prepared by the chemical reduction method. The thickness of the Au shell was well controlled by repeating the reduction time of HAuCl₄ on silica/3-aminopropyltriethoxysilane (APTES)/initial gold nanoparticles. The prepared SiO₂@gold core/shell nanoparticles were studied using x-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy and ultraviolet visible (UV–Vis) spectroscopy. The TEM images indicated that the silica nanoparticles were spherical in shape with 100 nm diameters and functionalizing silica nanoparticles with a layer of bi-functional APTES molecules and tetrakis hydroxy methyl phosphonium chloride. The gold nanoparticles show a narrow size of up to 5 nm and by growing gold nanoseeds over the silica cores a red shift in the maximum absorbance of UV–Vis spectroscopy from 524 to 637 nm was observed.