Synthesis of rod-like silica–gold core-shell structures

Synthesis of rod-like silica–gold core-shell structures is reported by using silica rods having length of ∼1 μm and diameter of ∼200 nm. Before deposition of gold nanoparticles the aforementioned silica rods were modified by using 3-aminopropyltrimethoxysilane (APTMS) in order to attach aminopropyl groups and consequently, to facilitate deposition of Au. There methods were used to deposit Au nanoparticles. The first method of deposition was performed by using nanosized Au nanoparticles obtained by reduction of tetrachloroauric acid with borohydride. The second route was performed by direct reduction of tetrachloroauric acid with formaldehyde, which led to the formation of Au nanoparticles of about 50 nm. In the third route Au nanoparticles were obtained by reduction tetrachloroauric acid with borohydride but their deposition was carried out on the silica rods pre-decorated with small Au colloids. Each of these methods led to the formation of Au less or more uniform nanoshells on siliceous rods.