Synthesis and physicochemical characterization of tunable silica–gold nanoshells via seed growth method

Gold nanoshells are a class of nanocomposites consisting of a core surrounded by a gold shell. They are known to exhibit attractive optical property due to the excitation of surface plasmon resonance. This paper reports synthesis and characterization of gold nanoshells using two different sizes of gold colloids obtained by citrate and borohydride for nucleation step. Silica nanoparticles with an average diameter of 100 nm were synthesized and were modified with 3-aminopropyltriethoxysilane (APTES). The functionalized silica nanoparticles were initially decorated with gold colloids. Then gold hydroxide was reduced into decorated silica particles to obtain gold shell. The results reveal that the silica surface coverage with gold nanoparticles and gold shell thickness depends on size of gold nanoparticles. They show that smaller gold colloids provide better coverage at seeding step; hence, a uniform and complete shell is the consequence for these kinds of particles. Furthermore, tunability of gold nanoshells into appropriate wavelength according to desire application while using 4.5 nm gold nanoparticles for decoration is more facile due to possibility to control shell growth progress and shell thickness.