Gold Hollow Nanospheres: Tunable Surface Plasmon Resonance Controlled by Interior-Cavity Sizes

Abstract

Uniform gold hollow nanospheres with tunable interior-cavity sizes were fabricated by using Co nanoparticles as sacrificial templates and varying the stoichiometric ratio of starting material HAuCl₄ over the reductants. The formation of these hollow nanostructures is attributed to two subsequent reduction reactions: the initial reduction of HAuCl₄ by Co nanoparticles, followed by the reduction by NaBH₄. In addition, a thick layer of silica was successfully coated onto the gold hollow nanospheres. These nanostructures are extensively characterized by TEM, XRD, HRTEM, SEM, electron diffraction, energy-dispersive X-ray analysis, and UV−visible absorption spectroscopy. It is evident that the SPR peak locations corresponding to these hollow nanospheres are shifted over a region of more than 100 nm wavelength due to changes of shell thickness, which make these optically active nanostructures of great interest in both fundamental research and practical applications.