Synthesis and characterization of hollow gold nanoparticles using silica spheres as templates

In this paper, we report preparation and characterization of monodispersed hollow gold nanoparticles with the average thickness of about 25 nm through the template method. The formation of these hollow nanostructures involves three subsequent steps: preparation and functionalization of silica nanospheres, formation of a thick gold shell around the templates and following selective etching of silica particles by HF solution. In order to obtain monodispersed hollow particles, the optimum amount of trisodium citrate was used as stabilizing agent. The results show that although for both concentrated and diluted HF solution, pure gold nanoparticles were obtained, but the 10 volume percent HF solution destroys the hollow structures and just agglomerated gold particles were generated. Furthermore, by investigation the optical response of the synthesized metallic nanoparticles consisting gold nanoparticles, silica-gold nanoshells and hollow gold nanoparticles, it can be inferred that the hollow structures are capable to absorb wavelengths mainly within near infrared region. Hence, this paper introduces a new strategy to produce the metallic nanostructures with optical response within NIR range which may provide new opportunities for their applications in variety of fields such as photoelectronics, catalysis and cancer therapy.