Thermal diffusivity monitoring during the stages of formation of core–shell structures of SiO₂@Au

The thermal and optical properties in the formation of gold nanoshells on SiO₂ were studied by thermal lens (TL) and absorption spectroscopy. The formation of SiO₂@Au particles was realized in four stages: First, SiO₂ spheres were synthesized using the Stöber method. Later the attachment of amino groups and the adsorption of hydroxide gold nanoparticles on surface of silicon dioxide were realized. Finally, the growth of gold shell was obtained. The UV–Vis spectrum of SiO₂@Au nanostructures showed an absorption band in the near-infrared region around of 740 nm associated with the presence of a gold shell on the dielectric platform. Transmission electron microscopy and scanning electron microscopy confirmed the formation of well-defined gold nanoshell on SiO₂ spheres. Silicon dioxide nanospheres with an average size of 293 nm and Au-nanoshell with thicknesses of ~ 14 nm were obtained. The high crystalline quality of Au-nanoshell was demonstrated by X-ray diffraction. The thermal diffusivity during the different steps of formation of the gold nanoshell was studied using absorption spectroscopy and the mode-mismatched TL. A redshift of absorption band optic was observed by UV–Vis, and a very significant increase in the thermal diffusivity as the Au shell was completed.