'One-pot' synthesis of fluorescent Au@SiO2 and SiO2@Au nanoparticles

A class of fluorescent Au@SiO2 and SiO2@Au core–shell fluorescent nanoparticles has been synthesized using microemulsion assisted sol–gel method coupled with photoreduction reaction as an easy, rapid and versatile “one-pot” procedure. In the case of Au@SiO2-RhB (gold nanoparticles core coated with silica-Rhodamine B shell) different silica shell sizes were obtained ranging from 3 to 116 nm, while for RhB-SiO2@Au (Rhodamine B-silica core coated with gold nanoparticles shell) the size of gold shell falls within 3–38 nm interval. The synthesized core–shell nanoparticles have been characterized by a variety of techniques including Dynamic Light Scattering (DLS), High-Resolution Transmission Electron Microscopy (HR-TEM) coupled with Energy-Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), X-ray Diffractometry (XRD) and UV–VIS–NIR spectroscopy to confirm the size, shape, stability and topographic structure of the both core–shell nanostructures. The fluorescence enhancement of Rhodamine B (RhB) dye in the presence of gold nanoparticles (AuNPs) was demonstrated for the core–shell nanostructures synthesized in the present study, for different silica or gold shells. These interesting fluorescent core–shell nanoparticles provide ideal candidates for a variety of applications in materials science, biology, catalysis and optical fields.