Facile synthesis of Au@SiO2 core–shell nanoparticles with multiple Au nanodots by a reverse microemulsion (water-in-oil) method

Abstract A water-in-oil (W/O) microemulsion was prepared by mixing cyclohexane and HAuCl 4 aqueous solution at the presence of a nonionic surfactant Triton X-100 and 1-hexanol. By successively adding sodium borohydride (NaBH 4 ), ammonium hydroxide (NH 3 ·H 2 O) and tetraethyl orthosilicate (TEOS) to this microemulsion, Au@SiO 2 hybrid nanoparticles were produced which have been fully characterized by transmission electron microscopy (TEM) and high resolution TEM (HR-TEM) observations, UV–vis measurements and thermo gravimetric analysis (TGA). It was found that in each Au@SiO 2 hybrid nanoparticle, the silica shell can encapsulate multiple Au nanodots. The parameters of the Au@SiO 2 hybrid nanoparticles including the thickness of the silica shell, the number of encapsulated Au nanodots and the size of the nanoparticles can be easily tuned by changing the volume of TEOS and the reaction time before adding TEOS, respectively. These interesting core–shell nanoparticles provide ideal candidates for a variety of applications in materials science, biology and catalysis.