Hydrophobation and self-assembly of core-shell Au@SiO2 nanoparticles

Herein, we reported an efficient process for preparing monodisperse gold nanoparticles coated with silica shells (Au@SiO2) by vortex mixture instead of magnetic stirring. Without using any other surface coupling silane reagent such as 3-aminopropyltriethoxysilane (APS), core-shell Au@SiO2 nanoparticles could be easily obtained. TEM and UV–vis were employed to characterize the morphologies and the optical properties of Au@SiO2 nanoparticles. Subsequently, hydrophobic Au@SiO2 nanoparticles were obtained by grafting hydrocarbon chains on silica surfaces of the particles using the silane-coupling reagent octadecyltrichlorosilane (OTS). These hydrophobic Au@SiO2 nanoparticles could easily self-assemble onto the air–water interface to form close packed two dimensional nanoparticle arrays. The particle arrays could be transferred onto solid substrates to form Au@SiO2 film. The composition of the hydrophobic Au@SiO2 nanoparticles was examined by Fourier-transform IR spectroscopy (FTIR). The microstructure of the film of hydrophobic Au@SiO2 nanoparticles was investigated by the scanning electron microscope (SEM) and the atomic force microscope (AFM), respectively.