A silica shell has been successfully fabricated onto a planar gold substrate. In fact, prior to depositing silica, 4-mercaptobenzoic acid (4-MBA) with the bifunctional groups was assembled on the surfaces of the gold film by forming Au—S bond. Due to the presence of the carboxyl groups of 4-MBA, 3-aminopropyltriethoxysilane could be readily deposited on 4-MBA via electrostatic interaction, then through Si—O—Si cross-linking, the tetraethyl orthosilicate formed a coverlike structure under the base-catalyzed hydrolysis, covering the modified gold film core. The morphologies of the silica shell have been studied by means of atomic force microscopy and scanning electron microscopy, and its structures have been monitored through the reflection-absorption infrared Fourier transform and X-ray photoelectron spec-troscopy. The silica shell can also be derivatized easily with numerous biofunctional groups, enhancing the application prospects of the core-shell material to the development of a molecular sensing/recognition unit.

Key words: gold film, 4-mercaptobenzoic acid, tetraethyl orthosilicate, core-shell material