LAUSR

A simple dry process for preparing an ultrathin SiO2 shell on gold nanoparticle (Au NP) has been developed. The adsorption and reaction of 1,3,5,7-tetramethylcyclotetrasiloxane on Au NP-loaded ZnO (Au/ZnO) from gas phase at 353 K yields a multilayer of polymethylsiloxane (PMS) on the Au surface, while a monolayer is formed on the ZnO surface. The postheating in the air at 773 K transforms the PMS layer to a uniform SiO2 layer with thickness (lSiO2) of ∼2 nm on the surface of every Au NP (Au@SiO2/ZnO). UV-visible absorption spectra show that the SiO2 shell enhances the localized surface plasmon resonance of Au NP with its peak redshifted from 530 nm to 571 nm. The 3D finite-difference time-domain calculations for Au@SiO2(lSiO2 = 2 nm)/ZnO indicate that a strong local electric field is generated at the Au-SiO2-ZnO three-phase interface along the peripheral edge of Au NP with an enhancement factor of ∼107.