Novel approach for the preparation of metal colloid monolayers on modified surfaces

The morphology of Au colloid monolayers on modified silicon oxide surfaces (glass, silicon wafer, and ITO slides) has been studied. These monolayers were prepared by a new method described here. We also demonstrate several applications of this colloid monolayer surface. The preparation route creates rough metal surface, the morphology of which can be easily controlled. The colloid monolayers are prepared in two steps: (1) modification of the substrates with starburst dendrimers; (2) noble metal colloid deposition onto the dendrimer layer. Au particles of approximately 28 nm in diameter were deposited onto the dendrimer-modified surfaces. The spontaneous adsorption of the dendrimers to the silicon oxide surface was proven by x-ray photoelectron spectroscopy, contact angle, and grazing angle Fourier transform infrared spectroscopy. The thickness of the dendrimer layer has been calculated to be in the range of d=14-25 Angstrom. The structure and properties of the resulting particle arrangement have been studied by atomic force microscopy (AFM) and ultraviolet (UV-vis) spectroscopy. AFM data show that the colloids spontaneously form continuous films on the dendrimer-modified surfaces. The noble metal particles are well isolated, confined to a single layer, and aggregation does not occur on the surface. UV-vis spectroscopic data show that the microstructure controls the optical properties of the layer. The article demonstrates the practical applications of this rough metal surface as a platform for surface-enhanced Raman scattering and electrochemistry. (C) 1996 American Vacuum Society.