Gold nanoparticulate film bound to silicon surface with self-assembled monolayers

A simple method for attaching gold nanoparticles to silicon surfaces with self-assembled monolayers (SAMs) is described. Firstly, the silicon wafers were cleaned by a slightly modified RCA method, producing a hydrophilic and smooth surface, as revealed by the small contact angle with water (similar to 5 degrees) and the small RMS value (0.2 nm) for surface roughness given by atomic force microscopy (AFM). Then the wafers were modified with (CH3CH2O)(3)Si-(CH2)(3)-NH2 (APS) by vapor phase deposition. A homogeneous amino group-terminated surface was successfully created as proved by the contact angle with water (40 +/- 2 degrees), the X-ray photoelectron spectroscopy (XPS) results and the AFM images. Gold nanoparticles were quite uniformly scattered over such a surface with a submonolayer coverage through specific interactions with -NH2, leading to a sandwiched structure as Au nanoparticles/APS/Si. Such a silicon-based gold nanoparticulate film was also SERS-active as evidenced by the enhanced Raman scattering from the self-assembled monolayers (SAMs) of an azobenzene-derived thiol adsorbed on thus-prepared substrates. (C) 1998 Elsevier Science S.A. All rights reserved.