Preparation and Characterization of Ag Colloid Monolayers

The process of Ag colloid self-assembly onto organosilane-functionalized glass, carbon, and Au surfaces has been studied using UV−visible spectrophotometry, quartz crystal microgravimetry, and atomic force microscopy. Ag colloids prepared by citrate reduction and by ethylenediaminetetraacetic acid reduction of Ag+ yield different deposition kinetics, primarily a result of differences in particle concentration and monodispersity. The sticking probabilities and equilibrium constants for each type of colloid were measured. Surface-enhanced Raman scattering (SERS) and electrochemical properties of Ag colloid monolayers were compared to bulk Ag. Deposition of Ag colloid onto carbon electrodes improves the heterogeneous rate constant for electron transfer to [Ru(NH3)6]3+, but the modified electrodes still fall short of values obtained for bulk Ag. Likewise, Ag colloid monolayers are less SERS-active than roughened bulk Ag. The effects of particles polydispersity on these phenomena are discussed.