Scanning Force Microscopy Study of Methanol-Induced Changes in the Distribution of Silver Particles in Colloidal Metal Films

Colloidal silver particles were attached to a solid surface for use as a substrate for surface-enhanced Raman scattering and surface enhanced fluorescence spectroscopies. The enhancement of Raman scattering is dramatically increased after exposure of the substrates to methanol solution. Scanning force microscopy was used to visualize the substrate before and after the methanol treatment, and a statistical evaluation of the particle distribution revealed some differences. The nearest-neighbor distance was decreased after the exposure to methanol. This effect suggests that an aggregation of the particles occurred. This aggregation is probably based on increased attractive interactions and lateral mobility of the particles in methanol.