Adsorption kinetics of Au and Ag nanoparticles on functionalized glass surfaces

Well-defined two- or three-dimensional arrangements of nanosize Au and Ag particles were fabricated for surface-enhanced Raman scattering substrate applications and their unique optical properties. Two-dimensional arrays of colloidal films of Au and Ag were prepared on glass slides modified with silane compounds having bifunctional moieties that have specific affinity for gold or silver. During the formation of colloidal films of Au and Ag on glass slides, UV-vis absorption spectroscopy was used to monitor the progress of the surface immobilization reaction of colloidal particles on sold substrates. Adsorption characteristics could be accurately modeled by the well-known Michaelis-Menten kinetics. It was found that the k(3)/k(1) values were proportional to particle size. This indicates that the rate of formation of the first monolayer with relatively small particles is faster than that of the multilayers, whereas for larger colloids the multilayer formation rate is much faster. SERS spectra of p-aminothiophenol (PATP) on a silver colloidal film were obtained with 514.5-nm excitation. SERS intensities of PATP increased significantly with morphological change of the colloidal film. This morphological alteration, parallel to water evaporation from the colloidal film, was presumably induced by the difference in dielectric constants of air and water, (C) 1999 Academic Press.