Investigation of experimental parameters for surface-enhanced raman scattering from silver-coated sphere substrates

Studies of interfacial phenomena are important in order to assist in the advancement of high technology, to aid in the understanding of surface interactions, and to understand corrosion processes which cost U. S. industry billions of dollars yearly. While many good techniques are available to study interfacial phenomena, one of the most versatile techniques recently discovered is surface-enhanced Raman spectroscopy. Surface-enhanced Raman spectroscopy may also be useful as an analytical tool for analysis of trace compounds. In this study the experimental parameters for one useful type of substrate for surface-enhanced Raman spectroscopy were investigated. The intensity of surface-enhanced Raman scattering from silver-coated polystyrene latex sphere substrates was studied as a function of angle of incidence of exciting radiation, thickness of the silver layer, excitation wavelength, and sphere size.

The best surface-enhanced Raman scattering intensity was found for an exciting radiation angle of incidence between 60 degrees and 80 degrees to the substrate normal, a ratio of dielectric core radius to total particle radius ranging from 0.65 to 0.75, an excitation wavelength of 514.5 nm, and sphere diameters between approximately 176 nm and 482 nm, with a slight minimum occurring for the 261 nm sphere diameter. Acceptable correlation between electromagnetic enhancement theory and experimental results was found for angle of incidence of exciting radiation. Qualitative agreement between theory and experiment was found for silver thickness. There was poor agreement between theory and experiment for excitation wavelength and sphere size.