Wb. Lacy et al., CHARACTERIZATION OF SIO2-OVERCOATED SILVER-ISLAND FILMS AS SUBSTRATESFOR SURFACE-ENHANCED RAMAN-SCATTERING, Analytical chemistry, 68(6), 1996, pp. 1003-1011
Vapor deposition of a 45-Angstrom layer of silver and a subsequent 50-
65-Angstrom layer of SiO2 onto a glass slide is shown to be a viable s
ubstrate for surface-enhanced Raman spectroscopy (SERS) and a model of
the silica surface suitable for adsorption kinetic studies. The chemi
stry of the silica is characterized by UV absorption and contact angle
measurements. The physical structure is probed by atomic force micros
copy to compare the surface roughness of the silver-island film and it
s SiO2 overcoat. Auger electron spectroscopy and X-ray photoelectron s
pectroscopy are used to probe the silica layer for exposure of silver
through gaps in the overcoat. Comparison of SERS of dibenzyl disulfide
bound to a silver-island film versus that of a silver film protected
by the SiO2 overlayer tests the continuity of the SiO2 film and its ab
ility to block access of adsorbates to the underlying silver surface.
The model silica surface is used to detect the Raman spectrum of adsor
bed pyridine and its adsorption isotherm; the adsorbate vibrational fr
equencies are consistent with previous reports of pyridine on silica.