Selective Enhanced Raman Scattering from an Oxacarbocyanine Dye and 1-Phenyl-5-Mercaptotetrazole Adsorbed to Silver and Silver Halide Surfaces in Photographic Films

Enhanced Raman scattering (ERS) spectroscopy has been used to obtain characteristic vibrational spectra of two photographically-useful molecules adsorbed to the surface of silver-containing photographic coating (film) processing residues. Films containing gelatin dispersions of silver halide microcrystals were coated with a typical oxacarbocyanine spectral sensitizing dye and subsequently treated with a common photographic silver image modifier, 1-phenyl-5-mercaptotetrazole (HPMT). With the selection of a laser excitation frequency within the absorption band of the J-aggregate of the dye (λ_max ≈ 550 nm), Raman spectra which are unique to the adsorbed dye were observed. When the laser excitation was shifted bathochromically (647.1 nm), characteristic spectra of the adsorbed silver salt of HPMT (AgPMT_ads), which does not normally absorb light efficiently at this wavelength, were obtained from the same coatings. This work represents the first time vibrational spectra from both chromophoric and nonchromophoric (in the visible frequency range) Raman-active molecules have been observed within a common photographic chemical environment by the use of molecular resonance enhancement in combination with surface-enhanced Raman scattering (SERS).