Surface-enhanced infrared absorption and amplified spectra on planar silver halide fiber

We have discovered surface-enhanced infrared absorption (SEIRA) on a planar silver halide surface, the first time this effect has been observed on a nonmetallic substrate. The enhancement is not due to the presence of metallic silver on the surface as ruled out by X-ray photoelectron spectroscopy (XPS). In addition, the fibers show 10-fold spectral amplification due to the increased coupling of evanescent waves through an increased number of internal reflections to the samples on the surface of the thin planar element. A special cell for the fiber permits deposition of small quantities of solution followed by slow evaporation of the solvent with dry nitrogen and allows measurements to be made on much less than a monolayer of sample. The combination of easy access to the sample and high sensitivity promises many useful applications to biological, chemical, and physical problems in the mesoscopic and nanoscopic domains.