Improving surface-enhanced Raman spectroscopy (SERS) for better sensors

Surface-enhanced Raman spectroscopy (SERS) results in million-fold enhancements of the Raman signal. SERS has recently been recognized as a promising platform for reversible, rapidly responding sensors. Techniques for monitoring ions, aromatics, and chlorinated ethylenes in aqueous solutions have been demonstrated. High specificity is achieved because of the distinct Raman signal of each analyte. A major obstacle to implementing this technology is the lack of appropriate SERS substrates compatible with optical-fiber excitation and collection. Typically, SERS spectra are collected from a monolayer of analyte over an area the size of a laser spot or slit image. The minuscule quantity of analyte results in SERS spectra with modest signal-to-noise ratios. We report a new technique for fabricating island-film SERS surfaces over larger areas. This technique is intrinsically compatible with optical fibers. The SERS signal will increase in direction proportion to the area or volume of analyte observed.