Surface-enhanced Raman spectrometry with silver particles on stochastic-post substrates

A special type of substrate for surface-enhanced Raman scattering (s.e.r.s.) is evaluated. The substrates consist of silver particles deposited on stochastically arranged SiO₂ posts produced by plasma etching of a quartz surface using a silver island film as an etch mask. The optimization of various experimental parameters such as silver layer thickness, silver evaporation angle, and excitation energy are discussed in detail. Comparative studies with p-nitrobenzoic acid as the model compound indicate that this present substrate is at least one order of magnitude more effective than other common s.e.r.s. substrates, such as the silver island film and the crossed-grating surface, which were previously found to induce the strongest s.e.r.s. signals. The preparation of these silver-particle-post substrates avoids the elaborate lithographic procedures required for crossed-grating structures. The quantitation of species in a three-component mixture illustrates the selectivity of the s.e.r.s. technique.