The SERS effect was initially discovered in the 1970s. Early research focused on understanding the phenomenon and increasing enhancement to achieve single molecule detection. From the mid-1980s to early 1990s, research started to move away from obtaining a fundamental understanding of the phenomenon to the exploration of analytical applications. At the same time, significant developments occurred in the field of photonics that led to the advent of inexpensive, robust, compact, field-deployable Raman systems. The 1990s also saw rapid development in nanoscience. This convergence of technologies (photonics and nanoscience) has led to accelerated development of SERS substrates to detect a wide range of chemical and biological analytes. It would be a monumental task to discuss all the different kinds of SERS substrates that have been explored. Likewise, it would be impossible to discuss the use of SERS for both chemical and biological detection. Instead, a review of the most common metallic (Ag, Cu, and Au) SERS substrates for chemical detection only is discussed, as well as SERS substrates that are commercially available. Other issues with SERS for chemical detection have been selectivity, reversibility, and reusability of the substrates. How these issues have been addressed is also discussed in this review.

The use of shifted-spectra, first-derivative spectroscopy (or edge detection), and fast Fourier transform filtering techniques for fluorescence rejection in Raman spectra is demonstrated. These techniques take advantage of the fact that Raman signals are very narrow in comparison to fluorescence bands in order to discriminate between the two. None of these techniques require modification of existing instrumentation. Fast Fourier transform filtering and deconvolution techniques also provide a means of improving spectral resolution and the signal-to-noise ratio.

The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver and gold substrates to detect polyatomic anions in aqueous environments is examined. For normal Raman spectroscopy, using near-infrared excitation, linear concentration responses were observed. Detection limits varied from 84 ppm for perchlorate to 2600 ppm for phosphate. In general, detection limits in the ppb to ppm concentration range for the polyatomic anions were achieved using cationic-coated SERS substrates. Adsorption of the polyatomic anions on the cationic-coated SERS substrates was described by a Frumkin isotherm. The SERS technique could not be used to detect dichromate, as this anion reacted with the coatings to form thiol esters. A competitive complexation method was used to evaluate the interaction of chloride ion with the cationic coatings. Hydrogen bonding and pi-pi interactions play significant roles in the selectivity of the cationic coatings.

Surface enhanced Raman spectroscopy (SERS) has been widely used for chemical detection. Moreover, the inherent richness of the spectral data has made SERS attractive for use in detecting biological materials, including bacteria. This review discusses methods that have been used to obtain SERS spectra of bacteria. The kinds of SERS substrates employed to obtain SERS spectra are discussed as well as how bacteria interact with silver and gold nanoparticles. The roll of capping agents on Ag/Au NPs in obtaining SERS spectra is examined as well as the interpretation of the spectral data.

The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated, silver substrates to detect nitrate and sulfate ions in aqueous environments is examined. For normal Raman spectroscopy using near-infrared excitation, a linear concentration response was observed with detection limits of 260 and 440 ppm for nitrate and sulfate, respectively. Detection limits in the low parts-per-million concentration range for these anions are achieved by using cationic-coated, silver SERS substrates. Adsorption of the anions on the cationic-coated SERS substrates is described by a Frumkin isotherm.