Research project: Russell: Infrared at Surfaces: RAIRS and SEIRAS

n the group we have used RAIRS to study both electrode surfaces (i.e. metal surfaces at the electrode/electrolyte interface) and the surfaces of metal single crystals at the metal/gas or metal/vacuum interface. In both cases the changes in the IR signals that are observed are very small. In fact for studies of metal-adsorbate bonding where the vibrations are in the far-infrared part of the spectrum (less than 700 cm-1) we have used synchrotron sources for the IR as these have greater brightness than conventional thermal sources. In the last 15 years surfaces have been developed that appear to provide enhanced sensitivity and greater signals in RAIRS type experiments. The method is known as surface enhanced infrared spectroscopy (SEIRAS) and uses roughened metal surfaces that are very similar to those traditionally used for surface enhanced Raman spectroscopy (SERS). The magnitude of the enhancement for IR is only approximately x10, compared to the x10⁶ to x10¹³ reported for SERS and the origins of the enhancement are not very well understood (is it just the increase in the surface area?). We are currently investigating whether the sculpted surfaces we have developed as SERS substrates can be tailored to provide SEIRAS enhancements and, if so, we may be able to determine the origins of the observed enhancements and then go on to apply our new SEIRAS substrates to a variety of detection problems.