SURFACE-ENHANCED RESONANCE-RAMAN SCATTERING - AN INFORMATIVE PROBE OFSURFACES

Surface-enhanced resonance-Raman scattering (SERRS) experiments using a citrate-coated silver colloid have been performed. Transmission elec tron microscopy showed that the colloid consists of nearly mondisperse hexagonal particles with a maximum dimension of 36 nm. For maximum se nsitivity, SERRS requires the controlled aggregation of the colloid. T he nature of the aggregate formed is dependent on the method of aggreg ation. The effect of poly-L-lysine on the aggregation procedure was ch aracterised using transmission and scanning electron microscopy. With SERRS, sensitivities down to 6.87 x 10(-18) mol dm(-3) were obtained u sing rhodamine dye. This corresponds to less than 200 molecules in the beam at any one time and suggests a sensitivity equal to or greater t han that of fluorescence. A comparison of the use of SERRS with surfac e-enhanced Raman scattering (SERS) to follow adsorbate reactivity on a surface at less than monolayer coverage was obtained by studying meta l complex formation using a preresonant Schiff base (SERRS) and 2-hydr oxy-1-naphthaldehyde excited off resonance (SERS). In the former case, complex formation on the surface at well below monolayer coverage was observed and differences between the surface and the bulk complex cha racterised. In the latter complex formation was again observed but the bands were broad and problems of contamination, photodecomposition an d selectivity evident.