Surface-enhanced Raman scattering: Imaging and mapping of Langmuir-Blodgett monolayers physically adsorbed onto silver island films

The point-by-point mapping of the surface-enhanced resonance Raman scattering (SERRS) and surface-enhanced Raman scattering (SERS) spectra obtained from Langmuir-Blodgett (LB) monolayers of bis(n-butylimido)perylene (BuPTCD) on silver island films are reported. Wide field global images of the SERRS signal are also discussed. The mapping and global Raman images of the LB-coated silver surfaces, obtained using the 514.5 nm and the 780 nm laser lines, give a visual picture of the variation of the intensity of the SERRS/SERS signal on the rough metal surface with ca. 1 mu m(2) spatial resolution. Neat and mixed LB monolayers of BuPTCD with arachidic acid of 20% and 1% molecular concentration of the analyte were used as samples in the SERRS and SERS experiments. This is the first report of SERS and SERRS mapping and imaging of single Langmuir-Blodgett monomolecular layers. The use of BuPTCD is particularly important, since the molecules are not chemically hound to the surface. SERRS spectra with large signal-to-noise ratio (100) are observed from a maximum of 40000 molecules of the analyte with a collection time of 10 s.