The observation of high order overtones and combinations in the SERRS spectra of a perylenedye spin coated onto silver island films

Abstract

The intensity of high harmonics and the background observed in the SERRS spectra of the bis(4-chlorbenzylimido)perylene (CLPTCD), spin-coated onto silver nanostructures are discussed. The SERRS spectra of an Ag island film spin coated with 50 μL of a 8.7 × 10⁻⁷ M of CLPTCD in CH₂Cl₂ excited at 514.5 nm show signals from the first to the third overtones and combinations of fundamental vibrational modes observed between 1200 and 1600 cm⁻¹. SERRS spectra were obtained where 2nd overtones were seen with relative intensity equal to that of the 1st overtones and in other SERRS spectra the 3rd overtones were more intense than the 2nd overtones. These varying intensity patterns are seen at submonolayer coverage where there is a breakdown of statistical average, and the spatial distribution of enhancement factors becomes evident. The apparent correlation between the background intensity profile and the enhancement of the overtones and combinations is also discussed.