SECARS imaging of thiophenol adsorbed on silver colloids

Abstract

The very large enhancement of the Raman signal observed in SERS (Surface-enhanced Raman Spectroscopy)[1] enabling single molecule sensitivity in some cases, makes it very appealing to apply this same experimental approach to non-linear techniques like CARS spectroscopy as higher enhancement factors are expected due to the quadratic dependence of the signal with the pump laser intensity. In spite of this and though several groups have tried the SECARS (Surface-enhanced Coherent Anti-Stokes Raman Spectroscopy) with different success [2], there is not yet a definitive proof-of-principle of this experimental approach. To this latter gaol has been devoted this work. We have recorded the forward CARS images of thiophenol adsorbed on silver nanoaggregates through the 8a ring stretching mode resonance at 1574 cm-1.