Using gold to enhance raman scattering techniques

In contrast to luminescence spectroscopy, Raman spectroscopy results in intrinsically small cross-sections which typically preclude analyte detection at low concentration levels if an interface or surface-based enhancement process is not used. Alternative methods of creating a large increase in cross sections have involved resonance enhancement - which occurs when the incident photon frequency of the excitation source matches that of an electronic transition of the molecules being interrogated - and non-linear processes, such as coherent anti-Stokes Raman scattering. However, these techniques require excitation sources of multiple wavelengths and high power, respectively, which has limited their widespread use. Another promising enhancement approach is to use the excited electronic states of nanostructured noble metals, such as silver and gold, as in surface-enhanced Raman spectroscopy.