Surface-enhanced Raman scattering (SERS)?a new tool for single molecule detection and identification

This report describes surface-enhanced Stokes and anti-Stokes Raman scattering of molecules in aqueous colloidal silver solution using non-resonant near-infrared excitation. We demonstrate that extremely large surface-enhanced Raman cross sections of the order of 10−16 cm2 per molecule can be combined with favorable conditions for excitation and collection of Raman scattered light provided by a Raman microscope to achieve single molecule sensitivity. Surface-enhanced Raman spectroscopy will be compared with fluorescence spectroscopy as a tool for single molecule detection.