A novel amplification mechanism for surface enhanced Raman scattering

Macromolecules in contact with both metallic colloids and oxygen may display unusually large dynamic hot-spots for surface enhanced Raman spectroscopy (SERS). The effect has been shown to exist in systems as different as proteins (hemoglobin) and carbon chain segments, but we also show here its existence in SERS of single-stranded DNA. The physicochemical origin of this effect is inquired into, and a specific model based on resonant charge–transfer interactions (mediated by oxygen) between the surface plasmons and the molecules is proposed as a microscopic origin. It is argued that, by a proper choice of lasers, the effect could be used for biomolecules to detect traces down to a single-molecule level.