Detection and identification of a single DNA base molecule using surface-enhanced Raman scattering (SERS)

Nonresonant Raman cross sections of ~10^-16 cm² per molecule are shown to be related to surface-enhanced Raman scattering (SERS) on colloidal silver clusters at near-infrared (NIR) excitation. The enhancement is found to be independent of cluster sizes between 100 nm and 20 {μ}m. These experimental findings demonstrate that NIR SERS on colloidal silver clusters is an excellent technique for single molecule detection that is applicable for a broad range of molecules including ``colorless'' biomolecules, for example nucleotides in DNA sequencing. As an example, we present the detection of a single adenine molecule without any labeling based on its intrinsic surface-enhanced Raman scattering.