DETECTION AND IDENTIFICATION OF A SINGLE DNA-BASE MOLECULE USING SURFACE-ENHANCED RAMAN-SCATTERING (SERS)

Nonresonant Raman cross sections of similar to 10(-16) cm(2) per molec ule 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 mu m. These experimental findings demonstrate that MR SERS on colloidal silver clusters is an excellent technique for single molecul e detection that is applicable for a broad range of molecules includin g ''colorless'' biomolecules, for example nucleotides in DNA sequencin g. As an example, we present the detection of a single adenine molecul e without any labeling based on its intrinsic surface-enhanced Raman s cattering.