Tip-Enhanced Raman Spectroscopy for the Base Interrogation of DNA

A combination of scanning probe and Raman microscopies allows for the label-free chemical mapping of surfaces with spatial resolutions one to two orders of magnitude below the diffraction limit. Because Raman spectroscopy provides a highly specific molecular "fingerprint," the resulting spectra allow speciation of even highly similar chemical compounds. The surface enhancement phenomenon allows Raman signals from a species to be enhanced by many orders of magnitude within the vicinity (similar to 10 nm) of a source of free electrons such as a noble metal. Presenting the metal surface as a single highly localized point, and moving this point with angstrom accuracy across a distributed, heterogenous surface while collecting Raman spectra, is what is known as tip-enhanced Raman spectroscopy, or TERS.