Gold and silver nanostructures are enabling single molecule detection by Surface-enhanced Raman scattering (SERS). The massive signal enhancements (105 – 1015) in Raman scattering on SERS substrate are attributed to existence of “hot-spots”-the junction between nanostructures. However, creating SERS substrates with accurate control over ‘hot-spots’ or interparticle distance has proved to be a difficult task. Some of the previous attempts at creating SERS active substrate with accurate control over interparticle distance included-Nanospehere Lithography (NSL), Film Over Nanosphere (FOS) and On-Wire-Lithography (OWL).
However, a new approach developed by scientists at Seoul National University makes it possible to synthesize and characterize SERS active nanostructures with high yield and efficiency. Heterodimers of gold nanoparticle with tailored gap between nanoparticles are prepared by first activating two set of gold nanoparticles, one with DNA sequence containing SERS active molecule and second with complementary sequence of DNA. The activation is done so that there is only one DNA sequence per gold nanoparticle. Mixing two sets of DNA creates Gold nanoparticle heterodimers with controllable interparticle distance.
Additional, deposition of silver shell around gold nanoparticles completes the process of creating gold silver nano dumbbells (GSNDs) for single molecule detection. The GSNDs can be used for biosensing application for example by labeling antibodies to be used in Immunoassays.