Single Molecule detection by SERS active Gold-Silver-Core-Shell Nanodumbbells

Detection methods using plasmonic nanostructures based on Surface-enhanced Raman scattering (SERS) have been widely investigated for imaging and sensing applications.However, SERS-based single-molecule detection generally faces a problem with structural reproducibility, as particle structure and interparticle distance can markedly affect Raman signals and constructing robust SERS-active nanostructures still remain a challenge.

Recently, in a article in Nature Materials, researchers have reported a high-yield synthetic strategy to obtain gap-tailorable gold–silver core–shell nanodumbbells (GSNDs) and subsequent hot SERS-based single-molecule detection with structurally reproducible dimetric nanostructures.

Gold nanoparticle heterodimers were successfully synthesized in a relatively high yield by means of a single-target-DNA hybridization (displayed in the figure). A single Raman-active Cy3 dye molecule is located between two DNA-tethered particles. In another step, Ag shells were formed on the surface of the dimeric Au nanoparticles, and the Ag shell thickness was controlled on the nanometre scale to generate gap-engineerable, DNA-embedded GSNDs. To detect a Raman signal from each single-DNA-captured GSND, atomic force microscope (AFM)-coupled nano-Raman spectroscopy was used.

To prove that single-DNA detection is possible from a single GSND structure, several characterization experiments were suggested in the article.It has been demonstrated that as formed Raman-active GSNDs have single-molecule sensitivity with high structural reproducibility. This research is important because of following reasons:

- opens new opportunities in the high-yield synthesis of specific nanostructures for materials science and bio-detection applications..

- unlike the conventional strong electrolyte-induced nonspecific nanoparticle aggregation, this synthesis method can be easily scalable to produce targeted SERS-active nanoprobes.

- the nanogap-engineering of GSNDs allows for exploring hot SERS structures in an efficient and straightforward fashion

To summarize, these SERS-active GSNDs could be further modified by other biomolecules (such as proteins) and used as both in vitroand in vivo bio-labelling probes with ultrahigh sensitivity, quantification potential and multiplexing capability.

reference: Nature Materials (13 December 2009) doi:10.1038/nmat2596