Plasmon-based nanolenses assembled on a well-defined DNA template.

The controlled and reproducible synthesis of closely spaced noble metal nanoparticle groupings is an essential step toward the rational design of nanostructures for surface enhanced Raman scattering with single-molecule sensitivity. In this communication, we demonstrate the facile synthesis of 5, 8, and 18 nm gold particle groupings on a well-defined DNA template by hybridizing monoconjugated gold-DNA building blocks. The obtained nanometer interparticle gaps should yield local intensity enhancements up to 4 orders of magnitude as estimated by Generalized Mie Theory. By tuning the particle size and relative curvatures, we calculate that the maximum enhancement can be optimized and localized on a specific part of the nanostructure. These groupings act as plasmon-based nanolenses assembled on a biomolecular backbone that can be functionalized in proximity to the region of highest field.