Gold nanolenses self-assembled by DNA origami

Here, we present a bottom-up approach to create plasmonic gold nanolenses (AuNLs), consisting of three differently-sized gold nanoparticles. The programmable technique of DNA origami is used to self-assemble 10, 20 and 60 nm gold nanoparticles in three different geometrical arrangements in solution and in billions of copies. Correlated atomic force microscopy (AFM), Raman mapping, scanning electron microscopy (SEM) and dark field spectroscopy are used to characterise sets of single AuNLs from each of the three designs. The surface-enhanced Raman scattering (SERS) capabilities of single AuNLs are assessed and the same AuNLs are further characterised by localised surface plasmon resonance (LSPR) spectroscopy. For the design which showed best properties, SERS signals from the two different internal gaps were compared by selectively placing probe dyes. The highest Raman enhancement was found for the gap between the small and medium nanoparticle, which agrees well with theoretical predictions.