Size-Dependent Surface Enhanced Raman Scattering Activity of Plasmonic Nanorattles

Surface enhanced Raman scattering (SERS) is considered to be a highly attractive platform for chemical and biological sensing and molecular bioimaging. Most of the SERS substrates and contrast agents rely on individual or lightly aggregated metal nanostructures that either offer limited enhancement or suffer from poor stability and reproducibility. We have recently demonstrated that plasmonic nanorattles, owing to the internal electromagnetic hotspots, offer significantly higher SERS enhancement compared to their solid counterparts. In this work, we investigate the size- and shape-dependent SERS activity of plasmonic nanorattles comprised of Au nanospheres and nanorods as cores and porous Au nanocubes and cuboids as shells. The SERS activity of Au nanorattles with spherical core was found to increase with increase in the edge length of the cubic shell. On the other hand, the SERS activity of Au cuboid nanorattles with AuNR core was found to decrease with increase in the size of the cuboid shell. Finite difference time domain electromagnetic simulations show excellent agreement with our experimental results. Comprehensive understanding of the size- and shape-dependent SERS activity of this novel class of nanostructures can lead to the rational design and fabrication of highly efficient SERS substrates for chemical and biological sensing and ultrabright contrast agents for SERS-based molecular bioimaging.