A close-packed 3D plasmonic superlattice of truncated octahedral gold nanoframes
We report the surface-enhanced Raman scattering (SERS) enhancement of three-dimensional (3D) close-packed plasmonic superlattices of truncated octahedral gold nanostructures. Experimentally, we resolved two different types of hot spots, one originates from the face-to-face contacts and the other is from the edge-to-edge contacts among the 3D close-packed plasmonic superlattice of gold nanostructures. The high degree of homogeneity of truncated octahedral Au@Pt nanoparticles (TOh Au@Pt NPs) and truncated octahedral Pt@Au nanoframes (TOh Pt@Au NFs) allowed them to self-assemble into remarkable 3D close-packed plasmonic superlattices. The morphological evolution and the corresponding optical behavior of TOh Pt@Au NFs were systematically monitored during each synthetic process. The measured SERS enhancement on the hot spots from the edge-to-edge contacts of TOh Pt@Au NFs was five times greater than the SERS response from the analogous face-to-face contacts of TOh Au@Pt NPs under the same given experimental conditions. The hollow interior and well-defined structural morphology of TOh Pt@Au NFs will allow researchers to design highly programmable 3D plasmonic superlattices for efficient SERS enhancement.