Plasmonic planet-satellite analogues: hierarchical self-assembly of gold nanostructures.

In the past few years, a remarkable progress has been made in unveiling novel and unique optical properties of strongly coupled plasmonic nanostructures, known as plasmonic molecules. However, realization of such plasmonic molecules using nonlithographic approaches remains challenging largely due to the lack of facile and robust assembly methods. Previous attempts to achieve plasmonic nanoassemblies using molecular ligands were limited to dipolar assembly of nanostructures, which typically results in polydisperse linear and branched chains. Here, we demonstrate that core-satellite structures comprised of shape-controlled plasmonic nanostructures can be achieved through self-assembly using simple molecular cross-linkers. Prevention of self-conjugation and promotion of cross-conjugation among cores and satellites plays a key role in the formation of core-satellite heteroassemblies. The in-built electromagnetic hot-spots and Raman reporters of core-satellite structures make them excellent candidates for surface-enhanced Raman scattering probes.