Self-Assembled Plasmonic Dimers of Amphiphilic Gold Nanocrystals

We report a new strategy to assemble large (>40 nm) gold nanoparticles with isotropic surface chemistry into anisotropic plasmonic dimers by taking advantage of the chain reorganization of the amphiphilic polymer brushes grafted on nanoparticle surfaces in selective solvents. Production of high-purity dimers is of considerable interest for applications requiring strong near-field coupling of surface plasmon resonances. The formation of nanoparticle dimers is confirmed by imaging and spectroscopic characterization at both bulk and single-particle levels. The interparticle plasmonic coupling can be reversibly controlled by modulating the assembly/disassembly of the amphiphilic nanocrystals. The general applicability of surface modification of nanocrystals of diverse chemical compositions and morphologies through tandem grafting to and grafting from reactions offers the possibility to extend this concept to other types of functional nanocrystals.