Rational Approach to Plasmonic Dimers with Controlled Gap Distance, Symmetry, and Capability of Precisely Hosting Guest Molecules in Hotspot Regions.

Plasmonic dimers not only provide a unique platform for studying fundamental plasmonic behavior and effects but also are functional materials for numerous applications. The efficient creation of well-defined dimers with flexible control of structure parameters and thus tunable optical property is the prerequisite for fully exploiting the potential of this nanostructure. Herein, based on a polymer-assisted self-assembly approach in conjugation with molecular cage chemistry, a strategy was demonstrated for constructing cage-bridged plasmonic dimers with controlled sizes, compositions, shape, symmetry, and interparticle gap separation in a modular and high-yield manner. With a high degree of freedom and controllability, this strategy allows facilely accessing various symmetrical/asymmetrical dimers with sub-5 nm gap distance and tailored optical properties. Importantly, as the linkage of the two constituent elements, the molecular cages embedded in the junction endow the assembled dimers with the ability to precisely and reversibly host rich guest molecules in hotspot regions, offering great potential for creating various plasmon-mediated applications.