Sub-1.5 nm-gapped heterodimeric plasmonic nanomolecules.

Plasmonic molecules are discrete assemblies of similar/dissimilar nanomaterials (atomic equivalents) with efficient inter-unit coupling toward electromagnetic hybridization. Albeit fundamentally and technologically very important, these structures are rare due to the lack of a general way to manipulate the structure, composition, and coupling of the nanoassemblies. While DNA nanotechnology offers a precious chance to build such structures, the weak coupling of DNA-bonded materials and the very limited material building blocks are two obstacles. This work aims to remove the bottlenecking barriers on the road to dimeric (and possibly more complicated) plasmonic molecules. After solving key synthetic issues, DNA-guided, solvo-driven Ag ion soldering is utilized to build a whole set (10 combinations of 4 metals) of homo/heterodimeric plasmonic nanomolecules with prescribed compositions. Importantly, strong in-solution electric-dipole coupling mediated by a sub-1.5 nm interparticle dielectric gap is achieved for materials with strong (Au, Ag) or damped (Pt, Pd) plasmonic responses. The involvement of Pt/Pd materials is of great value for plasmon-mediated catalysis. The broken dimeric symmetry is desirable for Fano-like resonance and photonic nanodiode devices, as well as lightening-up of plasmon dark states. The generality and reliability of the method would allow excitonic, nonlinear-optical, and magnetic units to be involved toward correspondingly enhanced functions.