DNA-Mediated Three-Dimensional Assembly of Hollow Au–Ag Alloy Nanocages as Plasmonic Crystals

Oligonucleotide–nanoparticle conjugates are promising building blocks for stimuli responsive, reconfigurable functional materials in wet environments. Here, we demonstrate the self-assembly of DNA-linked hollow Au–Ag alloy nanocages into supracrystals in an aqueous solution. Initially, the surface of Ag nanoparticles is modified by depositing porous layers of gold, which allows the functionalization of the particles with thiolated DNA following established approaches for functionalizing Au nanoparticles. Galvanic replacement in an aqueous Au-ion solution transforms the solid DNA conjugates into hollow, DNA-terminated Au–Ag alloy nanocages that can be linked into three-dimensional, long-term stable nanocage arrays by self-assembly during slow cooling. Cathodoluminescence of individual hollow nanostructure assemblies demonstrates a collective plasmonic behavior with strong localized surface plasmon resonance enhancement at the surface of the supracrystals. Our results identify an approach toward the programmable, DNA-mediated self-assembly of hollow noble metal nanocages for applications as plasmonic crystals.