Plasmonic photonic crystals realized through DNA-programmable assembly

Three-dimensional dielectric photonic crystals have well-established enhanced light–matter interactions via high Q factors. Their plasmonic counterparts based on arrays of nanoparticles, however, have not been experimentally well explored owing to a lack of available synthetic routes for preparing them. However, such structures should facilitate these interactions based on the small mode volumes associated with plasmonic polarization. Herein we report strong light-plasmon interactions within 3D plasmonic photonic crystals that have lattice constants and nanoparticle diameters that can be independently controlled in the deep subwavelength size regime by using a DNA-programmable assembly technique. The strong coupling within such crystals is probed with backscattering spectra, and the mode splitting (0.10 and 0.24 eV) is defined based on dispersion diagrams. Numerical simulations predict that the crystal photonic modes (Fabry–Perot modes) can be enhanced by coating the crystals with a silver layer, achieving moderate Q factors (∼10 ²) over the visible and near-infrared spectrum. Significance DNA-programmable methods provide unprecedented control over the assembly of nanoparticles into complex structures, including superlattices with deliberately tailorable compositions, crystal symmetries, lattice constants, and crystal habits. In principle, such bottom-up approaches can be used to assemble interesting photonic structures, including ones containing quantum dots and metal nanoparticles. Herein we show that we can tune the interaction between light and the collective electronic modes of gold nanoparticles by independently adjusting lattice constants and gold nanoparticle diameters. This opens up exciting possibilities for tuning the interaction between light and highly organized collections of particles at the nanoscale for applications ranging from lasers to quantum electrodynamics to biosensing. The structures reported herein are the first devices to our knowledge prepared by DNA guided colloidal crystallization.