Designing Hybrid Plasmonic Superlattices with Spatially Confined Responsive Heterostructural Units.

Plasmonic superlattices enable the precise manipulation of electromagnetic fields at the nanoscale. However, the optical properties of static lattices are dictated by their geometry and cannot be reconfigured. Here, we present a surface-interface engineered plasmonic superlattice with confined polyelectrolyte-functionalized metal-organic framework (MOF) hybrid layers to tune plasmon resonance for ultrafast chemical sensing. The surface lattice resonance frequency in the visible spectrum was achieved using electron-beam lithography with a humidity-responsive polyelectrolyte brush grafted onto the thiol-initiator-modified gold nanoparticle surface through atom transfer radical polymerization. An MOF thin film was assembled on the polyelectrolyte-functionalized gold nanoparticle lattice via a layer-by-layer immersion. Surface lattice resonance was observed without additional matched dielectric environment around the NPs, and the resonance frequency was tuned by adjusting the thickness and refractive index of the polyelectrolyte layer. Furthermore, high chemical sensitivity and ultrafast response were achieved due to the coherence between the MOFs and polymer layers.