Elevated Surface Lattice Resonances Enabled Quasi‑Uniform Refractive Index Sensing

Nanophotonic structures enable transformative sensing in miniaturized platforms but are fundamentally constrained by their limited sensitivity across broad refractive index (RI) ranges. Here, we developed novel “propped” plasmonic nanoparticle lattices as a universal platform for elevated high‐quality surface lattice resonances (SLRs). This architecture decouples the SLRs from the substrate, enabling effective operation in arbitrary RI environments and achieving sensitivity exceeding 1000 nm/RIU (Δn = 0.02)—surpassing the theoretical periodicity‐correlated limit. By integrating functional materials, we further validate platform versatility through proof‐of‐concept detections of (1) gas concentration by integration of metal–organic framework films with > 40 nm resonance shifts and illustrate sensitivity (∼0.8 nm/%VOL) at room temperature; (2) polymer height dynamics (resolutions at ΔH/Δλ = 24.3 nm/nm of height change/wavelength shift); (3) pH alterations (pH sensitivity up to Δλ/ΔpH = 2.8 nm/pH of wavelength shift/pH change). This work redefines the limits of RI detection and establishes a scalable and viable platform for next‐generation nanophotonic sensors across diverse applications.