Pyrene-Tagged Polyimidazolium Nanoclays Enable Modular Excimer Emission for Multi-Analyte Fluorescence Sensing

Abstract

We introduce a modular platform for engineering excimer-active fluorescent nanoclays by covalently installing pyrene onto imidazolium-functionalized polyionic nanoclays (PINCs) using thiol-maleimide Michael addition. Precise control of pyrene surface densities (0.1–15 mol %) affords a synthetically tunable monomer–excimer landscape, with systematic shifts in excimer-to-monomer intensity ratios (IE/IM) and solvent-dependent photophysics that confirm periodic probe spacing rather than clustering. The cationic PINC framework dramatically enhances analyte accessibility and local concentration, enabling solution-phase detection of nitroaromatic and nitrate-based explosives with Stern–Volmer constants of up to 1.56 × 104 M–1 for TNT, an order-of-magnitude enhancement over neutral pyrene (Py) controls. Py-PINCs also exhibit strong and selective quenching by halides, highlighting synergistic electrostatic and collisional pathways. In the solid state, PINC-immobilized pyrene functions as an environment-responsive oxygen sensor, displaying linear quenching (KSV = 5.29 bar–1) and a rapid reversible response (2.5 s). These results establish pyrene-tagged PINCs as an attractive class of charge-amplified, excimer-programmable 2D hybrid materials that unify tunable photophysics with multimodal chemical sensing, expanding the functional scope of designer PINCs for security, environmental, and analytical technologies.