Boosting Electrochemiluminescence of Carbon Nitrides via Molecular Capacitor-Mediated Spatiotemporal Electron...

Carbon nitride (CN) enables non-toxicity, low cost, high quantum efficiency, and tunable spectrum. Nevertheless, there co-exists a timescale mismatch among kinetic steps of electrochemiluminescence (ECL) and a spatial competition of electrons between radiative recombination and interfacial redox reactions. Herein, a spatiotemporal coordination strategy is reported to enhance Φ_ECL of CN by molecular capacitor functionalization. Mechanism studies show the capacitor, consisting of N-vacancies and -C≡N terminal groups, dynamically regulates electron capture and accumulation. Interestingly, the spatial confinement of accumulated electrons in molecular capacitors effectively enhances the radiative recombination probability. Meanwhile, the accumulated electrons construct a new pathway for fast electron transport, and the relaxation of the accumulated electrons coordinates the electron transfer in bulk CN and redox reactions at the electrode surface on the µs-ms timescale, establishing temporal coordination across multiple time domains. As a result, the Φ_ECL of CN increases by up to 100 times, reaching 1480 times that of the standard Ru(bpy)₃Cl₂/K₂S₂O₈ system. Accordingly, compared to pristine CN, the as-developed ECL sensors using CN with molecular capacitor functionalization demonstrate significantly improved performance in the visual detection of nitrite ions (a typical environmental pollutant), for example, a 3600 fold lower detection limit and a 3-order of magnitude broader detection linear range.