Urea-Derived Carbonyl as an Active Site for Self-Catalysis in High-Efficiency Electrochemiluminescence Sensing at...

Electrochemiluminescence (ECL) holds great promise for biosensing and imaging, yet its advancement is constrained by high operational potentials, reliance on external coreaction accelerators, and a lack of clear structure-activity relationships for catalyst design. To address these limitations, we screened small nitrogenous molecules and identified urea as the most effective coreaction accelerator for classical Ru(bpy)₃²⁺ and quantum dot-based cathodic persulfate (S₂O₈^2-) ECL systems. Inspired by this finding, we designed a self-catalytic perylene imide emitter (Urea-PDI) by structurally integrating a urea-derived carbonyl (-C═O) group as an endogenous active site. This emitter showcased a 924.1-fold enhancement in ECL efficiency compared to that of the pristine PTCDA/S₂O₈^2- system at an ultralow potential of -0.3 V. Mechanistic studies revealed that urea-derived -C═O not only acts as an electron-rich site to mediate suitable adsorption but also serves as a Lewis base to activate S₂O₈^2- on-site, which achieves self-catalytic cathodic ECL without exogenous catalysts for intense ECL emission. As a proof of concept, an ultrasensitive biosensing platform for detecting phosmet was constructed using only 1 mM S₂O₈^2- as the coreactant, achieving an impressive detection limit as low as 2.85 × 10^-7 μg/mL. This work not only offers fundamental insights into the functional group-mediated self-catalysis in cathodic ECL but also paves an intelligent approach to construct simple, ultrasensitive, and low-interference ECL systems for advanced applications.