Anodic Self‐Electrochemiluminescence of Carboxyl‐Functionalized Tetraphenylethylene Derivatives for SOD2 Detection

ABSTRACT The self‐electroluminescent (self‐ECL) behaviors of tetraphenylethylene carboxyl derivatives (TPED‐(COOH) x ) during the anodic process are first reported in this work. This study establishes a genuine co‐reactant‐free self‐ECL system driven by electrogenerated radical disproportionation, which is mechanistically distinct from classic annihilation and co‐reactant‐mediated ECL pathways. The self‐ECL mechanism involves the disproportionation of electrogenerated TPED •+ ‐(COO − ) x radicals to directly populate a charge‐transfer excited state, which then decays radiatively. The results of the structure‐activity analysis indicate that the electronic structure (determined by the conjugation length and substitution position) and intermolecular packing interactions are more important than either the aggregation‐induced emission property or the oxidation potential for self‐ECL. Furthermore, numerous controlled experiments have confirmed that the carboxyl group is essential for triggering self‐ECL and this strategy can be extended to other AIE molecules. Notably, 4″,4″″′,4″″″″,4″″″″″′‐(ethene‐1,1,2,2‐tetrayl) tetrakis ([1,1′:4′,1″‐terphenyl]‐4‐carboxylic acid) (H 4 TCTPE) achieved a high self‐ECL efficiency of up to 411% (relative to Ru(bpy) 3 2+ , Φ ECL = 5%). Under optimal experimental conditions, an immunosensor for superoxide dismutase 2 (SOD2) was constructed based on H 4 TCTPE, with a linear range of 0.01–100 ng/mL, a detection limit of 7.9 pg/mL, excellent selectivity, reproducibility, and stability, and was successfully applied to serum analysis. This work provides a theoretical basis and design principles for the development of next‐generation self‐ECL luminophores.