Peripheral hydrophilic molecular engineering of porphyrin luminophores for enhanced aqueous electrochemiluminescence and environmental sensing

Porphyrins are attractive electrochemiluminescence (ECL) luminophores, yet their poor aqueous compatibility and aggregation-caused quenching (ACQ) limit their application in aqueous solution. Herein, a peripheral molecular engineering strategy was developed to enhance the aqueous ECL properties of tetraphenylporphyrin (TPP). Glucose (Glu) and tryptophan (Trp) were separately introduced onto the meso-positions of TPP, affording two asymmetric porphyrin derivatives, TPP-Glu and TPP-Trp. Peripheral functionalization improved aqueous compatibility and suppressed intermolecular π-π stacking, thereby reducing ACQ and enhancing both photoluminescence and ECL emission. Among the derivatives, TPP-Trp exhibited the highest ECL performance in the K₂S₂O₈ coreactant system, with a relative ECL efficiency of 5.29 times that of TPP. The enhanced ECL response was further exploited for Mercury (Hg²⁺) sensing through the intrinsic coordination capability of the porphyrin core and the Trp moiety. The resulting ECL sensor enabled sensitive Hg²⁺ detection in the linear range of 0.03-60 nM, with a detection limit of 0.01 nM. This work demonstrates that peripheral hydrophilic functionalization suppresses aggregation and enhances aqueous ECL. The approach a versatile design for porphyrin-based ECL luminophores and sensing platforms.