Insight into the charge transfer behavior of an electrochemiluminescence sensor based on porphyrin-coumarin derivatives with a donor-acceptor configuration.

The excellent photophysical and electrochemical properties of porphyrins have inspired widespread interest in the realm of electrochemiluminescence (ECL). The aggregation-caused deficiency of ECL emission in aqueous solution, however, still severely impedes further applications. Herein, a molecule with a donor-acceptor (D-A) configuration, ATPP-Cou, consisting of monoaminoporphyrin as an electron donor and coumarin as an electron acceptor, was designed as an ECL luminophore to address the susceptibility of the porphyrin to aggregation-caused quenching (ACQ) in aqueous solution. ATPP-Cou demonstrated a three-fold enhanced ECL signal compared to pristine ATPP. Despite the acknowledged significance of intramolecular charge transfer (ICT) in generating excited states in ECL, there is a lack of quantitative descriptions. Herein, intensity-modulated photocurrent spectroscopy (IMPS) and scanning photoelectrochemical microscopy (SPECM) were utilized to validate the influence of ICT on the enhancement performance of D-A type ECL molecules. Additionally, ATPP-Cou was also developed as a probe for the successful detection of Cu in aqueous solution. The present study not only enriches the repertoire of efficient porphyrin-based ECL luminophores applicable in aqueous environments but also exemplifies the successful integration of novel measurement techniques to provide more comprehensive insights into the underlying mechanisms responsible for improved ECL performance.