Depolymerization-Induced Electrochemiluminescence of Insoluble Porphyrin in Aqueous Phase

Exploring efficient and robust electrochemiluminescence (ECL) performance of liposoluble porphyrins in aqueous phase for analytical purposes especially for important biological targets is still very challenging. In this work, a novel depolymerization-induced electrochemiluminescence (DIECL) of porphyrin and beta-cyclodextrin (beta-CD) self-assembly through a coreactant route was discovered. Among the studied mesotetrasubstituted porphyrins, self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl) porphyrin (THPP) and beta-CD (THPP@beta-CD) exhibits the best DIECL behavior with high efficiency (21.8%) as well as good reproducibility and stability. A mechanistic study suggests that the facile complexation of porphyrins with amphiphilic beta-CD via hydrogen bonding interaction greatly improves the water insolubility and the aggregation-caused deficient ECL of liposoluble porphyrins in aqueous solution. Furthermore, because of the strong hydrogen bonding between the hydroxyl groups on THPP@beta-CD and a highly electronegative substrate, such THPP@beta-CD is found to serve as an efficient luminophore for recognition of most electronegative fluoride (F-) in the aqueous phase with high sensitivity and selectivity, together with a low limit of detection (0.74 mu M). The simplicity of this THPP@beta-CD and its unique DIECL property in current work provides a new guide for the ECL applications of liposoluble porphyrins in aqueous phase.