Multifunctional Zinc Oxide Promotes Electrochemiluminescence of Porphyrin Aggregates for Ultrasensitive Detection of Copper Ion.

The design and exploration of highly efficient organic luminophores for an electrochemiluminescence (ECL) sensor is a fascinating and promising subject. Herein, we present a surfactant-assisted self-assembly of 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) J-aggregate as a robust organic luminophore to construct the solid-state ECL sensing platform with significantly enhanced and constantly stable signals, by using peroxydisulfate (SO) as the coreactant, and l-cysteine capped zinc oxide nanoflowers (ZnO@Cys NFs) as the multifunctional energy donor and coreactant accelerator. Compared with TCPP monomer, this TCPP J-aggregate possesses a unique aggregation-induced electrochemiluminescence (AIECL) performance, which results in 5-fold enhancement in red-light ECL emission at 675 nm. The resonance energy transfer from the ZnO@Cys NFs (energy donor) to the TCPP J-aggregate (energy acceptor) substantially improves the ECL intensity and stability. ZnO@Cys NFs have also been used as a coreactant accelerator to promote the conversion of more SO into SO. The corresponding ECL mechanism has been investigated by UV-vis absorption spectrum, photoluminescence, ECL, and density functional theory. Since l-cysteine on ZnO@Cys NFs can efficiently realize bidentate chelation with Cu, the proposed ECL sensor shows a highly selective and sensitive quenching effect for the detection of Cu with a wide linear range from 1.0 pmol·L to 500 nmol·L and a detection limit of 0.33 pmol·L, paving a bright research direction for the development of TCPP aggregates in ECL field.