A coumarin-appended cyclometalated iridium(III) complex for visible light driven photoelectrochemical bioanalysis.

In this study, a coumarin-appended cyclometalated iridium (III) complex was prepared and demonstrated to be an efficient photoelectrochemical (PEC) active species with stable and reproducible cathodic photocurrent illuminated by visible light. A gold nanoparticles (AuNPs)-based PEC probe was assembled using the as-prepared iridium (III) complex as signal reporter. Integrating aptamer/protein proximity binding-triggered strand displacement and catalytic hairpin assembly (CHA) amplification strategy, an enzyme-free and sensitive PEC assay was developed. Benefiting from superior photon-to-current conversion character of the iridium (III) complex and effective amplification strategy, the proposed assay exhibited enhanced sensitivity for thrombin detection with a detection limit of 23 fM. It also showed a high specificity in serum samples. This study further demonstrated that cyclometalated iridium (III) complexes could be adopted as favorable photoactive material for bioanalysis by improving their ability of absorbance in the visible region.