A novel strategy for the construction of photoelectrochemical sensing platform based on multifunctional photosensitizer

Abstract A novel strategy was proposed for the construction of photoelectrochemical (PEC) sensing platform based on multifunctional photosensitizer which can simultaneously achieve photo-sensitization, target-recognition and interface conjugation. Herein, N3 dye, bis(4,4′-dicarboxy-2,2′-bipyrid ine) dithiocyanato ruthenium (II), was employed as a model multifunctional molecule and covalently tethered on amino-functionalized TiO2 nanowires. The obtained photoanode can produce a sensitive photocurrent response towards Hg2+ under visible illumination (∼540 nm). The decrease in photocurrent can be attributed the larger HOMO-LUMO gap, the higher LUMO energy level and the reduced electron cloud density of N3–Hg2+ complex compared with the free N3 dye, which is demonstrated by DFT calculations. Under optimized conditions, the PEC assay displayed a linear dynamic range of 0.5–50 μM for Hg2+ with a detection limit of 0.13 nM. Moreover, the long-term stability of the PEC sensor was achieved due to the covalent conjugation of the photosensitizer to the TiO2 nanowire. The proposed sensing strategy, by utilizing the multifunctional molecule photosensitizers for direct responding to targets, presents a novel methodology for the development of high performance PEC sensors in future.