Photogenerated Hole-Induced Chemical Redox Cycling on Bi₂S₃/Bi₂Sn₂O₇ Heterojunction: Toward General Amplified Split-Type Photoelectrochemical Immunoassay

This work reports the elegant bridging of enzymatic generation of electron donor with photogenerated hole-induced chemical redox cycling amplification (RCA) for innovative photoelectrochemical (PEC) immunoassay, by the aid of a heterojunction photoelectrode with split-type strategy. Specifically, the system was exemplified by the alkaline phosphatase (ALP) catalytic generation of ascorbic acid (AA), the redox cycling of AA by tris (2-carboxyethyl) phosphine (TCEP) as reductant, and the use of a novel Bi₂S₃/Bi₂Sn₂O₇ heterojunction and myoglobin (Myo) as the photoelectrode and the target, respectively. After the immunoreaction and ALP-induced production of AA, the subsequent oxidation of AA by the photogenerated holes of the Bi₂S₃/Bi₂Sn₂O₇ heterojunction could be cycled via the regeneration of AA by TCEP from the oxidized product of dehydroascorbic acid, leading to easy signal amplification for the sensitive immunoassay of Myo in real samples. It is believed that this work provided a basis for further design and development of general RCA-based PEC immunoassays.