CuO-ZnO heterojunction derived from Cu-doped ZIF-8: A new photoelectric material for ultrasensitive PEC immunoassay of CA125 with near-zero background noise.

By direct calcination of Cu-doped ZIF-8 in oxygen atmosphere, a new photoelectric material, CuO-ZnO heterojunction, was prepared. The morphology and structure were investigated in detail by several methods, such as scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption method and X-ray diffraction. Under visible light irradiation, CuO-ZnO heterojunction exhibits excellent PEC behavior in aqueous media with the presence of ascorbic acid (AA) and dissolved oxygen at -0.3 V. Taking the CA125-antibody functionalized CuO-ZnO heterojunction (CuO-ZnO-Ab) as a signal source, a novel photoelectrochemical (PEC) immunosensing platform was developed for ultrasensitive assay of CA125. Because of the target-induced introduction of photoelectric material to the sensing platform, the proposed PEC immunosensor has excellent performance for CA125 assay: near-zero background noise, wide linear response range (1 × 10 U/mL to 100 U/mL) and low detection limit (3.16 × 10 U/mL). The developed CuO-ZnO heterojunction and the related PEC sensing platform may have promising applications in ultrasensitive and highly accurate monitoring of various proteins in bioanalysis and disease diagnosis.