Dual Direct Z-Scheme Heterojunction with Growing Photoactive Property for Sensitive Photoelectrochemical and Colorimetric Bioanalysis.

A dual direct Z-scheme heterojunction photoactive material of CoTiO 3 /g-C 3 N 4 /Bi 2 O 3 was designed based on calcination and in situ illumination-assisted process for sensitivity bioproteins detection which combined with MnO 2 nanoflowers to achieve signal quenching strategy. The complex consists of two direct Z-scheme heterojunctions of g-C 3 N 4 and two photoactive materials CoTiO 3 and Bi 2 O 3 . This great structure could augment the migration of photogenerated electrons obviously, which boost the photocurrent greatly and prefer the photoelectric application of perovskite oxide. To improve sensitivity, the nanoflower like MnO 2 with oxidation performance is introduced into the system and used as a label fixed on secondary antibody to oxidize electron donor (AA) to achieve an enlarged signal quenching value. Interestingly, MnO 2 also showed an effective oxidation activity for TMB oxidation, leading to a chromogenic reaction. With the change of antigen concentration, the color of the test electrolyte also changes. Herein, the designed smart photoelectrochemical sensor shows a wide detection range (neuron specific enolase as an example) from 0.00005 to 200 ng/mL with a detection limit as low as 28 fg/mL. And the colorimetric assay for target detection owns a liner range from 0.1 to 20 ng/mL accompany with a detection limit of 0.05 ng/mL. These two designed sensing modes offer a new strategy for signal amplification of perovskite oxide and the possibility of real-time detection.