Target-Triggered In Situ Construction of Bi4O5Br2/Bi2S3 Heterojunction for Dual-Mode Detection of Estradiol

Abstract A dual-mode sensor based on the target-triggered in situ formation of a Bi4O5Br2/Bi2S3 heterojunction was constructed for the detection of estradiol (E2). A ZIF-8-diallyl trisulfide (DATS)-cDNA composite probe (ZDC) was prepared, and the specific recognition of the E2 aptamer enabled target-triggered dissociation of the ZDC probe, which could be degraded under acidic conditions. After the high-efficiency reaction between DATS and GSH and the pH adjustment, the generated Na2S served as a precise sulfur source for the in situ formation of the Bi4O5Br2/Bi2S3 heterojunction on the Bi4O5Br2-modified ITO electrode. Here, we screened the substrate materials and explored the mechanism of the formation of the Z-scheme heterojunction. The abundant electrons generated under illumination induced the electrochromic conversion of Prussian blue to Prussian white, enabling EC visual detection quantified by the RGB values. Owing to the in situ formation of a compact and ordered heterojunction, the sensor achieved detection limits as low as 0.56 pM in PEC mode and 7.7 pM in EC mode, with a total assay time of 110 min and simple operation, verifying its reliability and practicality for environmental estrogen monitoring.