Photoelectrochemical Assay Based on SnO2/BiOBr p–n Heterojunction for Ultrasensitive DNA Detection

Herein, a photoelectrochemical (PEC) assay was designed for a highly sensitive DNA determination relying upon the SnO2/BiOBr p–n heterojunction as a photoactive material and SiO2 as a signal quencher. Compared with most traditional heterojunctions, the SnO2/BiOBr p–n heterostructure not only lessened the recombination of the photogenerated electron–hole pairs but also promoted the light-harvesting in the ultraviolet–visible (UV–vis) region, leading to further enhanced photoelectric conversion efficiency and photocurrent, which demonstrated 12.1-fold and 6.4-fold increments versus those of pure SnO2 and BiOBr, respectively. Additionally, the limited quantity of target DNA (a fragment of p53 gene) could be transformed into abundant output DNA–SiO2 by employing the Nt·BstNBI enzyme-assisted signal amplification procedure, leading to a highly improved detection sensitivity of the biosensor. Then, output DNA–SiO2 hybridized with the capture DNA anchored on the modified electrode surface, remarkably diminishing the PEC signal and thus achieving sensitive DNA determination. The elaborated PEC biosensor demonstrated outstanding performance within the linear range between 0.5 fM and 5 nM and a low limit of detection down to 0.18 fM, paving a new way for fabricating heterojunction with exceptional photoactive performance and demonstrating the enormous potential for detecting multitudinous biomarkers in bioanalysis and clinical therapy.