Homogeneous Photoelectrochemical Aptasensors for Tetracycline Based on Sulfur-Doped g-C3N4/n-GaN Heterostructures Formed through Self-Assembly

The complex synthesis of photoelectric materialsand the difficulty offixing the identification elements on thephotoelectrode are long-standing problems in thefield ofphotoelectrochemical (PEC) biosensing. In this work, a simplePEC aptasensor construction strategy based on a sulfur-doped g-C3N4(SCN)/n-GaN heterostructure photoelectrode was proposed.The SCN/n-GaN heterostructure can be formed through self-assembly in solution since SCN can be uniformly dispersed insolution. In addition, as a dual-function mediate, an aptamer can befixed on an SCN substrate automatically because of the goodadsorption performance of SCN. Therefore, tedious steps of PECelectrode preparation and thefixing of recognition elements wereboth avoided. Compared with the traditional ones, the constructiondifficulty and time cost of the prepared PEC aptasensors are greatly reduced. The simplified experimental process improves thestability and reproducibility of the aptasensor. Finally, tetracycline (TET) was used as a model target to verify the sensingperformance of the proposed PEC strategy. TET can consume the photogenerated holes of the SCN/n-GaN heterostructure,promote carrier migration, and result in the change in the photocurrent. The linear relationship between the change in thephotocurrent intensity and the TET concentration can be used to detect TET. The aptasensor has a linear range of 0.10-10.0 nmolL-1and the detection limit is 0.030 nmol L-1(3S/N). The aptasensor was applied to the detection of TET in milk samples withsatisfactory results