Highly sensitive field-effect transistor sensor based on ZnO/TiO2 for quantification of aflatoxin G2 with optimized initial measurement

Aflatoxin G2 (AFG₂) is a secondary metabolite produced by certain molds that contaminate agricultural products, including grains, nuts, and spices. If humans consume contaminated products, severe liver damage and cancer can occur, so measuring its concentration is necessary to ensure food safety. In this study, a highly sensitive ion-sensitive field-effect transistor (ISFET) sensor based on a ZnO/TiO₂ gate structure was developed for the detection of AFG₂. The fabrication steps included the oxidation of p-type silicon, followed by the simultaneous synthesis and sequential deposition of ZnO and TiO₂ using a hydrothermal method. Characterization by FESEM and XRD confirmed the structure of ZnO nanorods and TiO₂ nanoparticles. Electrical measurements then determined the correct operation of the ISFET and the optimum sensing voltage. The sensor exhibited a clear and robust response to increasing AFG₂ concentration in 0.01 M phosphate-buffered saline, with a low detection limit and sensitivity of 4.610 nM and 2.068 µA/nM, respectively (SD 2.89 µA). The sensor was able to detect AFG₂ at pH levels ranging from 3 to 10; however, the optimum pH range was found to be 7-8, and it also exhibited good reusability and stability. The pseudo-first kinetic mechanism was consistent with the assay results and detected concentrations much lower than the thresholds set by the FDA in corn juice. The quantitative detection of AFG₂ by the proposed sensor is confirmed by its acceptable performance, high sensitivity, real-time operation, and well-defined kinetic response. Thus, it is proposed as a new method and a good complement to traditional methods in AFG₂ detection.