Chitosan-based molecularly imprinted photoelectric sensor with ZnO/Bi₂O₃/Bi₂S₃ sensing layer for thiamethoxam...

A molecularly imprinted photoelectrochemical sensor with high sensitivity and stable structure was constructed and applied to detect thiamethoxam pesticide. ZnO/Bi₂O₃/Bi₂S₃ heterojunction photoelectric material was formed on the fluorine-doped tin oxide (FTO) electrode by seed layer growth, drip coating, and in situ ion exchange. A chitosan-imprinted polymer membrane was prepared using chitosan as the functional monomer, glutaraldehyde as the cross-linking agent, and thiamethoxam as the template molecule. The photoelectric material was characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy analyses. The electron transfer mechanism of Z-type heterojunction was verified by ultraviolet-visible curve and Mott-Schottky curve. When thiamethoxam was re-adsorbed on the imprinted membrane, the current recorded at 0 V (vs. Ag/AgCl) was reduced because the thiamethoxam molecule blocked the electron transfer. The molecularly imprinted sensor exhibited a linear relationship to thiamethoxam concentration in the range from 7.0 × 10^-13 mol/L to 7.0 × 10^-10 mol/L and the detection limit was 3.32 × 10^-13 mol/L, which is lower than the values reported by other detection methods. Most pesticides, such as propoxur and isoprocarband carbaryl, do not interfere with the determination. The sensor also showed good practicability and suitability for the determination of trace thiamethoxam in environmental water and soil leaching solutions, with a recovery of 99.6-102.1% (RSD < 3.74%). A novel molecularly imprinted photoelectrochemical (MI-PEC) sensor with high sensitivity and selectivity for the determination of thiamethoxam (TMX) was developed. A Z-type heterojunction ZnO/Bi₂O₃/Bi₂S₃ photoelectric material was synthesized for the first time. The MI-PEC sensor was prepared with ZnO/Bi₂O₃/Bi₂S₃ as the sensitive material and MI membrane as the recognition element. The sensor exhibits an extremely sensitive response to thiamethoxam with a detection limit of 3.32 × 10^-13 mol/L due to the excellent photoelectrochemical properties of ZnO/Bi₂O₃/Bi₂S₃.