Molecularly imprinted photoelectrochemical sensor based on tin(III) oxide/multi-walled carbon nanoflowers for ultrasensitive detection of 2,4-Dichlorophenoxyacetic acid

The extensive use of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) calls for the development of robust methods for its trace-level monitoring in the environment, owing to the associated ecological and health risks. Herein, a novel molecularly imprinted photoelectrochemical (PEC) sensor is rationally designed for the ultrasensitive and specific detection of 2,4-D. The sensor is constructed on a synergistic Tin(III) oxide/multi-walled carbon nanotube (Sn 3 O 4 /MWCNT) nanocomposite, where Sn 3 O 4 nanoflowers act as an efficient photoactive matrix and the MWCNTs serve as an electron highway. This synergy significantly enhances charge separation, suppresses recombination, and provides a strong, stable photocurrent. A highly selective molecularly imprinted polymers (MIPs) layer is subsequently fabricated on this composite via in situ electrophmerization of pyrrole, creating specific recognition cavities for 2,4-D. The resulting MIP-PEC sensor displays an ultra-broad linear range spanning five orders of magnitude (0.1 nM ∼ 100 μM) and achieves an impressively low detection limit of 16.1 pM (S/N = 3). It also demonstrates excellent selectivity against structural analogs, high reproducibility, and satisfactory recoveries (93.8–106.7%) in real water samples. This work not only provides a robust analytical tool for trace pesticide analysis but also offers a versatile sensing strategy through the integration of advanced nanomaterials with molecular imprinting technology.