Structural and Compositional Engineering of a Heterojunction Nanocomposite for Enhanced Photoelectrochemical Sensing: Selective and Simultaneous Detection of Organophosphate Pesticides

Simultaneous detection of chlorpyrifos (CPF) and glyphosate (Glyp), two widely used organophosphate pesticides, remains a significant challenge for current electrochemical sensors. This study addresses that challenge by developing a high-performance, cost-effective photoelectrochemical sensor capable of detecting both pesticides either individually or simultaneously. The sensor is based on a graphene-incorporated vanadium-silver metal oxide/metal sulfide nanocomposite (Gr/V₂O₅-Ag₂O@VS₄-Ag₂S, denoted GVA) synthesized through a one-step hydrothermal process. The GVA nanocomposite is further modified with gold nanoparticles (AuNPs) and integrated onto an ITO substrate, yielding the GVA@AuNPs/ITO electrode. Compared to the unmodified GVA nanocomposite electrode, the GVA@AuNPs/ITO electrode demonstrated significantly enhanced sensitivity for the simultaneous detection of CPF and Glyp, as confirmed by various electroanalytical techniques. Furthermore, under sunlight irradiation, the photon-assisted GVA@AuNPs/ITO electrode exhibited superior photoelectrochemical sensing performance with broad linear ranges, attributed to the increased accessibility of electroactive sites, enhanced electron transfer kinetics, and improved interfacial charge transfer capability. In addition to its high sensitivity, the GVA@AuNPs/ITO electrode showed excellent selectivity, reproducibility, and stability, even in the presence of potentially interfering molecules. Finally, in real sample analyses involving fruit samples (apple, orange, and pineapple), the photon-assisted GVA@AuNPs/ITO electrode achieved high recovery rates of 98 and 99% for CPF and Glyp, respectively.