Co-Pi-assisted S-scheme photoelectrochemical platform for enhanced charge separation toward ultrasensitive dimethoate detection

Novel S-scheme heterojunction boosts light absorption/charge separation. • In-situ Co-Pi co-catalyst reduced electron-hole recombination. • Polypyrrole-MIP membrane ensures DIM recognition with maintained conductivity. • The sensor achieves ultra-sensitivity: LOD 0.83 fmol/L, 1.0 fmol/L-100 pmol/L range. • The new sensors demonstrated reliable DIM detection in real samples. An S-scheme TpPzda-COF@ZnIn 2 S 4 @Co-Pi core–shell hybrid was fabricated via in situ growth of a ZnIn₂S₄ nanoflower shell on a β-ketoenamine-linked TpPzda-COF core, followed by photodeposition of a cobalt-phosphate (Co-Pi) cocatalyst. The resulting hierarchical architecture facilitated efficient interfacial charge transfer and synergistic effects, leading to enhanced light absorption, charge separation, and catalytic activity. Based on this photoactive material, a molecularly imprinted photoelectrochemical (MIP-PEC) sensor was constructed through electropolymerization using pyrrole as the functional monomer and dimethoate (DIM) as the template. The imprinted cavities enabled selective recognition of DIM, regulating interfacial electron transfer and producing distinct photocurrent responses. Benefiting from the π-conjugated structure of TpPzda-COF, the visible-light activity of ZnIn 2 S 4 , and the hole-extraction capability of Co-Pi, the proposed sensor exhibited high sensitivity, good stability, and satisfactory reproducibility. An ultralow detection limit of 0.83 fmol·L −1 was achieved over a wide linear range of 1.0 fmol·L −1 to 100 pmol·L −1 . Furthermore, successful determination of DIM in real fruit and vegetable samples demonstrated the applicability of the sensor for food safety and environmental monitoring. Download: Download high-res image (95KB) Download: Download full-size image