Wide-spectrum response direct Z-scheme ZnIn2S4/polypyrrole heterojunction for photoelectrochemical aptasensing of di(2-ethylhexyl)phthalate in food.

A direct Z-scheme ZnIn2S4/polypyrrole (PPy) heterojunction with wide near-infrared (NIR) response range was established by in situ electropolymerization of pyrrole monomers on ZnIn2S4 nanosheets surface, which was integrated into photoelectrochemical (PEC) aptasensing system for sensitive determination of di(2-ethylhexyl)phthalate (DEHP) based on hemin monomer-mediated biocatalytic precipitation effect. Driven by interfacial electric field, NIR-response ZnIn2S4/PPy heterojunctions exhibited effective charge carrier separation, thereby enhancing initial photocurrent response. The hemin monomers decorated on bridge-shaped DNA nanostructures triggered biocatalytic precipitation to impede interfacial electron transport and hinder electron donors from approaching heterojunction surface. This biocatalytic precipitation effect was inhibited by target-induced collapse of double-hemin-decorated bridge-shaped DNA nanostructures, further amplifying aptasensing signal. The developed PEC aptasensor achieved a linear range from 0.5 pM to 1 μМ with a detection limit of 0.34 pM. Moreover, it exhibited excellent selectivity, stability, and reproducibility, showcasing significant potential for detecting DEHP in milk and bottled water samples.