Dual near-infrared AgInS₂ and CuInS₂ co-sensitized ZnO photoelectrode array enabled paper-based ratiometric photoelectrochemical aptasensing

Herein, a dual near-infrared (NIR)-response AgInS₂ and CuInS₂ co-sensitized ZnO photoelectrode array consisting of two spatial-resolved paper working electrodes (PWE₁ and PWE₂) was established to enable paper-based ratiometric photoelectrochemical (PEC) aptasensing of Di(2-ethylhexyl)phthalate (DEHP) based on triple-helix molecular switch (THMS)-mediated “on–off” switching of co-sensitization effect. Profiting from the co-sensitization of AgInS₂ and CuInS₂ on paper-based ZnO, the dual NIR-response cascade sensitization structure of AgInS₂/CuInS₂/ZnO exhibited a wide light response range and high charge separation efficiency, giving a “switch on” state of co-sensitization effect with markedly high photocurrent response. The “switch off” state of the co-sensitization effect was made by RecJf exonuclease-assisted target recycling-induced conformation change of THMS, which caused the detachment of AgInS₂ quantum dots from the aptasensing interface, leading to a significantly decreased photocurrent signal. Accordingly, the constant I₁ of PWE₁ and varying I₂ of PWE₂ were collected based on the incubation of constant concentration of DEHP on PWE₁ and various concentrations of DEHP on PWE₂. The ultrasensitive detection of DEHP was realized by calculating the ratio of I₂/I₁. This work brought new insights into the establishment of a high-performance paper-based ratiometric PEC aptasensing platform for highly sensitive quantification of DEHP.