A self-powered molecularly imprinted photoelectrochemical sensor based on a Cr(III)-8-hydroxyquinoline complex...

A self-powered molecularly imprinted photoelectrochemical sensor was developed based on metal-complex imprinting for the determination of Cr³⁺ in injection solutions. AgInS₂/Ti₃C₂ and CuInS₂/Ti₃C₂ Schottky heterojunction photoelectric materials were synthesized and used as the photoanode and photocathode, respectively. The complex formed by Cr³⁺ and 8-hydroxyquinoline(Ox) (Cr-Ox) was used as a template molecule to prepare a molecularly imprinted polymer(MIP) film on the CuInS₂/Ti₃C₂ photocathode, constructing a dual-Schottky junction self-powered molecularly imprinted photoelectrochemical sensor for the first time. After being specifically recognized and adsorbed by the MIP, Cr-Ox exerts three synergistic effects. First, Cr-Ox acts as an electron trap, capturing photogenerated electrons and promoting charge carrier recombination, i.e. an electron trapping effect. Second, the cation exchange between Cr³⁺ and Cu²⁺ on the CuInS₂ photocathode surface generates photoinert Cu-Ox, leading to the cation exchange-induced passivation effect. Third, the physical blockage of incident light by Cr-Ox located within the imprinted cavities produces a light-blocking effect. The synergy of these three effects causes a sharp decrease in photocurrent. Taking advantage of this signal change, indirect determination of Cr³⁺ was achieved with a detection limit of 7.64 × 10^-14 mol/L, demonstrating significantly higher sensitivity compared to other Cr³⁺ detection methods. Furthermore, the selectivity of the sensor was improved by the MIP film, eliminating interference from common metal ions. The sensor has been applied to the determination of trace Cr³⁺ in injection samples.