Polypyrrole participates in the construction of a polarity-switchable photoelectrochemical molecularly imprinted sensor for the detection of acrylamide in fried foods

Designing a polarity-switchable photoelectrochemical (PEC) sensor is important, but there are significant challenges due to the difficulty in adjusting the polarization of photoelectric or photoactive materials. In this manuscript, we established a simple and polarity-switchable molecularly imprinted polymer (MIP)-PEC sensor based on a "Z-scheme" strategy for detecting acrylamide (AM). First, we prepared a composite material of MoS2/rGO/Au (MGA) with a large specific surface area and good electrical conductivity that was sensitive to visible light. Second, the photoactive material MGA was used as the substrate material and polypyrrole (PPy) was acted as the functional monomer associated with the template molecule AM to construct the MIP working electrodes. PPy not only dressed up as a functional monomer but also as a polarity switcher, creating an in-situ-grown PPy/MGA heterojunction with a charge-carrier transport path similar to the letter "Z." The design of the Z-scheme strategy not only increased the signal intensity of the photocurrent but also switched the photocurrent polarity from the anode to the cathode, avoiding the interference of a false positive or a false negative. When using this PEC-MIP sensor for the quantitative detection of AM, the detection limit was 1.7 pmol for the linear range of 0.25–10000 nmol. The proposed sensor exhibited satisfactory sensitivity and selectivity, and it has great potential for monitoring emerging food safety risks.