Electroactive poly(thionine) as imprinted polymer and reference probe simultaneously for ratiometric ion imprinted electrochemical Pb2+ sensor

In this work, an electrochemical sensor based on ion-imprinted polymer/Au nanoparticles/porous biochar (IIP/AuNPs/PBC) composite was proposed for the highly selective and sensitive detection of Pb²⁺. In this work, poly (thionine) (pTHI) served simultaneously as imprinted polymer and reference probe. It could not only realize the specific detection of Pb²⁺, but also provide an internal reference signal to eliminate the influence of human and environmental factors on the detection signal and further improve the stability of the sensor. In addition, the AuNPs/PBC composite with large specific surface area, excellent electron transport and electrocatalytic performance could effectively enhance the detection signal as a carrier material. At the same time, the AuNPs on the PBC surface would promote the formation of uniform and stable IIP through Au-S bonds. The synergistic effect between IIP, AuNPs/PBC and ratiometric signal mode gave the Pb²⁺sensor excellent performance, including a wide linear range (0.1-1000μg l^-1), low detection limit (0.03μg l^-1, S/N = 3), excellent selectivity and stability. All these results indicate that the proposed sensor could provide a meaningful reference for highly selective detection of heavy metal ions (HMIs).