Porphyrin and molecularly imprinted polymer double sensitized cathode photoelectrochemical sensor for chlortetracycline

A molecularly imprinted photoelectrochemical (PEC) sensor was fabricated for the detection of chlortetracycline (CTC) based on 5,10,15,20-tetrakis(4-carboxylphenyl) porphyrin (TCPP) and poly(o-phenylenediamine) (PoPD) sensitized ZnO-MWCNTs-NH2, which was prepared by a three-steps synthetic route: a simple one-step hydrothermal method for ZnO-MWCNTs-NH2, a successive self-assembly for TCPP loading and in situ electro-polymerization for multifunctional PoPD. Here MWCNTs-NH2 was introduced not only to narrow the band gap of ZnO for enhance visible light absorption, but also to upgrade the surface property for TCPP and PoPD loading, which improved the photocurrent of the photoactive electrode greatly. Besides good selectivity, PoPD film exhibited well energy level matching with ZnO-MWCNTs-NH2/TCPP, thus benefiting for the formation of heterojunction and the separation and transmission of photogenerated carriers. Based on the good matching of organic and inorganic components, a novel cathode MIP-PEC sensor for CTC with good sensitivity and selectivity was constructed. Under the optimized conditions, the MIP-PEC sensor possessed a good linear relationship between the photocurrent intensity and concentration of CTC from 0.5 nmol/L to 10 μmol/L with a detection limit of 0.17 nmol/L (S/N = 3). And it could be used for the detection of CTC in actual samples (e.g. lake water, milk and pork) with recoveries among 86.4%–112.0%, indicating its good practicality.