One step preparation of CN-WS2 nanocomposite with enhanced photoactivity and its application for photoelectrochemical detection of 5-formylcytosine in the genomic DNA of maize seedling.

Carbon nitride and WS2 nanocomposite (CN-WS2) with excellent photoelectric activity was prepared by one-step thermal polymerization. By the new strategy of simultaneously loading C and N elements on pure WS2, the formation of CN-WS2 brings high mobility, ultra-fast charge carrier separation and transport, and slows down the recombination rate of electrons and holes. Then, a novel photoelectrochemical biosensor was constructed for 5-formylcytosine detection based on CN-WS2 composite, aldehyde reaction probe (ARP) and ZnFe2O4, where CN-WS2 composite was employed as photoactive material, ARP was used as 5-formylcytosine capture reagent, and ZnFe2O4 was adopted as artificial mimic enzyme. Under the catalysis effect of ZnFe2O4, 4-chloro-1-naphthol was quickly oxidized by H2O2 to produce the insoluble substance of benzo-4-chlorohexadienone, which would be deposited on the electrode surface and caused a decreased PEC response. Under optimal experimental conditions, the biosensor showed low detection limit of 3 pM. This method can also discriminate 5-formylcytosine with other cytosine derivatives. More importantly, the applicability of this method was demonstrated by assessing the effect of antibiotics on the content of 5-formylcytosine in the root, stem and leave of maize seedlings.