Design three-dimensional CoFe2O4 nanocage via ion exchange route for ultra-sensitive electrochemical sensing of nitrobenzene

Bimetallic transition metal oxide materials have rich valence states, good biocompatibility, conductivity, high stability, and satisfactory catalytic performance, and stand out among many materials. Therefore, we develop a simple synthesis method of CoFe2O4 nanocage by ion exchange for the detection of nitrobenzene (NB) in this work, which uses the zeolitic imidazolate framework-67 (ZIF-67) as cobalt source and three-dimensional hollow organic framework Co-Fe PBA as precursor. The continuous conversion between ionic valence states in CoFe2O4 enhances the conductivity of the material, showing a good synergistic coupling effect. The low-density hollow structure of nanocage offers various types of sites for adsorbing reactants, and the thin shell structures provide more channels for ion migration and electron transport, facilitate charge transfer, and further improve their electrical sensing ability. Electrochemical tests proved that the material demonstrated excellent electrocatalytic activity for NB, with the limit of detection as low as 0.038 mu M, a wide linear response (0.05-1664.55 mu M), higher sensitivity, good repeatability, long-term stability and selectivity. More importantly, the sensor has been suc-cessfully applied to the determination of trace NB in water samples with satisfactory recovery (98.7%-104.7%). This work provides a novel idea for the detection of low content of NB and expands the application of bimetallic oxide materials in the sensing field.