Zr-doped CoOOH nano-enzymes with enhanced oxidase-like activity for the colorimetric determination malathion in Foods

Herein, a colorimetric platform is presented based on zirconium-doped cobalt oxyhydroxide (Zr-CoOOH) nano-enzymes for the rapid detection of malathion (MAL). The CoOOH nano-enzymes showed excellent oxidase-like activity. With the use of 3,3',5,5'-tetramethylbenzidine (TMB) as the chromogenic substrate, the Zr-CoOOH nano-enzymes can oxidize the colorless TMB to the blue product (oxTMB), and the UV-visible spectral absorption band of oxTMB is 652 nm. The oxidase-like activity of Zr-CoOOH nano-enzymes was significantly enhanced, which was attributed to the high affinity between Zr-CoOOH nano-enzymes and TMB. The metal in the Zr-CoOOH nano-enzymes can be combined with the phosphate thiolate groups in the MAL molecule, thus inducing an enhanced catalytic activity of MAL for the reaction. The Zr-CoOOH+TMB+MAL system can achieve the quantitative detection of MAL. Under the optimized conditions, the constructed sensor exhibited a linear relation with MAL over the range of concentration from 0.1-10 μM, with a detection limit of 0.023 μM. The sensing platform showed excellent anti-interference and batch stability. This strategy expands the application of nano-enzymes to the area of rapid detection.