Preparation Of CoFe Nanocomposites With High Efficient Peroxidase-mimic Activity

In recent years,a variety of nanomaterials with intrinsic enzyme-like activity（i.e.nanozyme）were reported.Compared with natural enzyme,nanozymes have several advantages which make it useful for potential biological applications,such as high stability,long shelf life and easy for mass-production.In this work,we reported a novel hydrothermal method for preparation of cobalt/iron oxide nanocomposites with intrinsic peroxidase activities.The main work and results are as follows:1.Using Fe³⁺,Co²⁺,urea and Glycerol as starting materials,we reported a novel one-pot hydrothermal method for the preparation of cobalt/iron oxides nanocomposites.The nanocomposites were characterized by TEM,HRTEM,XRD,EDS,FTIR and VSM analysis.The results showed that by controlling the crystallization kinetics,nanocomposites with different crystalline,morphology and particle size could be prepared:（1）when crystallizing time was 2h,crystals with nanorod morphology were obtained;（2）when crystallizing time was 7h,crystals with nanorods/nanoparticle morphology were obtained,showing saturated magnetization of 57.3emu/g;（3）when crystallizing was 20h,crystals with nanoparticle morphology were obtained,and the saturated magnetic intensity is 32.9emu/g.2.The peroxidase mimic activity of cobalt/iron oxides nanocomposites were investigated in detail.The experimental results show that the cobalt/iron oxides nanocomposites can efficiently catalyze the oxidation of TMB,ABTS,and OPD with the help of H₂0₂.Steady state dynamics analysis showed that all three kinds of nanocomposites exhibited typical Michaelis-Menten kinetics.The catalytic mechanism follows the ping-pong mechanism.The apparent Km with TMB as substrate for cobalt/iron nanorods,cobalt/iron nanorods/nanoparticle composites,and cobalt/iron nanoparticles was 0.16,0.26 and 0.37,respectively.All this values were lower than that of HRP（0.434）,indicating high affinity of nanozymes towards TMB.Based on the peroxidase activity of cobalt/iron nanorods/nanoparticle composites,a colorimetric method was developed for detection of hydrogen peroxide and glucose with high sensitivity and selectivity.The catalytic activity of cobalt/iron nanorods/nanoparticle composites was affected by reaction temperature,pH and the concentration of H₂0₂,with optimal value for these parameters of pH4.0,40℃ and 50mM,respectively.Under optimized conditions,the linear range of the method for detection of hydrogen peroxide is 2-20μM,the detection limit is 1.84μM.When coupled with GOX,the linear range of the method for detection of glucose is 2-200μM,the detection limit is 3.4μM.Compared with HRP,the method we developed using iron/cobalt nanocomposite materials as catalysts is simple,rapid,economic and reusable.