CeO₂-based Nanocomposites As Mimetic Enzymes And Their Applications In Analysis Of Ascorbic Acid

Nanomaterial-based mimetic enzymes are a class of inorganic nanomaterials which exhibit the catalytic activities of natural enzymes.Due to their easy preparation,low cost,good reusability,and stability in rough conditions,nanomaterial-based mimetic enzymes can rival the natural enzymes in the catalytic reactions.With the rapid improvement of nanotechnology,extensive research work has been carried out in order to broaden the type of mimetic enzymes,and manage their catalytic activities.And their applications in many fields such as biology,medicine,environment and food analysis have attracted our attention.In this paper,we focused on the optimization of the catalytic activities of CeO2 nanomaterials by adjusting their morphology and fabricating nanocomposites.And CeO2-based nanocomposites were applied in the detection of ascorbic acid.(1)CeO2 nanomaterials of different morphology were prepared,such as nanorods,nanocubes,nanopolyhedra,and their oxidase-like catalytic activities were investigated by using 3,3',5,5'-tetramethylbenzidine(TMB)as the substrate,and the nanopolyhedra particles with superior activities were chosen for further research.Zn-CeO2 nanocomposites were fabricated by doping zinc ions in the CeO2 nanopolyhedra particles.Based on the inhibitory effect of ascorbic acid on the catalytic activity of Zn-Ce02,a colorimetric sensing system was established for rapid detection of ascorbic acid.The system was successfully used to investigate the stability of ascorbic acid(AA)in the actual sample.(2)Ce02/rG0 nanocomposites were fabricated via a one-pot hydrothermal process,in which Ce02 nanoparticles were well anchored on the surface of rGO.The prepared Ce02/rGO nanocomposites exhibited excellent catalytic activity for the oxidation of TMB in the presence of 02.The effects of temperature and pH on the activities were investigated,and the reaction mechanism was discussed.Compared with the individual Ce02 nanoparticles,the nanocomposites had a higher affinity and adsorptivity towards the substrate TMB,which was because of the combination of graphene.In addition,based on the oxidase-like activity of Ce02/rG0 nanocomposites,a facile and sensitive colormetric sensor for ascorbic acid was investigated.The detection limit of AA was as low as 0.15?M and the linear range was between 0.5 and 40 ?M.Furthermore,the colorimetric sensing system was successfully used for the detection of AA in medicine and food analysis,such as tablets,beverage,and milk powder.Due to its excellent accuracy and sensitivity,the colorimetric system has potential applications in the field of medicine and food analysis.