The Study Of Regulating The Peroxidase-like Activity Of Nanoceria

Although natural enzymes have high activity and good selectivity,they are limited in practical applications because of their own intrinsic drawbacks,such as high cost,instability and ease to denatured,sensitivity to reaction environment,etc.Now,more and more nanomaterials have been found having enzyme mimic activities,named as nanozymes.As one kind of important nanozymes,CeO2 has been widely investigated over decades due to its unique redox property.It can mimic many natural enzymes activities,such as catalase,peroxidase,superoxide dismutase,etc.We focused mainly on its peroxidase-like activity in this thesis.Two approaches have been explored to improve its catalytic performance.One is doping other elements and the other is controlling its morphology.We prepared CeO2 and other transition metal elements doped CeO2 by a one-pot low-temperature hydrothermal method.Among these nanomaterials,the doping of Mn enhanced the catalytic ability most significantly.By optimizing the atom ratios of Mn/Ce,the best peroxidase mimic with a Mn/Ce ratio of 1:5(i.e.,Mn1Ce5)was obtained,which had the highest-Mn content solid solution,low Ce3+ fraction and the highest reactive oxygen Oβ.The decrease of Ce3+ fraction was beneficial for converting H2O2 into hydroxyl radicals(·OH),while Op promoted the catalyst to react with reactants.Meanwhile,the synergistic effect between Ce and Mn played a crucial role in the enhancement of catalytic activity.Using the same synthesis method,we prepared the CeO2 nanoparticles and CeO2 nanobranches simultaneously.Despite of having different morphologies,the crystal structure of these two nanomaterials retained the same.Detailed study on the process of nanobranches growth showed that the special structure formed by self-assembly of nanoparticles.First,tiny particles appeared and tended to string array,then several strings arranged side by side.Meanwhile,grain orientation tended to be consistent gradually and recrystallization occurred.Eventually,nanobranches with compact-structure and sharp-edged formed.Due to the different state of surface elements,the catalytic activity of nanoparticles was better than nanobranches,which was consistent with the conclusion above.