The Study On Peroxidase Mimetics Of Novel Doped Magnetic Nanomaterials And Its Application

Enzyme is a kind of natural macromolecular material which possesses biocatalysis activity. Almost all of the reactions in the cell require the participation of the enzyme. In many fields, such as pharmaceutical, chemical, food and agriculture, enzyme has been widely used as a biological catalyst. However, enzyme activity was easily affected by external environment, such as temperature and chemical environment (pH), so its qualitative will be changed owing to the loss of catalytic activity. Nanomaterials has small size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect, making it has many special aspects of performance in magnetic, optical, electrical, thermal, chemical and mechanical. Since it was found for the first time that Fe3O4 have the nature of the peroxidase, the study on Fe3O4 as peroxidase-like catalyst has attracted general attentions. Afterwards, a lot of other nanomaterials have also been proven to have peroxidase mimetics. This peroxidase-like nanomaterials not only have the high catalytic activity of enzymes, but also have the high stability and reusability of nanomaterials, which largely overcome the restrictions of the natural enzyme, and broadened the practical application of enzyme in more fields. Given this, in this dissertation, we prepared a new type of doped magnetic nanomaterials and studied their catalytic mechanism.Chapter 1:A brief overview of the peroxidase mimetics of nanomaterials was introduced, and several kinds of nanomaterials including magnetic and non-magnetic nanoparticles with peroxidase-like activity were summarized in detailed. Also, the applications of these nanomaterials as peroxidase-like catalyst in chemical and biology analysis was illustrated.Chapter 2:Cobalt doped magnetic composite nanoparticles (CoxFe3-xO4 MNPs) were firstly prepared through a simple and convenient coprecipitation approach. The characterization results from EDX, ICP-AES, TEM, XRD and XPS showed that the cobalt atoms might be located in the lattice position instead of the part of iron atoms. CoxFe3-xO4 MNPs possessed higher peroxidase-like activity comparing with MNPs, although they were similar in crystal structure, size distribution and morphology. CoxFe3-xO4 MNPs could effectively catalyze the reaction between H2O2 and 3,3',5,5'-tetramethyl benzidine (TMB) into blue solution, and dopamine (DA) could cause the blue shallowing. Based on the above phenomenon, a visual, sensitive and simple colorimetric method was developed for detecting DA. Under the optimum conditions, good linear relationship and recoveries for DA were obtained from 0.6 to 8.0?mol/L and 98.7 to 101.0%, respectively. This visual method has successfully been used to DA detection in Common Yam Rhizome (ShanYao) and human serum samples.Chapter 3:The Fe3O4@Ni magnetic nanocomposites (Fe3O4@Ni MNPs) were prepared through an in situ growth method. The characterization results from XRD, EDX, ICP-AES, TEM, and XPS showed that nickel was present as the form of NiO in Fe3O4@Ni MNPs. Further, the Fe3O4@Ni MNPs was proven to have peroxidase mimetics for the first time. Compared with HRP, Fe3O4@Ni MNPs have much higher catalytic activity to the reaction between H2O2 and TMB, which mainly depended on pH, temperature, the concentration of H2O2, and the content of Ni doped into the magnetic nanocomposites. Finally, a simple, economic, visual and new method was established to detect trace H2O2. Under the optimum conditions, good linear relationship and recoveries for H2O2 were obtained from 2.0 to 26.3?mol/L and 97.6 to 102.0%, respectively. The visual method was successfully applied to detect H2O2 in disposable chopsticks and hard bean curd.