Preparation And Carbon Transformation Of Polypyrrole Modified Metal Oxide And Chalcogenide Composite Nanocatalyst,and Its Properties Of Enzyme Catalysis

Since C.G.Overberger and co-workers found a class of enzyme-like reactions in 1969,people have synthesized a variety of artificial enzymes in a few decades.Compared with natural enzymes,the artificial enzymes show advantages of easy synthesis,easy purification and wide temperature range of application,thus it has a variety of applications in the fields of biosensors,chemical industry,food processing,environmental science and biotechnology.Up to now,the artificial enzymes mainly include cyclodextrins,aromatic hydrocarbons,porphyrins,proteins,supramolecular materials,inorganic nanomaterials,etc.Among those,inorganic nanomaterials have attracted much attention due to their good catalytic activity,high environmental stability and low cost.For example,metal oxides,metal sulfides,graphitized carbon nanomaterials etc.have demonstrated excellent peroxidase-like catalytic activityHowever,the catalytic activity of inorganic nanomaterials as enzyme mimics needs to be further improved.Recently,it has been found that the catalytic activity of metal oxide and sulfide nanomaterials can be improved by optimizing the morphology,size,composition and surface structure.In particular,the commixture of metal oxides or sulfides with other materials to prepare heterogeneous structure can play a synergistic effect between the components of the composite materials,thereby greatly enhancing the enzyme-like catalytic activity.In this thesis,we have prepared conducting polypyrrole and carbon nanomaterials modified metal oxide and metal sulfide nanomaterials based composites through combination of electrospinning,calcination and hydrothermal reaction.We will study on the peroxidase like catalytic properties of these nanocomposites.By using these three kinds of peroxidase-like catalytic reactions,the sensitive colorimetric sensors to realize the accurate detection of low concentrations of hydrogen peroxide,phenol,and ascorbic acid have been developed.It is anticipated that the experimental results have important reference value in the field of environmental monitoring and biosensors.The research results of this thesis mainly include three parts:（1）TiO₂/Fe₂O₃/PPy composite nanofibers were successfully prepared through electrospinning,calcination and hydrothermal methods.The TiO₂/Fe₂O₃/PPy composite nanofibers exhibited excellent peroxidase-like catalytic activity,which is much higher than those of individual TiO₂,Fe₂O₃ nanofibers,and also higher than that of TiO₂/Fe₂O₃ composite nanofibers,demonstrating the synergistic effect among the components in the composite nanofibers.A colorimetric sensor was constructed to determine the concentration of H2O2,with a detection linear range of 2-50 μM,and the detection limit of 2.4 μM（S/N=3）.（2）Fe₃O₄/N-C composite nanofibers were successfully fabricated through electrospinning,hydrothermal reaction and calcination methods.Owing to the intrinsic peroxidase-like activity of Fe₃O₄ and the synergistic effect between Fe₃O₄ and graphitized N doped carbon materials,the as-prepared Fe₃O₄/N-C composite nanofibers displayed excellent peroxidase-like catalytic activity.A colorimetric sensor was constructed to determine the concentration of H2O2 and ascorbic acid（AA）.Through the measurement analysis,low concentration H2O2 can be detected in a linear range of 0-50 μM with the detection limit at 0.58 μM（S/N=3）,low concentration of AA can be determined in a linear range of 0-50 μM with the detection limit at 0.04 μM（S/N=3）.（3）rGO/Cu₈S₅/PPy composite nanosheets were successfully obtained through a wet chemical and hydrothermal reaction.Owing to the intrinsic peroxidase-like catalytic activity of Cu₈S₅ and the synergistic effect among the three components in the composite nanosheets,the as-prepared rGO/Cu₈S₅/PPy composite nanosheets exhibited an outstanding peroxidase-like catalytic activity.A colorimetric sensor was constructed to determine the concentration of H2O2 and phenol.Through the measurement analysis,the material can be employed to detect low concentration of H2O2 with a detection range of 0-20 μM,and the detection limit was 0.69 μM（S/N=3）,and low concentration of phenol also can be detected in a detection range of 0-200 μM,with the detection limit at 1.78 μM（S/N=3）.