The Preparation Of Graphene Nanocomposites And Their Application In Colorimetric Detection Of Hydrogen Peroxide

Natural enzymes,known as the biocatalysts,can adjust every biological process in living organisms and catalyze the biochemical reactions effectively with high specificity in the mild conditions.Moreover,the chemical reaction rates can be accelerated to 1019 times for the specific substrates in the presence of natural enzymes.However,the practical application of natural enzyme has been restricted,due to their disadvantages,including inherent low stability,easy denaturation,high cost,and complex with the process of preparation and purification,etc.Recently,the development of nanotechnology have motivated people's endeavors to design and study functional nanomaterials.Compared with natural enzymes,the developed enzyme-mimicking nanomaterials have attracted considerable attention,because of several advantages,including low-cost in preparation,less vulnerable to denaturation,more stable,robust and tunable properties.Graphene oxide(GO),one of derivatives of graphene,is a two-dimensional(2D)lamellar flexible structure of sp2 hybridized carbon atoms with the hexagonal honeycomb lattice,and has been proved to possess peroxidase activity.Given its large specific surface area,high electrical and thermal conductivities,GO provides a promising support material for preparing graphene-based nanocomposites as peroxidase mimics.The synergistic effects between nanoparticles and GO lead to the enhancement of catalytic activity and thus improve sensitivity of detection.In the thesis,FePt nanoparticles loaded on the GO(FePt/GO)and NiS/MMT/GO ternary nanomaterials were fabricated as artificial enzymes for the first time.Based on their peroxidase activity,we proposed the sensing systems to detect hydrogen peroxide(H2O2)and glutathione(GSH).The main contents of this thesis are focused on the follows:1.FePt nanoparticles were dispersed uniformly to the surface of graphene oxide by polyol reduction method.The intrinsic peroxidase activity of FePt/GO nanocomposites was investigated using TMB as chromogenic substrate and the results showed higher mimetic enzyme catalytic activity was greatly dependent on pH and temperature,respectively.In addition,steady-state dynamics experiments indicated that the catalytic behavior followed the typical Michaelis-Menten model and FePt/GO had a high affinity towards H2O2.Based on the peroxidase properties of FePt/GO,a simple and rapid colorimetric method was developed to detect H2O2 with rapid response time over a wide linear detection range from 0.03-0.5 mM and a detection limit of 0.022 mM.Moreover,FePt/GO was successfully applied to the analysis of residual amount of H2O2 in contact lens solution.2.NiS/MMT/GO nanocomposites were prepared by a facile gas deposition method.The morphology,phase and element composition were characterized by powder X-ray diffraction(XRD),energy dispersive spectrometer(EDS),transmission electron microscopy(TEM),etc.A series of experiment results showed that the NiS/MMT/GO with high peroxidase activity was due to the synergistic effect from different components.Similar to natural enzyme,its catalytic activity mechanism followed the Michaelis-Menten enzymatic equation.Moreover,owing to the inhibiting effect of GSH towards peroxidase activity of NiS/MMT/GO,a simple and rapid colorimetric method was used for the sensitive detection of GSH as well as H2O2.The results showed a high sensitive towards both H2O2(the linear range was 10-100.M,LOD=9.73 ?M)and GSH(the linear range was 0.6-60.M,LOD?0.5043?M).