The Study On Synthesis And Catalytic Performance Of The Three-dimensional Graphene Nanohybrids And Its Application

Owing to the excellent physical and chemical properties of three dimensional graphene nanohybrids, it plays a very important role in different fields of science. Among those three dimensional graphene nanohybrids, metal loaded three dimensional graphene nanohybrids, especially precious metals (such as palladium and platinum) doped nanohybrids attracted increasing attentions. Their preparation and application have been the priority of the scientists in nanomaterials science, analytical chemistry and other fields. In addition to the traditional property of two-dimensional graphene, the three dimensional graphene nanohybrids have unique electronic conductivity, good mechanical performance, large specific surface area and better biological compatibility. It has been applied in many fields, such as ion battery, electrochemical devices, energy storage, biological sensors and catalyst. There are many reports on the preparation methods of three dimensional graphene nanohybrids, but they need complex operation and require additional reducing agent. What’s more, the size distribution of the metal particles is uneven and the three dimensional structure is irregular.On the basis of the previous work, this dissertation principally works on the study of preparation method and catalytic performance of three dimensional graphene nanohybrids, and their application in real samples. We carried out the following research works:(1) we developed a simple method for one-step and in-situ synthesis of dual metal-loaded three dimensional graphene nanohybrids, and further studied its catalysis performance on p-nitrophenol degradation and its reuse properties; (2) we studied its enzymatic properties deeply, and established a simple, sensitive method for colorimetric detection of hydrogen peroxide, glutathione and glucose; (3) furthermore, we studied its electrochemical behavior towards hydrogen peroxide in environmental and daily samples successfully.Chapter 1:The properties, research status and preparation methods of three dimensional graphene nanohybrids are principally introduced, and its applications in the fields of electrochemical devices, sensors and catalyst and so on are briefly summarized.Chapter 2:The self-assembled three-dimensional graphene nanohybrids with in situ formed Fe3O4 and Pd nanoparticles on it (3DRGO_Fe3O4-Pd) are first synthesized by the one-pot solvothermal method. The synthesis process are:the precursors of ferric and palladium were adsorbed to the surface of GO due to the electrostatic adsorption, converted to its hydroxide forms by adjusting pH to 13, and followed by thermal reduction and self-assembly to produce 3DRGO_Fe3O4-Pd nanohybrids. The nanohybrids are successfully characterized by TEM, SEM, XRD, FTIR, Raman, BET, VSM and TGA. Further,3DRGO_Fe3O4-Pd nanohybrids are applied to the catalytic study on p-nitrophenol degradation.Chapter 3:The peroxidase-like catalytic activity of 3DRGO_Fe3O4-Pd was detailedly studied, which can degrade H2O2 to produce hydroxyl radicals, and then oxidize the substrate 3,3’,5,5’-tetramethylbenzidine (TMB) to display a deep blue color. The catalytic mechanism is analyzed by the electron spin resonance (ESR), fluorescence, and electrochemical methods. The mimic enzyme catalytic activity of 3DRGO_Fe3O4-Pd is much higher than those of monometallic loaded nanohybrids and their physical mixture, probably caused by synergistic effect between Pd and Fe3O4 nanoparticles. The 3DRGO Fe3O4-Pd nanohybrids was reproducible, stable, and reusable. After 10 cycles, the catalytic activity was still higher than 90%, and the morphology and structure were basically unchanged. Based on its high peroxidase-like activity, especially the enhanced affinity toward H2O2, a new colorimetric detection method for reduced glutathione (GSH) and glucose has been designed using H2O2 as an intermediary, which provides a simple, sensitive, and selective way to detect urine glucose of diabetes with a wide linear range and low detection limit.Chapter 4:Further, the electrochemical catalytic behavior of 3DRGO_Fe3O4-Pd nanohybrids towards hydrogen peroxide is investigated. Similarly, the electrochemical catalytic activity of 3DRGO_Fe3O4-Pd is much higher than those of monometallic loaded nanohybrids. The kinetic mechanism is also examined under electrochemical conditions. Finally, the nanohybrids are applied to detect hydrogen peroxide in environmental and daily samples, which provide a new method for the detection of hydrogen peroxide in real samples.