Synthesis And Characterization Of Graphene And Graphene-based Assembled Materials

As a unique two-dimensional crystal structure material of carbon nanomaterials, graphene nanosheets (GNs) were first discovered and raised in2004by K.S.Novoselov and A.K.Geim. The perfect GNs mainly refer to a single layer of carbon atoms with a benzene ring structure. Based on its excellent performance in the electrical, optical, mechanical and thermal, GNs have become a hot topic in the fields of materials science and condensed matter physics. Meanwhile, with the deepening research about the related properties of GNs, graphene quantum dots (GQDs) gradually appeared in the scope of researchers and attracted much more interests for its good photoluminescence properties and remarkable application in the bio-imaging and bio-probe et al. In view light of this, many researchers have also paid most of their attention to the graphene-based composite materials. In this thesis, preparation and electrochemical properties of the GNs and preparation and photoluminescence properties of the GQDs have been primarily studied, and several types of graphene-based assembled materials and their performance applications have also been discussed. The main contents are as follows:(1) GNs were prepared respectively with oxidation-reduction method and ultrasonic peeling method. Firstly, using hydrazine hydrate as a reducing agent, graphene oxide prepared via traditional hummer’s method was reduced into GNs. Secondly, Slecting graphite powder as raw material and deionized water or ethanol as solvent, using neutral surfactant polyvinyl pyrrolidone (PVP) with concentrations of0.001M as dispersing agents and stabilizers, graphite nanosheets and graphene in the absolute ethanol or deionized water solution were prepared via the ultrasonic peeling method for the first time. Zeta potential and nanosize of graphene oxide and graphene were tested by dynamic light scattering (DLS), the results showed that a good negatively charge of graphene oxide and graphene nanosheets emerged. And then using quartz glass slip as substrate, via the layer by layer self-assembled (LBL) method, a homogeneous GNs film was made. A linear relationship of the assembled layers and the absorbance was characterized by UV-Vis; using electrophoretic deposition (EPD) method with conductive glass (ITO) as the base, graphene conductive thin film was obtained, and their application on the supercapacitor has also been preliminarily studied using electrochemical workstation (CHI).(2) Employing the GNs prepared by ultrasonic stripping method as raw materials, absolute ethanol and N-methyl pyrrolidone as solvent, the homogeneous GQDs with uniform size and excellent photoluminescence performance were synthesized via the simply and efficiently powerful ultrasonic method. Then its remarkable photoluminescence performance was discussed by fluorescence spectrometer (FL). Morphologies and UV-Vis absorption characteristic peaks of GQDs were performed on the TEM and UV-Vis spectrophotometer.(3) Selecting GNs as a template, zinc chloride and thiourea as zinc source and sulfur source, anhydrous ethanol as a solvent, the two unique ZnSQDs/GNs and ZnS QFs/GNs assembled materials were obtained with the Zn2+concentration of0.0001M and0.01M. Under visible light irradiation, these two assembled materials showed good photo-voltage response phenomenon, its voltage maximum values have reached respectively0.5mV and0.7mV.(4) Via solvothermal method and simply mixed/stirred at room temperature, TNTs/GNs assembled materials and TNTs/GQDs assembled materials were synthesized. Their photocatalytic performance about degradation of organic dyes MB under visible light was explored and compared. And meanwhile, as a comparison, the separate TNTs were also investigated for photodegradation of MB aqueous. The results showed that the photocatalytic properties of the composite materials are significantly superior to the individual TNTs. Under the visible light irridation, the GNs acted as a photosensitive. (5) Using graphene oxide and silver nitrate as raw material, sodium citrate and sodium borohydride as the reducing agent respectively, Ag/GNs assembled materials were in situ synthesized in liquid phase system. Selecting pyridine molecule as target object, the performance of Ag/GNs assembled materials as SERS active substrates for the enhancement of the pyridine molecule Raman signal were preliminary characterized and studied.(6) Firstly, the graphene thiolated covalent modification was achieved with2-aminoethanethiol; Secondly, the zinc oxide quantum dots (ZnO QDs) were prepared from zinc acetate dihydrate; Finally, ZnO QDs were successfully anchored on the surface of the graphene by means of Zn-S bond in cooperation. Under UV irradiation, using the organic dye rhodamine B (RhB) aqueous solution as analog factory effluent, photocatalytic degradation performance of ZnOQDs/GNs assembled materials photodegradation catalyst was tested, and the catalyzed degradation mechanism on Rhodamine B was also analyzed. The results showed that the photocatalytic properties of the composite materials are significantly superior to the individual ZnO. Under UV irridation, the presence of GNs produced negative effects to the photocatalytic properties.In brief, this thesis is mainly employing the chemically pure graphite powder as raw materials to synthesize the GNs and GQDs. And then, based on the graphene materials, the graphene-based composite materials were also prepared. The fluorescence properties, optoelectronic conversion performance photocatalytic properties and potential applications of surface-enhanced Raman (SERS) performance of the materials were invesgatied and studied.