Functionalization Of Sulfonic Acid Groups And Carboxyl Groups To Prepare Water-dispersible Graphene

Graphene is a honeycomb two-dimensional structure carbon nanomaterial which is closely connected to each other by sp~2 hybridization into a hexagonal structure and is deposited by a single layer of carbon atom thickness.The graphene sheet has a?-?conjugated structure with strong van der Waals force and very high chemical stability,which makes graphene easy to agglomerate and difficult to disperse in wate r,thus greatly limiting the application of graphene in various fields.In recent years,wa-ter-dispersible graphene has become one of the research hotspots of graphene carbon materials.Water-dispersible graphene has potential applications in the fields of energy,materials,drug delivery,and biomedicine.Therefore,the method of functionalization of covalent bonds and non-covalent bonds introduces hydrophilic groups on the su r-face of graphene to prepare water-dispersibility graphene,and it is necessary to solve the problem of inherent hydrophobicity of graphene.This thesis uses graphite powder as raw material,and graphite powder is inter-calated by intercalating agent to obtain expanded graphite.Graphene with water dispersibility was exfoliated by ultrasonic without the addition of a surfactant.The obtained water-dispersible graphene was characterized and analyzed by Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),Thermal gravity analysis(TGA),Laser Raman spectroscopy(Raman),X-ray diffrac-tion(XRD),Atomic force microscope(AFM)and Transmission electron microscope(TEM).The detailed contents are as fellows:(1)The expanded graphite was obtained by intercalation using 105%fuming sulfuric acid as an intercalation agent.Afterwards,the graphene which has good water dispersibility was obtained,and assisted with the oxidation of ozone by ultrasonication in water.FT-IR and XPS analysis showed that the obtained graphene surface contained a sulfonic acid group.TGA analysis further indicate that functional groups are introduced on the surface of graphene,and one sulfonic acid group is grafted per 150 carbon atoms by calculation.Raman and XRD results showed that by introducing oxygen-containing functional groups on the surface of graphene,some defects are introduced into the graphene surface.The AFM and TEM results showed that the average thickness of the graphene obtained is about 1 nm,and the number of layers is mainly a single layer or a few layers,and the size is on the order of microm-eters.(2)In order to further simplify the preparation process and shorten the sonication time,the graphite powder was intercalated with crotonic acid as an intercalation agent to obtain a graphite composite,and then ultrasonically exfoliated to obtain graphene with better water dispersibility.FT-IR and XPS results indicate that the graphene surface contains a hydrophilic carboxyl group.The TGA test further proves that the surface of the graphene has a hydrophilic group,and the grafting of the carboxyl group is calculated by grafting one carboxyl group per 90 carbon atoms,which has a high grafting ratio.Raman and XRD results indicate that the graphene surface intr o-duces an oxygen-containing functional group.AFM and TEM test analysis showed that the obtained graphene has a thickness of about 1.5 nm,and the number of layers is mainly a single layer or a few layers,and the size is on the order of m icrometers.