Improving The Dispersity Of Graphene In Aqueous Solution

In recent years,the study of graphene and its derivative graphene oxide?GO?has attracted wide attention.GO have broad prospects in the fields of electricity,mechanics,magnetics,biology and engineering owing to its unique two-dimensional structure,However,the lots of defects and poor dispersion existences in industrialized graphene,which hinders its further development.To address the above issues,the preparation and modification of graphene are studied in this paper.GO was prepared by modified Hummers method and the optimum way was explored.Then surface modification of GO and reduced graphene oxide?rGO?was carried out using surfactants,polyethylene glycol-polyamino acid(mPEG₂₂-PLPh₆)to explore the effect of this modification method on GO and rGO dispersion.The main work of this paper is as follows:Firstly,adding phosphate in the process of preparing GO by modified Hummers method can avoid excessive oxidation and shear of graphene lamellae,thus contributing to structural integrity and improving conjugation degree.The preparation process of GO was explored by orthogonal experimental design.As a result,it was found that when GO prepared by controlling the oxidation temperature at 40?,the oxidation time at 24 h,the amount of concentrated sulfuric acid at 70 mL and phosphate at 30 g can endow itself the high absorbanc and structural regularity,thin lamellar thickness,and bigger lattice plane.Besides,the surface was rich in oxygen-containing groups such as-COOH,-OH,C-O-C.Then,rGO was obtained by chemical reduction of GO with NaBH₄ as reducing agent.The decrease of the number of oxygen functional groups on the surface of the product resulted in the decrease of the steric resistance and electrostatic interaction between the layers of rGO and the reunification under van der Waals force.Therefore,surfactant sodium laury sulfonate and hexadecyl trimethyl ammonium bromide were used to modify rGO by non-covalent bond in order to improve its dispersion.The results show that both surfactants can improve the dispersion of rGO in water system,and the effect of mixing surfactants in a certain proportion is more obvious than that of using it alone.Finally,mPEG₂₂-PLPh₆ was successfully synthesized by L-phenylalanine-N-carboxyl intracyclic anhydride?L-Ph-NCA?ring-opening polymerization initiated by mPEG-NH₂.When the mass ratio of mPEG₂₂-PLPh₆ to GO is 3:100,the modified GO has the best dispersion in aqueous solution and is more stable than the unmodified one.This simple modification method can effectively address the issues of GO,and can be widely used in the field of biomedicine.