Graphene Oxide-chitosan Membrane Induced By Self-assembly: Preparation, Modification And Application

Graphene have attracted tremendous attention as new materials with excellent properties.As its important chemical precursor, graphene oxide (GO) has been making a profoundimpact in many areas of science and technology. Enormous effort has been focused ontomodification and preparation of graphene based materials. Though aelf-assembly is aneffective method to prepare graphene based materials, a facile and robust method is still underexploration. Herein, a self-supported GO/chitosan hybrid membrane was self-assembled at theair-liquid interface through the supermolecular interations between GO and chitosan.Meanwhile, modifications were conducted to the hybrid membrane. Polymer chains and silvernanoparticles are immobilized on the surfaces of hybird membrane.GO sheets are prepared following a modified Hummers’ method, which can disperseuniformly in water. The prepared GO sheets were dispersed in the mixture of DMF and water,then it was applied to the surface of chitosan solution. Golden membane formed as GOsuspension was applied, and the membrane was then transferred to silicon wafer. AFM andSEM were performed to investigate the surface morphology and structure of the as-preparedmembrane. FTIR and XPS were employed to study the interactions between GO and chitosan.The results show that the surface of hybrid membrane is covered with wrinkles, and there areraised structures on wrinkles whose shapes can be tuned by adjusting the concentration ofchitosan. The membrane is formed through hydrogen bond and electrostatic interactionsbetween GO and chitosan.Self-initiated photografting and photopolymerization (SIPGP) were conducted onas-prepared membrane. PS was grafted from the upper surface of membrane. After releasingfrom silicon wafer and reversal transfer, PDMAEMA was then grafted from opposite side ofPS brushes. The as-prepared membrane was investigated by XPS, SEM and water static angletest. Results reveal that polymer brushes grafted Janus GO/chitosan hybrid membrane, inwhich properties of two surfaces are different and without interference, is successfullyobtained.Meanwhile, Ag nanoparticles were immobilized on the as-prepared GO/chitosan hybirdmembane. Raman signal of melamine on the composite membrane were investigated. AFM was employed to investigate surface morphologies of original substrate and Ag nanoparticlesimmobilized substrate. The shapes of Ag nanoparticles are characterized by SEM. Ramansignal of melamine on different substrates and Raman signal of melamine with differentconcentrations were investigated. Results reveal that Ag nanoparticles immobilizedGO/chitosan membrane is the only effective SERS substrate for melamine among threesubstrates, and the signal is decreased with decreasing concentration of melamine.