Dispersion And Self-assembly Behavior Of Graphene Two-dimensional Materials In Water Phase And Its Application

Graphene has outstanding characters including electrical properties,thermal properties,mechanical properties,etc,which leads to a good application prospect in various fields.Graphene is widely used in its nanosheets style,whose main application forms are divided into two categories:one is in the form of dispersion,such as filler of polymer composites,conductive ink and filler of coatings;the other is in the form of assembly,such as thin films and aerogels.Both of the above applications involve a lot of surface and interface behaviors between graphene and liquid phase.The application of dispersion mainly focuses on the compatibility and matching of surface energy between graphene and liquid phase environment,which requires that graphene has the hydrophilicity to facilitate the dispersion of graphene in liquid phase.The application of assembly mainly considers the interface interaction of graphene in the liquid environment,which requires that graphene has the hydrophobicity so as to realize the assembly of graphene.Therefore,in this paper,we mainly studied the driving dispersion and self-assembly behavior of graphene nanosheets in aqueous environment.We achieved the goal of graphene dispersion and self-assembly by adjusting the surface modification of grapheneandliquid phase system.Furthermore,we explored the application and structure-activity relationship of related materials.This paper mainly includes the following three parts:(1)Polyether-assisted graphene dispersion in water and preparation of redispersible graphene monoliths.The graphene/polyether composites were prepared by mixing and drying the electrochemically exfoliated graphene and five polyether polymers in liquid phase.By means of SEM,AFM,UV-vis and Raman spectroscopy,it was found that the redispersibility of graphene/polyether composite increased with the increase of polyether content.It is found that the polyether-assisted graphene dispersion is related to the contact angle of polyether aqueous solution on the surface of graphene.According to the redispersibility of graphene/polyether composite,it is concluded that polyether P123 has the best assisted dispersion ability for graphene.When polyether P123 is blended with graphene nanosheets,graphene monoliths can be preparedwhich achieve 1.5 g/cm~3density,10%graphene content and100%redispersion rate.(2)Active driving dispersion behavior and adsorption application of graphene nanosheets in aqueous phase.In order to solve the problem that the dispersion of graphene monoliths needs external energy and the dispersion efficiency is low,inspired from effervescent tablet,we added citric acid and sodium bicarbonate into graphene/polyether composite to prepare graphene effervescent tablet.A large amount of carbon dioxide gas produced by the reaction of citric acid and sodium bicarbonate in the aqueous phase escapes,which causes the structure of the effervescent tablet to disintegrate and drives the graphene nanosheets to disperse into the water.In order to maximize the content of graphene in the effervescent tablets under the condition of ensuring the dispersibility,we explored the optimization conditions of the ratio of graphene/citric acid/sodium bicarbonate/polyether in the formulation of the effervescent tablets of graphene to 1:3:3:1.Under the optimized conditions,the content of graphene in the effervescent tablets was as high as 12.5%,and the effervescence could be completed in one minute.We use the graphene effervescent tablet as the water phase adsorbent to successfully adsorb dyes and heavy metal ions in water.(3)Study on the gas-liquid interface self-assembly and corrosion resistance of self-assembled nanofilm prepared through Marangoni effect.Using the Marangoni effect of low surface tension liquid contacting with high surface tension liquid to form the surface tension gradient,the graphene film was prepared by adding the graphene alcohol dispersion drop on the water surface.The graphene/BN hybrid films were prepared by changing the water phase environment into BN nanosheetswater dispersion.The morphology,distribution and thickness of the self-assembled films were systematically studied.It was found that the film formed by self-assembly was better than the traditional casting method and the spin coating method,with a thickness of several nanometers.Graphene nanofilm and graphene/BN hybridnanofilm were used as anti-corrosive coating on stainless steel surface.