Self-assembly Of Two-dimensional Nanostructures And Properties Of The Assembled Materials

Graphite and clay are two typical types of natural layered minerals and have beenwidely used in the history of human civilization. Single or few layers oftwo-dimensional nano-materials can be produced through top-down exfoliation route,which can be used to assemble three-dimensional macrostructures. The exfoliation ofgraphite can lead to graphene, and graphene oxide, as a two-dimensional functionalderivative of graphene, was mainly discussed in this thesis. Through interfacialself-assembly of graphene oxide, controllable construction of three-dimensionalgraphene-based macrostructures was realized. Electrochemical properties of thesemacrostructures were investigated. Two-dimensional vermiculite nano-layers werefabricated by exfoliation of vermiculite crystals using ion-exchange method. Flexiblevermiculite membranes with uniform interlayer spacings were constructed byinterfacial assembly. Ionic transport behavior through these interlayer spacings wasstudied.The main contents of this thesis include:(1) Owing to its amphiphilic nature, graphene oxide in aqueous solution is able toaccumulate at the liquid/air interface and then produce a macroscopically solidmembrane. It also can be used as a surfactant to disperse carbon nanotube in water,leading to a stable dispersion. By conducting liquid/air interfacial self-assembly onthe dispersion, a flexible graphene oxide/carbon nanotube hybrid membrane was built,whose electrochemical property was also discussed.(2) The functional groups on graphene oxide render it with remarkable chemicalactivity. Graphene oxide can form hydrogel at some metal or metal oxide films’surface. The liquid/solid interfacial self-assembly mechanism was proposed. Themechanical property of the hydrogel, the adsorption ability and the electrochemicalcapacity of the aerogel prepared from the hydrogel were also investigated.(3) The perfect sp2hybridized carbon network provides graphene withextraordinary physical features, while graphene with a certain degree of defectiveconcentration possesses higher chemical activity. The influence of morphology ofgraphene on the performance of platinum-based catalysts was analyzed via usinggraphene as the supporting material of the catalysts. Electrochemical measurementresults indicate that the defective graphene is more suitable for the growth of small and uniform platinum particles. The corresponding platinum-based catalyst alsomanifests stronger anti-poison ability.(4) Two-dimensional vermiculite nano-layers with high aspect ratio were obtainedthrough exfoliating vermiculite crystals using ion-exchange method, and thesetwo-dimensional nano-layers can readily stack into flexible vermiculite membranewith uniform interlayer spacings, and the as-prepared membrane has high thermalstability. These nano-scaled spacings can work as nanofluidic channels for iontransportation, and the assembly of the membrane is in fact the integration ofhundreds of nanofluidic channels. In this thesis, proton transportation through theintegrated nanofluidic channels was studied, and the conductance data demonstratedthat proton transportation in low concentration condition was governed by the surfacecharges on the vermiculite layers.