Synthesis And Characterization Of Monolayer And AB-type Stacked Bilayer Graphene Molecules

Graphene is a two-dimensional material with the thickness of single atomic layer formed by sp2-hybridization carbon atoms.It is the basic unit for constructing carbon materials with other dimensions.Since graphene was separated from graphite in 2004,after more than ten years of development,graphene has made major breakthroughs in basic research and application.As an important component of graphene,nanographene molecules have excellent properties in optical,electrical,and mechanical.Due to the certainty of structure and uniformity of size,they show extraordinary application value in biological imaging,wearable sensors,field effect transistors,etc.The control of the number of graphene layers plays an important role in the process of preparing graphene.However,there are few research reports on the monolayer nanographene and layers control using organic synthesis.This thesis focuses on the synthesis of single-layer nanographene,the double-layer nanographene with AB-type stacked and the control of layers.1.Based on the previously reported by our research group that double-layer nanographene with C96 as core,more groups are modified on the periphery to break the π-π stacking between layers,and finally obtain single-layer nanographite molecule with the precise structure.The mass spectroscopy shows that the C96 nanographene possesses monolayer structure.And further 1D and 2D NMR spectroscopy clearly confirms the monolayer structure in liquid phase condition.Furthermore,it is proved that the monolayer structure does not aggregation phenomenon in the liquid phase and shows excellent stability by changing the concentration,solvent and so on.By changing the number of functional groups,we synthesized a series of nanographene molecules C84 as core with different layers.X-ray crystallography confirms this C84 nanographene possesses the double layer structure in the solid state and the stacking method is AB-type stacked.And further 1D and 2D NMR spectroscopy clearly confirms the bilayer structure in liquid phase condition.We investigate the thermodynamics of the self-assembly behavior through the variable temperature ultraviolet absorption spectroscopy experiment.The results show that the formation of the dimer is a process with enthalpy-driven.