Preparation And Property Manipulation Of Alkyl Decorated Low-Dimensional Carbon Materials

The system of carbon allotropes has an astonishing range of extremes,such as graphite,diamond,carbon nano tubes,fullerene and graphene.The discovery of graphene enriched the carbon allotropes,which made the system integrated from zero-dimensional fullerenes and carbon quantum dots,one-dimensional carbon nano tubes to threedimensional graphite and diamond.Graphene exhibits many superior properties including superlative mechanical strength,large specific surface area,high thermal conductivity,high carrier mobility and good flexibility.These outstanding properties and the potential applications in capacitors,fuel cells,sensors transparent conductive films sparked researchers' interests.Carbon quantum dots(CQDs),which were discovered in 2004,possess many good properties,such as low toxicity,simple preparation and good fluorescent stability.Moreover,the unique chemical structure makes it unfold superior properties such as effective absorbance of solar light,tunable photoluminescence,unique photo-induced electron transfer and infrared-responsive up-converted photoluminescence.These distinct properties make CQDs unfold extensive investigations in different fields including bioimaging,drug delivery,photovoltaic devices and carbon quantum dots sensitized solar cells.The main purpose of this thesis is to obtain thermo-responsive graphene dispersions by liquid phase exfoliation of graphite and oil-soluble carbon quantum dots with high fluorescence quantum yield property.The main content of the thesis is divided into three parts:1.Preparation and characterization of low-dimensional carbon materials: Smart graphene dispersions with low defects and thermo-responsive properties were obtained by liquid phase exfoliation of graphite using an alkylated Percec monodendron(3,4,5-trioctadecyloxybenzaldehyde,1)as the stabilizing reagent.The dispersions were then characterized by a variety of techniques such as transmission election microscopy,Raman spectroscopy and differential scanning calorimeter.The preparation conditions of the graphene dispersions were optimized and the concentration of the dispersion was improved.By simply changing the temperature,the dispersed graphene and 1 can be detached,leading to the recovery of the two components.2.The stabilizing reagent 1 can be covalently attached to graphene through [3+2] cycloaddition.The covalently functionalized graphene sheets show improved dispersibility in organic solvents compared to the pristine graphene,which opens the door for their applications in various polymer matrixes.3.Preparation and characterization of oil-soluble carbon quantum dots: Oil-soluble carbon quantum dots(O-CQDs)were obtained by directly refluxing small organic moleculars with single tail chain in chlorobenzene.High-resolution transmission election microscopy,fluorescent spectroscopy were used to characterize them.We have investigated the influence of the alkyl chain length and functional groups on the fluorescent property of the oil-soluble carbon quantum dots and optimized the preparation conditions of them.Further,the so-obtained O-CQDs were used as fluorescent inks.