Synthesis And Application Of Graphene And Graphene Quantum Dots

Graphene has attracted wide attention due to its specific mechanical, thermal and electrical properties. However, the large-scale synthesis and effective dispersion in different solvents are still the main problems. At present, Reduction of graphene oxide is a common method for preparation of graphene. As the precursor of graphene, graphene oxide can be easily reduced by chemical or thermal approaches. Meanwhile, the present of oxygen functional groups can be modified to improve the dispersion of graphene in different solvents, which makes graphene applied in many fields.In addition, the macroscopic carbon-based materials are not the ideal fluorescent materials due to the lack of suitable band gaps. However, though the regulation of the size of carbon materials or chemical modification of the surface, it can be developed as a novel fluorescent materials in recent studies. Compared to the traditional fluorescent materials, the carbon-based fluorescent materials have many excellent characteristics such as good chemical inertness and bio-compatibility, low-toxicity, good resistance to photo-bleaching and water-soluble.The main research contents of this paper are as follows:1. In this report, we demonstrate an efficient low-temperature thermal treatment approach to prepare graphene. The entire experiment is only needed one step to complete exfoliation and reduction processes in air atmosphere without any special supplementary conditions. The results show that:graphene that thermal exfoliation and reduction graphene oxide (GO) under 300℃ is exfoliated and reduced to a large extent. In addition, the low-temperature thermal reduction of graphene oxide (TRGO) has integrated construction and excellent performances. Its conductivity is up to 215.16S/m after thermal treatment, which is much higher than that of GO. At the same time, TRGO also has good dispersion in aqueous and organic solvents, which provides favorable conditions to use graphene for different areas of application.2. A high-performance PB composites are prepared by solution blending. The composite material exhibits the excellent conductive and dielectric properties, meanwhile, the crystallization behavior, thermal and mechanical performances of the composites are also improved significantly, which is attributed to the property of graphene itself and the good dispersion in PB resin matrix. Particularly, the TR-300/PB composites also exhibits a sharp transition from insulator to conductor with a low percolation threshold of only 0.39vol.%. And the conductivity of composites is as high as 0.092S/m with 1.19vol.%, which makes this composites has a good prospect in the conductive-touch-panel, energy storage materials and anti-static aspects.3. Graphene quantum dots are prepared from graphene oxide by solvothermal method. The results indicate that:The graphene quantum dots have the monolithic structure of graphene, and the size is not more than 10nm. FT-IR spectrum of GQDs showed that there are a large number of hydroxyl and carboxyl functional groups on the GQDs surface. Graphene quantum dots emit the yellow-green fluorescence with 365nm excitation. Detection of the different concentrations of Cr(Ⅵ) ions in the aqueous phase were carried out due to Cr(Ⅵ) ions can selective quench the fluorescence. It was found that the detection limit was only 12.5nmol/L, indicating that it can be used as Cr(Ⅵ) probe sensor applied in the industrial waste-water detection.