Preparation And Properties Of Carbon Quantum Dots And Their Composite Materials

As a new member of the family of carbon nano materials, Carbon quantum dots not only have unique physical and chemical properties, such as wide absorption band, fascinating photoluminescent properties, chemical stability and environmental harmless, but also overcome the toxicity of the disadvantage of traditional quantum dots and have good biocompatibility. So carbon quantum dots can be described as the set of all the advantages of carbon nano materials and traditional quantum dots in a body and thus have great development potential and research value. In this paper, the blue fluorescent carbon quantum dots were prepared by one-step hydrothermal method. This method is simple and easy to operate. The products have good fluorescence performance, high quantum yield and great application potential. Subsequently, we use electrochemical method to synthesize carbon quantum dots, and then the carbon quantum dots were combined with the photocatalyst to synthesize composite materials with good photocatalytic performance. The main research contents are as follows:(1) The blue fluorescent carbon quantum dots were synthesized by one step hydrothermal method using citric acid and diethylenetriamine. The results show that the carbon quantum dots have good fluorescence properties, high quantum yield and up conversion fluorescence properties. Then the effects of storage time, pH value of solution system and metal ions on the fluorescence property of carbon quantum dots were analyzed. Experimental results show that the carbon dots have long time stability and low pH-sensitivity. In acidic solution, the fluorescence emission peak position will redshift from 465nm to 500 nm with the decrease of pH, and in alkaline solution it is more stable. Carbon quantum dots are sensitive to partial metal ions, which can cause the changes of fluorescence properties. In particular, Fe3+ can achieve specific recognition.(2) We use electrochemical method to synthesize carbon quantum dots, hydrothermal method to synthesiz bismuth based photocatalyst (Bi2MoO6、Bi2WO6), and then the carbon quantum dots and bismuth based photocatalyst were combined. Carbon quantum dots are used to sensitized bismuth based photocatalyst, broaden its absorption spectrum and improve its utilization of visible light. Photocatalytic test for degradation of methylene blue was carried out on these samples, the results show that the photocatalytic performance of Bi2Mo06/CDs、Bi2WO6/CDs is better than that of Bi2MoO6、Bi2W06 in the visible light.