Preparation Of Carbon Quantum Dots Composites And Studies Of Their Properties

Carbon quantum dots(CQDs)as a new type of zero-dimensional carbon nanomaterials,with many excellent physical and chemical properties,such as chemical stability,good water solubility,environment friendly and easy to functionalization,has attracted the widespread attention.Its application fields are involved with the ion detection,cell markers,biological imaging and redox,photocatalyst etc.However,due to the easyaggregation of CQDs,its applications were restrict.So,if the CQDs were dispersed uniquely into the other materiasl to obtain the composite materials,its applications can be largely extended.In this article,CQDs were dispersed into organic poly(vinyl alcohol)(PVA)and inorganic titanium oxide(TiO2)to obtain their composites and the photoluminesent properties and the catalytic performance of CQDs based composites were also explored.The main research contents are as follows:1.In the presence of nitric acid,the CQDs was prepared by a one-step oxidation method with carbon black as carbon source.Then the CQDs-PVA composites were prepared by an ultrasonic method.The obtained thin film shows light dependent absorption properties.The pure PVA and CQDs-PVA nanocomposites thin film show an excitation wavelength dependent fluorescent emission property and the PL intensity of the CQDs-PVA nanocomposites thin film were strongly reinforced.2.Graphite rod was used as carbon source,and the CQDs were prepared by an electrochemical process.Through a series of characterizations,the results show that the diameters of carbon quantum dots were about 4 nm.In addition,a series of CQDs-TiO2 composite materials were synthesized by a hydrothermal method.The characterization results show that the well combination between the CQDs and TiO2.The catalytic oxidation of alcohols to benzaldehyde with NaClO oxidation using water as a solvent by CQDs-TiO2 was developed.The catalytic results show that the optimum reaction conditions of CQDs composites for alcohol oxidation are: reaction temperature 50 ℃,dosage of catalyst 90 mg,10% NaClO 7 mL,reaction time 7 h.The conversion of 88 % for benzyl alcohol oxidation to benzaldehyde was achieved,and the selectivity was 99.9%.Compared to the pure CQDs,the catalytic performance was enhanced,demonstrating the high catalytic activities of the CQDs.CQDs composites catalyst also showed high activity in the oxidation of other different kinds of alcohols.The enhanced catalytic activities were mainly attributed to the highly dispersive CQDs with more active centers which caused by the TiO2 support.3.Research on photocatalytic reaction: with the introduction of photocatalysis,the conversion of the benzyl alcohol increased to 96% and the selectivity stayed at99.9%,indicating the further improvement of the catalytic activities.These results showed CQDs composites may have broad application in photocatalysis,due to its unique optical properties.