Preparation Of Water-solubie Carbon Dots Via Hydrothermal Method And Their Fluorescence Properties And Applications

With the generation and development of nanotechnology, the carbon materials family is growing biger. As a new member of the big family, Carbon dots have attracted researchers intensive interest because of their remarkable properties such as small size, low toxicity, good water-solubility, excellent fluorescence performance and strong light stability. The research of carbon dots is still in its infancy in recent, there are many of question in experiments and theoretical worth exploring and solving. For example, how to synthesis the better performance and higher quantum yield carbon dots use the more green carbon source and more simple and safe method; As a new fluorescent probe, the more further application on biomarkers; The more research in based on carbon dots composite material of the photocatalyst, and so on. Predictably, the research and exploration of the carbon dots not only effect our production and life, but also lead us into a new step toward the direction for the sustainable development of green. Based on the above, the main research works on this thesis are as follows:1 Sucrose as the carbon source, a method using hydrothermal method was used to synthesize good water-solubility and excellent fluorescence performance of the carbon dots. By FTIR and XPS spectroscopy of the carbon dots explains the reasons of good water-solubility. A series of carbon dots were synthesized with different pH,temperature and time. When the change of the preparation conditions the effect of the obtained carbon dots fluorescence performance were discussed through the characterization of the morphology of the carbon dots, fluorescence emission spectrum, absorption spectrum and quantity yield. The experimental results show that due to the change of the reaction conditions, the particle size distribution of carbon dots change that cause the fluorescence spectrum redshift or blueshift.2 Use Pine needles of Cedrus deodara as the carbn source, the carbon dots synthesized by hydrothermal method have good water-solubility and excellent fluorescence performance. The carbon source of this work, green, abundant, cheap and safe, can be used for mass production of carbon dots. The size of carbon dots is 8-10 nm. They have excellent performance in the cell toxicity test, even the carbon dots concentration is as high as 1000 μg/mL, the cell survival rate is much higher than the international standard. Low toxicity of carbon dots shows that they have good biological compatibility, choose S180 cell to cell markers, with a laser confocal microscope photographs can be seen that the carbon dots successfully enter cells and emit fluorescence, further observed the carbon dots into cells mainly distributed in the cell membrane and cytoplasm.3 Use of reduced glutathione as carbon source, a one-step hydrothermal method was used to prepare the S doped carbon dots with high quantity yield and short fluorescent lifetime. The experimental demonstration, the fluorescence intensity of S doped carbon dots is reduced when the lead ions Pb2+ join, the quenching effect can be attributed to the combination of lead ions Pb2+ and S and N on the surface of the carbon dots lead to the fluorescence quenching of carbon points. So the synthetic S doped carbon dots can be used as a fluorescent probe for the detection of lead ions Pb2+. Through the qualitative detection experiment and interference ion experiment proved that the fluorescence probe about the detection of lead ion Pb2+ has a very high selectivity. Sensitive experiment proved that the fluorescence intensity of fluorescence probe is sensitive to concentration of lead ion Pb2+, the fluorescence intensity gradually reduce with the increase of concentration of lead ion Pb2+ and the sensitivity can be accurate to 0.1 nM.4 Using sucrose as carbon source of carbon dots, compound with tin oxide made by electrostatic spinning and cerium oxide made by hydrothermal method, respectively.The complex system was researched photocatalytic performance. Because of the wide band gap, pure tin oxide and cerium oxide photocatalyst unable to make full use of visible light. But the performance of the carbon dots on upconversion fluorescence can convert long wavelength to short wavelength and emission, so when tin oxide and cerium oxide compound with carbon dots the visible light catalytic efficiency improved significantly. Of course, the carbon dots can be used as receptor to accept photoproduction electronic thus effectively promote photoproduction electron and electron hole separate is also the reason of the increase in Photocatalytic efficiency.