Synthesis And Characterization Of Fluorescent Carbon Dots Doped WO₃ Composites And Their Application For Photocatalytic Degradation Of Methylene Blue

With the rapid development of society,the problem of environmental pollution has been paid more and more attention.As a kind of renewable clean energy,how to use solar energy to photocatalytic degradation of organic pollutants in sewage has become one of the hot spots.Tungsten trioxide can be used as a photocatalyst by using solar photocatalytic degradation of water pollutants,has become an effective way to solve water pollution problems.However,WO₃ has a low utilization rate for visible light,so its photocatalytic performance is not high.CDs have good photocatalytic performance,not only can degrade organic matter alone,but also can be combined with some of the catalyst to produce better performance of the photocatalyst.In this work,we used two different methods to prepare CDs and CDs-WO₃ composites,and their structures were characterized and studied.1 ? The yellow fluorescence CDs were synthesized by a facile one-pot slovethermal method using citric acid as carbon source and glycine as modifier and anhydrous ethanol as solvent.The morphology,structure,optical properties and surface functional groups of CDs were characterized by XRD,TEM,fluorescence spectrophotometer,UV absorption spectroscopy and FT-IR.The reaction conditions such as reaction temperature,reaction time and the amount of glycine were optimized.The effects of pH value and salt concentration on the fluorescence intensity were studied.The results show that the synthesized CDs contain the characteristic peaks of amorphous carbon,and the particle size is about 10 nm.The surface of the fluorescent CDs contains a large amount of oxygen and carboxyl groups,which enhance the hydrophilicity of CDs.Different excitation light,the CDs Showing a wavelength dependence,and measured the fluorescence yield of 26.0%;in addition to a good light-resistant bleaching.When the NaCl concentration is high,the fluorescence intensity is almost unchanged,that is,it has strong salt tolerance.CDs-WO₃ composites were prepared by adding WO₃ to the CDs in the process of solvent synthesis.The photocatalytic degradation ability of methylene blue was studied under visible light irradiation.The morphology,structure,element type,optical properties and functional groups of the composites were characterized by XRD,SEM,EDS,Raman,UV-Vis diffuse reflectance spectroscopy and infrared spectroscopy.The effects of light time,catalyst dosage,pH value and WO₃ addition on the photocatalytic degradation activity were studied.The experimental results show that CDs-WO₃ composites have good photocatalytic degradation properties for methylene blue under visible light irradiation.The initial concentration of methylene blue was 10 mg / L,the amount of CDs-WO₃ composites was 0.75 g,and the photodegradation rate reached 60.0% in two hours.2?The green fluorescence CDs were synthesized by a facile one-pot microwave method using tartaric acid as a carbon source and glycine as a passivation agent,ultra-pure water as a solvent.The morphology,structure,optical properties and surface functional groups of the obtained CDs were characterized by XRD,TEM,fluorescence spectrophotometer,UV absorption spectroscopy and FT-IR.In the study,the experimental conditions such as microwave power,heating time and glycine dosage were optimized.The effects of pH value and inorganic metal ions on the fluorescence intensity of CDs were discussed.The results show that the CDs prepared by this method have amorphous peaks and their particle size is about 10 nm.The surface of the CDs contains a large number of functional groups such as hydroxyl groups and carboxyl groups,which enhance the water solubility.The CDs,under different excitation conditions,The fluorescence intensity of the emission peak was 11.8%,and it showed good photobleaching property.In the presence of higher salt concentration,the fluorescence intensity was almost constant,that is,it was strong salt tolerance.The optimized CDs and WO₃ were placed in a hydrothermal reactor and heated at 90 ? for 90 min to prepare CDs-WO₃ composites.The photocatalytic degradation ability of methylene blue was studied under visible light irradiation.The morphology,structure,element type,optical properties and functional groups of the composites were characterized by XRD,SEM,EDS,Raman,UV-Vis diffuse reflectance spectroscopy and infrared spectroscopy.The effects of irradiation time,catalyst dosage,pH value and WO₃ addition amount on the photocatalytic degradation activity were investigated.The experimental results show that CDs-WO₃ composites have good photocatalytic degradation properties for methylene blue under visible light irradiation.The initial concentration of methylene blue was 10 mg / L,the amount of CDs-WO₃ composites prepared by adding 6m L CDs solution was 25 mg,and the photodegradation rate in the two hours reached 55.0 %.3? In this paper,the composite materials were doped with WO₃ doped with two kinds of CDs,and the photocatalytic performance was improved remarkably,which indicated that the doping CDs could improve the catalytic performance and become a feasible method.