Preparation And Optical Applications Of Carbon Quantum Dot Composites

This paper was committed to study preparation,properties,and application of carbon quantumdots.The main research work is listed as follows:1.Nitrogen-doped carbon quantum dots?NCDs?have been synthesized by one-pot synthesis using creeper,leaves and citric acid.The optical performance and structure characteristics of NCDs was further researched by XRD,TEM,XPS,UV-Vis and FTIR.The results show that NCDs are functionalized with N-H,C=O,C=C,C-N,O-H and exhibited excellent water-solubility and up-conversion fluorescence performance.This is because the N-H bond formed on the surface of NCDs can be connected with the oxygen-containing group.Based on the results,the formation mechanism of NCDs was also discussed.2.NCDs induced ultrasmall BiOI nanosheets with assembled hollow microsphere structures were prepared at room temperature condition.The composition,structure,morphology,and photochemical properties were investigated by multiple techniques.Using RhB as degradation target to analyze the photocatalytic performance and influencing factors of materials.The NCDs/BiOI hollow microspheres structure displayed improved photocatalytic activities than pure BiOI;the results showed that NCDs have a great influence on the photocatalytic activity of materials.The introduction of NCDs could induce the formation of ultrasmall BiOI nanosheets with assembled hollow microsphere structure,strengthen the light absorption within full spectrum,increase the specific surface areas and improve the separation efficiency of the photogenerated electron-hole pairs.3.Preparation of novel NCDs/Bi₂₄O₃₁Br₁₀ nanosheet composite photocatalyst by chemical precipitationand ultrasound-assisted method.SEM show NCDs are tightly bound to Bi₂₄O₃₁Br₁₀ nanosheets,and control the content of NCDs to adjust the structure of the composite.The degradation of RhB under visible light showed that:All NCDs/Bi₂₄O₃₁Br₁₀ scomposites exhibited significantly enhanced photocatalytic activity,and 2.0%NCDs/Bi₂₄O₃₁Br₁₀ sample displayed the highest degradation efficiency,which was 75%.The excellent photocatalytic properties of composites are due to:Introducing NCDs to enhance catalyst light absorption,the substantial light harvesting and efficient separation and transfer of photogenerated electron-hole pairs;the main active species were determined to be ·O^2-.4.N,S-CQDs have been synthesized by one-step with hydrothermal methods using lotus leaf ash.A method was developed for the detection of sparfloxacin,morpholinium and streptomycin using N,S-CQDs as fluorescent probes.In pH=7.00 buffer solution,the relative fluorescence intensity increases linearly proportional to the sparfloxacin concentration over the range of 0.05?0.3 ?mol/L and 2?10?mol/L,with a limit of detection of 0.026 ?mol/L.In pH=5.50 buffer solution,the relative fluorescence intensity increases linearly proportional to the moroxydine concentration over the range of 0.01?1nmol/L,with a limit of detection of 0.004 nmol/L.In pH=5.80 buffer solution,the relative fluorescence intensity increases linearly proportional to the moroxydine concentration over the range of 0.1?10 ?mol/L,with a limit of detection of 0.0193 ?mol/L.