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Preparation And Characterization Of Fluorescence Carbon Quantum Dots As Sensor For Picric Acid

Posted on:2019-03-10Degree:MasterType:Thesis
Country:ChinaCandidate:X Y ChangFull Text:PDF
GTID:2371330551458572Subject:Analytical Chemistry
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Carbon quantum dots(CDs),a new type of quasi-spherical nanoparticles with particle size less than 10 nm,have attracted increasing attention since their discovery in 2004.As they have numerous advantages such as luminescence property,understanding water solubility,fluorescence stability,biocompatibility,low toxicity and facile preparation,precursors available,etc.CDs have been widely used in many fields,such as fluorescence sensors,biological imaging and so on.Especially,CDs can serve as fluorescent probes for the detection of metal ions and anions,organic small molecules,etc.On the other hand,trinitrophenol,(named as picric acid,PA or TNP)are widely used in pharmaceutical,military industries,pesticides,dyestuff and other fields.Because of their toxicity and non-degradability,industrial wastewater containing PA will pollute water or soil to a certain extent.Based on the interaction between the electron-rich effects of CDs and the electron deficiency of PA,a sensitive and rapid fluorescence detection method for PA can be established.In this paper,three kinds of CDs were synthesized by a simple hydrothermal method,whose morphology,structure and optical properties were characterized.It was also found that the potential applications of high fluorescence carbon dots in fluorescent dyes and imaging were further developed.Chapter 1: The synthesis,functionalization,sensing mechanism,applications in sensing and imaging of CDs as well as the harm of PA are briefly reviewed.The application of fluorescence analysis in the detection of PA is also described.The research contents of this paper are putting forward.Chapter 2: Herein,blue fluorescent nitrogen-doped CDs were synthesized by one step hydrothermal method using persimmon peel and ethylenediamine as carbon source and nitrogen source,respectively.PEI-NCDs were obtained by passivation of Polyethyleneimide(PEI),and the quantum yield was improved.The modified CDs were characterized by TEM,UV-Vis,FT-IR,FL and so on.At the same time,the effects of different conditions on the fluorescence intensity of PEI-NCDs,such as pH value,ionic intensity,storage time as well as some interfering substances were also investigated.It was found that the fluorescence of PEI-NCDs could be selectively quenched by PA based on the internal filtration effect.The quenching degree was linearly related to the concentration of PA in a certain range with a linear range of 0.99~34.3 μmol/L and a LOD of 0.0147 μmol/L.The recovery of the method fell into 99.48%~105.33%,which can be used for quantitative determination of PA in real water samples.Chapter 3: We used a simple,fast and green one-step hydrothermal method for synthesized Nitrogen doped CDs by using mandelic acid and ethylenediamine as precursors.The relatively high QY of N-CDs was 41.4%.The prepared water-soluble N-CDs were successfully used in the sensing of PA in aqueous solution.The fluorescence intensity of N-CDs decreased linearly with the concentration of PA in the range of 0.5~30 μmol/L and with a detection limit of 0.041 μmol/L.The concentration of PA in the actual tap water was determined,confirmed the application of synthesized N-CDs.The recovery is between 96.05%~110.00%,the RSD is 1.64%~2.80% with satisfactory results.The fluorescence resonance energy transfer between them has been inferred by the determination of UV absorption spectrum and fluorescence lifetime.Chapter 4: Blue fluorescent carbon quantum dots with high quantum yield(QY)were synthesized using citric acid and ethylenediamine as carbon source and nitrogen source,respectively.Besides,sodium tetraphenylboron was used as dopant.The elemental contents of N,B-CDs were analyzed by X-ray photoelectron spectroscopy(XPS),which proved that B successfully doped on the surface of N,B-CDs.It was found that B doping had a significant effect on the increasing of QY.The influence of different conditions on the fluorescence intensity of N,B-CDs and its sensing ability to PA were also investigated.There was a linear relationship between thefluorescence quenching degree and concentration of PA at 0.1~24.7 μmol/L with a detection limit of 0.019 μmol/L.The recovery of tap water samples were determined respectively,which proved the feasibility of this method.The possible quenching mechanism was discussed by UV absorption spectrum and fluorescence lifetime.In addition,as a result of the high QY of N,B-CDs,it can be used to dye the samples as fluorescent dyes,fluorescent ink and cell imaging.Chapter 5: We summarized the research results and future work,and challenges we will face are prospected.
Keywords/Search Tags:Carbon quantum dots, Surface functionalization, Picric acid, Fluorescence sensing
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