Preparation Of Fluorescent Carbon Dots And Its Application In Environmental Detection

Carbon dots,as a new type of nanomaterial,have been widely used in environmental detection,biological imaging and photoelectric fields due to its excellent biocompatibility,surface functionalization,environmental friendliness and low cost.At present,carbon dots have been relatively mature in the synthesis method,but the luminescence of the carbon points prepared at present is mainly concentrated in the blue and green zone,due to the poor penetration of biological tissue,this feature limits its application in such aspects as biological imaging.Therefore,it is of great significance to improve the fluorescence properties of carbon dots and synthesize carbon dots with long wavelength emission characteristics.In this paper,three kinds of carbon points with excellent functions were successfully prepared through structural design,reasonable selection of carbon sources and synthesis methods,and their structures,properties and rapid detection of pollutants were explored.The main contents are as follows:In Chapter 1,the composition,structure,preparation and optical properties of carbon dots are briefly discussed.Then,the applications of carbon points in environmental detection,biological imaging and optoelectronics are reviewed.Chapter 2:Nitrogen-doped carbon points（N-CDs）were prepared from anhydrous citric acid and D-leucine by one-pot hydrothermal method.The prepared N-CDs has good fluorescence properties,good photostability and fluorescence quantum yield up to 20.8%.Meanwhile,based on the properties that nitroimidazole antibiotics（metronidazole,Tinidazole and ornidazole）can effectively quenched N-CDs fluorescence by internal filtration effect（IFE）,a fluorescence sensor for the detection of metronidazole,Tinidazole and ornidazole was constructed using the prepared fluorescent carbon points.The experimental results showed that the sensor showed high sensitivity and selectivity in the detection of metronidazole,Tinidazole and ornidazole.The detection linear ranges of the three objects were 2.5～66,2.5～100 and 2.5～120μM,and the detection limits were 97,57.8 and 69 n M,respectively.In addition,the fluorescence sensor can be applied to the detection of metronidazole,Tinidazole and ornidazole in environmental water bodies,and the recovery rate is between 89.1%and 108.8%.The carbon point has potential application value for timely detection of environmental water pollution.Chapter 3:Yellow fluorescent carbon point（Y-CDs）was synthesized by hydrothermal method using 4-nitro-1,8-naphthalene dicarboside and phenylalanine as raw materials.The optimal excitation and emission of this carbon point are 422 nm and 547nm,and the fluorescence quantum yield is 9.3%.Lemon yellow can quenched the fluorescence of Y-CDs rapidly through the internal filtration effect,so a fluorescence sensor was constructed to detect lemon yellow,and the longest emission wavelength fluorescence method was realized.The linear range was 0.25～14.80μmol/L,and the detection limit was 58 nmol/L,showing good selectivity.The sensor was applied to the determination of lemon yellow in Fenhe water samples and drinks,and the recovery rate was 94.58%～101.99%.In addition,Y-CDs can also be used to prepare Y-CDs/PVA composites as fluorescent luminous films,showing bright yellow solid fluorescence.These results show that Y-CDs has potential application value in environmental detection and solid luminous films.Chapter 4:Orange-yellow fluorescent carbon dots（O-CDs）were successfully prepared with magdala red and salicylic acid,which has good fluorescence properties,long emission wavelength and high quantum yield of 41.38%.Based on static quenching,Ser can quench the fluorescence of O-CDs.Therefore,a fast,simple,stable and low-cost fluorescence detection strategy for Ser is proposed.In the range of 5～89.2μM,（F₀-F）/F₀has a good linear relationship with Ser,and the detection limit is 0.52μM,which has been successfully applied to the detection of Ser in environmental water.In addition,the sensor has great potential in cell imaging applications.