Synthesis Of Multicolor Fluorescent Cqds And Studies On Preparation Of CQDs/polymer Composite Fluorescent Films

In recent years,carbon quantum dots(CQDs)as a new type of nano-fluorescence materials have attracted widespread attention from the scientific community due to their non-toxic environmental protection,biocompatibility,and excellent optical properties such as excitation wavelength coherence and upconversion fluorescence.However,the CQDs have shortcomings such as low fluorescence efficiency and emission at blue wavelength,which limit the CQDs application in light emitting materials and devices and so on.At present,there are various modification methods to increase the luminous efficiency of CQDs and to emit multicolor fluorescence,such as modification of CQDs surface functional groups,element doping,and compounding with other quantum dots.In this thesis,multicolor fluorescent CQDs is synthesized by surface modification and element doping modification,and CQDs is composed with high molecular polymers to stabilize their luminous property.The contents and results of this thesis are as follows:1.CQDs solution is synthesized by electrolysis using different graphite carbon rods as electrodes,and ethanol solution of NaOH as an electrolyte.Among them,CQDs prepared from commercially available graphite rods as raw materials has a size distribution of 2?4 nm and they are in a highly dispersed state.When ?ex=365 nm,the maximum peak emission intensity of fluorescence is at 420 nm.CQDs/PMMA composite films and CQDs/PVA composite films are prepared by solvent evaporation method,which effectively overcomes the disadvantages of poor fluorescence stability of CQDs solutions and has good fluorescence stability.2.Multi-color fluorescent CQDs without post-treatment is in one pot prepared by a series of solvent refluxing methods using citric acid and urea as raw materials.Among them,the CQDs obtained by refluxing solvent toluene with a boiling point of 110? has a particle size of 3?6 nm,and the best fluorescence performance.The oil-soluble CQDs and PMMA are composed into CQDs/PMMA composite films.When?ex=415 nm and ?ex=450 nm,they have red,yellow and green bright fluorescence.The CQDs/PVA composite films and CQDs/white latex composite film were prepared by combining water-soluble CQDs with PVA and white latex,respectively.When ?ex=415 nm and ?ex=450 nm,CQDs/PVA composite films have macroscopic red,yellow,and green fluorescence.When ?ex= 365 nm,the CQDs/white latex composite films has green fluorescence.3.Multi-color fluorescent CQDs were prepared by solvothermal method through a series of temperature changes using citric acid and thiourea as raw materials.Among them,the CQDs obtained at 160? has a particle size of 6?8 nm and the best fluorescence performance.When?ex=365 nm,the CQDs fluorescence has the emission intensity of 7200,bright red,orange,yellow,blue and other multicolor fluorescence and the excellent up-conversion fluorescence characteristics.The CQDs are composited with PMMA and PVA to form the CQDs/PMMA composite films and the CQDs/PVA composite films,respectively.When ?ex=415 nm and ?ex=450 nm,CQDs/PMMA composite films and CQDs/PVA composite films have red,yellow and green fluorescence,respectively.