The Preparation And Fluorescent Probes Applications Of N-doped Carbon Quantum Dots

Carbon quantum dots?CQDS?,with its rich raw materials and simple preparation process,have attracted more and more researchers attention.Moreover,because of its excellent fluorescence performance,adjustable luminescent properties,good water solubility and biocompatibility,carbon quantum dots have a wide application prospect in chemical sensors.In this thesis,three kinds of carbon quantum dots were synthesized by doping method with different materials,which were characterized by a variety of modern instruments,and used as probes in the application of ion detection and biological imaging.The specific research is as follows:Firstly,N-doped high fluorescence carbon nanopoint probe 1?N-cds-1?was synthesized by using citric acid and ethylenediamine as raw materials under normal pressure and solvent-free conditions.The quantum yield of fluorescence is as high as 20%.The optical properties are studied by UV-Vis absorption spectrum and fluorescence spectrum.The composition and morphology of carbon quantum dots are characterized by transmission electron microscope,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy and other methods.The nanoparticles with stable structure and uniform particle size are prepared by simple and green synthesis method.The surface of carbon quantum dots is covered with carboxyl?-COOH?and amino?-NH2?functional groups,which make them have excellent water solubility.The UV absorption peak is located at 350 nm,the optimal fluorescence excitation is 355 nm,and the maximum absorption wavelength is 460 nm.By analyzing the p H stability of N-cds-1,the p H dependence of N-cds-1 is small.Then,the sensitivity and anti-interference ability of the iron ion response of N-cds-1 were tested,and almost no interference from other cations was detected,and the detection limit was 8.73×10 –8M.The complexation constant is 3.27×105 M^-1,and the interference of other cations on the recognition performance of N-cds-1 is small.Two kinds of probes?N-cds-2 and N-cds-3?for the detection of iron ions were synthesized by hydrothermal synthesis of carbon quantum dots doped with ethylenediamine,using natural plant powder peach blossom and rosemary as carbon sources.The synthesis conditions of N-cds-2 and N-cds-3 were optimized.The morphology and optics of N-cds-2and N-cds-3 were characterized.The optimal excitation wavelength of N-cds-2 and N-cds-3 is360 nm and 340 nm respectively,and the maximum emission wavelength is 465 nm and 460 nm respectively under the optimal excitation wavelength.The results show that the p H dependence of N-cds-2 and N-cds-3 is small,the anti-interference ability of detecting iron ion is strong,the sensitivity is high,and the detection limit is 0.161 ?M and 0.235 ?M respectively.The complexation constants were 3.07×105 M^-1 and 2.58×105 M^-1,and othercations had little interference on the recognition performance of N-cds-2 and N-cds-3.The fluorescence recovery of N-cds-2 with the best quenching effect?F/F0 = 0.05,the lowest of the three probes?was tested.It was found that the fluorescence of N-cds-2 was restored in the presence of PO₄^3-,and it had good stability and anti-interference ability.The detection limit of PO₄^3-was 0.79 ?M.