Preparation And Doping Of Carbon Quantum Dots And Its Application As Fluorescent Probes

The photoluminescent carbon dots have attracted great research interest as a desirable alternative to metal-based quantum dots and dye probes due to their unique optical performance,absence of toxicity,great biocompatibility,and surface modification,which also makes them applied in biochemical sensing,biological imaging,drug carriers,photocatalysis and other biological fields.So far,researchers have successfully synthesized carbon quantum dots by laser ablation,microwave irradiation and hydrothermal methods,but their fluorescence quantum yields are generally not high,and the mechanism of photoluminescent of carbon dots has not yet been clear,which greatly limits the application of carbon quantum dots,especially in the field of analytical chemistry.Therefore,synthesis of carbon dots with good luminescent properties and applied it in the field of analytical chemistry has become a hot research topic for researchers.In this paper,the carbon quantum dots with high fluorescence quantum yield have synthesized with cheap carbon source,the fluorescence properties of carbon quantum dots and its interaction with some small drug molecules have been studied.The quantitative method of detecting the small molecule of the drug was established with the photoluminescent carbon dots as a fluorescent probe,and realizing the sensitive and convenient fluorescence analysis of the small molecule of the drug.There are two parts in the paper: one is literature review,the other is research report which including the following four contents:1.The luminescent carbon quantum dots were synthesized by low temperature reflux with ascorbic acid as carbon source.At the maximum excitation wavelength of 340 nm and the maximum emission wavelength of 415 nm,the rutin（RT）concentration and the CDs fluorescence intensity quenching value ΔF with a good linear relationship at the range of 9.0×10-8¹.0×10^-5 mol/L,with a correlation coefficient of 0.9998,and the detection limit（3s/k）was 8.4×10-8 mol/L.The method had been applied to determine rutin in the samples with recovery in the range of 99.7%¹03%.The luminescent properties of the carbon quantum dots were studied by fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy.Based on the interaction between RT and CDs,a fluorescence quenching analytical method was developed to detect RT with CDs as fluorescent probe.The interaction mechanism between CDs and RT was studied,and the static quenching process between CDs and RT was determined.2.The luminescent carbon quantum dots were synthesized by reflux with charcoal as carbon source.It was found that the addition of famotidine could enhance the fluorescence of carbon quantum dots in Tris-HCl buffer solution at p H 7.10,and its concentration is linearly related to the increase of the intensity of the fluorescence intensity ΔF of the carbon quantum dots at the range of 8.0×10-9¹.0×10^-7 mol/L,with a correlation coefficient is 0.9993.According to above,a new method for determination of famotidine with carbon quantum dots as a fluorescent probe was proposed,the detection limit（3s/k）was 2.0×10-9 mol/L.The method was simple,rapid and sensitive,and has been used to the determination of famotidine in the sample,and the recovery range was 98.5% ¹03%.The results are satisfactory.At the same time,the interaction between the carbon dots and famotidine was studied by fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy.3.In this paper,nitrogen-doped carbon dots（N-CDs）were synthesized by low temperature reflux using ascorbic acid（AA）and ethylenediamine as original materials.Based on the interaction between N-CDs and nitrofurantoin,a new method was developed for the determination of nitrofurantoin with N-CDs as a fluorescent probe.Under optimum conditions,the quenched fluorescence intensity ΔF（F0-F）is in good proportional to the concentration of nitrofurantoin content at the range of 2.0×10^-72.0×10^-5 mol/L（at the maximum excitation wavelength 377 nm,the maximum emission wavelength 454 nm）,with a correlation coefficient of 0.9995,and the detection limit（3s/k）is 1.6×10^-7 mol/L,the recovery range was 99.5%¹02%.The above method has been successfully applied to the determination of the actual sample of nitrofurantoin,the results are satisfactory.The luminescent properties were investigated by fluorescence spectroscopy and ultraviolet-visible absorption spectroscopy.At the same time,taking quinine bisulphate as a reference,fluorescence quantum yield of the N-CDs was measured to be 4.68% and an average lifetime of 6.42 ns.In addition,the interaction mechanism between N-CDs and nitrofurantoin was further studied by the interaction between N-CDs and nitrofurantoin.The results show that the fluorescence quenching process between the two substances was a dynamic quenching process.4.N-doped carbon quantum dots（N-CDs）were synthesized by hydrothermal method using honey and ethylenediamine as original materials.In the experiment,at the maximum excitation wavelength of 363 nm and the maximum emission wavelength of 445 nm,the fluorescence quenching of N-CDs ΔF（F0-F）is in good proportional to the concentration of rifampicin（RFP）at the range of 1.0×10^-72.0×10^-5 mol/L,with a correlation coefficient of 0.9991,and the detection limit（3s/k）was 8.2×10-8 mol/L.So a fluorescence quenching method was developed for the detection of RFP with N-CDs as a fluorescent probe.The method has been used for the determination of RFP in samples,and the recovery range was 97.3%¹02%.The synthesis conditions of N-CDs were optimized,and the N-CDs were characterized by UV-Vis absorption spectroscopy,fluorescence spectroscopy and transient/steady-state fluorescence spectroscopy.The quantum yield of N-CDs was calculated.At the same time,the mechanism of interaction between N-CDs and RFP was further studied,the results show that the quenching process between N-CDs and RFP was a dynamic quenching process.