Chemiluminescence Of Fluorescent Carbon Quantum Dots And Its Analytical Application

Chemiluminescence（CL）has been proved to be a sensitive and simple analytical method because of its fast response,wide linear range,low background signal and simple instrument operation.However,high CL intensity is the key to obtain high sensitivity in further analytical applications.Therefore,it is very important to choose suitable catalyst,sensitizer or surfactant to enhance the CL intensity.As a rising star of carbon nanomaterials,carbon dots（CD）have attracted a wide range of research interests due to its various significant advantages,including low toxicity,chemical inertness,good biocompatibility and excellent optical and electronic properties.Up to now,the application of CD as sensitizer,catalyst and emitters in various CL systems has greatly improved the sensitivity of CL reaction and expanded the analytical application range of CL detection.In this paper,the nitrogen doped carbon dots（MFCD）were synthesized by simple hydrothermal method with citric acid,melamine and formaldehyde as raw materials,and its optical properties and chemical structure were characterized by means of ultraviolet,fluorescence,infrared and transmission electron microscopy.The MFCD were applied to three CL systems,and the determination of different analytes were completed.The specific research contents are as follows:1.Under acid condition,the response of MFCD to the systems composed of NaHSO₃ and different oxidants was studied.It was found that MFCD can significantly enhance the weak CL reaction between K₂Cr₂O₇and NaHSO₃.The mechanism research found that the process of energy transfer from excited sulphur dioxide（SO₂^*）to MFCD and the radiative recombination of oxidant-injected holes and electrons promote the generation of strong CL emission.Further study showed that iodide was effective in enhancing the CL intensity of this system.Based on this finding,the MFCD-NaHSO₃-K₂Cr₂O₇CL system as a sensitive and selective probe was applied for detection of n M levels of iodide ions.Under optimum conditions,the system had a linear calibration range from 0.03 to 5.0mM with a detection limit of 5.6 n M.The developed CL method was applied for the detection of iodide in milk and mineral water samples.2.As one of the ultra weak CL systems,H₂O₂-K₃Fe（CN）₆system has attracted more and more attention.MFCD acted as a new fluorophores instead of conventional fluorescent dyes to enhance H₂O₂-K₃Fe（CN）₆system CL signal.With the addition of tannic acid（TA）,the CL intensity of MFCD-H₂O₂-K₃Fe（CN）₆system was inhibited to some extent.Therefore,this was exploited to develop a CL detection method for TA.Under the optimal experimental conditions,there was a good linear relationship between the relative CL intensity and the logarithm of TA concentration in the range of 0.2-10μM,and the detection limit was 39.3 n M.The method was further applied to the quantitative analysis of TA concentration in red wine.3.Peroxynitrite（ONOOH）could be formed by the reaction of NaNO₂and acidic H₂O₂,which could produce weak CL emission.The weak CL was enhanced by a factor of～400times in the presence of MFCD.Therefore,the MFCD-H₂O₂-NaNO₂system was constructed and analyzed.It was found that 2-naphthol（2-NAP）had obvious quenching effect on MFCD-H₂O₂-NaNO₂system,so a new method for the determination of 2-NAP was established.It had also obtained a stable response concentration range from 0.3 to 20μM for 2-NAP with a detection limit as low as 48 n M.At the same time,to demonstrate the potential application of this method,the designed platform was applied for the quantifcation of 2-NAP in environmental water samples.