Synthesis Of N-doped Carbon Quantum Dots With Gluconic Acid And Its Study On Optical Properties

Carbon quantum dots（CQDs）are increasingly becoming a hot attention point due to abundant raw materials and various preparation method.The optical performance of CQDs provide a more broad prospects about the development and application of the fluorescent nanomaterials.In the water phase,The fluorescence of carbon quantum dots can be quenched and recovered by some cationic and anionic.Thus groping for the best preparation method to increase fluorescence quantum yield of carbon quantum dots is a precursor for application.Based on this purpose,we studied the preparation of carbon quantum dots of different methods,optical properties and applications,the main work is as follows:（1）With gluconic acid as carbon source,kinds of carbon quantum dots（CQDs）were synthesized by microwave method,pyrolysis method and hydrothermal method,respectively.The factors which influence the fluorescence intensity of carbon quantum dots,such as microwave time,pyrolysis temperature and time,hydrothermal time and the concentration of gluconic acid have been discussed.The particle size and optical properties of synthesis of carbon quantum dots were compared under three different methods.The carbon quantum dots prepared by microwave method and pyrolysis method showed excited dependent optical properties,but to hydrothermal prepared carbon quantum dots,its fluorescence does not depend on excitation wavelength with highest fluorescence quantum yield of 6.01%.（2）With gluconic acid as carbon source and ethylenediamine as nitrogen source,the nitrogen doped carbon quantum dots（N-CQDs）was successfully prepared by the hydrothermal method.In the paper,volume of ethylenediamine,pH of diluter,concentration of sodium chloride were studied on the influence of the fluorescence intensity of N-CQDs.Preparation of N-CQDs shaped spherical and were uniform dispersion.The average particle size was 6.22 nm with clear similar to that of the graphene lattice fringe.The fluorescence yield of N-CQDs is 24.66% which was nearly 4 times than undoped carbon quantum dots（CQDs）.It’s fluorescence emission was also not depend on excitation and the fluorescence peak was at 386 nm,fluorescence lifetime was 6.22 ns.（3）Based on the high fluorescence quantum yield,N-CQDs was applied to ion detection.Through the fluorescence quenching,it can be used for the detection of mercury ion.Hg²⁺ show a liner relationship between F/F0 and in the range 0.1⁵.0 μM with the detection limit of 0.06 μM（12.1 μg/L）.Then continue to add 12 kinds of anion in N-CQDs-Hg²⁺system.Iodide anion was be selected according to the fluorescence recovery phenomenon.In this part,we explored different pH of diluent to find the optimum pH for iodine ion detection.Adding different concentrations of iodine ion,concentration range 0.1⁵ μM of I-can be detected with the detection limit of 0.11 μM（13.9 μg/L）.In consideration of the wide linear range,N-CQDs-Hg²⁺system can be used to detect the iodine ion content in some drugs.Finally the actual drug cydiodine buccal tablets have been verified in the test of iodine ion.