Study On Preparation Of Carbon Dots Of The Coal-Based Regenerated Humic Acid And Their Fluorescence Properties

Fluorescent carbon dots are a new type of functional carbon nanomaterials with low cytotoxicity,good biocompatibility,and high photostability.They have broad application prospects in the fields of biomedicine,ion detection,sensors,and energy storage.In view of the low yield,serious pollution,high cost and other shortcomings existed in the currently preparation of carbon dots,a kind of carbon dots with good fluorescence properties were successfully prepared through solvothermal oxidation with a cheap lignite regenerated humic acid as raw material in this paper.Combining the structure characterization and the fluorescence measurement,the influences of solvent,atmosphere,temperature and other factors were investigated,and the formation and photoluminescence mechanism of prepared carbon dots were discussed.Further,the application performance of prepared carbon dots in the fields of antibiotic detection and luminescent materials were also explored.The research results show that coal-based regenerated humic acid has high aromaticity and rich oxygen-containing functional groups.With this regenerated humic acid as raw material,a kind of carbon dots with good fluorescence properties can be prepared by solvothermal oxidation.Solvent,atmosphere and reaction temperature are the main factors affecting the preparation of carbon dots.Among them,oxygen is the key to the preparation of coal-based humic acid carbon dots;DMF and water as solvents are suitable for the preparation of carbon dots.The excitation wavelength range of carbon dots prepared in DMF is wide and the emission wavelength range is relatively narrow.However,for the carbon dots prepared in aqueous medium,its excitation wavelength range is narrow,and emission wavelength covers the entire visible light region.The reaction temperature mainly affects the mass yield and the fluorescence quantum efficiency of carbon dots.Among them,the fluorescence quantum efficiency of carbon dots prepared at 240 ~oC can reach17.5%.The prepared carbon dots are a carbon polymer dot,which exhibit obvious concentration and excitation wavelength dependence.The fluorescence peak gradually redshifts with increasing concentration of carbon dots,so that it processes good fluorescence tunable characteristics.It was found that solvothermal oxidation can tailor the molecular structure of humic acid to form molecular carbon dots with photoluminescence ability.Then,molecular carbon dots gather to form carbon polymer dots by non-covalent bonding.The aggregation and de-aggregation of molecular carbon dots are reversible,which enduring obvious concentration dependence of prepared carbon dots.In addition,it was also found that the prepared carbon polymer dots have good selective detection ability for enrofloxacin and other antibiotics,and can be applied to the qualitative and quantitative analysis of antibiotics.Meanwhile,a kind of the fluorescent carbon polymer dots with cold white light(0.32,0.38)and a kind of fluorescent ink with yellow-green light were also obtained by adjusting the preparation process.In summary,the coal-based regenerated humic acid,as raw material,has abundant sources and low cost.By solvothermal oxidation reaction,the carbon dots are easy to be obtaining via simple process under mild conditions with high yield.The prepared carbon dots have good application prospects in the fields of antibiotic detection,light-emitting devices,and fluorescent signs.