Preparation And Application Of Nitrogen-doped Carbon Dots

Carbon dot(CD)is a type of fluorescent carbon nanoparticle with a diameter of less than 10 nm.In recent years,carbon dots have been widely used in the fields of biomedicine,catalysts,energy,photoelectric applications,and sensing due to their excellent high chemical stability,good electrical conductivity,and luminous properties.The preparation of carbon dots by nitrogen doping can effectively adjust the original performance of the carbon dots,thereby opening up the research and application fields of carbon dots.In this thesis,ammonia water,ethylenediamine and triethylamine were selected as nitrogen sources.Three kinds of nitrogen-doped carbon dots with excellent properties were successfully synthesized,and their performance and application were analyzed and explored.The main research content includes:1.Using p-phenylenediamine and ammonia as precursors,a bright orange nitrogen-doped carbon dot(N-CD₁)was synthesized by a one-step hydrothermal method.The surface of the prepared N-CD₁has rich surface functional groups,and has certain water solubility,good biocompatibility,and high fluorescence quantum yield(15.8%).N-CD₁shows obvious fluorescence quenching effect on Fe³⁺and pH in aqueous solution,and the fluorescence color of N-CD₁solution will change with the change of Fe³⁺concentration and pH,so as to achieve the purpose of visual detection of Fe³⁺and pH.In addition,with its excellent biocompatibility,N-CD₁was successfully applied to detect Fe³⁺in cells.2.Using p-phenylenediamine and ethylenediamine as precursors,a yellow nitrogen-doped carbon dot(N-CD₂)was synthesized by a one-step hydrothermal method.The N-CD₂can successfully detect Ag⁺and glutathione(GSH)based on the"off-on-off"mode.Under the optimal reaction conditions,Ag⁺can significantly enhance the fluorescence of N-CD₂solution,and the degree of fluorescence enhancement of N-CD₂shows a good linear relationship with Ag⁺concentration(0-25?M),R²=0.992,and the detection limit is 0.091?M.When GSH is added,the fluorescence of N-CD₂solution can be restored to its original intensity,which makes N-CD₂can be used for the selective detection of GSH.In addition,N-CD₂has also been successfully used for colorful cell imaging of Hela cells.3.Using p-phenylenediamine and triethylamine as precursors,a blue nitrogen-doped carbon dot with double emission(N-CD₃)was prepared by a one-step hydrothermal method.N-CD₃of fluorescence can be effectively quenched by dopamine(DA).In the range of 50-80?M,the concentration of DA was linear with the degree of fluorescence quenching of N-CD₃,and the linear index R²=0.976.Through UV-vis and infrared spectroscopy,the possible quenching mechanism was explored.The ratio fluorescence sensor is constructed with a simple preparation method and low cost.To our knowledge,this is the first time that an N-CD₃-based ratio fluorescence sensor has been prepared to detect dopamine.