Study On The Synthesis And Application Of Carbon Dots By Gaseous Detonation

Carbon dots(CDs),divided into three classes:Graphene quantum dots(GQDs),Carbon nanodots(CNDs)and Polymer dots(PDs),are a new type of photoluminescence(PL)carbon-based zero-dimensional nanomaterial.Due to their good biocompatibility,low toxicity,unique fluorescence tunability,prominent catalysis,excellent light stability and environmental friendliness,they have been widely used in biomedicine,photoelectric devices,catalysis and chemical sensing.At present,many methods such as chemical oxidation,laser stripping,electrochemical method,hydrothermal/solvent-thermal method and microwave method have been developed to prepare CDs,and the applications of CDs in memory materials,self-healing materials and energy storage materials have been further explored.However,there are still great challenges in large-scale preparation,fluorescence mechanism and scale application of CDs.Therefore,it is urgent to develop a method for the large-scale preparation of CDs,reveal the fluorescence mechanism of CDs and find a new field of scale application.Gaseous detonation is a new method for preparation of nanomaterials,successfully applied to the synthesis of TiO₂,SiO₂,carbon nanotubes,carbon coated metal and other nanomaterials.It has the advantages of large yield,fast reaction,high purity and simple operation.Therefore,in the paper gaseous detonation approach is employed to fabricate a series of GQDs and PDs with different morphology and optical properties through adjusting the experimental parameters based on the design of orthogonal test.The deduced fluid dynamics equation of detonation containing solid particles in non-standard state is used to calculate the detonation parameters under different experiments.Then the effects of different detonation parameters on the morphology and optical performance of GQDs and PDs are studied,and the fluorescent mechanisms and formation mechanisms of GQDs and PDs are revealed.Finally,the applications of GQDs and PDs in lubrication and photoelectric devices are studied.The main research contents are as follows.(1)The fluid dynamics equation of detonation containing solid particles in non-standard state is derived,and its accuracy is verified.In order to calculate the parameters of gaseous detonation with solid particles under non-standard conditions,the fluid dynamics equation of detonation with solid particles is deduced by combining the C-J detonation model and the adiabatic index K expression of solid particles.Then considering the influence of initial temperature and pressure on detonation parameters,the fluid dynamics equation of detonation containing solid particles in non-standard state is proposed.The error between the theoretical detonation velocity calculated by the equation and the actual detonation velocity measured by high-speed photography is within 5%,verifying the equation accuracy.(2)GQDs are prepared by gaseous detonation,and their fluorescence mechanism and formation mechanism are revealed.Using the benzoic acid(BA)as the carbon source,H₂ and O₂ as the detonation sources,the highly fluorescent GQDs are prepared in one step within milliseconds by gaseous detonation.Through adjusting the experimental parameters according to the design of orthogonal test,a series of different GQDs are fabricated.The fluid dynamics equation of detonation containing solid particles in non-standard state is employed to calculate the detonation parameters under different experiments,and the effects of different detonation parameters on the morphology and optical performance of GQDs are studied.At the same time,based on the optical properties of reducing GQDs(R-GQDs)and thermal annealing GQDs(A-GQDs),the fluorescent mechanism and formation mechanism of GQDs are revealed.(3)Solid-state fluorescence PDs are prepared by gaseous detonation,and their fluorescence mechanism and formation mechanism are revealed.Using citric acid(CA)and urea as carbon and nitrogen sources respectively,H₂ and O₂ as detonation sources,PDs are prepared in one step within milliseconds by gaseous detonation.The aggregation induced fluorescence quenching effect can be overcome and solid-state fluorescence can be emitted without the addition of any solid dispersing agent.Through adjusting the experimental parameters according to the design of orthogonal test,a series of different PDs are fabricated.The fluid dynamics equation of detonation containing solid particles in non-standard state is used to calculate the detonation parameters under different experiments,and the effects of different detonation parameters on the morphology and optical performance of PDs are studied.At the same time,based on the optical properties of thermal annealing PDs(A-PDs),the fluorescent mechanism and formation mechanism of PDs are revealed.(4)The as-prepared GQDs and PDs are applied in lubrication and optoelectronic devices.The prepared GQDs and PDs are used as anti-friction and anti-wear additives for 150SN and PEG400,respectively.The tribological properties of GQDs and PDs are tested by four-ball model experiments.Based on the morphology,tribological properties and wear scar analyses of GQDs and PDs,the lubricating mechanisms of GQDs and PDs are proposed.The as-prepared GQDs and PDs are applied as the white light conversion layers of LED to prepare white LED(WLED).