Synthesis And Properties Of Carbon Dots Based On Aromatic Compounds

Carbon dots received extensive attention of people due to their excellent optical performance,strong electron transfer ability,low toxicity,high sensitivity,good biocompatibility and stability.Meanwhile,its application value in the potential areas such as electroluminescent devices,biological imaging,photocatalysis,solar cells,ions detection was gradually presenting.As more carbon dots had been reported successively,on the one hand,the workers hoped to further realize the application of carbon dots in various fields,on the other they developed higher performance to contrapose different aspects.Developing novel carbon dots and expanding their applications should be a top priority.In this paper,three different kinds of multicolor carbon dots were synthesized,based on aromatic compounds as carbon sources,by solvothermal method in a bottom-up synthesis route.By optimizing the preparation process and purification means,the luminescence properties of carbon dots were regulated,and a reasonable mechanism explanation was put forward.The luminescence mechanism of carbon core state and surface state was completely supplemented.The main contents and research results are as follows:(1)Through the screening of classical carbon sources,resorcinol and urea were determined as the synthetic carbon sources,N,N-dimethylformamide and anhydrous ethanol were selected as the reaction solution,and a new type of high-efficiency fluorescent carbon dot with a quantum yield of 78.6% was prepared through the mixing of solvent and the optimization of reaction conditions.The blue fluorescent carbon dots at 465 nm with three excitation peaks at278 nm,378 nm and 412 nm were obtained by silica gel column chromatography and rotary evaporation.After a series of optical properties testing and characterization,it was determined that the emission was the type of intrinsic carbon core state.The composite material of polyvinylpyrrolidone and carbon dots was prepared on phenolic resin as fluorescent film,and a good monochromatic material was obtained by excitation independent property.(2)Using resorcinol and urea as raw materials,using hydrothermal method,adding sulfuric acid as passivating agent,multi-color high-efficiency fluorescent carbon dots of oil phase and water phase were successfully prepared.The carbon dots were purified and separated by silica gel column chromatography with the expansion of organic solvent.The blue,green,yellow and orange fluorescent carbon dots were separated by two-step through column method.After purification,carbon dots with good dispersibility and fluorescence stability were obtained,including those with lipid solubility.Through the optimization of reaction conditions and purification process,the characteristics of easy oxidation of carbon dots were effectively overcome.(3)Using hydroquinone and urea as carbon sources and ethylenediamine as reaction solvent,a novel fluorescent carbon dot with solvent properties and amphiphilic properties of water and oil was prepared.Through the optimization of purification means,three kinds of pure carbon dots were obtained.The surface of a-CDs was mainly hydrophobic group,but it can dissolved in water to form the effect of phase separation.b-CDs had both hydrophilic and hydrophobic properties and also had phase separation effect.c-CDs was hydrophilic.Combined with the characterization methods,the surface functional group analysis of the three carbon dots was carried out,and the luminescence from the surface state was proposed,which reasonably explained the phase separation phenomenon of carbon dots.