Separation Strategy And Photoluminescence Mechanism Of Hydrophobic Carbon Dots

Carbon dots(C-dots)have unique optical properties,such as excellent tunable photoluminescence,high quantum yield,good fluorescence stability and chemical stability,low cost,etc.Therefore,exploring the photoluminescence mechanism of C-dots is of great significance for understanding the exact photoluminescence process of C-dots and developing wider applications.In this paper,C-dots were synthesized by hydrothermal method and a combined separation system was proposed for the separation of C-dots.Based on its strong separation performance,three C-dots with very similar structure and optical properties were separated,and its structure was found to be simple by characterization,and then its luminescence mechanism was investigated and used to prepare hydrophobic luminescent films.The main work is as follows:1.Using o-aminophenol as a single precursor,C-dots were synthesized by hydrothermal method,and then separated by a combined separation system,including crude filtration、extraction and thin layer chromatography,three C-dots(C-dots-1,C-dots-2 and C-dots-3)were dispersed in n-hexane,a non-polar solvent,with bright green fluorescence.Through the characterization,it is found that the composition is single and the separation effect is good.2.The obtained C-dots-1,C-dots-2 and C-dots-3 were characterized and further size separation of C-dots-1 was carried out,and strictly multiparameter(component,size,optical spectroscopy,etc.)contrastive analysis has been achieved for studying their composition/structure/size related optical properties,and puts forward the uniform unitsemitting and molecular level repeatable photoluminescence mechanism:the mechanism suggests that C-dots are composed of graphene flakes in the core and PAH emission units on the surface,The C-dots’ photoluminescence comes from uniform surface polycyclic aromatic hydrocarbon units instead of the whole particles,which is both size-and oxygenindependent.A small number of oxygen atoms in C-dots are located in the optically inert region on the surface of C-dots,which plays a role of separating emission units and does not participate in the luminescence process of C-dots.In addition,C-dots also showed high luminance and stable photobleaching resistance,and by comparing the spectra of different batches of C-dots-1,it is found that C-dots-1 has molecular repeatable photo luminescence,which is a good combination of the advantages of photoluminescence nanomaterials and small molecular organic dyes.3.Based on the hydrophobicity of C-dots-1 and C-dots-2,C-dots/PDMS composite luminescent films were prepared by mixing C-dots with hydrophobic polymer polydimethylsiloxane(PDMS).The spectroscopic findings of its long-term placement were measured,it is found that the composite films have good water resistance and fluorescence stability.