The Preparation And Optical Properties Of Room-Temperature Phosphorescent Fluorine Nitrogen Co-Doped Carbon Dots

In recent years,as an emerging carbon-based luminescent material,carbon dots(CDs)have been widely used in various fields due to their ease of preparation and modification,excellent biocompatibility and excellent optical properties.The research of CDs has achieved great results after years of development,but there are still the following challenges:(1)At present,there are a large number of reports on the fluorescence properties of CDs,and the research on room temperature phosphorescence(RTP)is still to be studied;(2)At present The reported RTP performance of CDs is mainly achieved by compounding with a polymer matrix,which greatly limits the application of CDs,and it is of great significance to explore new methods;(3)At present,the traditional light-emitting materials-semiconductor quantum dots have biological toxicity,high price and other shortcomings,exploring various applications of CDs has prospects and value.Based on the above questions,the main research of this paper was concluded as follows:(1)We use fructose and diethylene triamine(DETA)as precursors to prepare fluorescent nitrogen-doped carbon dots(NCDs)by solvothermal method.The RTP are studied by compounding with polyvinyl alcohol(PVA),polyacrylamide(PAM),polyacrylic acid(PAA)and other polymer matrices.The RTP of NCDs was realized under the action of strong hydrogen bonds,and the longest room temperature phosphorescence reached 0.75 s.(2)We use nitrogen-doped carbon dots(NCDs)through further gas phase fluorination to obtain fluorine-nitrogen co-doped carbon dots(FNCDs).FNCDs exhibit a self-protecting RTP of 1.14 s without matrix embedding.By comparing the structure and performance of NCDs and FNCDs,we infer that the RTP of FNCDs is derived from the π→π*and n→π*electronic transitions of C-N/C=N,which is due to the small energy gap between the singlet and triplet.By comparing the properties between NCDsPVA and FNCDs-PVA,we further explored the mechanism of RTP:in the absence of oxygen barrier,the semi-ionic C-F bond strengthens the intramolecular and intermolecular hydrogen bonds and reduces the quenching of RTP.(3)We take advantage of the difference in luminescence properties of NCDs and FNCDs to realize the application of information anti-counterfeiting and encryption.