One-step preparation of green tea ash derived and polymer functionalized carbon quantum dots via the thiol-ene click chemistry

In this work, we developed a simple, economical and forthright strategy for synthesis of polyethylene glycol functionalized CQDs (PEG@CQDs) through a one-pot thiol-ene click reaction using mercapto polyethylene glycol and green tea ash. These PEG@CQDs displayed excellent water   dispersibility and intense blue-green fluorescence. The fluorescence emission wavelengths of these PEG@CQDs are depended on the excitation wavelengths. Furthermore, cell viability and cell internalization of PEG@CQDs were examined by MTT assay and confocal laser scanning microscopy. The results demonstrated that PEG@CQDs showed low cytotoxicity towards HepG2 cells and strong green fluorescence could be detected after HepG2 cells were excited with a 405 nm laser. All the above results demonstrated that PEG@CQDs possess small size, high water dispersibility and fluorescence properties and could be potentially utilized for cell fluorescent imaging. We hope the method will provide some novel ideas for preparation of functional CQDs and inspired the biomedical applications of these functional CQDs.