Preparation And Application Of Blue Fluorescent Carbon Quantum Dots

Carbon quantum dots?CQDs?can be regarded as a new star in carbon materials family.Based on their excellent photoluminescence and low toxicity,they have gradually become a perfect substitute for semiconductor quantum dots.In this paper,two kinds of carbon quantum dots with different properties were prepared in a green and safe method.Not only their morphology,structure and fluorescence properties were characterized,but also they were applied to ion sensing,p H sensing and biological imaging.1.We synthesized CQDs from caulis polygoni multiflori by a simple green hydrothermal method with high selectivity for Fe³⁺.As-prepared CQDs emit blue fluorescence and show excitation-dependent property.Combined with the analysis of transmission electron microscope and atomic force microscope,it is found that the average particle size of the synthesized CQDs is 2.3 ± 0.5 nm.The surface structure is analyzed by infrared spectrum and X-ray photoelectron spectroscopy,which show that the surface contains carboxyl and hydroxyl groups.The obtained CQDs are also used for in vitro cell imaging,and Fe³⁺detection in living cells.2.We selected citric acid as the carbon source and folic acid as the nitrogen source,and synthesized N-doped CQDs?N-CQDs?by hydrothermal method.As-synthesized N-CQDs with a size of about 3.6±1.0 nm emit bright blue fluorescence,and have the characteristics of low toxicity and excellent biocompatibility.Through the analysis of their structure,it is speculated that the surface contains amino and carboxyl groups.We applied the obtained N-CQDs for Hg²⁺ sensing,p H detection,and fluorescent labeling of cells.More interestingly,the N-CQDs can be utilized to visualize Hg²⁺ and p H fluctuation in living cells.