Preparation Of Carbon Quantum Dots And Application In Fluorescence Detection And Photolysis Water

Carbon quantum dots（CQDs）,a nevel member of the carbon nanoscale family,they have been widely used in photoelectric sensors,cell imaging,photocatalysis,fluorescent probes due to their attracting properties such as simple preparation,high water solubility,low toxicity and good biocompatibility.However,most of the preparation processes of CQDs used sulfuric acid or other strong acids,which in harm to the environment and impact on the purity of CQDs.So using a green oxidant to prepare CQDs is very important.In this paper,CQDs with excellent performance were prepared by one-step oxidation method using cheap coal and anthracene oil as carbon source,ozone and hydrogen peroxide as green oxidizing agent.Main contents are as follows:（1）Phenol is considered as one of the most important pollutants in the water environment,thus its detection plays a cardinal role in environmental assessment and treatment.In this study,high quality carbon quantum dots（CY-CQDs）were successfully prepared by ozone oxidation,with cheap coal as carbon material.The as-prepared CY-CQDs exhibit a narrow size distribution between 2-9 nm,with an average size of approximately 4.2nm.The novel CY-CQDs showed high sensitivity and selectivity for phenol detection with a low detection limit of 0.076μM in water due to the fluorescence quenching effect of the CY-CQDs,which is attributed to the hydrogen bonds（C=O···H-O）between phenol and fluorescence CQDs according to the density functional theory（DFT）and time-dependent density functional theory（TDDFT）results.The theoretical calculation matches well with the experimental data,which provide us a new way to investigate the detective mechanism of the CQDs for other pollutants.（2）For the problem of low quantum yield of CQDs,anthracene oil with its own fluorescence effect was used as the carbon source.Water soluble AO-CQDs were prepared by ozone oxidation,which can be used to detect Hg²⁺in soil.The AO-CQDs can emit stronger blue fluorescence and the fluorescence quantum yield can reach 41%,and the particle size and fluorescence intensity of the prepared AO-CQDs can maintain good stability under different pH conditions.The novel AO-CQDs showed high sensitivity and selectivity for Hg²⁺detection with a low detection limit of 0.02μM,and the actual sample recovery test proved the effectiveness and feasibility of this method.（3）FC-CQDs prepared by hydrogen peroxide oxidation from fat coal and their optical properties were good.After modification of TiO₂ with FC-CQDs,the performance of photolysis water can be significantly improved.