The Preparation And Application Of Fluorescent Carbon Dots

Carbon dots(CDs) have attracted great attentions in recent years due to their excellent photostability, superior fluorescence property, non-toxicity and extremely small particle sizes, which show promising applications in biological and chemical sensing, bio-imaging, drug delivery etc. Until now, a variety of methods have been developed for the preparation carbon dots. However, most of the present method needs high temperature, voltage, microwaves, ultrasonic and/or other external stimulus, which is energy consuming. Therefore, it is still necessary to develop new convenient and energy-saving method for the preparation of carbon dots with excellent property.On the basis of these, two methods were developed for the preparation of carbon dots with high fluorescence quantum yield, and the fluorescence property as well as the application of the as-prepared carbon dots was discussed carefully. The main researches and results of this context are as follows:(1) Using PEG400 as the carbon precursor and the passivant, new CDs with high fluorescence were prepared in 10 min under the strong alkaline solution provided by Na OH. The new method possesses the advantages of facile, rapid, energy-saving, without any external stimulus and environment friendly. By changing the concentration of Na OH, the CDs with blue-emitting, yellow-emitting, orange red-emitting and red-emitting were obtained, and it was found that more fragments were polymerized under high concentration of Na OH, and a greater sp2 clusters formed, which reduced the energy gap between p and p(9) and resulted in the red shift of the fluorescence emission of CDs. The carbon dots prepared in this manuscript have good stability, the fluorescence intensity were not affected when p H changes from 4.0 to 11.0. Meanwhile, the biocompatibility of the new prepared carbon dots were investigated, the results showed that the prepared carbon dots have no toxicity to the test cells and can be used as a fluorescent probe in cell imaging.(2). Used PEG400 as the carbon source and the passivant, and Na2S2O3 as the doping agent, the sulfur doped carbon dots(S-CDs) were facile prepared. Compared with non-doped carbon dots prepared before, the fluorescence quantum yields were greatly improved, and the S-CDs have a better fluorescence stability. In addition, a sensitive fluorescence sensor were developed for Fe3+ detection based on S-CDs since the fluorescence of S-CDs could be quenched by Fe3+ through electron transfer, and the Fe3+contents in real water samples were successfully detected with the proposed sensor. Which can realize the detection of Fe3+ in environmental water samples.