Preparation And Bio-Imaging Of Carbon Dots With High Quantum Yield

Fluorescent carbon dots as a new carbon material with size less than 10 nm,has great potential for application in biology and biomedical research due to their good water solubility,suitability for subsequent functionalization,resistance to photobleaching,low toxicity,better biocompatibility,and low environmental hazard.In order to realize the application of fluorescent carbon dots in these fields,we must prepare carbon dots with long wavelength emission and high quantum yield.However,the emission wavelengths of the carbon dots are mostly in the blue light region,and the background interference is large,then the fluorescen quantum yield is low,most of the bare carbon dots are less than 10%.In this paper,We synthesized zinc-doped carbon dots with different characteristics by different carbon sources and applied to cell imaging,and the mechanism of fluorescence enhancement was studied.(1)In order to synthesize the fluorescent carbon dots with long wavelength emission,In this paper,we used p-phenylenediamine as carbon source and zinc chloride as the dopant.The zinc doped carbon point R-CDs was prepared by hydrothermal method.The optimum synthesis process is explored by changing the reaction conditions.It is found that the R-CDs fluorescence peak is located in the red light region of 630 nm,which is much better than most of the blue light to green light emission.The TEM results showed R-CDs had uniform size was about 4-5 nm.The FTIR and XPS results revealed that R-CDs contained carbon,nitrogen,oxygen,zinc elements and had rich hydroxyl,carboxyl,amino groups,which made them possess good solubility in water.The fluorescence spectrum and stability indicated that R-CDs can exist stably in high concentration salt and complex environment.The results of cell toxicity test also indicated carbon dots has good biocompatibility.At the same time,with the He La cell as the object,the effects of carbon as cell imaging reagents,experimental results show that R-CDs can be a good cell uptake,while after entering the cell showed a steady red fluorescence,and no toxicity the cells so that it has good potential application in the field of cellular imaging.(2)In order to synthesize the fluorescent carbon dots with high quantum dots,In this paper,we used o-phenylenediamine as carbon source and zinc chloride as the dopant.Synthesised of high quantum yield of zinc doped carbon dots Zn-CDs by one step hydrothermal method.The optimum synthesis process is explored by changing the reaction conditions.It is found that the peak of Zn-CDs fluorescence is located at 623 nm,with the highest quantum yield of 40.31%,which is much higher than the quantum yield of most bare carbon 10%.The morphology was characterized by high power transmission electron microscopy and atomic force microscopy.The results showed that Zn-CDs had a uniform particle size distribution,the average particle size was 3.62 nm,and the lattice spacing was 0.334 nm.The FTIR and XPS results revealed that R-CDs contained carbon,nitrogen,oxygen,zinc elements and had rich hydroxyl,carboxyl,amino groups.The influence mechanism of carbon dot structure and doped substance on its properties was investigated by XPS.The results show that the change of Zn-CDs quantum yield is related to the surface oxygen containing functional groups,and zinc plays an inductive role in it.