Preparation And Properties Of Fluorescence Carbon Dots

Recently, considerable attention has been paid to the fluorescent carbon nanodots for wide applications due to their small size, a wide range of excitation wavelength, tunable fluorescence wavelength, high quantum yield, good photo-stability and easy modification surface. Compared with the traditional luminescent semiconductor quantum dots, carbon dots (CDs) have attracted widespread research in bioimaging and biosensor fields as a result of their low toxicity and good biocompatibility. The composites materials of carbon nanodots are prepared by tunable surface functionalities, which not only provide the optical properties of CDs, but also some special functions. The application of carbon nanodots composites have been developing rapidly, for example in optoelectronic devices, organic solar cells and photocatalysis fields.It has made some achievements to synthesize carbon dots with excellent optical properties by choosing a new carbon precursor or changing experimental approach. On the other hand, carbon-dots composites materials by doping metal or surface coated are prepared by surface modification, however, the research of CDs is still in initial phase while their mechanism and more extensive application still needs further research. The main contents of the thesis are as following:1) Carbon dots (Milk-CDs) and their L-cysteine (S doped CDs) and urea (N doped CDs) doped analogues were made by using the simple and low cost carbon source-pure milk, which has mild reaction conditions, simple reactants and easy steps to operate. The effect of the L-cysteine and urea doped on the spectroscopic and photophysical properties compared with Milk-CDs were studied by means of UV/vis absorption, steady-state, and time-resolved fluorometry. Moreover, the confocal microscopy experiments showed that Milk-CDs, S doped CDs and N doped CDs can be used within living cells for long time testing. It can prove that the prepared three CDs are all low-toxiciry and good biocompatibility.2) Firstly, we prepared the CDs by heating citric acid. Then Ni and Ni@SiO2 had been successfully synthesized by thermolysis. Lastly, CDs was linked to the surface of Ni@SiO2 in only one simple step. The synthesed Ni@SiO2-CDs composites materials not only offer the optical properties of CDs, but also magnetic properties. CDs and Ni@SiO2-CDs nanocomposites were studied by means of UV/vis absorption, steady-state, and time-resolved fluorometry. It is proved that the photoluminescence properties of the fluorescent Ni@SiO2-CDs magnetic nanocomposite are quite different in solid state and in ethanol solution. At room temperature, magnetic properties of Ni, Ni@SiO2 and Ni@SiO2-CDs nanostructures have also been studied by using vibrating sample magnetometer (VSM). The saturation magnetization (Ms) of Ni, Ni@SiCh and Ni@SiO2-CDs nano-materials are characterized and tested.