The Synthesis Of Fluorescent Carbon Dots And Its Application Research

Carbon dots, as a new type of fluorescent materials, exhibit many advantages, such as good photostability, good biocompatibility. Hence, they have a wide application in biological imaging and other fields. The superior properties of fluorescent carbon-based materials distinguish them from traditional fluorescent materials and make them promising candidates for numerous exciting applications, such as bioimaging and biosensor fields.Currently, many interesting methods have been developed to synthesize carbon dots, including top-down and bottom-up methods. Typically, these fabrication strategies involve complex processes, harsh reaction conditions and expensive equipment. The photo-luminescence quantum yield(Q.Y.) of those carbon dots is commonly very low(typically less than 10%). In view of the significant potential of this zero-dimension carbon nanomaterial in various field, a moderate, facile, cheap, and fast synthetic route to give bright fluorescence carbon dots is highly desired. In this work, the carbon dots were prepared by a hydrothermal method which could be utilized as a biosensor for the detection of Fe(Ⅲ) in aqueous samples and bioimaging. The main research works are as follows:(1) Synthesis of green fluorescent carbon dots based on the hydrothermal method with bovine serum albumin(BSA) as carbon source. Good water soluble and bright carbon dots was successfully synthesized by optimizing the temperature and reaction time. The particle-size of fluorescent carbon dots was characterized by dynamic light scattering(DLS) and transmission electron microscopy(TEM). The optical properties of fluorescent carbon dots were investigated by fluorescence spectrophotometer(FL) and ultra-violet visible absorption spectrometry(UV-Vis). The chemical composition and structure of fluorescent carbon dots was explored with X-ray photoelectron spectroscopy(XPS), X-ray diffraction(XRD) and fourier transform infrared spectroscopy(FT-IR). Fluorescent carbon dots were treated with Fe(Ⅲ) ion which causes quenching of the emission of the carbon dots. The nanoprobe is highly selective toward Fe(Ⅲ) and was used for the determination of Fe(Ⅲ) with detection limit of 500 nM. The measured recovery of spiked Fe(Ⅲ) in the spring water were 99%. Carbon dots is expected to be applied to detect Fe(Ⅲ) in drinking water in the future.(2) The optical properties of fluorescent carbon dots were investigated by high spatial resolution of optical microscopy imaging techniques to explore the interaction between the polypeptide modified nanocarriers and the cell membrane. The results showed that carbon dots presented higher fluorescence intensity, excellent photostability, low toxicity and good biocompatibility. What is more, the carbon dots can be easily uptaken by the cells and used in cell labeling. Therefore, the carbon dots is expected to be used as an alternative to organic dyes and quantum dots in the field of cell imaging analysis.(3) A ratiometric fluorescent temperature sensor was synthesized based on the temperature-sensitive material rhodamine B grafted to the surface of the carbon dots via a covalent bond. The nanoprobe showed excellent characters, such as stable optical properties, and low cytotoxicity and so on. What is more, the nanoprobes could be unitized as temperature sensor for the temperature detection in living cells.