Detection Of Water Content In Organic Solvent Based On Carbon-Dots Ratiometric Fluorescent Probe And Its Application In Cell Imaging

Water is the most common impurity in organic solvents and plays a vital role in chemical reactions and industrial applications.Especially in chemical reaction,the presence of water causes quenching of the active compounds,inhibiting the reaction or reducing the yield.Therefore,it is critical to detect the moisture in organic solvents.Karl titration is a traditional method,but it usually requires specialized instruments and skilled operators,and is costly.Recently,several other methods have been developed,such as nuclear magnetic resonance,surface resonance,and so on.However,compared with these methods,the illuminating sensor technology has the advantages of high sensitivity,simple operation and fast response.Therefore,it has promising application prospects.Recently,some new metal ion complex-based ethanol water fluorescence sensors have been synthesized,while they are difficult to be applied in cells.The aim of this study was to construct a fluorescent probe for the detection of trace amount of water in organic solvent such as ethanol.This probe has precise detection capability and high selectivity.At the same time,it can also perform organelle imaging.The first chapter introduces the existence,damage and detection methods of water in industrial productions and experiments,and summarizes the classification,properties,preparation methods and applications of carbon dots.In the second chapter,preparation of nitrogen-sulfur-doped blue fluorescent carbon dots was conducted(bCDs)by hydrothermal method with citric acid as carbon source and L-cysteine as nitrogen source.A red fluorescent carbon dot(rCDs)was prepared by using o-phenylenediamine and dopamine hydrochloride as raw materials.Another carbon dots r-bCDs were obtained by linking amino groups and carboxyl groups on their surface.The carbon dots and ratio probes were characterized by UV-Vis absorption spectroscopy(UV-vis),fluorescence spectroscopy(FS),Fourier transform infrared spectroscopy(FT-IR),transmission electron microscopy(TEM)and X-ray photoelectron spectroscopy(XPS).bCDs exhibit excitation-dependent fluorescence characteristics,while rCD s exhibit excitation-independent fluorescence characteristics.Stokes shift of rCDs exhibits significant polarity dependence.There is a good Boltzmann function correlation between the fluorescence intensity ratio of r-bCDs and the solvent polarity.The morphology of bCDs,rCDs and r-bCDs was characterized by TEM images.The result showed that they were evenly distributed in aqueous solution,with good dispersion and uniform particle size.As well,FTIR and XPS indicated that bCDs and rCDs were successfully connected.In the third chapter,the analytical performance of the carbon-based fluorescence ratio probe r-bCDs in organic solvents and the lysosomal imaging in cells were investigated.The result showed that the probe has high selectivity for water in organic solvents.It can also detect water content in real samples such as white spirits.In addition,its performance remains stable under high saline conditions.Furthermore,this probe has the advantages of low toxicity and good biocompatibility in cells.Colocalization studies of cells using laser confocal microscopy showed that r-bCDs were well targeted to lysosomes.This is due to its ability to detect polarity.Therefore,r-bCDs,based on pure carbon dots,is a kind of green probe without metal doping.It will provide a new idea for research on physicopathological processes and mechanisms related to lysosomes.