Microfluidic Synthesis And Analytical Application Of Novel Fluorescent Carbon Dots

Carbon dots（CDs）,as a new type of fluorescent carbon nanomaterials,have attracted researchers’ attention,because of their excellent fluorescent properties,low photobleaching,low toxicity and good biocompatibility.At present,CDs have been applied in chemical sensing,biological imaging,catalysis photoelectric applications and other fields.However,their preparation still has some limitations,such as high energy consumption and poor repeatability among different batches.Therefore,it is necessary to develop simple,green and energy-efficient methods to synthesize novel CDs.Continuous microfluidic synthesis is a technology to perform synthesis in microfluidic channels through the manipulation of fluids.Advantages of this technology include rapid mass and heat transfer,easy control of reaction conditions and high repeatability.Herein,microfluidic chips were used to synthesize CDs through light irradiation at room temperature and the applications of the produced CDs in some chemical sensing and cell imaging were tested.The dissertation contains five chapters:Chapter 1,the background of carbon dots（CDs）was briefly introduced,the classification,synthesis methods,properties and applications of CDs were systematically summarized.The background,structure and applications of microfluidic continuous synthesis were elaborated.Chapter 2,inside the lab-made microfluidic chips,a series of nitrogen-doped carbon dots（CDs）with high fluorescence was prepared by using o-phenylenediamine（OPD）and adipic acid（AA）at room temperature.The effects of different synthesis conditions,including the light source,the type and the molar ratio of acid and reaction time on fluorescence intensity were studied.The performance of CDs synthesized in microchip and conventional beaker was compared.The results showed that the CDs synthesized by microchip had narrower size distribution and higher quantum yield（chip: 14.90%,beaker: 6.23%）.Chapter 3,glutathione was detected by CDs synthesized in Chapter 2.The detection conditions were optimized and the detection limit was 4.0 μM.The determination of glutathione in beer samples was successfully performed with recoveries of 92.9-108.7%.Normal cells and tumor cells were stained and imaged with the prepared CDs,significant fluorescence differences could be observed in two kinds of cells,which is consistent with the difference of the glutathione content in normal and tumor cells.Chapter 4,the fluorescence emission properties of the prepared CDs in different polar organic solvents including dimethyl sulfoxide（DMSO）,N,N-dimethylformamide（DMF）and 1,4-dioxane（Diox）were studied,and the fluorescence changes of CDs in organic solvents with different water content were explored.The content of trace water in 1,4-dioxane solvent was detected by the maximum fluorescence emission wavelength,and the detection limit was 0.05%.Chapter 5,a fluorescence detection device was built,using a smartphone as the detector,combined with microfluidic chips.The analytical performance of the device was investigated by using the CDs synthesized in Chapter 2.The results showed that the prepared device had good light uniformity,and the detection limit of CDs was0.02 mg/m L,which is equivalent to that of commercial fluorescence detectors,indicating its application potential.