Synthesis Of Carbon Quantum Dots With Microfluidic Chip And Property Research

Carbon quantum dots(CQDs) possess excellent physical, chemical and biological properties, such as aqueous dispersibility, low cytotoxicity and high resistance to chemical and photo bleaching, making it gain wide attention and application in chemistry, biomedicine, sensormetrics and optoelectronics for the past few years. Disadvantages such as complex operations, difficult to control and large reagent consumption appeared when utilized traditional method to synthesize CQDs. Microfluidic chip can realize mixing, reaction, separation and detection of sample within a chip of a few square centimeter, greatly simplifying the experimental operation. Accuracy control of different reaction conditions can be achieved by computer system control of sample injection. Dosage of reactants will be extremely reduced because of the micro-scale channels of microfluidic chip. Microfluidic chip has been widely applied to the field of chemical synthesis on its superiority, but few research were reported for preparing CQDs.In this research, a newly delicate microfluidic chip was designed for the synthesis of CQDs. CQDs could be synthesized through thermal decomposition of ascorbic acid accelerated by Cu2+ in aqueous solution. A comparison of optical properties, chemical composition, morphology and structure of CQDs prepared both in macro and micro systems were intensively studied. Meanwhile, CQDs prepared with the microfluidic chip were used for the field of pH and Fe3+ detection.Firstly, hydrophilic CQDs, which emitted blue-fluorescence under 365 nm UV-irradiation, could be successfully prepared in macrosystem. Amount of hydroxyl and carboxyl existed on the surface of the spherical CQDs with clear crystal structure. Secondly, a novel microfluidic chip was designed based on the properties of reaction. The microfluidic chip was composed of two parts, a serpentine with many a microstructures channel for mixing and a main spiral channel for growth of CQDs. With this novel microfluidic chip, hydrodynamic and thermodynamics parameters of the reaction could be controlled precisely and automatically. CQDs with fluorescence property were collected from the outlet. Different characterization results, such as XPS, FTIR and UV-vis, revealed surface of CQDs prepared in this microfluidic chip contained more C=C bond than that prepared in macrosystem, showing carbonization reaction had been carried out more thoroughly in microsystem. Thirdly, CQDs prepared with microfluidic chip had the best fluorescence property under neutral condition in aqueous solution, overly acidic or alkaline conditions could lead fluorescence quenching of CQDs. By the way, fluorescence intensity of CQDs was linearly proportional to pH within the scope of acid and alkali. At last, Fe3+ could specifically quench the fluorescence of CQDs, and the quenching rate was linearly enhanced by the increase of Fe3+ concentration within 0.5mmol/L.In this research, CQDs with good fluorescent property were prepared by ameliorating the design of chip and control of reaction conditions. Meanwhile, application prospect of CQDs prepared with microfluidic chip in the field of pH and Fe3+ qualitative and quantitative detection was verified.