Controllable Preparation Of Dual Emission Fluorescence Carbon Quantum Dots And Its Application As High Efficiency Multifunctional Fluorescence Sensors

As a new type of fluorescent nanomaterial, carbon nanodots, due to strong emission, alterable emission wavelength, low cytotoxicity and excellent fluorescent stability, can be potentially applied in fluorescent imaging, detection, photo catalysis and so on. Herein, based on the preparation and application of carbon nanodots, dual-emission carbon nanodots(DECNDs) were firstly and simply synthesized by one-step hydrothermal treatment using ascorbic acid(AA) as a carbon source in alcohol-water binary systems, and then these unique DECNDs were constructed as multifunctional fluorescent sensors. The main contents of dissertation are summarized as follows:(1) Fluorescent dual-emission carbon nanodots(DECNDs) were firstly and simply synthesized by one-step hydrothermal treatment using ascorbic acid(AA) as a carbon source in alcohol-water binary systems, such as methanol, ethanol, n-propanol and ethylene glycol. In this assay, the DECNDs were characterized by several methods, for instance, transmission electron microscopy(TEM), ultraviolet-visible(UV-vis) absorption and fluorescence spectra. To understand the formation mechanism of DECNDs, the influences of alcohol-water ratios, reaction time and temprature on properties of DECNDs were investigated in detail.(2) The prepared DECNDs were utilized as a fluorescent probe to detect p H values, which were controlled by the addition of Na OH or HCl. Besides, the fluorescence of DECNDs was investigated in a series of HCl-Na Ac, Tris-HCl, Na OH-glycine buffer solutions. Finally, a novel p H sensor was developed based on dual emissions.(3) We combined the special optical properties of DECNDs with super quenching ability of graphene oxide(GO) to develop a fluorescent turn-off/on biosensor for hemoglobin(Hb) detection. The dual emissions of DECNDs could be quenched effectively by GO via inner filter effect(IFE) and fluorescence resonance energy transfer(FRET), while with addition of Hb, the fluorescence of this analytical system restored rapidly. Moreover, both single emission and ratiometric dual-emissions could be used to construct linear calibration curves for Hb, and the multi-detection strategies ensured the reliability, accuracy, and good selectivity of this sensing system.(4) The dual emissions of DECNDs could be quenched effectively by ?OH from the Fenton reaction, realizing the detection of H2O2. Meanwhile, both glucose and glucose oxidase(Gox) were measured indirectly according to the reaction that they reacted with each other to yield H2O2. This proposed method was simple, highly sensitive and low-cost. This study showed that DECNDs could serve as promising nano-carriers for fabricating practical and multifunctional fluorescent nanosensors.