Preparation Of Carbon Quantum Dots And Its Application In Fluorescence Sensor

Fluorescent analysis has been widely applied in the biological detection. Because the operation is simple, response fast, and it has high sensitivity and good selectivity. In recent years, fluorescent carbon dots, as a new member of the family of carbon nanomaterials, has been widely application in biochemical analysis. Carbon dots has excellent optical properties and small size, what's more the low toxicity and good biocompatibility, all of these made it become the best choice for biological imaging. In this study we prepared fluorescent carbon quantum dots with good optical properties, then two kinds of sensors based on carbon quantum dots were used to detect paraoxon and glutathione, respectively. The main contents are summarized as follows:(1) There are variety methods to produce carbon quantum dots. It has great significance to explore simple and fast prepartion methods to synthesize carbon quantum dots. In Chapter 2, Nitrogen doped carbon quantum dots (NC-dots) were papered by microwave heating of ethylenediamine and citric acid solution. While carbon quantum dots (C-dots) were obtained by hydrothermal synthesis through heating of histidine-citric acid solution. Then we characterized the morphology and structure of NC-dots and C-dots by dynamic light scattering, IR, UV and fluorescence spectra. In addition, the light stability, fluorescence quantum yield, and environmental pH influence on fluorescent intensity were investigated.(2) Organophosphorus pesticides are widely used in the production of human beings, at the same time it also brought environmental pollution and food safety problems. It is important to establish a simple, easy operation, high sensitive method to detect organophosphorus pesticides. In Chapter 3, We constructed a fluorescence quenching type sensor to detect organophosphorus pesticides based on the NC-dots. NC-dots are adsorbed on the surface of AuNPs assembled into "NC-dots shell ", fluorescence resonance energy transfer (FRET) occurs between the NC-dots and AuNPs, NC-dots fluorescence is quenched. AchE can catalytic hydrolysis substrate ATI to generate sulfur choline, which can replace NC-dots on the surface of the AuNPs, so that NC-dots desorption followed by fluorescence recovery. Organophosphorus pesticides inhibit the catalytic activity of AChE, so the NC-dots fluorescence intensity recovery degree is suppressed. We can quantify the concentration of organophosphorus pesticides, such a paraoxon, by fluorescence intensity of NC-dots. The sensor is applied to the detection of paraoxon, when the concentration of paraoxon increases from 1.0×10-9 to 1.0×10-4 g/L, the proposed biosensor show tow linear response regions with a detection limit of 1.0×10-9 g/L. The sensor can be used to detect the actual sample, and provides a rapid and sensitive method for monitoring organophosphorus pesticides in food.(3) Glutathione (GSH) is antioxidants and free radical in the human body, GSH play an important role on anti-aging, anti-radiation, scavenging free radicals, detoxification, protect the liver and anticancer. In Chapter 4, we constructed a fluorescence enhanced sensor for the detection of GSH based on the competition reaction between GSH and C-dots. The fluorescence of C-dots could be effectively quenched by Cu2+, which is according to the Stern-Volmer equation in the concentration of Cu2+ between 0 and 80?M. In the presence of GSH, the binding ability between GSH and Cu2+ is much stronger than that of the C-dots and Cu2+. Therefore the C-dots are released and the fluorescence is restored. Liner responses are observed with the concentration of GSH between 20 and 150?M. The sensor has high sensitivity and good selectivity.