Microwave-assisted Rapid Green Synthesis Of Photoluminescent Carbon Dots And Their Optical Properties

As a new member in the family of carbon nanomaterials, fluorescent carbon dots (CDs) have attracted wide attention because of their unique optical and electrical properties. Compared to conventional fluorescent dyes and quantum dots, the CDs exhibit unique properties such as high fluorescent stability, resistance to photobleaching, good biocompatibility, low toxicity, tunable emission, small size and high photocatalytic activity, which endow CDs with great potential in various fields. In addition, the CD preparation process is usually facile and no expensive instruments or raw materials are needed, making CDs good candidates for extensive study.In this dissertation, we employed a microwave-assisted synthesis method and obtained three types of CDs with different carbonation levels by controlling the reaction time and temperature. The fluorescence properties and nonlinear optical properties of the as-synthesized CDs were thereafter thoroughly investigated. Specifically, the dissertation is mainly divided into five sections:1. Background introduction.2. In this section, we used glycerol and3-aminopropyl triethoxysilane as raw materials for one pot synthesis of fluorescent carbon dots by microwave-assisted synthesis method. Through varying the reaction temperature and time, we controlled the carbonization degree of these CDs. Meanwhile, the morphology, surface structure and optical properties of the CDs were systematically characterized.3. We measured the nonlinear optical properties of the as-synthesized CDs in solution by Z-scan technique. All of these CDs exhibited detectable saturable absorption, which were however significantly influenced by the carbonization degree of the product. It was found that the nonlinear response of these CDs were not only caused by saturable absorption but also by the existing free-carrier absorption. The nonlinear response of the CDs as a function of their linear transmittance in solution, laser energy and solvent were also thoroughly investigated. 4. We measured the nonlinear optical properties of CDs films by Z-scan technique. The results proved that these films demonstrated obvious nonlinear optical response under532nm wavelength light pulses, implying their potential for practical applications.5. The conclusion and the prospects of CDs in the field of nonlinear optics.