Design & Synthesis Of Carbon-based Nanomaterials And The Study Of Their Optical Properties

The unique structure and special physical and chemical properties of carbon-based materials have made them became hot material in many fields, such as photocatalysis, detection and optoelectronic devices. However, the photo-chemistry properties of carbon dots still not clear; and the study on nonlinear optical properties of carbon dots is relatively rare. Based on the research of its properties,we study the photocatalytic properties and make it as photoluminescence（PL） probes in detection of glucose, and further research the nonlinear optical properties of carbon dots. In our work, the main works included the following parts:1. The Cu nanoparticle/carbon dots hybrids（Cu/CQDs） were prepared by a simple wet-chemistry method from Cu（NO3）2 and CQDs. Under mild condition the Cu/CQDs hybrids as photocatalyst exhibit excellent catalytic activity in oxidation of cyclohexane 60 ℃ with tert-butyl hydroperoxide as oxidant. After 48 h, the conversion of cyclohexane up to 50.2 %, while the selectivity of cyclohexanone can reach 78.3 %. The experimental results show that the excellent photocatalytic activity of Cu/CQDs is attributed to the synergistic effect of copper nanoparticles and carbon dots. There are three advantages to the Cu/CQDs catalyst:（1） the synthesis pathway of Cu/CQDs hybrids are fairly simple, requiring neither complicated devices nor complex preparation processes;（2） the raw materials for manufacture Cu/CQDs hybrids are cheap; and（3） the reaction processes of cyclohexane oxidation requires neither high temperature nor high pressure.2. The stronger fluorescence carbon quantum dots（quantum yields: 12 %） is obtained from polyethylene glycol by alkali-assisted reflux method. The carbon dots are used as label-free photoluminescence（PL） probes in detection of glucose, and the detection limit reached up to 1 nM. This method can detect glucose efficiently and rapidly. H₂O₂ produced from the reaction of glucose catalyzed by glucose oxidase can enhance the fluorescence of carbon dots effectively.3. We fabricated the N-doped carbon dots（N-CDs） from C₃N₄ by using a simple reflux method. The N-CDs（concentration is 0.63 g·L-1） exhibit strong NLO response under both 532 nm, 4 ns and 21 ps laser pulses, with the third-order nonlinear susceptibility χ³ of 12.5×10-12 and 0.725×10-12 esu. The oxygen functional groups on the N-CDs surface should have important influence on their nonlinear optics properties.4. The CNDs with different size are fabricated by an electrochemical etching method from graphite rod. Exhibited by pulsed laser（532 nm, 4 ns）, the third order susceptibility χ³ of CNDs is strongly dependent on the diameter of the CNDs. The carbonyl groups on the CDs surface have significant impact on the third order susceptibility χ³.