Controlled Synthesis Graphene Nanocomposites Based On Copper Species And Properties Investigation

Graphene, a flat one-atom-thick monolayer carbon atoms tightly packed into a two dimensional (2D) honeycomb carbon material, is the basic structural units for other sp2hybridized carbon allotropes. such as zero-dimensional fullerenes, one-dimensional carbon nanotubes and three-dimensional bulk graphite. The thickness of single-layer graphene is only0.335nm. which is the thinnest kind of the existing materials. Due to the unique nanostructure and extraordinary properties, graphene based materials has become one of the hottest topics in materials, chemistry, physics. And studies have shown that such materials show promising applications in electronics, optics, magnetism, biomedical, catalytic sensors, energy storage etc. In this dissertation, a series of graphene nanocomposites based on copper species have been obtained via different reduction means. Also, several copper salts and graphene oxide were used as precursors in every reaction system. Certain properties characterization and unique properties investigation of the obtained nanocomposites were studied in detail. The main contents are as follows:1. The CuO/rGO nanocomposites were successfully synthesized through syn-graphenization strategies (one pot approach) between graphene oxide (GO) sheets and CuCl without extra reducing agent. The reduction of GO and the deposition of CuO on the rGO sheets occurred simultaneously after the Cu(NH4)+was absorbed to the negatively charged GO surface during reaction process, resulting in a uniform and tight distribution of CuO nanoparticles on graphene sheets. We also discussed the experimental conditions and proposed the reaction mechanism of this reaction system. The as-prepared nanocomposite was exploited in the electrocatalytic oxidation of catechol in aqueous media via cyclic voltammetry(CV), and the cyclic voltammetry (CV) results indicated that the as-prepared copper oxide/rGO nanocomposite exhibited a higher electrocatalytic activity due to the synergistic effect of the CuO nanoparticles and rGO nanosheets can effectively prevent the detachment and agglomeration. In addition, the as-prepared nanocomposite had a higher BET surface area (235m2/g) and the porosity formed, which can facilitates interfacial charge transfer. The prepared catechol biosensor had a good linear correlation with the electrolyte pH and displayed high sensitivity, good reproducibility and long-tem stability.2. We successfully prepared the graphene-stabilized copper nanocrystals via a one-step wet process using graphene oxide (GO) and copper chloride as precursors and the L-ascorbic acid (L-AA) as the reducing agent. In the reaction system, the graphene serve as molecular templates for hybridizing with copper nanoparticles to fabricate graphene-based composites. We found that this Cu/rGO nanocomposite had an excellent longtime air stability after exposure to air for months, which is attributed to the copper nanoparticles tightly contact with the reduced state graphene. The density functional theory calculations (DFT) demonstrate that reduced state graphene can effectively prevent Cu nanoparticles from spontaneous oxidation due to its lower ionization potential than that of copper metal. Furthermore, the as-prepared graphene-stabilized copper nanocrystals can serve as an effective catalyst for the degradation of4-nitrophenol and exhibit surface enhanced raman scattering in the detection of crystal violet.3. Controlled synthesis of CuO with various hierarchical structures consisting of self-organized nanoparticles was realized by using n-octylamine (OLA) as a structure inducing agent via a facile hydrothermal synthetic method. Different hierarchical CuO can also be easily fabricated by adjusting the preparative parameters. Based on the investigation for the mechanism of the capping surfactant OLA. we found that its unique hydrophobic forces is the key of the successfully preparation of the different hierarchical CuO structures. The electrochemical performances of the as-synthesized different products for sensing nitrite oxidation in are evaluated. The result revealed that the electrocatalytic activity was related to its hierarchical nanostructures. BET and EIS demonstrate the reasons for the enhancement electrocatalytic activity of the hierarchical CuO structures.We then introduced graphene oxide into this reaction system and successfully obtained the graphene wrapped CuO copper oxide nanomaterials. In this reaction system, the n-octylamine not only act as a structure-directing agent for forming sphere-like CuO nanoparticles, but also as the surfactant for modifying the surface of graphene oxide (GO). Therefore, we successfully obtained the graphene wrapped CuO nanospheres via a facile hydrothermal synthetic method. We also discussed the experimental conditions in detail. Respect to the electrocatalytic activity towards glucose, we found that graphene wrapped CuO nanospheres nanostructures had a significantly enhanced cycle stability than pure CuO nanospheres,which is attributed to the presence of graphene can prevent the aggregation of the CuO nanospheres and stablize the CuO crystal form in the electrocatalytic oxidation process.