The Synthesis And Characterization Of Several Carbon Nanomaterials

Carbon nanomaterials have attracted broad attention because of their unique structures, novel properties and wide potential applications in chemistry, physics and material science. In this paper, three of the most important carbon nanomaterials (endohedral metallofullerenes, single-walled carbon nanohorns and graphene) were studied using the direct current (DC) arc-discharge method and some of meaningful results were achieved.1. By the DC are-discharge of graphite rods doped with other substances in He and NH3 mixing gas, higher endohedral metallofullerenes (EMFs) were synthesized in high efficiency. This lays foundation for the separation, purification and further study of higher EMFs. The doped materials act as heat carriers and at the same time catalyze the growth of higher EMFs, whereas NH3 suppresses the formation of fullerenes such as C60 and C70, etc. These have increased the relative content of higher EMFs.2. N-doped graphene sheets were synthesized in large scale by the method of DC arc-discharge between pure graphite rods. For the use of NH3 as one of the buffer gas, the graphene sheets were doped with N without the addition of other nitrogen source. The product so obtained has been characterized by transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and element analysis. The graphene sheets are mainly of 2～6 layers and their sizes are 100～200 nm. The graphene sheets can be purified by a simple heat treatment process. The content of N atoms on the graphene sheets can be tuned by simply changing the proportion of NH3 in the atmosphere.3. Single-walled carbon nanohorns (SWNHs) with different morphologies were generated by DC arc-discharge between pure graphite rods in different atmospheres, including air. CO2 and CO. In the arc-discharge process, the O2 in the air reacted with carbon atoms and transformed into CO so that the formation of SWNHs was a result of a combination of CO and N2. The effect of different volume ratios of CO/N2 on the formation of SWNHs was examined and a mechanism for the formation of SWNHs is proposed.4. Graphene-Ag nanocomposite material was synthesized through the ultrasonic method. In the experimental process, Ag(NO3) and ethylene glycol act as the Ag source and the solvent respectively. The product was characterized by transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy.5. Graphene-CuO nanocomposite was synthesized by a simple wet chemical approach. Using Cu(CH3COO)2 as the starting material, CuO was synthesized and loaded on the graphene sheets through the reaction with NH3·H2O in alkaline system. Transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and Thermogravimetric analysis were employed to characterize the as-prepared sample. The detailed investigations revealed that the nanoparticles, which loaded on the graphene sheets, were pure CuO with the size of 4～10 nm and possessed a monoclinic structure.6. The graphene-supported Pd catalyst was synthesized using the graphene-Pd salt as precursor. Transmission electron microscopy and powder X-ray diffraction analysis indicated the Pd nanoparticles, which supported on the surface of the graphene sheets possessed a face-centered cubic structure and with the size of 4～8 nm. The Suzuki reaction was employed to analyze the catalytic activity of the graphene-supported Pd catalyst. HPLC analysis indicated that the yield of biphenyl was 97% when the reaction only lasted 10 min. The graphene sheets were great support for ligand-free Pd catalyst.