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Crystalline Graphene Nanoribbons with Atomically Smooth Edges via a Novel Physico- Chemical Route

Year: 2012 Volume: 6 Issue: 1 84 - 88 Pages

• Authors:
• A. Morelos-Gómez
• S. M. Vega-Díaz
• V. J. González
• F. Tristán-López
• R. Cruz-Silva
• K. Fujisawa
• H. Muramatsu
• T. Hayashi
• Xi Mi
• Yunfeng Shi
• H. Sakamoto
• F. Khoerunnisa
• K. Kaneko
• B. G. Sumpter
• Y.A. Kim
• V. Meunier
• M. Endo
• E. Muñoz-Sandoval
• M. Terrones

Abstract: A novel physico-chemical route to produce few layer graphene nanoribbons with atomically smooth edges is reported, via acid treatment (H2SO4:HNO3) followed by characteristic thermal shock processes involving extremely cold substances. Samples were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy. This method demonstrates the importance of having the nanotubes open ended for an efficient uniform unzipping along the nanotube axis. The average dimensions of these nanoribbons are approximately ca. 210 nm wide and consist of few layers, as observed by transmission electron microscopy. The produced nanoribbons exhibit different chiralities, as observed by high resolution transmission electron microscopy. This method is able to provide graphene nanoribbons with atomically smooth edges which could be used in various applications including sensors, gas adsorption materials, composite fillers, among others.

• Keywords:
• Carbon nanoribbons
• carbon nanotubes
• unzipping.

Structural and Electronic Characterization of Supported Ni and Au Catalysts used in Environment Protection Determined by XRD,XAS and XPS methods

Year: 2011 Volume: 5 Issue: 7 580 - 586 Pages

• Authors:
• N. Aldea
• V. Rednic
• F. Matei
• Tiandou Hu
• M. Neumann

Abstract: The nickel and gold nanoclusters as supported catalysts were analyzed by XAS, XRD and XPS in order to determine their local, global and electronic structure. The present study has pointed out a strong deformation of the local structure of the metal, due to its interaction with oxide supports. The average particle size, the mean squares of the microstrain, the particle size distribution and microstrain functions of the supported Ni and Au catalysts were determined by XRD method using Generalized Fermi Function for the X-ray line profiles approximation. Based on EXAFS analysis we consider that the local structure of the investigated systems is strongly distorted concerning the atomic number pairs. Metal-support interaction is confirmed by the shape changes of the probability densities of electron transitions: Ni K edge (1s → continuum and 2p), Au LIII-edge (2p3/2 → continuum, 6s, 6d5/2 and 6d3/2). XPS investigations confirm the metal-support interaction at their interface.

• Keywords:
• local and global structure
• metal-support interaction
• supported metal catalysts
• synchrotron radiation
• X-ray absorptionspectroscopy
• X-ray diffraction
• X-ray photoelectron spectroscopy.