Curvature, Hybridization and Contamination of Carbon Nanostructures Analysis Using Electron Microscopy and XANES Spectroscopy

Abstract

The ability to control the nanoscale shape of carbon nanostructures during wide-scale synthesis process is an essential goal in research for Nanotechnology applications. This paper reports a significant progress toward that goal. Variant CVD has been used for the synthesis of the samples studied. Curvature, hybridization and contamination are analyzed using Electron Microscopies and XANES spectroscopy. The investigations of the results show that four types of samples are obtained. They are carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanowalls (CNWs) and carbon nanoparticles (CNPs). Almost all of them have catalyst nanoparticles (metal) on top in top growth model or on base in base growth model and encapsulated or adsorbed in sidewalls. The orientation of tubular carbon nanomaterials depends on operating parameters. They are classified in three groups: the poorly oriented, the medium oriented and the highly oriented. Their contamination (radicals, atoms and molecules) and hybridization are intrinsically related to the curvature of their graphene layers. XANES spectroscopy allows quantitative characterization of nanomaterials.

Adsorption and desorption phenomena on thermally annealed multi-walled carbon nanotubes by XANES study

“…The XANES spectra can be divided into three main regions as described in Ref. [18]. The first region located at 285.5 eV corresponds to peak A.…”

“…2) is attributed to the potassium element which appears accidentally during the synthesis process. [18] Tables 1 and 2 show the intrinsic and non-intrinsic adsorbates with their corresponding intensities and final states in the Brilouin zone, for annealed and un-annealed samples contaminated with potassium, respectively. Each adsorbate corresponds to a specific electronic transition which is assigned to peaks A , A , A , and A or P, P , and P .…”

“…[17] The experimental details and the CCVD growth process of our studied MWCNTs have been fully described elsewhere. [7,18] 3.…”

X-ray absorption near edge spectroscopy of the electronic structure of potassium adsorbed single walled carbon nanotubes

“…XANES measurements were performed at Carbon K-edge on the SWCNTs in the SACEMOR beamline [17] at the Laboratoire pour l′ Utilisation du Rayonnement Electromagnétique (LURE, ORSAY, France). A high-energy TGM monochromator with a resolution greater than 0.2 eV at the carbon K-edge was used.…”