Abstract
Single walled carbon nanotubes (SWCNTs) are attractive in the nanotechnology industry where they find applications in the field of pharmacy and medicine due to high surface area capable of transporting drugs and vaccines to active sites; for fabrication of energy storing devices due to excellent electrical conductivity and accessible pore sizes; in transport for the fabrication of strong and lightweight vehicle and aircraft parts and in composite materials to enhance physical and chemical properties such as toughness, durability, conductivity and strength. The most efficient and cost effective method of obtaining these precious materials is the Chemical Vapour Deposition (CVD), however, obtaining SWCNTs of desired electronic type via this method, has remained a global challenge for over 20 years. This has limited the availability of these products in the global research and technological industries, contributing to the problem of lack of raw materials to sustain them. In this report, metallic SWCNTs (11, 8) are selectively synthesized via chemical vapor deposition (CVD) method, by the pyrolysis of C<sub>6</sub>H<sub>14</sub>/N<sub>2</sub> feedstock on Fe<sub>2</sub>O<sub>3</sub>/Al<sub>2</sub>O<sub>3</sub> catalyst matrix. Catalyst design and preparation was achieved by correlating the numerical magnitudes of chiral index (n, m) of the desired SWCNTs with mole fractions of metal/support, respectively. Field emission scanning electron microscopy analysis reveals densely entangled tubular bundles, while high resolution transmission electron microscopy confirms rigid arrangements of SWCNTs in the bundles. Values of the radial breathing modes, diameter and energy band gaps of the sample obtained from Raman analysis conforms to that of SWCNTs (11, 8), established via Extended Tight Binding (ETB) model. Outcome of this report suggested that our catalyst design and preparation may help alleviate the stated global challenge.
Highlights
Single walled carbon nanotubes (SWCNTs) are generally formed by rolling a single graphene sheet into a seamless cylinder, which makes it very difficult and expensive to produce for commercial application [1]
Modern research reports on selective synthesis of single walled carbon nanotubes (SWCNTs) via Chemical Vapor Deposition (CVD) method using catalysts were based on the in situ epitaxial growth model, which attributed the dependence of SWCNT growth control on the crystal size or Danlami Umar Zuru et al.: Selective Synthesis and Characterization of Single Walled Carbon Nanotubes (11, 8)
We have proposed and reported both theoretical and experimental models for selective synthesis of SWCNTs [5]
Summary
Single walled carbon nanotubes (SWCNTs) are generally formed by rolling a single graphene sheet into a seamless cylinder, which makes it very difficult and expensive to produce for commercial application [1] These materials are reported to exhibit metallic or semiconducting character, depending on the orientation of a chiral vector composing of two chiral index (n, m), which signifies a unique molecule of SWCNT and determines the thermal, optical, mechanical, electronic and magnetic properties of the material [2]. The feasibility of obtaining nano particles of same sizes, shape and high thermal stability are the limiting factors that undermine the effectiveness and efficiency of this method This has necessitated the need for new innovative approaches that are more simple and cost effective, which may be used to selectively grow SWCNTs of desired chirality [4]. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM) analyses were performed to compliment the Raman analysis
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