Thiolation of carbon nanotubes and sidewall functionalization
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Jiri Cech Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany
Donghui Zhang New Mexico State University, Department of Physics, and Department of Chemistry and Biochemistry, Las Cruces, New Mexico 88003-8001
James L. Dewald New Mexico State University, Department of Physics, Las Cruces, New Mexico 88003-8001
Aditya Avadhanula and Madhuvanthi Kandadai New Mexico State University, Department of Physics, and Department of Chemical Engineering, Las Cruces, New Mexico 88003-8001
Siegmar Roth Max-Planck-Institute for Solid State Research, 70569 Stuttgart, Germany (Received 6 September 2005; accepted 17 January 2006)
We have used transmission electron microscopy to observe the structural changes that have occurred in multi-walled carbon nanotubes (MWCNTs) because of acid treatment. After a thiolation reaction of the acid-treated MWCNTs using P4S10 in refluxing toluene, we have also used electron energy loss spectroscopy to characterize the changes on the nanotubes from sidewall functionalization. We have determined that the sulfur content bonded to the nanotubes is 0.6% in terms of the atomic content of the samples. Raman spectroscopy was used to examine the vibrational changes that occurred to the nanotubes as well as identifying new vibrational modes around 500 cm−1 characteristic of carbon-sulfur bonds.
I. INTRODUCTION
Since the initial discovery of carbon nanotubes (CNTs) by Iijima1 in 1990s, CNTs have been shown to possess many unique properties such as high mechanical strength,2 good electrical and thermal conductivity,3,4 and high thermal stability.4,5 Because of these unique properties, many technical applications have been alluded to that include field emission guns,6,7 fillers for polymer composites,8 and various nanoelectronic devices.9–11 To successfully integrate CNTs into various applications, modification of the CNT surfaces by molecular self-assembly or chemical functionalization is normally required to maximize the effect of CNTs and enhance the overall performance. Introduction of other molecular structures such as organic dyes,12–14 metal nanoparticles,15–18 and covalently bonded side-groups19 offers the possibility of developing new carbon-based materials with very specifically designed constructs and applications.9 For instance, boron-doped CNTs20,21 offer
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0125 1012 J. Mater. Res., Vol. 21, No. 4, Apr 2006 http://journals.cambridge.org Downloaded: 12 Mar 2015
alternative uses in terms of carbon-based morphologies and optical and electronic properties.22,23 This introduces the prospect that altered tubular constituents could yield a wealth of new materials for applications across the vista of science, from biological constructs24 to actual nanoassembled semiconductors.9,25 The key to working with CNTs is to functionalize the surface, whether at the tip19,26–29 or the body,19,27,30–36 and to use those functional groups to produce our desired nanomaterials. Much effort has been
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