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Journal of Nanotechnology
Volume 2012, Article ID 780815, 6 pages
http://dx.doi.org/10.1155/2012/780815
Research Article

Theoretical Investigation on the Solubilization in Water of Functionalized Single-Wall Carbon Nanotubes

1Physics Department, De La Salle University-Manila, Taft Avenue, Manila 1004, Philippines
2Physics Department, Mapúa Institute of Technology, Muralla Street, Intramuros, Manila 1002, Philippines

Received 14 July 2011; Revised 28 August 2011; Accepted 5 September 2011

Academic Editor: Lifeng Dong

Copyright © 2012 Michael Mananghaya et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An important technique to increase the solubility and reactivity of carbon nanotube is through functionalization. In this study, the effects of functionalization of some single-walled carbon nanotubes (SWCNTs) were investigated with the aid of density functional theory. The SWCNT model used in the study consists of a finite, (5, 0) zigzag nanotube segment containing 60 C atoms with hydrogen atoms added to the dangling bonds of the perimeter carbons. There are three water-dispersible SWCNTs used in this study that were functionalized with (a) formic acid, as a model of carboxylic acid, (b) isophthalic acid, as a model aromatic dicarboxylic acid, and (c) benzenesulfonic acid, as a model aromatic sulfonic acid. Binding energies of the organic radicals to the nanotubes are calculated, as well as the HOMO-LUMO gaps and dipole moments of both nanotubes and functionalized nanotubes. Binding was found out to be thermodynamically favorable. The functionalization increases the electrical dipole moments and results in an enhancement in the solubility of the nanotubes in water manifested through favorable changes in the free energies of solvation. This should lower the toxicity of nanotubes and improve their biocompatibility.