Structural Analysis of Single Wall Carbon Nanotubes Exposed to Oxidation and Reduction Conditions in the Course of Gamma Irradiation Svetlana P. Jovanovic ́ ,* ,† Zoran M. Markovic ́ , † Dus ̌ ka N. Kleut, † Miroslav D. Dramic ́ anin, † Ivanka D. Holclajtner-Antunovic ́ , ‡ Momir S. Milosavljevic ́ , † Valeria La Parola, § Zois Syrgiannis, ∥ and Biljana M. Todorovic ́ Markovic ́ † † Vinč a Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade, Serbia ‡ Faculty of Physical Chemistry, University of Belgrade, P.O. Box 47, 11158 Belgrade, Serbia § Istituto per lo Studio dei Materiali Nanostrutturati (ISMN-CNR), I-90146 Palermo, Italy ∥ Department of Chemical and Pharmaceutical Sciences, INSTM, Center of Excellence for Nanostructured Materials (CENMAT), University of Trieste, 34127 Trieste, Italy * S Supporting Information ABSTRACT: Single wall carbon nanotubes (SWCNTs) were exposed to gamma irradiation in oxidative (H 2 O, NH 4 OH) and reductive (H 2 O and NH 4 OH both mixed with isopropyl alcohol) media. The structure has been investigated with microscopic (atomic force and transmission electron microscopy), spectroscopic (Raman, X-ray photoelectron, and FTIR spectroscopy) techniques, and by thermogravimetric analysis. Reductive media offer the possibility for green chemistry reduction of SWCNTs: after gamma irradiation, SWCNTs lose C−O bonds. Furthermore, irradiation in these media increases the fraction of sp 2 hybridized carbon atoms in structure of SWCNTs and prevents their amorphization. The presence of isopropyl alcohol in reductive media contributed to the preservation of structure’s unity. On the other hand, the most effective procedure is the one that occurs in oxidative media and yields in debundled, cut, and annihilated carbon nanotubes. The smaller diameter and the metallic ones are the most affected. 1. INTRODUCTION Because of their unique properties, single walled carbon nanotubes (SWCNTs) have drawn scientist’s great attention in diverse research fields such as physics, chemistry, biology, medicine, etc. 1−7 High aspect ratio and hollow structure of SWCNTs make them a promising agent for drug delivery, 8 sensing applications, 9,10 nanosorbents for removal of contam- inants in drinking water, 11 agents in a photothermal therapy, etc. 12−14 Major obstacles in the processing of SWCNTs are the intrinsic solubility in any type of solvent and the fact that the production techniques yield a mixture in terms of length and diameter. Their chemical functionalization is recognized as the key to overcome this obstacle. 3 Apart from the conventional methods regarding the chemical transformation of the carbon nanotubes, nonstandard techniques such as gamma irradiation have recently appeared in the literature. 15,16 Gamma irradiation seems to have found wide application in the functionalization of multi walled carbon nanotubes (MWCNTs). 17,18 A linear relationship between the amount of gamma irradiation and the introduction of functional moieties and defects on MWCNTs has been reported. Taking advantage of these findings, several groups have been able to functionalize the sidewalls of MWCNT with polymer chains, by simply applying gamma rays to monomer−MWCNT mixtures. 19,20 We have also established that gamma irradiation is a very useful pretreatment in the process of noncovalent functionalization of SWCNTs with DNA. 21 Hulman et al. have shown that gamma irradiation creates defects and destroys the coherence motion of C atoms on the nanotube circumference. 22 Moreover, our previous research has shown that an irradiation dose of 100 kGy can yield to the decrease of the SWCNT length of about 50%. 23 Except for the functionalization and the cutting effects, certain media for gamma irradiation can cause the decrease of interwall distance in MWCNT structure and the improvement of their graphitic order or, on the contrary, the increase of the interwall distance of MWCNTs and the structure disorder. 24,25 Li et al. have shown that when the irradiation dose exceeds 200 kGy, the defect dynamics is changed and the nanotubes are annealed. 26 In this work, SWCNTs were gamma irradiated in two different types of media: with and without the presence of isopropyl alcohol (IPA). IPA was added as a quencher of • OH Received: March 18, 2014 Revised: May 29, 2014 Article pubs.acs.org/JPCC © XXXX American Chemical Society A dx.doi.org/10.1021/jp502685n | J. Phys. Chem. C XXXX, XXX, XXX−XXX