INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Density Functional Study of Curvature Effects on Carbon Nanotube Unzipping
Autor/es:
GUILLERMINA LETICIA LUQUE; MARIANA ISABEL ROJAS; EZEQUIEL PEDRO MARCOS LEIVA
Lugar:
Washington
Reunión:
Congreso; 11th Spring Meeting of the International Society of Electrochemistry; 2012
Institución organizadora:
International Society of Electrochemistry
Resumen:
Density Functional Study of Curvature Effects on Carbon Nanotube Unzipping G.L. Luque, M.I. Rojas, E.P.M. Leiva INFIQC, Departamento de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina. e-mail: eleiva@fcq.unc.edu.ar Graphene nanoribbons (GNRs) are promising materials for a wide range of applications, due to its unique conductive, catalytic and biocompatible properties, which make them very attractive as an alternative to carbon nanotubes (CNTs). One way of obtaining this material is from CNTs. Kosynkin [1], by means of a chemical treatment with a solution of potassium permanganate in acid medium, obtained GNRs from longitudinal opening of multi-walled CNTs. This procedure offers the possibility of producing at large-scale GNRs of controlled width, which are of interest because their electric properties vary with their width. The aim of the present work is to contribute to the understanding of the unzipping mechanism of CNTs, to yield GNRs of zig-zag edges by means of quantum mechanical calculations based on Density Functional Theory (DFT), considering the role played by the radius of the CNT. With this purpose, we use the SIESTA computer code [2]. We consider a set of arm-chair CNTs of different radii, as well as corrugated sheets which emulate the curvature of CNT of larger radii. This approach was found useful to reduce the number of atoms and so the computational cost. Thus, we could study the properties of a wide range of nanotube radii involving only 80 carbon atoms in the calculations. The minimum energy configuration was obtained with the conjugate gradient (CG) technique. The minimum energy path (MEP) for the oxidation reaction was undertaken using the Nudged Elastic Band method (NEB) [3]. This is a very useful calculation method that allows obtaining the MEP of an elementary step with the only assumption of its initial and final states. The charges on the different atoms were evaluated by means of the Mulliken population analysis. It was found that permanganate adsorption energies become more negative with increasing curvature of the surface. This favors the energetics of the oxidative reaction, since for smaller radii the reaction of the CNTs becomes spontaneous, leading to diona formation and the generation of  a hole in the CNT. As the unzipping process goes on, a second permanganate group is adsorbed in the C-C bond adjacent to the hole, leading to longitudinal unzipping and yielding nanoribbons of zig-zag edges. [1] D. V. Kosynkin, A.L. Higginbotham, A. Sinitskii, J. R. Lomeda, A. Dimiev, B.K. Price, J.M. Tour, Nature 458 (2009) 872. [2] J. M. Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón, D. Sánchez-Portal, J. Phys.: Condens. Matter 14 (2002) 2745. [3] G. Henkelman, B.P. Uberuaga, H. Jonsson, J. Chem. Phys. 113 (2000) 9901.