A DFT study of chemical functionalization of graphene sheet by carboxyl groups on stone-wales defects

GUILLERMINA LETICIA LUQUE; MARIANA ISABEL ROJAS; EZEQUIEL PEDRO MARCOS LEIVA

Beijin

Congreso; 60th Meeting of the International Society of Electrochemistry; 2009

International Society of Electrochemistry

A DFT study of chemical functionalization of graphene sheets by carboxyl groups on Stone-Wales defects   E.P.M. Leiva, M.I. Rojas, G.L. Luque Unidad de Matemática y Física, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina. mrojas@fcq.unc.edu.ar   The progress in the synthesis of novel carbonaceous compounds has facilitated the study of their properties and applications. Nowadays, they are employed in the construction of electrodes and biosensors. In order to manufacture the biosensor, it is necessary an acidic treatment to solubilize them because the nanotubes are arranged in bundles. The strong acidic medium produces open ends and sidewall defects on them and some carboxyl (COOH) groups are also adsorbed on the defects. The chemical functionalization of carbon nanotubes with carboxyl groups modify their physical and chemical properties [1], so it is of technological importance to understand how these properties change. For example, the hydrogen peroxide oxide-reduction reaction at nanotubes is important in the development of glucose biosensors because it allows glucose quantification [2]. In this work we attempt to contribute to the understanding of the behaviour of carboxyl group adsorbed on a Stone-Wales (SW) defect by means of density functional calculations. SW defects are common sidewall defects on nanotubes. Since the nanotubes are graphene sheets rolled up into a compact tube of finite diameter, we decided to work in a first approach with a graphene sheet because the system can be represented with a small number of atoms and so has lower computational requirements. The graphene sheet is modified by SW defects with carboxyl groups adsorbed on them. For this system, we also studied the adsorption energy of hydrogen peroxide close to the carboxyl group. The local minima where found through the conjugate gradient (CG) technique, employing Density Functional Theory (DFT) calculations with spin polarization (sp) as implemented in SIESTA [4]. In order to study the minimum energy path for the present reaction we employed the nudged elastic band method (NEB) [3].   [1] C.Wang, G. Zhou, H. Lui, J. W,Y. Qiu, B.Gu, W. Duan, J. Phys. Chem. B 110 10266-10271 (2006). [2] P. Du, B. Zhou, C. Cai, J. Electoanal. Chem. 614 149-156 (2008). [3] G. Henkelman, B.P. Uberuaga, H. Jonsson, J. Chem. Phys. 113 (2000) 9901-04.   G. Henkelman, H. Jonsson, J. Chem. Phys. 113 (2000) 9978-85. [4] J. M. Soler, E. Artacho, J. D. Gale, A. García, J. Junquera, P. Ordejón, D. Sánchez-Portal, J. Phys.: Condens. Matter 14 2745 (2002).