Estudo estrutural e eletrônico da influência de dopantes em coronenos funcionalizados

Abstract

Recently, graphene oxide (GO) has become a material of great physical and technological interest and not only an intermediate material in the synthesis of graphene, but also as a product for direct applications. In an attempt to make GO closer to graphene, structurally and technologically speaking, the material undergoes a process of reduction of adhered oxygenated functional groups. Howe-ver, this reduction process does not completely remove the functional groups, and this material which is not completely free of oxygen-based groups, is called redu-ced graphene oxide (rGO). Over the past few years, RGO has become the target of research and many scientific and technological applications, such as organic electronic devices such as light-emitting diodes (OLEDs), solar cells, and many others. To make this material even more interesting to the area of organic elec-tronics, we propose the doping of our reduced graphene oxide molecules (rGO m) with boron, nitrogen, silicon aluminium, phosphorus, gallium, germanium and arsenic, one at a time and in a substitute way. Our goal is to make our material become a better conductor, maintaining or improving its transparency, thinking of using this material as electrodes in organic devices. In this work, we aim to study our reduced graphene oxide molecules (rGOm) in their structural and electronic aspects, using semi-empirical and ab initio methods at the DFT level, implemented in the GAMESS and MOPAC programs. We used as RGO models structures containing 42, 84 and 154 atoms derived from the coronon molecule with addition of three oxygenated functional groups: hidroxyl, carboxyl and epoxy. We begin the work by making a conformational search of the structure of our rGOm including each oxygenated functional group attached to the carbon atoms of the coronenes. We study the rGOm along with doping, replacing carbons in the structure with the following atoms: nitrogen (N), boron (B), phosphorus (P), silicon (Si), aluminium (Al), arsenic, germanium (Ge) and gallium (Ga). We replace one atom of the carbon sheet each time. We analyzed the energy gap between the border electronic states of the material in order to find both the site with the lowest total energy and the site with the least gap value. We performed the energy calculations and gap value of the above-mentioned dops at different levels of methods, we used both semi-empirical methods (PM3, PM6) and DFT (B3LYP, based on 6-31G), we also compared different types of approximations (UHF and RHF) in order to know if these were compatible with each other comparing total energy, gap and geometry. Finally, one of the main results was the doping of rGOm with aluminium. Aluminium when placed at some specific sites promotes the approach of border orbitals by reducing the gap, making aluminium-doped rGOm a material with a propensity for better electrical conduction than rGOm without doping, which increases the interest in using this material for organic electronics.