Estudo teórico da adsorção de monômeros derivados de tiofeno em grafeno

Abstract

Graphene is an inorganic semiconductor with interesting physical and chemical properties. It has been consolidated as an important functional material for applications in electronic and optoelectronic devices. In other way, organic semiconductors have received prominence due to advantages such as chemical and mechanical flexibility, compatibility with plastic substances and relatively low cost. In this context, thiophene derivatives develop a crucial role. Thiophene is an important aromatic heterocyclic molecule with a great variability of potential substituent groups, which make its derivatives excellent active components for electronic and optoelectronic organic devices. According to the literature, hybrid inorganic-organic semiconductors present improved characteristics compared to the isolated materials. Thus, in order to study a hybrid inorganic-organic semiconductor model by first-principles calculations, it was considered simultaneous adsorption of thiophene pairs, both unsubstituted or both substituted, on a single graphene sheet. For derivatives, it was used a thiophene monomer functionalized with a charge-releasing group (N(CH3)2) and a monomer with a charge-withdrawing group (NO2). First-principles calculations were performed using density functional theory (DFT), as implemented in the VASP package. The wave functions and pseudopotential were generated within the projector augmented wave (PAW). Exchange-correlation effects and van der Waals (vdW) forces were treated in the generalized gradient approximation (GGA) by using the optB86b-vdW functional. According to the results, there is no significant change on geometric properties when the thiophene and graphene systems are isolated or adsorbed. The differential charge density (DCD) analysis showed a small increase of the electron density between the adsorbed systems. Lastly, the density of states (DOS) and the band structures showed that the adsorption does not significantly affect the electronic structure of the graphene, indicating a very weak physical adsorption.