RESUMO
In this research, we perform a theoretical interpretation of molecular and electronic properties of reduced graphene oxide (rGO) nanoflakes through the density functional theory. Here, two pristine graphene nanoflake systems were passivated by hydrogen atoms at their edges, armchair (C58H20) and zigzag (C54H20); besides, we implemented 12 rGO systems with a range of low oxide coverage (1, 3, and 4%). Computational calculations were carried out employing the functional hybrid B3LYP and the basis 6-31G(d, p) and 6-311G(d, p) levels of theory. We brought the proposed molecular structures to a stable minimum. We determined the global reactivity descriptors through chemical potential, hardness, softness, and index of electrophilicity. Besides, the maps of electrostatic potential were generated. We found that the hydroxyl and epoxy functional groups dope the graphene molecule in p-type and n-type forms, respectively. In addition, we could attribute the increases of the oxide coverage and the chemical potential to the softness of the molecule. These results suggest that structures with this type of doping can help in developing advanced electronics of sensors and devices.
RESUMO
We report here on the development of composite thick films exhibiting hybrid superconducting and ferromagnetic properties, produced through a low-cost, fast, and versatile process. These films were made of high Tc cuprate superconductor Bi2Sr2(Ca,Y)2Cu3O10 (with Y:Ca ratio of 5%) and ferromagnetic perovskite La2/3Ba1/3MnO3, synthesized by melting-quenching annealing process on a MgO substrate. Curie temperature for La2/3Ba1/3MnO3 was determined (~336 K ) by magnetic field assisted thermogravimetric analysis (TGA), while superconducting behavior of Bi2Sr2(Ca,Y)2Cu3O10/MgO films was observed through temperature-dependent resistance measurements. Superconducting features in our hybrid compound were corroborated by temperature-dependent resistivity and magnetic susceptibility.