RESUMO
The initial nucleation of gold clusters Aun (n = 1-5) on TiO2 rutile (110) reduced surface is studied using density functional theory and a full-potential augmented-plane-wave method implemented in the WIEN2k code. The first two gold atoms remained tied to the surface with a bond length similar to those belonging to other well-known related materials, while the other gold atoms do not spread over the surface; they preferred to form a new layer. The occurrence of relativistic effects produced a preferential triangle geometry for Au3 and a combination of triangular units for Au4 and Au5 . The Au-Au average distance increased from n = 2 to n = 5, indicating an expansion with a tendency to the bond distance found in the bulk. We are reporting an early 2Dâ3D transition of small folding, from Au3 âAu4 , followed by an Au4 âAu5 transition of evident 3D character.
RESUMO
We have performed a Density Functional study of the CO adsorption in B-doped, N-doped and BN-co-doped graphene considering a coronene based model in order to estimate the applications of this systems as CO-sensor. Different monosubstituted, disubstituted and trisubstituted alternatives of combining these two heteroatoms in a substitutional chemical doping and the influence of the relative positions of the heteroatoms are analyzed. In this study, the stability selectivity for CO adsorption and the change in the electric properties for the presence of this molecule, have been evaluated through the calculation of binding energy, CO-adsorption's energy and the gap HOMO-LUMO change due to CO adsorption. The results indicated that, even though all the configurations were stables and was confirmed a CO physical adsorption in all of them, the relative positions of Nitrogen and Boron gave different stabilities and different responses to the CO adsorption. Since monosubstituted Boron-coronene was the second in stability respect to pristine coronene, showed the highest CO adsorption energy and was also the second highest ∆(∆HOMO-LUMO) value, this structure could be potentially a good CO-sensor.