Fernando Sato

Triple Doped Monolayer Graphene with Boron, Nitrogen, Aluminum, Silicon, Phosphorus and Sulfur

The structure, stability, electronic properties and chemical reactivity of X/B/N triple-doped graphene (TDG) systems (X=Al, Si, P, S) are investigated by means of periodic density functional calculations. In the studied TDGs the dopant atoms prefer to be bonded to one another instead of separated. In general, the XNB pattern is preferred, with the exception of sulfur, which favors the SBN motif. The introduction of a third dopant results in a negligible decrease of the cohesive energies with respect to the dual-doped graphene (DDG) counterparts. Thus, it is expect that these systems can be prepared soon. For SiNB TDG, the introduction of the B dopant reduces the gap opening at the K point and restores the Dirac cones that are destroyed in SiN DDG. On the contrary, for PNB TDG, the bandgap is increased with respect to PN DDG, probably because the introduction of B weakens the PN bonding, and thus the electronic structure is rather similar to that of P-doped graphene. Finally, with regard to the reactivity of the TDGs, for AlNB, PNB, and SNB the carbon atoms are more reactive than in their AlN, PN, and SN DDG counterparts. On the contrary, the reactivity of SiNB is lower than that of SiN DDG. Therefore, to increase the reactivity of graphene, Al, P, and S should be combined with BN motifs.

Structural and vibrational study of graphene oxide via coronene based models: theoretical and experimental results

We use the Coronene (C24H12), a simple and finite molecule, to make a model to study the spectroscopic and structural alterations generated by oxygenated groups in graphene oxide (GO). Based on the Lerf–Klinowski model, we chose the hydroxyl [OH−], the carboxyl [COOH−] and the epoxy [the ring C2O inside the molecule] as our radicals of interest and study their collective and isolated effects. We perform geometry optimization, vibrational IR (via AM1 and DFT-B3LYP) and Raman spectra (via DFT-B3LYP) of a series of functionalized coronene molecules. As results, we obtain some useful data for the analysis of IR and Raman spectra of GO, which facilitate the understanding and identification of the peaks found in the experiment. Finally, we suggest a new model to study GO, producing an accurate signature when compared to our experimental data. Such molecule shows in more details of the structural effects caused by functionalization when compared to experimental data.

Rectangular and hexagonal doping of graphene with B, N, and O: a DFT study

First-principles density functional theory (DFT) calculations were carried out to investigate the rectangular and hexagonal doping of graphene with B, N, and O. In both of these configurations, though the dopants are incorporated at the same sublattices sites (A or B), the calculated values of the band gaps are very different with nearly the same amount of cohesive energies. In this study, the highest value of the band gap (1.68 eV) is achieved when a maximum of 4 O atoms are substituted at hexagonal positions, resulting in a lower cohesive energy relative to that of the other studied systems. Hexagonal doping with 3 O atoms is significantly more efficient in terms of opening the band gap and improving the structural stability than the rectangular doping with 4 O atoms. Our results show the opportunity to induce a higher band gap values having a smaller concentration of dopants, with better structural stabilities.

Enhancement of Nonlinear Optical Properties of Graphene Oxide-based Structures: Push-Pull Models

Through DFT calculations and the finite field approach, it is possible to identify some structural and electronic aspects that could lead to enhancement of the nonlinear optical (NLO) molecular properties of graphene oxide and its derivatives. We proposed a molecular design scheme of NLO response based on push–pull structures. The best NLO models contain –COOH at their edges, acting as electron acceptors, and –OH in the basal plane, acting as an electron donor.

Theoretical study of nonlinear optical properties of cobalt bis (dicarbollide) derivatives: the effect of substituents

In the present work, molecular first-order hyperpolarizability (

Ground state study of the thin ferromagnetic nano-islands for artificial spin ice arrays

beta _{mathrm{tot}}

van der Waals potential barrier for cobaltocene encapsulation into single-walled carbon nanotubes: classical molecular dynamics and ab initio study

βtot) and dipole moment (d) are obtained at B3LYP/6–31G(d,p) level of theory by coupled perturbed Hartree–Fock method within the static approach. The investigated molecules are a series of substituted cobalt bis (dicarbollide) derivatives: Hydrogens bonded to the two carbon atoms are replaced by acceptor and donor electron substituents. Correlations between the Hammett electronic parameters of the substituents and the molecular properties are tested. Among them, the named push–pull compounds produced the largest calculated values of