In-silico study of the adsorption of H2, CO and CO2 chemical species on (TiO2)n n=15-20 clusters: The (TiO2)19 case as candidate promising.

In order to obtain an adsorption tendency of H2, CO and CO2 molecules on (TiO2)n n = 15-20 clusters, DFT calculations were carried out to evaluate the interaction among these systems. The (TiO2)19 cluster emerges as the best candidate to storage these chemical species. Then, two adsorption sites were considered to attach these molecules onto (TiO2)19 cluster: through of surface formed by i) titanium and ii) oxygen atoms, respectively. The adsorption energy values are more favored for case 1 than the case 2, due to short distances between titanium atom and these chemical species. In this sense, the larger values of chemisorption are related to great decreasing of values of vibrational modes for gases isolated respect to those bonded to bare cluster. In general, the values of electronic gap do not suffer drastic changes, however the HOMO iso-surfaces are displayed in different way for both cases, and LUMO is located at center of cluster for the whole set of systems analyzed in this study. The electronic transference occurs from chemical species toward atoms at adsorption site, in all systems. These results reveal that this (TiO2)19 cluster is good candidate to storage or sense different kind of gases; thereby, this system can be used as a hydrogen storage device for energy green applications.

Interactions of B12N12 fullerenes on graphene and boron nitride nanosheets: A DFT study.

In the search of nanomaterials to be used in drug delivery applications, Density Functional Theory calculations were implemented to study the interaction between graphene (G) and hexagonal boron nitride nanosheet (hBNN) with octahedral B12N12 fullerenes. These B12N12 fullerenes were considered in two cases: pristine and the modified one with boron-boron, nitrogen-nitrogen (tetragon) and boron-boron-boron (hexagon) homo-nuclear bonds. The whole systems were analyzed in the gas and aqueous phases. The results reveal for all these systems that the interaction is in the range of physisorption (Eads = from -0.03 to -0.37 eV) for both phases, limiting its functions as a vehicle. However, for the nano-composite: B12N12 fullerene modified and hBNNs, the values of average chemical reactivity and HOMO-LUMO gap decreased whereas the polarity was improved, thereby this combination of quantum descriptors lead them to be considered as potential vehicle for drug delivery.

Design of the magnetic homonuclear bonds boron nitride nanosheets using DFT methods.

Design and characterization of the structural, electronic, and magnetic properties of armchair boron-nitride, BN (B27N27H18), nanosheets were performed by means of density functional theory all-electron calculations. The HSEh1PBE-GGA method together with 6-31G(d) basis sets were used. Non-stoichiometric B30N24H18 and B24N30H18 compositions: rich in boron or nitrogen atoms, forming homonuclear B or N bonds, respectively, were chosen. The obtained results reveal that these BN nanosheets reach structural stability in the anionic form, where semiconductor and magnetic behaviors are promoted. Effectively, the HOMO-LUMO gap is of 2.03 and 2.39eV, respectively and the magnetic moments are of 1.0 magneton bohrs, coming from the boron atoms in both systems. The rich in boron nanosheets present high-polarity, either in the gas phase or embedded in aqueous mediums like water, as well as low chemical reactivity, signifying potential applicability in the transportation of pharmaceutical species in biological mediums. These systems are also promising for the design of electronic devices, because they possess low-work functions, mainly arising from the homonuclear boron or nitrogen bond formation.

Non-covalent functionalization of hexagonal boron nitride nanosheets with guanine.

Density functional theory (DFT) calculations were performed to analyze changes in the structural and electronic properties generated by the interaction of a single nucleobase group (guanine) with the surface of boron nitride nanosheets with hexagonal symmetry (hBNNs). Nanosheets in two contexts were tested: pristine sheets and with point defects (doped with carbon atoms). The criterion of energy minimum was used to find the ground state of the nine possible isomers generated by the hBNNs-guanine interaction. The phenomenon of physisorption is known to occur at values less than 1.0 eV; the adsorption energy results revealed that the preferential geometry was a parallel arrangement between the two partners, with van der Waals-type bonds generated for the hBNNs doped with two carbon atoms. This was the only energetically stable configuration, thus revealing a vibrational mode rather than imaginaries. Furthermore, the hBNNs/C-guanine system has a low value for work function, and therefore could be used in health applications such drug transport and delivery. The increased polarity values suggest that these nanosheets could be solubilized in common solvents used in experimental processes.

Armchair BN nanotubes--levothyroxine interactions: a molecular study.

The density functional theory has been applied to investigate the structural and electronic properties of single-wall boron nitride nanotubes (SW-BNNT) of (5,5) chirality, with surface and ends functionalized by the drug levothyroxine (C15H11NI4O4). The exchange-correlation energies have been modeled according to the Hamprecht-Cohen-Tozer-Handy functional within the generalized gradient approximation (HCTH-GGA) and a base function with double polarization has been used. The (5,5) BNNT-Levothyroxine structural optimization has been done considering the minimum energy criterion in nine possible atomic structures. Simulation results indicate that the preferential adsorption site (chemical adsorption) of the levothyroxine fragment is at the nanotube ends. The BNNT-Levothyroxine system polarity increases which indicates the possible dispersion and solubility both non-solvated and solvated in water. The BNNT-Levothyroxine solvated in water modifies its chemical reactivity which may allow the drug delivery within the biological systems. On the other hand, the decrease in the work function is important for the optoelectronic device design, which also makes these materials suitable to improve the field emission properties.