M. Salazar Villanueva

Possibility of a magnetic [BN fullerene:B6 cluster]− nanocomposite as a vehicle for the delivery of dapsone

Functionalization of a boron nitride fullerene (BNF−), having homo-nuclear nitrogen bonds, with a magnetic octahedral boron cluster (B6−) is addressed in this work by means of density functional theory. Adsorption of the antibiotic dapsone molecule on the magnetic [BNF:B6]− nanocomposite is also studied. There is a geometric transition of the B6− cluster, from the octahedral to pyramidal pentagonal form, when it is adsorbed on the BN fullerene. The adsorption energy (−8.52 eV) reveals a strong interaction between them. The [BNF:B6]− nanocomposite exhibits electronic behavior like a conductor, intrinsic magnetism (1.0 μB), high polarity, and low chemical reactivity, suggesting that this functionalized fullerene is a good candidate for use as a nano-vehicle for drug delivery. Further, these quantum descriptors remain invariant when such magnetic systems ([BN]− fullerene and [BNF:B6]− nanocomposite) interact with a dapsone molecule. Additionally, low chemisorption (Ead = −0.71 and −0.75 eV, respectively) is achieved; therefore, they have practically the same technological applications as the pristine cases.

Ideal strength on clusters from first principles: the Ti13 case

The mechanical behavior of a Ti(13) cluster, based on total energy mechanical quantum calculations is studied. The cluster geometry has been optimized and good agreement with previous reports has been found. Axial strain is applied along one of the principal axes and the changes on the energetic and vibrational properties of the system are followed. To characterize the cluster stability as a function of strain, vibrational frequencies and total energy have been calculated, to obtain the cluster maximum load tolerance for compression (C) and tensile (T). If the maximum load is defined through a vibrational instability, it happens to be two and half, and three times larger than when the maximum total energy is considered (C and T respectively). As a result of the induced strain along of the C(5) symmetry element, the cluster changes its point group symmetry from I(h) to D(5d), with an energy difference of 1.17 eV (for compression) and 0.33 eV (for tension) with respect to the ground state geometry. The electronic changes are also characterized, as function of the strain, by following the modifications of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO) and changes on the total atomic population.

In silico studies of the magnetic octahedral B6 − cluster—nitric oxide and [B6 −–NO]−–O2 interactions

All-electron calculations based on density functional theory (DFT) for B6−, [B6–NO]−, and [B6–NO–O2]− were done in gas and aqueous phases, in order to validate their feasibility as nanovehicle for drug delivery. The quantum descriptors reveal that the octahedral B6− cluster shows semiconductor and magnetic behavior, low chemical reactivity, and zero polarity. On the other hand, bonding of the NO molecule with the B6− cluster produces a complex where the physic-chemical properties do not suffer drastic alterations, except that the polarity increases and a reduction of the work function takes place. These results suggest that the new [B6–NO]− cluster can be applied for some biological function. Furthermore, the interaction between [B6–NO]− and O2 generates a geometric transition from octahedron to pentagonal bipyramid, where the NO molecule remains bonded and the O2 molecule is activated in such superoxide cluster.

Importance of the electrolyte in obtaining porous silicon and how it modifies the optical and structural proprieties: optical and microstructural investigation

The effect of using different electrolytes in the physical and optical properties of porous silicon was studied. To do this porous silicon (PS) samples photoluminescent in the visible range from (100) oriented n-type crystalline silicon prepared by anodic etching were obtained. The first electrolyte was composed of a mixture of hydrofluoric acid (HF) and ethanol (CH3-CH2-OH) in a ratio of 1 : 2, respectively. The second was composed of hydrofluoric acid (HF), ethanol (CH3-CH2-OH), and hydrogen peroxide (H2O2) in a ratio of 1 : 1 : 2, respectively. Raman scattering, photoluminescence (PL), gravimetry, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) measurements on the PSL were carried out. Raman scattering showed that the disorder in the samples obtained with H2O2 is greater than in the samples obtained without this. The PL from PS increased in intensity with the incremental change in the anodization time and showed a blueshift. The blueshift of PL is consistent with the reduction in size of the silicon nanocrystallites. The sizes of nanocrystals were estimated to be 3.08, 2.6, and 2.28 nm. The gravimetric analysis showed that the porosity increased with the incorporation of H2O2. SEM images (morphological analysis) showed an incremental change in the quantity and in the porous size.

Adsorption and possible dissociation of glucose by the [BN fullerene-B 6 ] − magnetic nanocomposite. In silico studies

The adsorption, activation and possible dissociation of the glucose molecule on the magnetic [BN fullerene-B6]− system is performed by means of density functional theory calculations. Three models of magnetic nanocomposites were inspected: i) pristine BN fullerene, BN fullerene functionalized with a magnetic B6 cluster which generates two structures: ii) pyramidal (P) and iii) triangular (T). Chemical interactions of glucose appear for all these cases; however, for the BNF:B6(T)—glucose system, the interaction generates an effect of dissociation on glucose, due to the magnetic effects, since it has high spin multiplicity. The latter nanocomposite shows electronic behavior like-conductor and like-semi-conductor for the P and T geometries, respectively. Intrinsic magnetism associated to values of 1.0 magneton bohr (µB) for the pyramidal and 5.0 µB for the triangular structure, high polarity, and low-chemical reactivity are found for these systems. These interesting properties make these functionalized fullerenes a good option for being used as nano-vehicles for drug delivery. These quantum descriptors remain invariant when the [BN]−fullerene and [BNF:B6 (P) or (T)]− nanocomposites are interacting with the glucose molecule. According to the determined adsorption energy, chemisorption regimes occur in both the phases: gas and aqueous medium.

Plane Wave-Perturbative Method for Evaluating the Effective Speed of Sound in 1D Phononic Crystals

A method for calculating the effective sound velocities for a 1D phononic crystal is presented; it is valid when the lattice constant is much smaller than the acoustic wave length; therefore, the periodic medium could be regarded as a homogeneous one. The method is based on the expansion of the displacements field into plane waves, satisfying the Bloch theorem. The expansion allows us to obtain a wave equation for the amplitude of the macroscopic displacements field. From the form of this equation we identify the effective parameters, namely, the effective sound velocities for the transverse and longitudinal macroscopic displacements in the homogenized 1D phononic crystal. As a result, the explicit expressions for the effective sound velocities in terms of the parameters of isotropic inclusions in the unit cell are obtained: mass density and elastic moduli. These expressions are used for studying the dependence of the effective, transverse and longitudinal, sound velocities for a binary 1D phononic crystal upon the inclusion filling fraction. A particular case is presented for 1D phononic crystals composed of W-Al and Polyethylene-Si, extending for a case solid-fluid.