Current Physical Chemistry - Volume 3, Issue 4, 2013

Wurtzite-structured ZnS nanostructures have been synthesized by means of a microwave-solvothermal method at 140°C using three precursors (chloride, nitrate and acetate). Different techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements have been employed to characterize this material. The structure, surface morphology, chemical composition and optical properties were investigated as function of precursor. In order to complement experimental results, first principles calculations at DFT level were carried out in order to obtain the relative stability of the proposed intermediates along the formation mechanism.

Ba1-xZr0.8Y0.2O3-δ(x = 0, 0.025, 0.05 and 0.075) powders were successfully prepared via a combustion method. Coupled with La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF), LSCF-Ba1-xZr0.8Y0.2O3-δ composite powders were evaluated as potential cathode materials for proton-conducting solid oxide fuel cells (SOFCs). LSCF showed chemical compatibility with Ba1-xZr0.8Y0.2O3-δ powders up to 1000 °C. LSCF-Ba1-xZr0.8Y0.2O3-δ composite cathodes were painted on both sides of sintered BaZr0.8Y0.2O3-δ pellets, used as electrolytes, and fired at 1000 oC to form symmetrical cells. Electrochemical impedance spectroscopy results for symmetrical cells indicated that the A-site deficiency in BaZr0.8Y0.2O3-δ increased the polarization resistance for the composite cathode compared with the deficiency-free sample, and the larger the increase in the A-site deficiency, the larger the polarization resistance.

SrTiO3, SrTi0.99Nd0.01O3 and Sr0.99Nd0.01TiO3 thin films were synthesized by pulsed laser deposition at 700 °C on different substrates (silica, R-sapphire, (100) LaAlO3 and (100) MgO). The influence of Nd3+ substitution into the A and B sites of SrTiO3 perovskite on film growth was studied. The films were characterized by X-ray diffraction (–2, - and φ-scans), micro-Raman spectroscopy, UV–Vis spectroscopy and field-emission scanning electron microscopy. All of the films exhibited a (h00) orientation and high-quality epitaxial growth on LaAlO3. The films grown on MgO, with the exception of the SrTi0.99Nd0.01O3 film, also exhibited a (h00) orientation. The polycrystallinity of the SrTi0.99Nd0.01O3 film may be related to the increased lattice distortion when Ti4+ was replaced with Nd3+. A polycrystalline growth was observed for all of the films deposited on silica and R-sapphire, as expected. The Raman results showed that Nd doping led to an increase in the short-range disorder. The morphology strongly depended on the nature of the substrate and on Nd doping, specially in the case of SrTi0.99Nd0.01O3.

We have studied zinc oxide single-walled nanotubes and the effects of increasing the diameter of the nanotube and the size along its c-axis. The armchair and zigzag structures were calculated using the semiempirical AM1 and ab initio RHF/3-21G method. The Zn-O distance was optimized in order to search for the stable structure minimum energy. The structure of minimum energy for the dZn-O distance is used for the analysis of energy variation, gap (HOMO-LUMO) and charge values. Our results show that increasing the nanotube size the Zn-O distance tends to 1.96Å and 2.0Å for the armchair and zigzag nanotubes near the experimental bulk value, respectively.

We have investigated novel PIM-1 hybrid inhibitors in cancer using drug design and ADMET studies. Different modeling methods and medicinal chemistry strategies were used including isosteric replacement. We have worked with active inhibitors reported in the literature investigating pharmacophore models, physicochemical and pharmacokinetic properties. We have applied Lipinski's rule of five and synthetic accessibility. Flexible docking simulations were done using GOLD in order to predict the binding modes of the novel hybrids inside the PIM-1 active site. Our results suggest two candidates as promising novel PIM-1 inhibitors with good pharmacotherapeutic profiles for the fight against cancer.

A shift of the photoluminescence (PL) emission was observed in ZnS prepared by microwave assisted solvothermal method with the increase of the time in microwave. In this work we reported a study of the optical behavior linking with the structural disorder according to XRD and FEG-TEM results. The reduction of intrinsic defects in the lattice is responsible for the decrease of electronic levels in the band gap changing the PL profile. This effect was confirmed by electronic structure calculations.

Alzheimer´s disease (AD) is the most important cause of mental disease in elderly people. The progress of the symptoms of the disease are associated with structural modifications of cholinergic synapses in determined regions of the brain, and consequently the reduction of cholinergic neurotransmission potential. The research on acetylcholinesterase (AChE) has increased due to discoveries indicating the involvement of the enzyme in the formation of the β-amiloid peptide during the pathogenesis of AD. It has been noted that this enzyme plays a key role in acceleration of the senile plaques of β-amiloid peptide which is toxic for the neurons. For the development of new potential inhibitors of the enzyme AChE, different techniques of molecular modeling were used as a strategy for the rational design of pharmaceuticals, having as basis the AChE inhibitors described in the literature in addition to those deposited in the PDB, including some which have been already used for the treatment of AD. The objective is to design and test new potential inhibitors of this therapeutical target, with the aim of obtaining and future optimizing new pharmaceutical candidates for Alzheimer. The objectives extend to proposals of new potential leads, selected from data basis of commercial compounds with properties of pharmaceuticals. The virtual screening tend towards structures of inhibitors already reported in the literature as well as pharmacophoric patterns common to them, to be modeled.

The effect of gamma radiation on poly{[2,5-bis(3-(N,N-diethylamino)-1-oxapropyl)-1,4-phenylene]-alt-1,4- phenylene} (PPP); poly{[2,5-bis(3-(N,N-diethylammonium bromide)-1-oxapropyl)-1,4-phenylene]-alt-1,4-phenylene} (PPP-Br); and the polymerized dye poly-1-ethyl-2-[3-(1-ethyl-1,3-dihydro-3,3-dimethyl-2H-indol-2-ylidene)-1-propenyl]- 3,3-dimethyl-3H-indolium perchlorate (Poly-CyC) has been investigated. The stability and response of poly [2-methoxy- 5-(2'- ethyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV) in mixed solutions have also been explored. To this end, samples with concentrations ranging from 0.005 to 0.500 mg/mL were irradiated with a 60Co gamma-ray source at room temperature, using doses up to 1 kGy, and the response was analyzed by UV-Vis spectroscopy. The obtained results reinforce the previously proposed mechanism and suggest that the effect depends on specific structural characteristics of the main chain of the polymers. Moreover, the polymerized dyes display interesting dosimetric properties. Additionally, it has been noted that, contrary to what happens in other solvents, MEH-PPV is degraded in bromoform solution. Protective effects have also been observed for bromoform+toluene mixtures (1:1 vol/vol) and solutions containing molecular dyes.

Three-strands helical shell structures of M19 (M=Fe, Co, and Ni) nanowires (NWs) are obtained by means of the molecular dynamics (MD) method. The magnetic, optical and electrical transport properties of NWs are investigated. The electronic transport properties of optimized NWs sandwiched between two gold electrodes are investigated using non-equilibrium Green´s function (NEGF) formalism. The DOS, transmission functions (T-E), current-voltage (I-V) characteristics, and conductance spectra (G-V) were analyzed in detail. The optical properties of NWs were studied using density functional theory (DFT) calculations. The variation curves of reflectivity R(ω), absorption I(ω), refractive index n(ω), dielectric function ε (ω), conductivity δ (ω) and Loss function L(ω) as the frequency were discussed. The magnetic properties were investigated within non-spin-polarized (NSP) and spin-polarized (SP) ab initio calculation. The density of states (DOS) and electron density difference were also obtained. The calculations indicate that the Co19 NWs have potential to develop electronic, optical and spin-polarized transport nanodevice.

Nanotubes and nanowires are promising materials since they show novel physical-chemical properties and potential applications in many new technologies. SnO2 is a semiconductor of n-type with a band gap of 3.6 eV at 300K. Nanotubes of tin oxide have been widely studied. SnO2 nanotubes are known for different applications, e.g., gas sensors, transistors, and solar cells. This semiconductor has been obtained as a nanomaterial with a large number of morphologies and properties. We have built the geometries for the [(SnO2)n]m nanotubes using the structure of the rutile crystal lattice, where n represents the number of SnO2 units for nanotube layer (n=6,...,30), and m stands for the layer number. The semi-empirical MNDO, DFT-B3LYP-Huzinaga and HF-Huzinaga were used in order to optimize the dSn-Sn, dO-O, dSn- O interatomic distances. The minimum energies (eV) corresponding to the structures are given as well as the gap (HOMOLUMO) for the variation of three different distances for each unit number of [(SnO2)n]m.

Nanostructured iron (III) oxide (α-Fe2o3) was synthesized using Fe(NO3)3 PEG and different bases (NaOH and NH4OH) as precursors via hydrothermal microwave method. Several experimental techniques were employed to formulate an optic-structural model. The results proved the efficient synthesis of α-Fe2O3 and demonstrated that the material's behavior could be tuned using different conditions in the reaction. Ultra fast synthesis (1 min) of α-Fe2o3 was obtained when NH4OH was used as the alkalinizing agent. Evaluating the short- and long-range order before and after microwave heating was possible. PEG and the alkalinizing agent fundamentally influenced the material morphology; three different particle shapes were observed: hexagons (NaOH with PEG), rods (NaOH without PEG) and spheres (NH4OH with PEG).

The nature of the orbital ordering in the frustrated spinel CdV2O4 was examined on the basis of first-principles electronic structure calculations. GGA predicts the ferromagnetic half-metallic ground state while GGA+U shows antiferromagnetic Mott insulator with a staggered dxy1dxz1 (V2) and dxy1dyz1 (V1) orbital order. The magnetic moments were found to be close to the experimental results. Results show that electron correlation and co-operative Jahn-Teller distortions play a significant role in determining the orbital ordering.

Super Paramagnetic Iron-Oxide Nanoparticles (SPION) are currently used as magnetic resonance imaging (MRI) contrast agents. The functionalization of their surface with organic and biocompatible molecules has the purpose to produce carriers selective for different tissues and organs. In this paper, we present the preparation of new cystine-coated ultra small super paramagnetic iron-oxide nanoparticles (USPION) of different core size, from 4 nm to 11 nm. The physical-chemical characterization of these nanoparticles was performed by using several experimental techniques, such as atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM) and magnetic measurements. 1H NMR relaxation times at different magnetic field strengths have been measured for several waterdispersions of cystine-coated iron-oxide nanoparticles of the smallest dimensions (4 nm). These preliminary results confirm their potentialities as molecular imaging probes and MRI contrast agents.

At elevated temperatures and pressures substances may become supercritical. Supercritical fluids have properties resembling both gasses and liquids, meaning that these fluids are interesting for various applications. This work describes some general aspects of the supercritical phase and the properties of near and supercritical water. The properties of supercritical water are related to the changes in dielectric constant, auto-dissociation of water and the significant decrease in the degree of hydrogen bonding at supercritical conditions.