Toward Understanding the Photocatalytic Activity of PbMoO4 Powders with Predominant (111), (100), (011), and (110) Facets. A Combined Experimental and Theoretical Study

A complementary combination of experimental work and first-principle calculations, based on the density functional theory (DFT) method, has been used to increase our limited understanding of the enhanced photocatalytic activity of PbMoO4 powders with predominant (111), (100), (011), and (110) facets. In this work, PbMoO4 powders were prepared by the coprecipitation method and processed on a hydrothermal reactor at 100 °C/10 min. The variation of different types of modifiers such as acetylacetone (acac) or polyvinylpyrrolidone (PVP) is found to play a crucial role in controlling the particle size and morphology of products and their photocatalytic properties. The structure and morphology of these crystals were characterized by X-ray diffraction (XRD), micro-Raman (MR) spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM), and ultraviolet visible (UV-vis) absorption spectroscopy. Furthermore, the as-synthesized PbMoO4 micro-octahedrons without the presence of the (001) surface exhibit enhanced activity for the photodegradation of rhodamine B (RhB) under ultraviolet-visible light irradiation. On the basis of the theoretical and experimental results, we provide a complete assignment of the micro-Raman spectra of PbMoO4, while a growth mechanism for the formation of PbMoO4 micro-octahedrons was systematically discussed. A schematic illustration of the probable formation of morphologies in the whole of the synthetic process was also proposed, which reveals that the high photocatalytic activity is attributed to the absence of the (001) facet.The authors thank the financial support from the following Brazilian research financing institutions: CNPq, FAPESP, CAPES, RECAM (Rede de Pesquisa em Catalisadores Ambientais) processo no 564913/2010-3; MCT/CNPq no 74/2010 and Universal 14/2011 processo no 481288/2011-2, and no 150753/2013-6 National Council for Scientific and Technological Development (CNPq), Prometeo/2009/053 (Generalitat Valenciana) and Ministerio de Economiá y Competitividad (Spain), CTQ2012-36253-C03-02, and the Spanish−Brazilian program (PHB2009-0065-PC) for their financial support

Antibody-Mediated Neutralization of the Exotoxin Mycolactone, the Main Virulence Factor Produced by Mycobacterium ulcerans

Mycolactone, the macrolide exotoxin produced by Mycobacterium ulcerans, causes extensive tissue destruction by inducing apoptosis of host cells. In this study, we aimed at the production of antibodies that could neutralize the cytotoxic activities of mycolactone.; Using the B cell hybridoma technology, we generated a series of monoclonal antibodies with specificity for mycolactone from spleen cells of mice immunized with the protein conjugate of a truncated synthetic mycolactone derivative. L929 fibroblasts were used as a model system to investigate whether these antibodies can inhibit the biological effects of mycolactone. By measuring the metabolic activity of the fibroblasts, we found that anti-mycolactone mAbs can completely neutralize the cytotoxic activity of mycolactone.; The toxin neutralizing capacity of anti-mycolactone mAbs supports the concept of evaluating the macrolide toxin as vaccine target

Photoluminescent properties of ZrO2: Tm3+, Tb3+, Eu3+ powdersd-A combined experimental and theoretical study

Rare-earth (RE) element-based materials for optical applications have received increasing attention owing to the emission properties of RE ions, which render these materials suitable for use in color displays, lasers, and solid-state lighting. In the present work, ZrO2:RE (RE = Tm3+, Tb3+, and Eu3+) powders were obtained via complex polymerization, and characterized by means of X-ray diffraction (XRD), Raman spectroscopy, UV–visible absorption spectroscopy, and photoluminescence measurements. The XRD patterns and Raman spectra revealed the tetragonal phase of ZrO2 co-doped with up to 4 mol.% RE3+ and stabilization of the cubic phase, for up to 8 mol.% RE3+. In addition, the photoluminescence measurements revealed simultaneous emissions in the blue (477 nm), green (496.02 nm and 548.32 nm), and red-orange (597.16 nm and 617.54 nm) regions. These emissions result from the Tm3+, Tb 3+, and Eu3+ ions, respectively. Energy transfers, such as 1G4 levels (Tm3+) → 5D4 (Tb3+) and 5D4 levels (Tb3+) → 5D0 (Eu3+), occurred during the emission process. Calculations based on density functional theory (DFT) were performed, to complement the experimental data. The results revealed that structural order/disorder effects were generated in the cubic and tetragonal ZrO2 phases in the ZrO2:Eu3+ powders, and changes in the electronic structure were manifested as a decrease in the band gap values. The chromaticity coordinates of all the samples were determined from the PL spectrum. The coordinates, x = 0.34 and y = 0.34, of the ZrO2:8%RE sample corresponded to a point located in the white region of the CIE diagram and color correlated temperature (CCT) was found to be 5181 K. More importantly, the present results indicate that ZrO2:RE powders constitute promising photoluminescent materials for use in new lighting devices.The authors gratefully acknowledge the financial support of the Brazilian governmental research funding agencies CAPES, CNPq 402127/2013-7, FAPESP2013/07296-2 and INCTMN2008/57872-1

Optical characterization of europium-doped indium hydroxide nanocubes obtained by Microwave-Assisted Hydrothermal method

Crystalline europium-doped indium hydroxide (In(OH)3:Eu) nanostructures were prepared by rapid and efficient Microwave-Assisted Hydrothermal (MAH) method. Nanostructures were obtained at low temperature. FE-SEM images confirm that these samples are composed of 3D nanostructures. XRD, optical diffuse reflectance and photoluminescence (PL) measurements were used to characterize the products. Emission spectra of europium-doped indium hydroxide (IH:xEu) samples under excitation (350.7 nm) presented broad band emission regarding the indium hydroxide (IH) matrix and 5D0 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3 and 5D0 → 7F4 europium transitions at 582, 596, 618, 653 and 701 nm, respectively. Relative intensities of Eu3+ emissions increased as the concentration of this ion increased from 0, 1, 2, 4 and 8 mol %, of Eu3+, but the luminescence is drastically quenched for the IH matrix.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal do Rio Grande do Norte Centro de Tecnologia Departamento de Engenharia de MateriaisUniversidade Federal de São Paulo (UNIFESP)Universidade de São Paulo Instituto de Física de São CarlosUniversidade Estadual Paulista Instituto de Química Laboratório Interdisciplinar de Eletroquímica e CerâmicaUNIFESPFAPESP: 2013/07296-2SciEL

A DFT Study of Structural and Electronic Properties of ZnS Polymorphs and its Pressure-Induced Phase Transitions

A systematic first-principles investigation, by using the density functional formalism with the nonlocal B3LYP approximation including a long-range dispersion correction, has been performed to calculate the structural and electronic properties and phase transitions under pressure of the three phases of ZnS (cubic zinc blende, ZB, hexagonal wurtzite, W, and cubic rock salt, RS). Numerical and analytical fittings have been carried out to determine the equilibrium unit cell geometry and equation of state parameters for the ZnS phases. The band structures, energy gap, density of states, and vibrational frequencies and their pressure dependences are investigated. The present results illustrate that both phases, W and ZB, present very similar enthalpy and the RS phase becomes thermodynamically more stable than ZB and W structures at 15.0 and 15.5 GPa, respectively. These phase transitions are accompanied by an increase of the first shell coordination number of Zn atom and by a cell volume collapse of 13.9% and 14.3% for ZB and W phases, respectively. The atomic contributions of the conduction and valence bands, as well the binding energy for the Zn 3d orbital have been obtained.The authors gratefully acknowledge the financial support of the Brazilian agencies CAPES, CNPq (573636/2008-7) and FAPESP (2013/07296-2 and 2013/19289-0). J.A. also acknowledges Generalitat Valenciana for Prometeo/2009/053 project, Ministerio de Ciencia e Innovación for project CTQ-2012-36253-C03-01CTO, and Programa de Cooperación Científica con Iberoamerica (Brasil), Ministerio de Educación (PHB2009-0065-PC)

Functional results after hiatal repair and gastropexy without fundoplication in patients with paraoesophageal hernia.

Paraoesophageal hernias (PEH) are associated with a high complication rate and often occur in elderly and fragile patients. Surgical gastropexy without fundoplication is an accepted alternative procedure; however, outcomes and functional results are rarely described. Our study aims to evaluate short-term outcomes and the long-term quality of life after gastropexy as treatment for PEH. Single center cohort analysis of all consecutive patients who underwent gastropexy for PEH without fundoplication. Postoperative outcomes and functional results were retrospectively collected. Reflux symptoms developed postoperatively were reported using the validated quality of life questionnaire: GERD-Health Related Quality of Life Qestionnaire (GERD-HRQL). Thirty patients (median age: 72 years (65-80)) were included, 40% classified as ASA III. Main PEH symptoms were reflux (63%), abdominal/thoracic pain (47%), pyrosis (33%), anorexia (30%), and food blockage (26%). Twenty-six laparoscopies were performed (86%). Major complications (III-IVb) occurred in 9 patients (30%). Seven patients (23%) had PEH recurrence, all re-operated, performing a new gastropexy. Median follow-up was 38 (17-50) months. Twenty-two patients (75%) reported symptoms resolution with median GERD-HRQL scale of 4 (1-6). 72% (n = 21) reported operation satisfaction. GERD-HRQL was comparable between patients who were re-operated for recurrence and others: 5 (2-19) versus 3 (0-6), p = 0.100. Gastropexy without fundoplication was performed by laparoscopy in most cases with acceptable complications rates. Two-thirds of patients reported symptoms resolution, and long-term quality-of-live associated to reflux symptoms is good. Although the rate of PEH recurrence requiring a new re-intervention remained increased (23%), it does not seem to affect long-term functional results

Computational procedure to an accurate DFT simulation to solid state systems

The density functional theory has become increasingly common as a methodology to explain the properties of crystalline materials because of the improvement in computational infrastructure and software development to perform such computational simulations. Although several studies have shown that the characteristics of certain classes of materials can be represented with great precision, it is still necessary to improve the methods and strategies in order to achieve more realistic computational modeling. In the present work, strategies are reported in a systematic way for the accurate representation of crystalline systems. The crystalline compound chosen for the study as a case test was BaMoO4, both because of its potential technological application and because of the low accuracy of the simulations previously reported in the literature. The computational models were carried out with the B3LYP and WC1LYP functionals selected from an initial set containing eight hybrid functionals in conjunction with an all-electron basis set. Two different strategies were applied for improving the description of the initial models, both involving atomic basis set optimization and Hartree-Fock exchange percentage adjustment. The results obtained with the two strategies show a precision of structural parameters, band gap energy, and vibrational properties never before presented in theoretical studies of BaMoO4. Finally, a flowchart of good calculation practices is elaborated. This can be of great value for the organization and conduction of calculations in new research

First principle investigation of the exposed surfaces and morphology of β-ZnMoO4

Crystal shape is a critical determinant of the physical and chemical properties of crystalline materials; hence, it is the challenge of controlling the crystal morphology in a wide range of scientific and technological applications. The morphology is related to the geometry of their exposed surfaces, which can be described by their surface energies. The surface properties of β-ZnMoO4 have not yet been well explored, either experimentally or theoretically. Thus, the first-principle calculation at the density functional theory level was carried out for different low-index surfaces of β-ZnMoO4, specifically (001), (010), (110), (011), (101), and (111), and the surface energy values (Esurf) were reported. The surface stability was found to be controlled by the undercoordinated [MoOn…yVxO] and [ZnOn…yVxO] (n = 4 and 5; y = 1 and 2) clusters, i.e., their local coordination of Mo and Zn cations at the exposed surfaces, respectively, with the (111) surface being the most stable. A complete map of investigated β-ZnMoO4 morphologies was obtained using the Wulff construction and changing the values of the calculated energy surfaces. The final geometries from this map were compared with field emission-scanning electron microscopy images showing excellent agreement, prevising rectangular and hexagonal plates. Our findings will promote the use of facet engineering and might provide strategies to produce β-ZnMoO4-based materials for achieving morphology-dependent technological applications

Improving the Performance of the Layered Nickel Manganese Oxide Cathode of Sodium-Ion Batteries by Direct Coating with Sodium Niobium Oxide

This research highlights the efficacy of NaNbO3 as a coating for P2-Na2/3Ni1/3Mn2/3O2 cathodes in sodium-ion batteries. The coating enhances the kinetic behavior and cyclability of the electrochemical cells, as shown by electrochemical measurements. XRD analysis indicates that Nb does not incorporate into the cathode structure, implying a physical interaction between the coating and the cathode material. XRF analysis and EDX mapping confirm the actual composition and uniform dispersion of elements throughout the sample, while the electron micrographs evidence the occurrence of NaNbO3 particles modifying the surface of the layered oxide. The Ni4+/Ni3+ and Ni3+/Ni2+ redox pairs, along with the partially reversible oxidation of oxide to peroxide anions, contribute significantly to cell capacity, as revealed by XPS spectra. This last effect and the appearance of a co-intercalated phase at high voltage are positive factors to provide fast kinetics. Cyclic voltammograms show that samples coated with 2–3% NaNbO3 have superior rate capability, with high capacitive response and apparent diffusion coefficients. These samples also have low impedance at the electrode–electrolyte interface, which helps deliver a high capacity at 5C. Further cycling at 1C shows improved cyclability in the bare and 3% coated samples, due to their higher diffusion coefficients on charging. Notably, the 3% NaNbO3-coated sample exhibits excellent cyclability below 0 °C, making it a promising cathode material for sodium-ion batteries