Vanadium doping effect on multifunctionality of SnO2 nanoparticles

In the present study, tin oxide (SnO2) nanoparticles were synthesized by a precursor polymeric method. The obtained nanoparticles were doped with vanadium. The samples were characterized by powder XRD, TEM, optical UV and EPR studies. XRD and TEM showed the rutile crystal structure and its revealed that the lattice cell parameters and particles size were decreased with dopant level. Optical and EPR data confirmed that the doped V enters into SnO2 and distorted the host material symmetry. The films sensing characteristics have been studied from the aspect of doping level of sensing material and microstructure. It is found that V doping on SnO2 enhance sensor sensitivity towards CO gas. The results demonstrated that V doping can improving numerous applications which the SnO2 response is maximized.Fil: Alvarez Roca, Roman. Universidade Federal do São Carlos; BrasilFil: Desimone, Paula Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: da Silva, Mitchell. Universidade Federal do São Carlos; BrasilFil: Ponce, Miguel Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Longo, Elson. Universidade Federal do São Carlos; Brasi

Vanadium Doping Effect on Multifunctionality of SnO2 Nanoparticles

 In the present study, tin oxide (SnO2) nanoparticles were synthesized by a precursor polymeric method. The obtained nanoparticles were doped with vanadium. The samples were characterized by powder XRD, TEM, optical UV and EPR studies. XRD and TEM showed the rutile crystal structure and its revealed that the lattice cell parameters and particles size were decreased with dopant level. Optical and EPR data confirmed that the doped V enters into SnO2 and distorted the host material symmetry. The films sensing characteristics have been studied from the aspect of doping level of sensing material and microstructure. It is found that V doping on SnO2 enhance sensor sensitivity towards CO gas. The results demonstrated that V doping can improving numerous applications which the SnO2 response is maximized

Surfactant-Mediated Morphology and Photocatalytic Activity of α‑Ag2WO4 Material

In the present work, the morphology (hexagonal rod-like vs cuboid-like) of an α-Ag2WO4 solid-state material is manipulated by a simple controlled-precipitation method, with and without the presence of the anionic surfactant sodium dodecyl sulfate (SDS), respectively, over short reaction times. Characterization techniques, such as X-ray diffraction analysis, Rietveld refinement analysis, Fourier-transform (FT) infrared spectroscopy, FT Raman spectroscopy, UV–vis spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy (FE-SEM), and photoluminescence emission, are employed to disclose the structural and electronic properties of the α-Ag2WO4 material. First-principles calculations were performed to (i) obtain the relative stability of the six low-index surfaces of α-Ag2WO4; (ii) rationalize the crystal morphologies observed in FE-SEM images (using the Wulff construction); and (iii) determine the energy profiles associated with the transformation process between both morphologies induced by the presence of SDS. Finally, we demonstrate a relationship between morphology and photocatalytic activity, evaluated by photodegradation of Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and W cations (local coordination, i.e., clusters) of each surface

Selective Synthesis of α-, β-, and γ-Ag2WO4 Polymorphs: Promising Platforms for Photocatalytic and Antibacterial Materials

Silver tungstate (Ag2WO4) shows structural polymorphism with different crystalline phases, namely, orthorhombic, hexagonal, and cubic structures that are commonly known as α, β, and γ, respectively. In this work, these Ag2WO4 polymorphs were selectively and successfully synthesized through a simple precipitation route at ambient temperature. The polymorph-controlled synthesis was conducted by means of the volumetric ratios of the silver nitrate/tungstate sodium dehydrate precursors in solution. The structural and electronic properties of the as-synthesized Ag2WO4 polymorphs were investigated by using a combination of X-ray diffraction and Rietveld refinements, X-ray absorption spectroscopy, X-ray absorption near-edge structure spectroscopy, field-emission scanning electron microscopy images, and photoluminescence. To complement and rationalize the experimental results, first-principles calculations, at the density functional theory level, were carried out, leading to an unprecedented glimpse into the atomic-level properties of the morphology and the exposed surfaces of Ag2WO4 polymorphs. Following the analysis of the local coordination of Ag and W cations (clusters) at each exposed surface of the three polymorphs, the structure–property relationship between the morphology and the photocatalytic and antibacterial activities against amiloride degradation under ultraviolet light irradiation and methicillin-resistant Staphylococcus aureus, respectively, was investigated. A possible mechanism of the photocatalytic and antibacterial activity as well the formation process and growth of the polymorphs is also explored and proposed

Facet-dependent photocatalytic and antibacterial properties of a-Ag2WO4 crystals: combining experimental data and theoretical insights

In this paper, we have combined the various experimental results and first-principles calculations with a new and interesting discussion to explain the photocatalytic and antibacterial activities of α-Ag2WO4 crystals, which were obtained using the microwave-hydrothermal (MH) method with anionic surfactants. The advantages of the insights gained through the present work are two-fold. First, the mechanism and origin of the photocatalytic and antibacterial activities can be rationalized. Second, this facile and controllable synthetic method is expected to encourage the synthesis of complex metal oxides with specific active facets, and these insights can contribute to the rational design of new materials for multifunctional applications. X-ray diffraction and Rietveld refinement analysis confirmed that all the crystals have an orthorhombic structure without deleterious phases. Ultraviolet–visible diffuse reflectance spectroscopy indicated the presence of intermediary energy levels and a variation in the optical band gap values (3.09–3.14 eV) with the crystal growth process. The geometry, electronic properties of the bulk, and surface energies of these crystals were evaluated using first-principles quantum mechanical calculations based on the density functional theory. The crystal shapes was experimentally and theoretically modeled based on Rietveld refinement data, emission scanning electron microscopy images, and Wulff construction. To obtain a wide variety of crystal shapes, the morphologies were gradually varied by tuning the surface chemistry, i.e., the relative stability of the faceted crystals. The growth mechanisms of different α-Ag2WO4 crystals and their facet-dependent photocatalytic and antibacterial performances were explored in details. The combination of experimental and theoretical data revealed the presence of (110) and (011) planes with high surface energies together with the disappearance of faces related to the (010)/(0[1 with combining macron]0) planes in α-Ag2WO4 crystals are key factors that can rationalize both the photocatalytic and antibacterial activities. The different activities may be attributed to the different number of unsaturated superficial Ag and W atoms capable of forming the main active adsorption sites. Finally, we discuss how knowledge of surface-specific properties can be utilized to design a number of crystal morphologies that may offer improved performance in various applications.The authors acknowledge the financial support of the following Brazilian research funding institutions: the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP; 2012/14004-5 and 2013/07296-2), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq; 479644/2012-8 and 304531/2013-8) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). J.A. and L.G. are grateful to Prometeo/2009/053 (GeneralitatValenciana), Ministerio de Economia y Competitividad (Spain; CTQ2012-36253-C03-02), and the Spanish Brazilian program (PHB2009-0065-PC). We also acknowledge the Servei Informática, Universitat Jaume I for the generous allotment of computer time

Global, regional, and national life expectancy, all-cause mortality, and cause-specific mortality for 249 causes of death, 1980-2015 : a systematic analysis for the Global Burden of Disease Study 2015

Background Improving survival and extending the longevity of life for all populations requires timely, robust evidence on local mortality levels and trends. The Global Burden of Disease 2015 Study (GBD 2015) provides a comprehensive assessment of all-cause and cause-specific mortality for 249 causes in 195 countries and territories from 1980 to 2015. These results informed an in-depth investigation of observed and expected mortality patterns based on sociodemographic measures. Methods We estimated all-cause mortality by age, sex, geography, and year using an improved analytical approach originally developed for GBD 2013 and GBD 2010. Improvements included refinements to the estimation of child and adult mortality and corresponding uncertainty, parameter selection for under-5 mortality synthesis by spatiotemporal Gaussian process regression, and sibling history data processing. We also expanded the database of vital registration, survey, and census data to 14 294 geography-year datapoints. For GBD 2015, eight causes, including Ebola virus disease, were added to the previous GBD cause list for mortality. We used six modelling approaches to assess cause-specific mortality, with the Cause of Death Ensemble Model (CODEm) generating estimates for most causes. We used a series of novel analyses to systematically quantify the drivers of trends in mortality across geographies. First, we assessed observed and expected levels and trends of cause-specific mortality as they relate to the Socio-demographic Index (SDI), a summary indicator derived from measures of income per capita, educational attainment, and fertility. Second, we examined factors affecting total mortality patterns through a series of counterfactual scenarios, testing the magnitude by which population growth, population age structures, and epidemiological changes contributed to shifts in mortality. Finally, we attributed changes in life expectancy to changes in cause of death. We documented each step of the GBD 2015 estimation processes, as well as data sources, in accordance with Guidelines for Accurate and Transparent Health Estimates Reporting (GATHER). Findings Globally, life expectancy from birth increased from 61.7 years (95% uncertainty interval 61.4-61.9) in 1980 to 71.8 years (71.5-72.2) in 2015. Several countries in sub-Saharan Africa had very large gains in life expectancy from 2005 to 2015, rebounding from an era of exceedingly high loss of life due to HIV/AIDS. At the same time, many geographies saw life expectancy stagnate or decline, particularly for men and in countries with rising mortality from war or interpersonal violence. From 2005 to 2015, male life expectancy in Syria dropped by 11.3 years (3.7-17.4), to 62.6 years (56.5-70.2). Total deaths increased by 4.1% (2.6-5.6) from 2005 to 2015, rising to 55.8 million (54.9 million to 56.6 million) in 2015, but age-standardised death rates fell by 17.0% (15.8-18.1) during this time, underscoring changes in population growth and shifts in global age structures. The result was similar for non-communicable diseases (NCDs), with total deaths from these causes increasing by 14.1% (12.6-16.0) to 39.8 million (39.2 million to 40.5 million) in 2015, whereas age-standardised rates decreased by 13.1% (11.9-14.3). Globally, this mortality pattern emerged for several NCDs, including several types of cancer, ischaemic heart disease, cirrhosis, and Alzheimer's disease and other dementias. By contrast, both total deaths and age-standardised death rates due to communicable, maternal, neonatal, and nutritional conditions significantly declined from 2005 to 2015, gains largely attributable to decreases in mortality rates due to HIV/AIDS (42.1%, 39.1-44.6), malaria (43.1%, 34.7-51.8), neonatal preterm birth complications (29.8%, 24.8-34.9), and maternal disorders (29.1%, 19.3-37.1). Progress was slower for several causes, such as lower respiratory infections and nutritional deficiencies, whereas deaths increased for others, including dengue and drug use disorders. Age-standardised death rates due to injuries significantly declined from 2005 to 2015, yet interpersonal violence and war claimed increasingly more lives in some regions, particularly in the Middle East. In 2015, rotaviral enteritis (rotavirus) was the leading cause of under-5 deaths due to diarrhoea (146 000 deaths, 118 000-183 000) and pneumococcal pneumonia was the leading cause of under-5 deaths due to lower respiratory infections (393 000 deaths, 228 000-532 000), although pathogen-specific mortality varied by region. Globally, the effects of population growth, ageing, and changes in age-standardised death rates substantially differed by cause. Our analyses on the expected associations between cause-specific mortality and SDI show the regular shifts in cause of death composition and population age structure with rising SDI. Country patterns of premature mortality (measured as years of life lost [YLLs]) and how they differ from the level expected on the basis of SDI alone revealed distinct but highly heterogeneous patterns by region and country or territory. Ischaemic heart disease, stroke, and diabetes were among the leading causes of YLLs in most regions, but in many cases, intraregional results sharply diverged for ratios of observed and expected YLLs based on SDI. Communicable, maternal, neonatal, and nutritional diseases caused the most YLLs throughout sub-Saharan Africa, with observed YLLs far exceeding expected YLLs for countries in which malaria or HIV/AIDS remained the leading causes of early death. Interpretation At the global scale, age-specific mortality has steadily improved over the past 35 years; this pattern of general progress continued in the past decade. Progress has been faster in most countries than expected on the basis of development measured by the SDI. Against this background of progress, some countries have seen falls in life expectancy, and age-standardised death rates for some causes are increasing. Despite progress in reducing age-standardised death rates, population growth and ageing mean that the number of deaths from most non-communicable causes are increasing in most countries, putting increased demands on health systems. Copyright (C) The Author(s). Published by Elsevier Ltd.Peer reviewe

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Compacting and densification of TiO2 nanoparticles

This work investigated the compacting and densification behaviour of TiO2 nanoparticles prepared by the simple non-aqueous sol-gel process. The synthesized nanopowder has anatase TiO2 structure with the average crystallite size of 10 nm and agglomerated particles. The compressibility curve shows two well-defined linear parts that intersect at ~380MPa which is a measure of agglomerate compressive strength. The densification process was investigated by the dilatometric analysis using non-isothermal experiments. The apparent activation energy for the densification was calculated (88-102 kJ/mol). Grain rearrangement by grain boundary sliding was proposed as the dominant shrinkage mechanism

Formation of Ag Nanoparticles on β‑Ag2WO4 through Electron Beam Irradiation: A Synergetic Computational and Experimental Study

In the present work, a combined theoretical and experimental study was performed on the structure, optical properties, and growth of Ag nanoparticles in metastable β- Ag2WO4 microcrystals. This material was synthesized using the precipitation method without the presence of surfactants. The structural behavior was analyzed using X-ray diffraction and Raman and infrared spectroscopy. Field-emission scanning electron microscopy revealed the presence of irregular spherical-like Ag nanoparticles on the β-Ag2WO4 microcrystals, which were induced by electron beam irradiation under high vacuum conditions. A detailed analysis of the optimized β-Ag2WO4 geometry and theoretical results enabled interpretation of both the Raman and infrared spectra and provided deeper insight into rationalizing the observed morphology. In addition, first-principles calculations, within the quantum theory of atoms in molecules framework, provided an in-depth understanding of the nucleation and early evolution of Ag nanoparticles. The Ag nucleation and formation is the result of structural and electronic changes of the [AgO6] and [AgO5] clusters as a constituent building block of β-Ag2WO4, which is consistent with Ag metallic formationThis work was financially supported by the following Spanish and Brazilian research funding institutions: PrometeoII/2014/ 022 and ACOMP/2014/270 projects (Generalitat-Valenciana), Ministerio de Economia y Competitividad (CTQ2012-36253- C03-02), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2012/14004-5, 2013/07296-2 and 2013/ 26671-9), Conselho Nacional de Desenvolvimento Cientifí co e Tecnológico (CNPq; 479644/2012-8, 350711/2012-7, 304531/2013-8 and 151136/2013-0), Coordenação de Aperfeico̧ amento de Pessoal de Niv́ el Superior, and Programa de Cooperación Cientifíca con Iberoamerica (Brasil) of Ministerio de Educación (PHBP14-00020). J.A. acknowledges to Ministerio de Economia y Competitividad, “Salvador Madariaga” program, PRX15/00261. L.G. acknowledges Banco Santander (Becas Iberoamérica: Jóvenes profesores e investigadores)

Surfactant-Mediated Morphology and Photocatalytic Activity of α‑Ag2WO4 Material

In the present work, the morphology (hexagonal rod-like vs cuboid-like) of an α-Ag2WO4 solid-state material is manipulated by a simple controlled-precipitation method, with and without the presence of the anionic surfactant sodium dodecyl sulfate (SDS), respectively, over short reaction times. Characterization techniques, such as X-ray diffraction analysis, Rietveld refinement analysis, Fourier-transform (FT) infrared spectroscopy, FT Raman spectroscopy, UV–vis spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy (FE-SEM), and photoluminescence emission, are employed to disclose the structural and electronic properties of the α-Ag2WO4 material. First-principles calculations were performed to (i) obtain the relative stability of the six low-index surfaces of α-Ag2WO4; (ii) rationalize the crystal morphologies observed in FE-SEM images (using the Wulff construction); and (iii) determine the energy profiles associated with the transformation process between both morphologies induced by the presence of SDS. Finally, we demonstrate a relationship between morphology and photocatalytic activity, evaluated by photodegradation of Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and W cations (local coordination, i.e., clusters) of each surface