Synthesis and Characterization of functional ceramic materials at the nano- and microscale with enhanced properties

Semiconductor nanoparticles (NPs) and nanowires (NWs) of doped ZnO system have been synthesised at low temperature (190 °C) by a novel Polyol-Mediated Thermolysis (PMT) process and Vapour-Solid (VS) reaction. Ce/Ru doped ZnO NPs with different molar content (1-3--5-10%) have been synthesised by both experimental processes. The crystallite size, morphology, specific surface area and band gap have been evaluated. Also, the structural and functional characteristics were carried out by X-ray diffraction technique (XRD), high resolution transmission electron microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV-Vis diffuse reflectance spectra (DRS), UV-Vis spectroscopy and photoluminescence measurements (PL). Also, the photocatalytic activities of ZnO nanoparticles were evaluated by removal rate of methyleneblue (MB) under UV irradiation (365 nm) at RT. XRD patterns revealed a hexagonal ZnO wurtzite-type crystalline structure with a preferred orientation of(101) plane. Any secondary phases have been identified such as Ce02, Ce203, ee, Ru02, Ru304, Ru. HRTEM showed NPs in shape from spherical/ellipsoidal to hexagonal, that does not change significantly with the increasing of precursor solution concentration and kind of dopant element in the samples obtained from PMTprocess. The size of NPs was observed in the range from 16 to 23 run. Using the Kubelka-Munk treatment on the diffuse reflectance spectra, the direct band energy has been estimated at <3.0 eV in the Ru-doped samples. The PL spectra mainly consist of four emission bands: (i) a strong UV emission band, (ii) a weak blue band, (iii) a blue-green band and (iv) a green-yellow band, respectively. The reported results showed the photocatalytic efficiency of doped ZnO nanoparticles was always enhanced

Synthesis of Ce/Ru Doped ZnO photocatalysts to the degradation of emerging pollutants in wastewater

Semiconductor nanoparticles (NPs) and nanowires (NWs) of doped ZnO system with different dopant content have been synthesized by Polyol-Mediated Thermolysis (PMT) process and Vapour-Solid (VS) reaction. The average crystallite size, morphology, specific surface area, and direct band gap have been evaluated. The structural and functional characteristics have been studied by X-Ray Diffraction techniques (XRD), Field Emission Scanning Electron Microscope (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), Brunauer, Emmett and Teller (BET) method, UV-Vis Diffuse Reflectance Spectra (DRS), UV-Vis Spectroscopy, and Photoluminescence measurements (PL). Also, the photocatalytic activities of pure and doped ZnONPs were evaluated by removal rate of Methylene Blue (MB) under UV irradiation (365 nm) at room temperature. XRD patterns revealed the common hexagonal ZnO Wurtzite-type structures with a preferred orientation of (101) plane. Secondary phases as CeO2, Ce2O3, Ce, RuO2, Ru3O4, Ruhave been identified. For both dopant, Ceand Ru, and for all the concentrations in the precursor solution, FESEM and HRTEM showed NPswith morphologies ranging from spherical/ellipsoidal to hexagonal. The size of NPs was observed to decrease (from ~30 to ~16 nm) with increasing doping concentration due to the interaction between the Ce-O-Zn or Ru-O-Zn ions. EDS results confirmed the incorporation of Ce or Ru ions into ZnO lattice.Using the Kubelka-Munk treatment on the diffuse reflectance spectra, the direct band gap energy has been estimated to be slightly lower than 3.0 eV in both, the Ce and Ru-doped samples. Compared with pure ZnO NPs, the PL spectra of the doped NPs showed red-shifted UV emission and an enhanced blue emission with the typical broad green-yellow emission. The results showed that photocatalytic efficiency of doped ZnO NPs was always enhanced

Magnetically recoverable photocatalysts based on metal oxide nanostructures (Fe and Zn)

The synthesis of y-Fe203&ZnO hybrid nanocomposites has been carried out by a solvothermal process at low temperature evaluating the influence of different experimental parameters and conditions. Several techniques such as X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (HR-TEM), Vibrating Sample Magnetometry (VSM), Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Dynamic Light Dispersion (DLS), Thermogravimetric Analysis (TGA) and UV-Vis Spectroscopy have been used to characterize the size, shape, structure, chemical composition, purity, crystalline phase and spectroscopic, magnetic, and finally the photocatalytic properties of nanocomposites prepared. Based on the results obtained, under irradiation ofUV-Vis light, the nanocomposites of y-Fe203-ZnO synthesised both at 6 hand 12 hat 120°C demonstrate a high photocatalytic activity (PCA) compared to pure y-Fe203 and ZnO samples for the degradation of methylene blue (MB), used as a cationic dye model. The percentage of degradation obtained for both cases was much higher than that obtained for the pure compounds of y-Fe203 and ZnO (85% and 81% vs 51% and 46%, respectively). Also, the study of stability, magnetic recovery and recyclability in MB dye degradation was carried out. For this purpose, photocatalytic tests were performed by reusing these hybrid nanocomposites during successive cycles. It has been verified that the PCA of these nanocomposites is maintained after several cicles of experiments with new MB solutions demonstrating their high photocatalytic stability. In conclusion, y-Fe203-ZnO hybrid nanostructures are a suitable candidate for its use in environmental applications, and to solve problems of removal of organic contaminants in the wastewater treatments as a magnetically recoverable photocatalyst

Directed growth of nanoarchitected hydrid ceramic particles synthesised at low temperature

Nanotechnology is an emerging science involving synthesis and optimization of matter at the nanometer scale. The recent rise in the interest surrounding nanotechnology stems from its potential to revolutionize such fields as engineering and medicine. Nanoparticles, the building blocks of nanotechnology, have been broadly defined as having at least one dimension at 100 nm or less. Engineered nanoparticles are particles synthesized to exploit the size-related properties inherent in the nanoscale (e.g. conductivity, spectral properties, electrochemical properties, ... Spray pyrolysis is a versatile process regarding the powder synthesis of inorganic material. An atomizer (such as ultrasonic) is used to generate a mist from a water or organic solution of inorganic salts or metal organic compounds. The advantages of this method are that the control of particle size, particle size distribution, morphology, crystallite structure and chemical composition are possible. On the order hand, the hydrothermal synthesis is a useful method to prepare nanomaterials with homogeneous crystal structure and morphology, which has some advantages such as simple synthesis process and low energy consumption. In this work, different morphologies of zinc oxide (ZnO), including microrods, microspheres, hexagonal microprism, nanosheets or flower like have been obtained depending on what experimental conditions and synthesis method have been used. Also, hollow and spherical Ag/Y203:Eu (9% at) hybrid nanostructured particles by means of aerosol route from common nitrate solutions at 750°C in Ar atmosphere has been obtained. These as-prepared samples were additionally heated at temperatures up from 800° C to 1200 °C for 12h in argon atmosphere. The microstructures, morphologies and optical and functional properties of the as-prepared and heated samples were investigated by X-Ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), UV-VIS spectroscopy. The photocatalytic activity of ZnO synthesized by different methods and experimental conditions was evaluated by removal rate of methyleneblue under UV irradiation (365 nm) at room temperature. The results showed that the photocatalytic efficiency of ZnO particles was enhanced by increased precursor concentration. In the case of Ag/Y203 systems, the luminescence results reveal a huge rise in the final luminescence properties as consequence of the "mirror effect" due to the presence of Ag nanoparticles

Synthesis and Characterization of Magnesium Hydroxide Nanoparticles via Hydrothermal Method

The interest in the nanostructured magnesium hydroxide (Mg(OH)2) is rapidly growing due to the fact that its physical and chemical properties makes it appropriate for multiple applications. So far, it has been used in medicine, industry, or more recently, in the conservation of cultural heritage. The current research is based on the synthesis and the characterization of functional and nanocrystalline Mg(OH)2 with different particle sizes, morphologies and high purity. The synthesis was carried out via the hydrothermal method using hydrazine hydrate as a precipitator. Moreover, due to it is essential to study the behaviour of this type of nanoparticles under factors as the time of exposition, the relative humidity and CO2 concentration, they were exposed to controlled atmosphere at high relative humidity (75%RH). The carbonation process was also studied, identifying the different magnesium carbonate polymorphs.The physical and chemical property of synthesizedMg(OH)2 nanoparticles have been characterized by X Ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), High resolution Transmission electron Microscopy (HR-TEM), thermogravimetry (TG) and differential scanning calorimetry (DSC). The results showed the successful use of this synthesis route to obtain Mg(OH)2 nanostructured with important properties for the preservation of the stone heritage and promising CO2 adsorption properties

Structural, optical and electrical properties of SnO2 and SnO2:F films deposited by ultrasonic spray pyrolysis

In this research, we report the preparation and characterization of SnO2thin films preparation by the Ultrasonic Spray Pyrolysis technique using different fluorine content dissolved in ethanol as precursor solution, for its possible application as TCO's. The structural, optical and electric properties of synthesized SnO2:F films have been characterized by X-ray Diffraction (XRD), Profilometer, UV - Vis-NIR spectroscopy and electrical measurements by Hall Effect. Also structural changes were studied by X-ray diffraction. The main results show that the electrical resistivity of the films decreased with the fluorine content. The best electro-optical properties (electrical resistivity of 4.14x10-4O-cm and average transmittance of 80 [%]) were achieved in a fluorine content in relative with tin of about 0.52. Furthermore, a systematic change was observed in the intensity of the lines of the diffraction maxima of X-rays in function of fluorine content. ©Sociedad Mexicana de Ciencia y Tecnología de Superficies y Materiales.En esta investigación, reportamos la preparación y caracterización de películas delgadas de SnO2 preparadas por la técnica de Rocío Pirolítico Ultrasónico con diferente contenido de flúor disuelto en etanol como solución precursora, para su posible aplicación como TCO´s. Las propiedades estructurales, ópticas y eléctricas de películas SnO2:F sintetizadas se caracterizaron mediante Difracción de Rayos-X (DRX), Perfilometria, Espectroscopia UV-Vis-NIR y mediciones eléctricas por Efecto Hall. Asimismo los cambios estructurales se estudiaron mediante Difracción de Rayos-X. Los principales resultados muestran que la resistividad eléctrica de las películas disminuyó con el contenido de flúor. Las mejores propiedades electro-ópticas (resistividad eléctrica de 4.14x10-4 Ω-cm y transmitancia media de 80 %) se alcanzaron en un contenido de flúor con relación de estaño de aproximadamente 0.52. Además, se observó un cambio sistemático en la intensidad de las líneas de los máximos de difracción de rayos-X en función del contenido de flúor

Nanomaterials: size is the key

Nanomaterials deserve special attention since they constitute a kind of material that improves structural and functional properties compared to the bulk material. Nanomaterials have emerged as materials with at least one dimension in the range of 1 to 100 nm. They can be classified into different classes based on their properties, shapes (0D, 1D, 2D, or 3D), or sizes. Nanomaterials possess unique physical and chemical properties due to their high surface area and nanoscale size. They can be produced with outstanding magnetic, electrical, optical, mechanical, and catalytic properties that are substantially different from their bulk counterparts. Their optical properties are reported to depend on the size, which imparts different colors due to absorption in the visible region. Their reactivity, toughness, and other properties are also dependent on their unique size, shape, and structure. In summary, their properties can be tuned by controlling the size, shape, synthesis conditions, and appropriate functionalization. This talk will review the past, present, and future of nanomaterials. Based on our research developed in recent years in this area, we will review some of the most important milestones we have reached thanks to the collaboration with international research centers. We will mention the semiconductor systems (ZnO, TiO2,...), nanomaterials with luminescent properties (Gd2O3, Eu2O3,...), multi/single-wall carbon nanotubes, and many other "exotic" materials due to their small size

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Surgical site infection after gastrointestinal surgery in high-income, middle-income, and low-income countries: a prospective, international, multicentre cohort study

Background: Surgical site infection (SSI) is one of the most common infections associated with health care, but its importance as a global health priority is not fully understood. We quantified the burden of SSI after gastrointestinal surgery in countries in all parts of the world. Methods: This international, prospective, multicentre cohort study included consecutive patients undergoing elective or emergency gastrointestinal resection within 2-week time periods at any health-care facility in any country. Countries with participating centres were stratified into high-income, middle-income, and low-income groups according to the UN's Human Development Index (HDI). Data variables from the GlobalSurg 1 study and other studies that have been found to affect the likelihood of SSI were entered into risk adjustment models. The primary outcome measure was the 30-day SSI incidence (defined by US Centers for Disease Control and Prevention criteria for superficial and deep incisional SSI). Relationships with explanatory variables were examined using Bayesian multilevel logistic regression models. This trial is registered with ClinicalTrials.gov, number NCT02662231. Findings: Between Jan 4, 2016, and July 31, 2016, 13 265 records were submitted for analysis. 12 539 patients from 343 hospitals in 66 countries were included. 7339 (58·5%) patient were from high-HDI countries (193 hospitals in 30 countries), 3918 (31·2%) patients were from middle-HDI countries (82 hospitals in 18 countries), and 1282 (10·2%) patients were from low-HDI countries (68 hospitals in 18 countries). In total, 1538 (12·3%) patients had SSI within 30 days of surgery. The incidence of SSI varied between countries with high (691 [9·4%] of 7339 patients), middle (549 [14·0%] of 3918 patients), and low (298 [23·2%] of 1282) HDI (p < 0·001). The highest SSI incidence in each HDI group was after dirty surgery (102 [17·8%] of 574 patients in high-HDI countries; 74 [31·4%] of 236 patients in middle-HDI countries; 72 [39·8%] of 181 patients in low-HDI countries). Following risk factor adjustment, patients in low-HDI countries were at greatest risk of SSI (adjusted odds ratio 1·60, 95% credible interval 1·05–2·37; p=0·030). 132 (21·6%) of 610 patients with an SSI and a microbiology culture result had an infection that was resistant to the prophylactic antibiotic used. Resistant infections were detected in 49 (16·6%) of 295 patients in high-HDI countries, in 37 (19·8%) of 187 patients in middle-HDI countries, and in 46 (35·9%) of 128 patients in low-HDI countries (p < 0·001). Interpretation: Countries with a low HDI carry a disproportionately greater burden of SSI than countries with a middle or high HDI and might have higher rates of antibiotic resistance. In view of WHO recommendations on SSI prevention that highlight the absence of high-quality interventional research, urgent, pragmatic, randomised trials based in LMICs are needed to assess measures aiming to reduce this preventable complication

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta