New ZnO-based glass ceramic sensor for H2 and NO2 detection

In this study, a glass ceramic with a nominal composition 58ZnO:4Bi2O3:4WO3:33.3B2O3 was synthesized by melt quenching technique. A gas sensor was then manufactured using a ZnO sol-gel phase as a permanent binder of the glass–ceramic to an alumina substrate having interdigitated electrodes. The film sensitivity towards humidity, NH3, H2 and NO2 was studied at different temperatures. X-ray diffraction technique (XRD), field emission- scanning electron microscopy (FE-SEM) and differential thermal analysis (DTA) were used to characterize the prepared material. Though the response in the sub-ppm NO2 concentration range was not explored, the observed results are comparable with the latest found in the literature

Synthesis and Characterization of Nano-Tungsten Oxide Precipitated onto Natural Inorganic Clay for Humidity-Sensing Applications

A wet chemical method was used to obtain tungsten oxide nanoparticles from tungsten tetrachloride and natural microfibrous inorganic clay (sepiolite) as a starting material. Precipitation of tungsten oxide species onto sepiolite under basic conditions and subsequent thermal treatment was investigated, prompted by the abundance of sepiolite in nature and the useful environmental applications that could be attained. Laser granulometry, X-ray diffraction, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM) techniques were used to study the particle-size distribution, the morphology, and the composition of the prepared sample. Our findings show the presence of tungsten oxide nanoparticles, which are less than 50 nm, on the needles of the modified sepiolite

The sensing characteristics of ZnO tetrapods synthesized by microwave evaporation

ZnO tetrapods have been grown by an environmental microwave evaporation approach in air atmosphere without any use of organic solvents or precursors. The synthesized powder was characterized using X-ray diffractometry (XRD) and Field emission Scanning Electron Microscopy (FE-SEM). The grown ZnO tetrapods exhibited a noteworthy microstructure and phase formation of crystalline and pure structure. ZnO tetrapods were deposited on Pt electrode to be employed as ZnO tetrapods structure-based sensors, then, they were investigated at room temperature in the relative humidity ranging from 0.0 to 96.0%. The sensors have shown a significant response towards relative humidity starting from 30%. Cross-sensitivity was investigated with respect to N2O (150 ppm in helium) and methane (1000 ppm in helium). The ZnO tetrapods-based sensors were insensitive towards the interfering gases, indicating a potential applicability for humidity sensing purposes

Preparation and characterization of a zinc oxide nanopowder supported onto inorganic clay.

Zinc oxide nanoparticles are obtained by a wet chemical method using zinc sulphate as a raw material. Doping sepiolite, micro-fibrous inorganic clay, with ZnO after precipitation under basic conditions and subsequent thermal treatment is investigated as both materials are abundant. They are used for the development of humidity and gas sensors of great environmental importance. The particle size distribution, the morphology and the composition of the powder samples are characterized by X-Ray diffraction accompanied by Field Emission Scanning Electron Microscopy and High Resolution-Transmission Electron Microscopy techniques. The data obtained confirm the formation of zinc oxide nanoparticles of a size of 10 nm on the modified sepiolite grains

Survey on the Moisture and Ash Contents in Agricultural Commodities in Al-Rass Governorate, Saudi Arabia in 2017

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SARS-CoV-2 Infection Is at Herd Immunity in the Majority Segment of the Population of Qatar.

BACKGROUND: Qatar experienced a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic that disproportionately affected the craft and manual worker (CMW) population, who comprise 60% of the total population. This study aimed to assess ever and/or current infection prevalence in this population. METHODS: A cross-sectional population-based survey was conducted during July 26 to September 09, 2020, to assess both anti-SARS-CoV-2 positivity through serological testing and current infection positivity through polymerase chain reaction (PCR) testing. Associations with antibody and PCR positivity were identified through regression analyses. RESULTS: The study included 2641 participants, 69.3% of whom were <40 years of age. Anti-SARS-CoV-2 positivity was 55.3% (95% CI, 53.3%-57.3%) and was significantly associated with nationality, geographic location, educational attainment, occupation, and previous infection diagnosis. PCR positivity was 11.3% (95% CI, 9.9%-12.8%) and was significantly associated with nationality, geographic location, occupation, contact with an infected person, and reporting 2 or more symptoms. Infection positivity (antibody and/or PCR positive) was 60.6% (95% CI, 58.6%-62.5%). The proportion of antibody-positive CMWs who had a prior SARS-CoV-2 diagnosis was 9.3% (95% CI, 7.9%-11.0%). Only seven infections were ever severe, and only 1 was ever critical-an infection severity rate of 0.5% (95% CI, 0.2%-1.0%). CONCLUSIONS: Six in every 10 CMWs in Qatar have been infected, suggestive of reaching the herd immunity threshold. Infection severity was low, with only 1 in every 200 infections progressing to be severe or critical. Only 1 in every 10 infections had been previously diagnosed, which is suggestive of mostly asymptomatic or mild infections

New ZnO-Based Glass Ceramic Sensor for H2 and NO2 Detection

In this study, a glass ceramic with a nominal composition 58ZnO:4Bi2O3:4WO3:33.3B2O3 was synthesized by melt quenching technique. A gas sensor was then manufactured using a ZnO sol-gel phase as a permanent binder of the glass–ceramic to an alumina substrate having interdigitated electrodes. The film sensitivity towards humidity, NH3, H2 and NO2 was studied at different temperatures. X-ray diffraction technique (XRD), field emission- scanning electron microscopy (FE-SEM) and differential thermal analysis (DTA) were used to characterize the prepared material. Though the response in the sub-ppm NO2 concentration range was not explored, the observed results are comparable with the latest found in the literature

Novel Novolac Phenolic Polymeric Network of Chalcones: Synthesis, Characterization, and Thermal&ndash;Electrical Conductivity Investigation

A series of novolac phenolic polymeric networks (NPPN) were prepared via an acid-catalyzed polycondensation reaction of formaldehyde with chalcones possessing a p-phenolic OH group. When p-hydroxybenzaldehyde was treated with formaldehyde under the same conditions, a phenolic polymer (PP) was obtained. The resulting polymers were isolated in excellent yields (83&ndash;98%). Isolated polymers (NPPN, PP) were characterized using FTIR, TGA, and XRD. The results obtained from the TGA revealed that all prepared phenolic polymers have high thermal stability at high temperatures and can act as thermosetting materials. XRD data analysis showed a high degree of amorphousness for all polymers (78.8&ndash;89.2%). The electrical conductivities and resistivities of all chalcone-based phenolic networks (NPPN) and p-hydroxybenzaldehyde polymer (PP) were also determined. The physical characteristics obtained from the I-V curve showed that the conductivity of phenolic polymers has a wide range from ultimately negligible values of 0.09 &micro;S/cm up to 2.97 &mu;S/cm. The degree of polarization of the conjugated system&rsquo;s carbonyl group was attributed to high, low, or even no conductivity for all phenolic polymers since the electronic effects (inductive and mesomeric) could impact the polarization of the carbonyl group and, consequently, change the degree of the charge separation to show varied conductivity values

Studying the effect of doping metal ions onto a crystalline hematite-based humidity sensor for environmental control

Humidity sensors have several applications in both industrial processing and environmental control. Pure and doped hematite has proved to exhibit remarkable humidity sensing properties. The aim of this investigation is to study the effect of doping of some metal ions (Li+, Mg+2, Ba+2, Sr+2, and Na+) onto the crystalline hematite and to determine their sensitivity towards relative humidity (RH). The obtained crystalline samples were characterized by X-Ray Diffraction (XRD) combined with Field Emission Scanning Electron Microscopy (FESEM). The doped sodium metal ions (Na+) hematite sample showed a significant response towards relative humidity at room temperature

(The Sensing Characteristics of ZnO Tetrapods Synthesized by Microwave Evaporation)

Abstract—ZnO tetrapods have been grown by an environmental microwave evaporation approach in air atmosphere without any use of organic solvents or precursors. The synthesized powder was characterized using X-ray diffractometry (XRD) and Field emission Scanning Electron Microscopy (FE-SEM). The grown ZnO tetrapods exhibited a noteworthy microstructure and phase formation of crystalline and pure structure. ZnO tetrapods were deposited on Pt electrode to be employed as ZnO tetrapods structure-based sensors, then, they were investigated at room temperature in the relative humidity ranging from 0.0 to 96.0%. The sensors have shown a significant response towards relative humidity starting from 30%. Cross-sensitivity was investigated with respect to N2O (150 ppm in helium) and methane (1000 ppm in helium). The ZnO tetrapods-based sensors were insensitive towards the interfering gases, indicating a potential applicability for humidity sensing purposes