Structural, dielectric, and antimicrobial evaluation of PMMA/CeO2 for optoelectronic devices.

In the current report, we have successfully synthesized nanocomposites of PMMA incorporating different doping of CeO2 through a chemical approach. XRD results reflects decent matching for CeO2 nanoparticles with 29 nm crystallite size. FTIR spectroscopy demonstrates the characteristic functional groups validating the successful formation of the composite. The optical study of PMMA and the nanocomposites has proven that the optical properties such as band gap, refractive index, optical permittivity, and loss tangent factor are affected by adding CeO2 to the PMMA matrix.The peak residing around 420 nm by UV measurements is allocated to occurring electrons photoexcitation from the valence to conduction band inherent in CeO2. The dielectric measurements were achieved using broadband dielectric spectroscopy upon a wide span of frequencies (10-1-107 Hz) and within temperatures from - 10 to 80 °C with a step of 10 °C. The permittivity decreases by adding CeO2 and the dielectric parameters are thermally enhanced, however, the temperature influence is based on CeO2 content, the higher the CeO2 amount, the higher the influence of temperature. The results of the nanocomposites revealed antibacterial activity counter to gram-positive bacteria strain (S. aureus, and B. subtilis), and gram-negative bacteria (E. coli, and K. pneumoniae), yeast (C. albicans, as well as fungi (A. niger). Inherently, the change in CeO2 concentration from 0.01 to 0.1 wt% delivers maximum influence against gram-negative bacteria. These PMMA CeO2-doped composites are beneficial for optoelectronic areas and devices.

Estimating the in vitro cytotoxicity of the newly emerged zinc oxide (ZnO) doped chromium nanoparticles using the human fetal lung fibroblast cells (WI38 cells).

Advances in nanotechnology have been increased for more smart applications and getting the highest level of benefits, recently modification of the surface characters of nanoparticles is a new trend to get the optimal benefits, one of these modification is doping of zinc oxide with chromium nanoparticles (ZnO doped Cr NPs), the present study aimed to identify the surface characters of doped ZnO and their possible cytotoxic effects. The doped NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Field emission scanning electron microscope (FESEM), and Electromagnetic Data Exchange (EDX). Human fetal lung fibroblast cells (WI38 Cells) was treated with variable concentrations of pure ZnO and ZnO doped Cr (0.01 %, 0.02 %, 0.03 % and 0.04 %) for 24 hr at 37 °C followed by the MTT assay. The cells treated with the obtained half-maximal inhibitory concentration (IC50). The supernatant and cells were collected for oxidant/anti-oxidant and molecular analysis.The observed FESEM features are in line with the reported XRD analysis confirming the hexagonal crystal symmetry of all samples. The findings revealed that pure ZnO exhibited potent cytotoxic effects followed by (0.03 % and 0.04 %). All tested NPs produce lipid peroxidation significantly (0.03 % and 0.04 %). The significant up regulation of Bcl-2-associated X protein (BAX) and apoptotic Caspase (Cas-3) transcription level were reported in ZnO and 0.03 % and 0.04 % in contrast the anti apoptitic B-cell lymphoma 2 (Bcl-2) is elevated in 0.01 % and 0.02 %. Doping of ZnO with Cr causing significant morphological changes which effect on their toxicity especially with 0.03 % and 0.04 %.

Coupling between γ-irradiation and synchrotron-radiation-based XAFS techniques for studying Mn-doped ZnO nanoparticles.

γ-Irradiation and synchrotron-radiation-based X-ray absorption fine-structure (XAFS) spectroscopy have been used to induce structure disorder through the interaction of γ-rays (200 kGy) with fabricated Mn-doped ZnO nanoparticles (NPs) and then to examine thoroughly the resultant structural change. The extracted electronic/fine XAFS structural parameters reflect a compositional and γ-irradiation co-dependence. The average crystal structure of samples prepared by the sol-gel method was investigated by X-ray diffraction (XRD). A detailed structural XRD data analysis was carried out by applying a Rietveld refinement using the MAUD program. XAFS spectra were collected at the Zn K-edge (9659 eV) in transmission mode and at the Mn K-edge (6539 eV) in fluorescence mode. Direct evidence of the solubility of Mn ions in the ZnO structure was demonstrated by fitting the extended-XAFS (EXAFS) signal. Near-edge XAFS (XANES) analysis provided the oxidation states of Zn and Mn ions through fingerprint XANES spectra of the sample along with those of standard compounds. Linear combination fitting showed that the most fit chemical forms of Zn and Mn in the samples are ZnO and MnO, respectively. The oxidation states of both Zn and Mn XAFS absorbers were confirmed from pre-edge fitting. The results of the magnetic measurements were explained in light of the average and electronic/local structural information obtained from XRD, XANES and EXAFS techniques. The magnetic properties of the samples translate into an induced change in the average crystal and electronic/local structures upon Mn concentration change and γ-irradiation. XRD confirmed the successful preparation of hexagonal Mn-doped ZnO NPs with a crystallite size in the range 33-41 nm. Both XRD and EXAFS analysis detected a minor amount of Mn3O4 as a secondary phase. XANES and EXAFS provided information exploring the outstanding potential of the utilized protocol for detecting precisely the presence of the secondary phase of Mn3O4, which changes with Mn content (x). Mean-square relative displacement (σ2) values extracted from the EXAFS fitting were found to grow for Zn-Zn/Mn paths demonstrating the substitution of Mn/Zn into Zn crystal sites. The EXAFS analysis explains the reasons behind the enhancement in the magnetic properties and shows that the Mn doping content at x = 0.05 produces the most local atomic disorder in ZnO NPs. There is a strong harmony among the XRD, XANES, EXAFS and magnetization behavior of the Mn-doped ZnO NPs. Maximum magnetization was acquired at an Mn content of 0.05. γ-Ray-irradiated Zn1-xMnxO NPs are recommended as optimized candidates for showing the diversity of the applications.

Structural, Magnetic, and Dielectric properties of Sr4Fe6O13 ferrite prepared of small crystallites.

A stable Sr4Fe6O13 was prepared as small crystallites by auto-combustion of a sol-gel in air followed by annealing the later at pertinent temperatures. A green sample, as annealed at elevated temperatures, yields a single Sr4Fe6O13 phase of tailored magnetic properties. The structural, morphological, magnetic and electrical properties were investigated by X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer, and broadband dielectric spectrometer. Hard magnetic Sr4Fe6O13 properties arise with saturation magnetization Ms = 12.4 emu/g, coercivity Hc = 3956.7 Oe and squareness 0.512. Studies made at low temperatures reveals Ms decreasing on increasing temperature from 17.5 emu/g at 85 K down to 12.4 emu/g at 305 K, while Hc rises from 1483 Oe at 85 K to 1944 Oe at 305 K. The ac-conductivity follows the Jonscher relation. The dc-conductivity at high temperatures/low frequencies exhibits a plateau and it depends linearly on a characteristic frequency according to the Barton-Nakajima-Namikawa) relation.

Pathogenicity of the Egyptian A/H5N1 avian influenza viruses in chickens.

Long-term circulation of highly pathogenic avian influenza H5N1 viruses of clade 2.2.1 in Egyptian poultry since February 2006 resulted in the evolution of two distinct clades: 2.2.1.1 represents antigenic-drift variants isolated from vaccinated poultry and 2.2.1.2 that caused the newest upsurge in birds and humans in 2014/2015. In the present study, nine isolates were collected from chickens, ducks and turkeys representing the commercial and backyard sectors during the period 2009-2015. The subtyping was confirmed by hemagglutination inhibition (HI) test, RT-qPCR and sequence analysis. The Mean Death Time (MDT) and Intravenous Pathogenicity Index (IVPI) for all isolates were determined. Sequence analysis of the HA gene sequences of these viruses revealed that two viruses belonged to clade 2.2.1.1 and the rest were clade 2.2.1.2. Antigenic characterisation of the viruses supported the results of the phylogenetic analysis. The MDT of the isolates ranged from 18 to 72 h and the IVPI values ranged from 2.3 to 2.9; viruses of the 2.2.1.1 clade were less virulent than those of the 2.2.1.2 clade. In addition, clade-specific polymorphism in the HA cleavage site was observed. These findings indicate the high and variable pathogenicity of H5N1 viruses of different clades and host-origin in Egypt. The upsurge of outbreaks in poultry in 2014/2015 was probably not due to a shift in virulence from earlier viruses.

Structural, morphological and optical properties of ZnSe quantum dot thin films.

ZnSe powder was prepared via hydrothermal technique using zinc acetate and sodium selenite as source materials. The prepared ZnSe powder was used for preparing film with different thickness values (95, 135 and 230 nm) via thermal evaporation technique. X-ray diffraction showed that the prepared powder has cubic zinc-blende structure with a space group, F43m. The high resolution transmittance electron microscope results show that the films are composed of spherical-shaped nanoparticles with a diameter in the range of 2-8 nm. The optical properties of ZnSe films with differing thicknesses are investigated by means of spectrophotometric measurements of the photoluminescence, transmittance and reflectance. The absorption coefficient of the films is calculated and the optical band gap is estimated. The refractive index of the films is determined and its normal dispersion behavior is analyzed on the basis of a single oscillator model, in which oscillator energy, dispersion energy and dielectric constant at high frequency are evaluated. Drude model is also applied to determine the lattice dielectric constant and the ratio of the carriers' concentration to their effective mass.