Solvothermal Synthesis of Gd

Uniform Gd2O3 : Eu3+ luminescent nanowires were prepared on a large scale by a facile solvothermal method using polyethylene glycol (PEG-2000) as template and ethanol as solvent; the properties and the structure were characterized. X-ray diffraction (XRD) patterns and Fourier transform infrared spectrometry (FTIR) showed that the precursors are hexagonal phase Gd(OH)3 crystals, and the samples calcined at 800C° are cubic phase Gd2O3. Transmission Electron Microscopy (TEM) images indicated that the samples are nanowires with a diameter of 30 nm and a length of a few microns. Photoluminescence (PL) spectra showed that the ratio of D50→F72 to D50→F71 transition peak of the calcined samples is stronger than that of the precursors, which confirmed that the color purity of the Gd2O3 : Eu3+ is better than that of the precursors. The as-obtained Gd2O3 : Eu3+ luminescent nanowires show a strong red emission corresponding to D50→F72 transition (610 nm) of Eu3+ under ultraviolet excitation (250 nm), which have potential application in red-emitting phosphors and field emission display devices

Rapid and highly sensitive detection of formaldehyde gas via a polyoxometalate–CuBi2O4 composite gas sensor

Quick response and high sensitivity are equally important for the practical application of gas sensors. In this study, we introduced polyoxometalates (POMs) into a classical ternary metal oxide CuBi2O4 for the first time by convenient electrospinning and prepared a group of heater-type gas sensors by using CuBi2O4/PW12 composite nanofibers. The sensor performances to formaldehyde gas were explored. The results proved that the gas-sensing response of the CuBi2O4/PW12 (PW12 = H3PW12O40·xH2O) composite sensor to 100 ppm formaldehyde gas was increased to 6.68, which was 3.92 times greater than the sensing capacity of the pure CuBi2O4 sensor. Simultaneously, the sensor exhibited a highly rapid response/recovery time of only 1/2 s, which is significantly faster than performances of CuBi2O4 gas sensors reported in the past literature. The cause of the improvement of the sensing performance was assessed via mechanism study, and it was found that the introduction of PW12 into the sensor contributed to its enhanced performance. It was found that PW12, as an electron acceptor, increased carrier mobility and reduced electron–hole recombination, thus contributing to enhanced gas-sensing properties. Moreover, other gas-sensing parameters such as selectivity, humidity resistance, repeatability, long-term stability were investigated. Hence, this study contributed to the literature on the development of polyoxometalates-based gas sensors

Influence of aluminum substitution on microstructural, electrical, dielectric and electromagnetic properties of sol-gel synthesized yttrium iron garnet (YlG)

Aluminum-substituted Yttrium iron garnet, Al-YIG (Y3AlxFe5-xO12; x = 0.4, 0.8, 1.2, 1.6 and 2.0) samples were synthesized via auto combustion sol-gel technique. The obtained powder was heated at 950 °C, pressed into pellets and sintered at 1200 oC. The samples microstructures were studied using Field emissions scanning electron microscopy (FESEM). The average grain size decreased from 0.46 µm at x = 0.4 to a minimum value of 0.33 µm at x = 2.0. Elemental composition of the samples was studied by energy dispersive x-ray (EDX), while bulk density was measured by Archimedes principle. Electrical and dielectric measurements were carried out using Agilent impedance analyzer. Generally, the samples resistivity decreased with Al concentration. At 1 MHz frequency, the sample x = 0.4 has the highest resistivity of 2.19 × 105 Ωm which decreases down to its minimum value of 1.75 × 104 Ωm at x = 2.0. The dielectric constant for all the samples decreased with frequency. For the sample x = 0.4, the ε'r decreased from 49.03 at 40 Hz to 8.08 at 1 MHz. The dielectric loss tangent, tan δ decreased with increasing frequency, while it increased with Al substitution. Permeability values were calculated from permittivity data. The real ermeability decreases from 1263.12 at x = 0.4 to 6.96 at x = 1.2, and the decreased down to 11.74 at x = 2.0. The high dielectric constant, low resistivity and low loss values of the samples indicate their suitability for miniaturization of radio frequency devices, antenna and filter resonator

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Effect of PEO on the hydrophilicity of PLLA ultrafine fibers

The Polyethylene oxide (PEO) / Poly (L-lactic acid) (PLLA) ultrafine blend fibers have been prepared by electrospinning. The hybrid solvent of trichloromethane and ethanol was found to be the co-solvent for electrospinning. The PEO/PLLA blend solutions in various ratios were studied for electrospinning into ultrafine fibers. The morphology of the fibers was shown by scanning electron microscope (SEM). The hydrophilicity of fiber samples was characterized by determining their water contact angle. The spun ultrafine fibers are expected to be used in the native extracellular matrix for tissue engineering