The vibrational spectra and rotational isomerism of methyl ethyl sulphone-d0, -d3 and -d5

The infrared and Raman spectra of methyl ethyl sulphone, methyl ethyl sulphone-1,1,1-d₃ and methyl ethyl sulphone- 1,1,1,3,3-d₅ have been presented with vibrational assignments. Two solid states have been identified in which the molecules are either the trans or the gauche rotational isomers: one solid, the A form, occurs in cooled KBr disks used for infrared spectra while the other was found in CsI disks under ambient conditions. A mixed crystal form has also been found. In the liquid state the enthalpy of the B rotational isomer is slightly less than that of the A isomer by 90 (± 140) J mol⁻¹     

First-principles prediction of the electronic and magnetic properties of nitrogen-doped ZnO nanosheets

The electronic and magnetic properties of N-doped ZnO nanosheets are investigated by density functional theory using local spin density approximation. The results show that in an isolated N-doped ZnO nanosheet, there is a clear spontaneous polarization of N 2p state with a magnetic moment 1.0 μ_B/N. We also find that the doped nitrogen atoms in ZnO nanosheets have a clustering tendency with ferromagnetic coupling between them, and thus a high room-temperature ferromagnetic nature is expected. The ferromagnetic coupling in N-doped ZnO nanosheets can be attributed to the hole-mediated double-exchange mechanism through strong p–d interaction between nitrogen and zinc atoms.     

Enhancement of free space optical link in heavy rain attenuation using multiple beam concept

Free space optics (FSO) has attracted a lot of attention for a variety of applications in telecommunications area, and it is dream of every researcher and telecommunication society to make it a real alternative solution for the last mile problem, to replace fiber optics. FSO is much preferred because of its low maintenance cost and deployment time. FSO with single-beam system is vulnerable to atmospheric attenuation, so to overcome this, a multiple-beam FSO transceiver system has become prominent and is usually used. In this paper, average rain attenuation is evaluated from the collected rain intensity data which are collected for a period of seven months, and implemented in the study concerning results relating link distance, and received optical power of using multiple-beam FSO system in tropical rainy weather. Comparison is made in terms of received optical power, geometrical losses, atmospheric losses, and bit error rate (BER) on using different number of optical beams, based on simulation at data rate of 1 Gb/s. From the results it is clear that the quality of received power is improved by using up to four beams, along with link distance up to 1141.2 m as compared to one-beam, two-beam, and three-beam, with link distances 833.3 m, 991.0 m, 1075.4 m, respectively.     

Study of electrical conductivity and phase transition in Bi2O3–V2O5 system

The solid solutions of bismuth–vanadate were prepared by the conventional solid-state reaction. The sample characterization and the study of phase transition were done by using FT-IR, X-ray diffraction (XRD) and DSC measurements. AC impedance measurements proved that the oxide ion conductivity predominantly arises from the grain and grain boundary contributions as two well-defined semicircles are clearly seen along with an inclined spike. The electrical conductivity of Bi₂O₃–V₂O₅ has been studied at different temperatures for various molar ratios. The isothermal conductivity increases with an increase in the concentration of V₂O₅ due to the vacancy migration phenomenon. It has been found that the conductivity of different compositions of Bi₂O₃–V₂O₅ increases and shows a jump in the temperature range 230–260°C due to the phase transition of BiVO₄ from monoclinic scheelite type to that of tetragonal scheelite type. The endothermic peak in DSC at around 260°C reveals the phase transition, which is also confirmed by the XRD and FT-IR analysis. The XRD patterns confirmed the monoclinic structure of BiVO₄.     

Chelated complexes of cadmium(II), cobalt(II), copper(II), mercury(II), nickel(II), uranyl(II) and zinc(II) with benzil bis(4-phenylthiosemicarbazone)

Summary Complexes of Co^II, Ni^II, Cu^II, Zn^II, Cd^II, Hg^II and UO ₂ ^II with benzil bis(4-phenylthiosemicarbazone), H₂BPT, have been synthesized and their structures assigned based on elemental analysis, molar conductivity, magnetic susceptibility and spectroscopic measurements. The i.r. spectra suggest that the ligand behaves as a binegative quadridentate (NSSN) (Co^II, Cu^II, Hg^II and UO ₂ ^II complexes) or as a binegative quadridentate-neutral bidentate chelating agent (Ni^II, Zn^II and Cd^II complexes). Octahedral structures for the Co^II and Ni^II complexes and square-planar structure for the Cu^II complex are suggested on the basis of magnetic and spectral evidence. The crystal field parameters (Dq, B and _B) for the Co^II complex are calculated and agree fairly well with the values reported for known octahedral complexes. The ligand can be used for the microdetermination of Ni^II ions of concentration in the 0.4–6×10^–4 mol l^–1 range and the apparent formation constant for the species generated in solution has also been calculated.     

Supercritical carbon dioxide extraction and gas chromatography–mass spectrometry analysis of Gymnema sylvestre R.Br. roots

Supercritical fluid extraction (SFE) achieves a wide range of applications since the past decade as a sustainable green technology. The present study investigates the process for producing high yield by supercritical carbon dioxide (Sc-CO₂) extraction form Gymnema sylvestre R.Br. roots. The effect of temperature and pressure on the percentage of accumulative yield is demonstrated. It is found that the highest yield is obtained at the temperature of 60°C and the pressure of 10?MPa. A proper review showed that there is a lack in the study of Sc-CO₂ extraction of this plant especially for optimization of SFE process which makes this study useful and valuable. For more benefit, the extract which achieves highest percentage is subjected to gas chromatography–mass spectrometry to study its chemical composition and detect the active principle compounds which present with high concentration and expected to be responsible of the pharmaceutical properties of the extract.     

Synthesis, physical studies and uptake behavior of: copper(II) and lead(II) by Schiff base chelating resins

Two new chelating resins possessing multiple functional groups capable of coordinating with several metal ions are reported. The resins were synthesized by condensing Schiff bases derived from 2-aminophenol, 2-hydroxy-5-chloroaniline and terephthaldehyde with formaldehyde in an alkaline medium. The effects of pH and contact time of the Cu(2+) and Pb(2+) in aqueous solutions on the uptake behavior of the resins were studied. The metal ion uptake behavior of the resins was investigated by the batch method. Both the uptake and the selectivity of the resins towards the investigated metal ions were related to the structure of the resins, type of the metal ion and the uptake conditions. The resins showed maximum uptake capacity for Cu(2+) and Pb(2+) at pH 10. Cu(2+) was seen to undergo preferential adsorption in separate and mixture solutions of Cu(2+) and Pb(2+). Kinetic studies for the resins using Langmiur equation were also performed. The Schiff base monomers and their formaldehyde resins were characterized by elemental analyses, FTIR and (1)H NMR spectroscopy. The thermal stability of the resins was studied using TGA/DTG analysis.     

Enhancing electrochemical conversion of lithium polysulfide by 1T-rich MoSe2 nanosheets for high performance lithium–sulfur batteries

The sluggish conversion kinetics and shuttle effect of lithium polysulfides (LiPSs) severely hamper the commercialization of lithium–sulfur batteries. Numerous electrocatalysts have been used to address these issues, amongst which, transition metal dichalcogenides have shown excellent catalytic performance in the study of lithium–sulfur batteries. Note that dichalcogenides in different phases have different catalytic properties, and such catalytic materials in different phases have a prominent impact on the performance of lithium–sulfur batteries. Herein, 1T-phase rich MoSe₂ (T-MoSe₂) nanosheets are synthesized and used to catalyze the conversion of LiPSs. Compared with the 2H-phase rich MoSe₂ (H-MoSe₂) nanosheets, the T-MoSe₂ nanosheets significantly accelerate the liquid phase transformation of LiPSs and the nucleation process of Li₂S. In-situ Raman and X-ray photoelectron spectroscopy (XPS) find that T-MoSe₂ effectively captures LiPSs through the formation of Mo-S and Li-Se bonds, and simultaneously achieves fast catalytic conversion of LiPSs. The lithium–sulfur batteries with T-MoSe₂ functionalized separators display a fantastic rate performance of 770.1 mAh/g at 3 C and wonderful cycling stability, with a capacity decay rate as low as 0.065% during 400 cycles at 1 C. This work offers a novel perspective for the rational design of selenide electrocatalysts in lithium–sulfur chemistry.