Study on electrical conductivity and phase transition in singly doped BIPBVOX (Bi2V1−xPbxO5.5−x/2) solid electrolyte

Samples of bismuth lead vanadium oxide (BIPBVOX) (Bi₂V_1–xPb_xO_5.5–x/2) singly substituted system in the composition range 0.05 ≤ x ≤ 0.20 were prepared by sol–gel synthesis route. Structural investigations were carried out by using a combination of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique. Energy dispersive X-ray spectroscopy analysis (EDXA) of doped samples was carried out to predict the sample purity and doping concentration. Transitions, α?β, β?γ and γ′?γ were detected by XRD, DTA and variation in the Arrhenius plots of conductivity. The ionic conductivity was measured by AC impedance spectroscopy. The solid solutions with composition x ≤ 0.07 undergo α?β phase transition, at 329 °C and β?γ phase transition at 419 °C. The highly conducting γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.17 whose thermal stability increases with Pb content. At 300 °C, the highest value of conductivity 6.234 × 10^?5 S cm^?1 was obtained for composition x = 0.15 and at 600 °C the highest value of conductivity 0.65 S cm^?1 is observed for x = 0.17. AC impedance plots reveal that the conductivity is mainly due to the grain contribution to oxide ion conductivity.     

Ab initio study of magnetic property of BEST2 [Fe(CN)5NO] charge-transfer salt

By means of ab initio method of the full potential linearized augmented-plane-wave, electronic band structure and its magnetic property for a charge transfer compound of bis (ethylenediselena)-tetrathiafulvalene(BEST) with [Fe(CN)₅NO] anions are investigated for the first time, where the exchange-correlation effects of electrons are accounted in the generalized gradient approximation. The spin density of states and the magnetic moment are analyzed in detail. It is found that there exists a new antiferromagnetic coupling in the organic donors because of alternating spin population in the organic donors. Besides the localized 3d electrons of Fe in [Fe(CN)₅NO] anion, the ligand nitric oxide and the cyanogen radical play important roles in the magnetic properties of the system. Our results are in good agreement with the experimental observations.     

Base-promoted regioselective synthesis of 1,2,3,4-terahydroquinolines and quinolines from N-boc-3-piperidone

An efficient synthesis of 1,2,3,4-tetrahydroquinolines with donor and acceptor group has been delineated by base mediated ring transformation of 6-aryl-4-substituted-2H-pyran-2-one-3-carbonitriles by N-boc-3-piperidone followed by consecutive deprotection of Boc group under acidic conditions. This reaction involves 2 new bond formations namely C4a-C5 and C8a-C8 in order to create the nucleus. Various donor and acceptor functional groups like aryl, heteroaryl, nitrile, methylsulfanyl and secondary amine were installed in 1,2,3,4-tetrahydroquinolines. We extended our approach to synthesize the fused 1,2,3,4-tetrahydroquinolines by using 2-oxobenzo[h]chromenes as precursor. Further, we synthesized fused and isolated quinolines through aromatization of 1,2,3,4-tetrahydroquinolines by DDQ in excellent yields. Single-crystal X-ray analysis of the Boc protected tetrahydroisoquinoline 6t showed the steric hindrance between N-Boc and aryl group.     

Effect of Ni(II) substitution on phase stabilization electrical properties of BICo(III)VOX.20 oxide-ion conductor

The BICO_0.20–xNI_xVOX solid electrolyte was synthesized by the standard solid-state reaction. The effect of Ni(II) substitution for Co(III) on phase stabilization and oxide-ion performance has been investigated in the compositional range 0?≤?x?≤?0.20 using X-ray powder diffraction, differential thermal analysis and AC impedance spectroscopy. The highly conductive γ′-phase was effectively stabilized at room temperature for compositions with x?≥?0.13 whose thermal stability increases with Ni content. The complex plane plots of impedance were typically represented at temperatures below 380?°C, suggesting a major contribution of polycrystalline grains to the overall electrical conductivity. The dielectric permittivity measurements revealed the fact that suppression of the ferroelectric transition is compositionally dependent. Interestingly, the maximum ionic conductivity at lower temperatures (~2.56?×?10^?4?S^?cm^?1 at 300?°C) was observed for the composition with x?=?0.13. The variation of low-temperature conductivity with Ni content was accompanied with a general drop in the corresponding values of ΔE_LT. However, the local minimum high-temperature conductivity, σ₆₀₀?°C?~?2.26?×?10^?2?S^?cm^?1 for x?=?0.10, coupled with a local maximum value of ΔE_HT?~?0.48?eV was attributed to an increased defect trapping effect correlated with the V(V)?→?V(IV) reduction at elevated temperatures.     

Study on phase stability and oxide ion conductivity in the BIAGVOX system

A novel oxide ion conductor, BIAGVOX formulated as Bi₄Ag_xV_2?xO_11?(2x)?δ is obtained by substituting a fraction (x) of V⁵⁺ by Ag⁺ in Bi₄V₂O₁₁ samples of the BIAGVOX system in the composition range, 0.05≤x≤0.30 were synthesized using the standard solid-state reaction. XRPD, FT-IR, DTA and AC impedance spectroscopy were used for the investigation of the correlation between the structural phase stability and oxide ion performance of the BIAGVOX materials. It has been found that orthorhombic, β, and incommensurate tetragonal, γ′ were stabilized at room temperature for compositions with x≤0.15 and x≥0.20, respectively. The enthalpy of β→γ and γ→γ transition exhibited a general drop with increasing Ag content and a minimum transition temperature was observed for x=0.20. However, the oxide ion conductivity at lower temperatures remarkably increased in composition stability ranges of β- and γ-phase, while a maximum conductivity was reported for the high temperature γ-phase at x=0.15. However, the low temperature conductivity, σ₃₀₀°c measured for x=0.30 was found to be comparable with the maximum ionic conductivity of the BICUVOX system reported for x=0.20 at the same temperature.     

Laser performance and photostability of Rhodamin B in solid host matrices

Laser dye Rhodamine B was incorporated at different concentrations in GMA polymer, sol–gel glass and organic–inorganic hybrid material synthesized using the sol–gel process. The amplified spontaneous emission (ASE) was studied using Nd-YAG laser of 532 nm. The effect of laser excitation in transfer pumping configuration and the influence of dye concentration on the ASE were studied. Also, the gain and the energy conversion efficiencies were investigated. Relatively high efficiencies (to ～48%) were obtained with good photostabilities where a decrease to ～30% of the initial amplified spontaneous emission output energy were observed after pumping by 35000 shots at relatively high repetition rate (10 Hz) and energy (15 mJ). The composition and the properties of the matrix were found that optimize the laser performance and photostability of an investigated dye.     

Microscopic study on proton elastic scattering of light exotic nuclei at energies below than 100 MeV/nucleon

The proton elastic scattering data on some light exotic nuclei, namely, ^{6, 8}He, ^{9, 11}Li, and ^{10, 11, 12}Be, at energies below than 100MeV/nucleon are analyzed using the single folding optical model. The real, imaginary, and spin-orbit parts of the optical potential (OP) are constructed only from the folded potentials and their derivatives using M3Y effective nucleon-nucleon interaction. These OP parts, their renormalization factors and their volume integrals are studied. The surface and spin-orbit potentials are important to fit the experimental data. Three model densities for halo nuclei are used and the sensitivity of the cross-sections to these densities is tested. The imaginary OP within high-energy approximation is used and compared with the single folding OP. This OP with few and limited fitting parameters, which have systematic behavior with incident energy, successfully describes the proton elastic scattering data with exotic nuclei.     

Structural control of Fano resonances in semiconductor heterostructures

Structural control of quantum interference in the optical intrasubband absorption spectrum of GaAs/AlGaAs multi-quantum wells is investigated theoretically. Our study shows that pronounced Fano resonances are in general difficult to obtain in quantum well heterostructures, with a presence of distinct Fano resonance features being the exception rather than the rule. Guided by an analogy to Young’s double-slit experiment, we design increasingly improved structures to display Fano resonances. Best results are achieved in structures where there is strong overlap between the ground-state wavefunction and scattering states associated with the uncoupled continuum. Alternatively one may use ionization via two or more resonances. In this case, resonances should not be separated by more than 25 meV to give significant effects. Moreover, we show that resonance features may also be induced without potential barriers to a continuum merely via orthogonality between bound and excited states.     

Thermal and crystallization behaviour of gamma irradiated PLLA

Structure, crystallization behaviour and some thermal properties of poly-l-lactide (PLLA), gamma irradiated up to 300 kGy, have been studied. Through differential scanning calorimetry measurements, radiation-induced changes were evident in the enthalpy of melting and cold crystallization, as well as in the degree of crystallinity. Decay of the glass transition, cold crystallization and melting temperatures with irradiation dose was observed in all cases. The annealing treatment, which can substantially reduce the concentration of free radicals, also had a great impact on thermal/crystallization behaviour of irradiated PLLA. Extensive chain scission, as a dominant effect of gamma irradiation, confirmed by gel permeation chromatography, has as a consequence a growth of new thin crystal lamellae and occurrence of the second low-temperature melting peak. Thermogravimetric analyses have shown that irradiation lowered the thermal stability of PLLA.     

Chelation and Analytical Application of Thiosemicarbazides Toward Platinum(IV) Ions

N(1)H derivatives of ethyl- and phenyl-thiosemicarbazides have been prepared and identified so as to produce new complexes with H₂PtCl₆. The obtained complexes have been investigated by thermal, magnetic and spectral studies. They were found to be diamagnetic and to have an octahedral structure. The IR data reveal different modes of coordination for the investigated ligands. The thermal decomposition of some complexes ended with PtS₂ as a final product. The formation of a green associate with 1-phenyl-4-ethylthiosemicarbazide (HPETS) was found suitable for the preconcentration and determination of Pt(IV). A simple and effective separation–determination procedure was achieved through the use of the flotation technique. The deprotonation constants of the ligands and the stability constants of the complexes formed in solution were evaluated by electrochemical methods, Methylthiosemicarbazide (HMTS) complexes were found to be the most stable in solution.