Ceramic electrolytes based on (Ba1 − x Ca x )(Zr0.9Y0.1)O3 solid solution

The aim of this work was to study the electrical and electrochemical properties of the (Ba_1???x Ca _x )(Zr_0.9Y_0.1)O₃ solid solutions. The powders of different calcium content (x?=?0, 0.05, 0.1, and 1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. X-ray diffraction analysis showed that a small substitution of calcium for barium caused formation of cubic solid solutions with the decreasing cell parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H₂, and/or H₂O at temperature from 300 to 800 °C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. Overall, the electrical conductivity was higher in wet atmospheres that contained oxygen that was in accordance with the model of a proton transport in perovskite structure which assumed the presence of the oxygen vacancies. The solid solution containing 5 mol% of calcium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres; this can be attributed to the local changes in the cubic perovskite structure. Test results for CaZr_0.9Y_0.1O₃ used as an electrolyte in solid oxide galvanic cells involving CaCr₂O₄ as a reference electrode are also reported.     

Search for bioactive compounds from Cantharellus cibarius

Ground fruit bodies of Cantharellus cibarius (chanterelle) were extracted with dichloromethane and subjected to CC followed by preparative HPLC, which led to the isolation of glycerol 1,2- and 1,3-dilinoleates and glycerol tridehydrocrepenynate. Extraction of C. cibarius fruit bodies with ethanol or methanol afforded fatty acid ethyl or methyl esters as a result of esterification/transesterification reactions. Insecticidal activity of the isolated glycerides and esters was much lower than that of the crude extracts and chromatographic fractions suggesting a synergistic effect of some of the compounds present in the mixture.     

Mass spectrometric and quantum chemical studies of the thermodynamics and bonding of neutral and ionized LnCl, LnCl2, and LnCl3 species (Ln = Ce, Lu)

The mass spectral patterns of CeCl3(g) and LuCl3(g) and appearance energies for the identified ions were measured using a Nier-type mass spectrometer coupled with a Knudsen cell. The molecular ion CeCl3+ was found to be considerably less stable in comparison to LuCl3+. Partial pressures and sublimation enthalpies of LnCl3(s) to monomeric LnCl3(g) and dimeric Ln2Cl6(g) species were obtained in the ranges of 882-1028 (Ln = Ce) and 850-1004 K (Ln = Lu). The contribution of dimeric Ce2Cl6(g) species to equilibrium vapors of CeCl3(s) is considerably smaller than the Lu2Cl6(g) contribution in LuCl3(s) vapors. The measurements were supplemented by quantum chemical ab initio studies of structures, energetics, and vibrational frequencies of neutral and singly ionized LnCl, LnCl2, and LnCl3 species (Ln = Ce, Lu). The theoretical appearance energies of different ions, calculated from the energies of the gaseous species, are in good agreement with experimental data. The fragmentation energies of LnCl, LnCl2, and LnCl3 were also computed and compared with the mass spectral patterns of respective vapor species. The Mulliken and natural bond orbital electron population methods were applied for the systematic analysis of the bonding scheme in molecules and cations.     

Bias field influence on dielectric spectra of B phases of bent-core thioesters

Smectic B₂ phase of bent-core 1,3-phenylene bis{4-[(4-dodecyloxybenzoyl)sulfanyl]benzoate} (12OSOR) and a mixture 12R9AF have been studied using dielectric and electrooptic methods. 12R9AF is a mixture of bent-core 12OSOR and calamitic chiral MHPSBO9 materials. The B₂ phase of 12R9AF mixture is shifted to lower temperatures by about 10 °C in comparison with pure 12OSOR. Spontaneous polarization of the mixture is comparable with spontaneous polarization of pure compound. Dielectric measurements were done using dielectric spectrometer based on Agilent 4294A impedance analyzer. Dielectric spectra measured with bias field for B₂ phase of 12OSOR and 12R9AF show two well separated relaxation processes.     

Optical properties of Eu:CsGd2F7 downconversion phosphor

Luminescence spectra and excitation spectra in 150-420 nm spectral region have been recorded at room temperature for polycrystalline sample of (0.5%)Eu³⁺:CsGd₂F₇. The relatively intense emission has been observed from ⁵D₃, ⁵D₂ and ⁵D₁ levels. Emission and excitation spectra prove that the excitation energy is efficiently transferred from the ⁶G_J and ⁶I_J levels of Gd³⁺ ions to Eu³⁺ ions. The visible quantum cutting via downconversion has been detected, with efficiency of the cross-relaxation step of ∼50%.     

Retention-Mobile Phase Relationships for Methylxanthines and Biogenic Amine Metabolites in Adsorption Thin-Layer Chromatographic Systems

JPC – Journal of Planar Chromatography – Modern TLC - Relationships between RF values and mobile-phase composition have been determined for six methylxanthines and acidic and neutral...     

Evaluation of adsorption energy distribution of microporous materials by a multivariant identification

The applicability of new BET-like adsorption models (uLBET and LBET formulas) for the examination of microporous materials of irregular structure is discussed. The models are intended to handle the main effects of random pore geometry on the adsorption isotherm shape. They are based on a generalized BET theory and employ simple (but realistic) adsorption energy-pore geometry relationships. To overcome numerical problems inherent in fitting any more advanced adsorption model, a multivariant identification procedure is proposed with a subset of parameters being fixed in each variant. The reliability assessment of the system parameters evaluation is stressed. The paper outlines formal and numerical bounds for adsorption measurements-based identifiability of irregular porous structures. The LBET-type formulas are recommended for the examination of such materials, as a relatively simple alternative versus DFT-based techniques. Numerous simulation results and exemplary examinations of an empirical isotherm are discussed.     

Multifunctionality in Bimetallic LnIII[WV(CN)8]3− (Ln=Gd,Nd) Coordination Helices: Optical Activity,Luminescence, and Magnetic Coupling

Two chiral luminescent derivatives of pyridine bis(oxazoline) (Pybox), (SS/RR)‐iPr‐Pybox (2,6‐bis[4‐isopropyl‐2‐oxazolin‐2‐yl]pyridine) and (SRSR/RSRS)‐Ind‐Pybox (2,6‐bis[8H‐indeno[1,2‐d]oxazolin‐2‐yl]pyridine), have been combined with lanthanide ions (Gd³⁺, Nd³⁺) and octacyanotungstate(V) metalloligand to afford a remarkable series of eight bimetallic CN^?‐bridged coordination chains: {[Ln^III(SS/RR‐iPr‐Pybox)(dmf)₄]₃[W^V(CN)₈]₃}_n ? dmf ? 4 H₂O (Ln=Gd, 1 ‐SS and 1 ‐RR; Ln=Nd, 2 ‐SS and 2 ‐RR) and {[Ln^III(SRSR/RSRS‐Ind‐Pybox)(dmf)₄][W^V(CN)₈]}_n ? 5 MeCN ? 4 MeOH (Ln=Gd, 3 ‐SRSR and 3 ‐RSRS; Ln=Nd, 4 ‐SRSR and 4 ‐RSRS). These materials display enantiopure structural helicity, which results in strong optical activity in the range 200–450 nm, as confirmed by natural circular dichroism (NCD) spectra and the corresponding UV/Vis absorption spectra. Under irradiation with UV light, the Gd^III‐W^V chains show dominant ligand‐based red phosphorescence, with λ_max≈660 nm for 1 ‐(SS/RR) and 680 nm for 3 ‐(SRSR/RSRS). The Nd^III‐W^V chains, 2 ‐(SS/RR) and 4 ‐(SRSR/RSRS), exhibit near‐infrared luminescence with sharp lines at 986, 1066, and 1340 nm derived from intra‐f ⁴F_3/2→⁴I_{9/2,11/2,13/2} transitions of the Nd^III centers. This emission is realized through efficient ligand‐to‐metal energy transfer from the Pybox derivative to the lanthanide ion. Due to the presence of paramagnetic lanthanide(III) and [W^V(CN)₈]^3? moieties connected by cyanide bridges, 1 ‐(SS/RR) and 3 ‐(SRSR/RSRS) are ferrimagnetic spin chains originating from antiferromagnetic coupling between Gd^III (S_Gd=7/2) and W^V (S_W=1/2) centers with J _{1 ‐(SS)}=?0.96(1) cm^?1, J _{1 ‐(RR)}=?0.95(1) cm^?1, J _{3 ‐(SRSR)}=?0.91(1) cm^?1, and J _{3 ‐(RSRS)}=?0.94(1) cm^?1. 2 ‐(SS/RR) and 4 ‐(SRSR/RSRS) display ferromagnetic coupling within their Nd^III‐NC‐W^V linkages.     

Effect of Mobile-Phase pH on the Chromatographic Behavior of Biogenic Amine Neurotransmitters and their Metabolites

JPC – Journal of Planar Chromatography – Modern TLC - The dependence on mobile-phase pH of the retention behavior of biogenic amine neurotransmitters and their metabolites in...