Barium Holmium Zirconate, A New Perovskite Oxide: II, Synthesis as Nanoparticles through a Modified Combustion Process

Nanoparticles of barium holmium zirconate, a new complex perovskite ceramic oxide, has been synthesized using a modified self-propagating combustion process. The solid combustion products obtained were characterized by X-ray diffraction (XRD), electron diffraction, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, particle size analysis, surface area determination, and high-resolution transmission electron microscopy. The XRD and electron diffraction studies have shown that the as-prepared powder is phase pure Ba₂HoZrO_5.5 and has a complex cubic perovskite (A₂BB'O₆) structure with a lattice constant a = 8.428 Å. The transmission electron microscopic investigation has shown that the particle size of the as-prepared powder was in the range 4–16 nm with a mean grain size of 8.2 nm. The nanoparticles of Ba₂HoZrO_5.5 obtained by the present method could be sintered to 98% theoretical density at 1500°C.     

Nonaqueous Cold Extrusion as a Route for Yttrium Barium Copper Oxide Wires

Yttrium barium copper oxide (YBCO) superconducting wires of diameter 0.2 to 1 mm in the form of spirals up to 50 cm long were made by a novel nonaqueous cold extrusion technique. Finely ground YBCO powder having a set particle size distribution was intimately mixed with a polypropylene compound and extruded manually into wires which were heat-treated at controlled rates followed by oxygen annealing at 940°C for 10 h. These wires are superconducting with a T _c of 89.5 K, the XRD pattern exhibiting an orthorhombic single phase. Current density at zero field was measured to be 223 A/cm². The surface morphology of the extruded wires and microstructure of the polished cross section of the sintered wires are also presented.     

Structural Characterization of Lanthanum Chromite Perovskite Coating Deposited by Magnetron Sputtering on an Iron-Based Chromium-Containing Alloy as a Promising Interconnect Material for SOFCs

Chromium-containing stainless steel (SS) is a prospective material for use as an interconnect in solid oxide fuel cells (SOFCs). However, during operations at high temperatures, the growth of oxide scales causes the performance of the interconnect and SOFC as a whole to deteriorate. The coating of SS 446 with a conducting perovskite is a potential method of slowing the growth of oxide scale and, therefore, improving overall SOFC performance. In the present research, the structural characterization of a pure LaCrO₃ thin film on the SS 446 substrates has been performed as a model material that can be used as a barrier coating for the metallic interconnect. The deposition of an amorphous La-Cr-O thin film on SS 446 was performed using radio-frequency (rf) magnetron sputtering. The deposited amorphous film was annealed in air to form the desired perovskite phase. The film underwent an amorphous to LaCrO₄ phase transition during annealing at 500°C with further transformation to LaCrO₃ orthorhombic phase during annealing at 700°C. A self-organized dendritic structure was reported as a result of the perovskite-phase formation. Although formation of various oxides, such as Fe₂O₃ and Fe₃O₄, was observed during the annealing of uncoated SS 446 in air, the coating of SS 446 surface with LaCrO₃ film prevented formation of various oxide phases at the interconnect surface. The structural characterization of the films and SS 446 surfaces was accomplished using scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffractometry, micro-Raman spectroscopy, and nanoindentation.     

Synthesis and Characterization of Manganese Oxide Catalysts for the Total Oxidation of Ethyl Acetate

Manganese oxide catalysts were synthesized by direct reaction between manganese acetate and permanganate ions, under acidic and reflux conditions. Parameters such as pH (2.0–4.5) and template cation (Na⁺, K⁺ and Cs⁺) were studied. A pure cryptomelane-type manganese oxide was synthesized under specific conditions, and it was found that the template cation plays an important role on the formation of this kind of structure. Cryptomelane was found to be a very active oxidation catalyst, converting ethyl acetate into CO₂ at low temperatures (220 °C). This catalyst is very stable at least during 90 h of reaction and its performance is not significantly affected by the presence of water vapour or CO₂ in the feed stream. The catalyst performance can be improved by the presence of small amounts of Mn₃O₄.     

新型黄光铱磷光配合物的合成、表征及性能研究

通过在2,4-二氯吡啶上引入3-联苯基,合成了一种以2,4-二(3-联苯)吡啶为主配体,以2,2,6,6-四甲基-3,5-庚二酮为辅助配体的新型有机电致磷光材料,通过元素分析、红外光谱、~1H NMR和质谱对产物进行了结构表征,利用X射线单晶衍射仪测定了配合物的晶体结构。并对其用紫外-可见吸收、光致发光、热稳定性等进行研究。研究表明,配合物在395和465nm处存在单重态~1MLCT(金属到配体的电荷跃迁)和三重态~3MLCT的吸收峰;其初始分解温度为405℃(对应于10%质量损失),最大发射波长为570nm,是一种可用于白色有机电致发光器件的新型黄色发光磷光材料。     

Catalytic and Electrochemical Properties of Doped Lanthanum Chromites as New Anode Materials for Solid Oxide Fuel Cells

Defective perovskites contained in the general formula La(Sr)Cr(Ru,Mn)O_3–δ are successfully synthesized by spray pyrolysis. Powders of high phase purity are obtained after annealing, and they are used to prepare homogeneous films by spray printing. From a catalytic point of view for the methane steam reforming, these powdered perovskites do not generate a carbon deposit. Catalytic results, focused on doped ruthenium perovskites, confirm that the insertion of ruthenium in the structure of the lanthanum chromite presents a real benefit for the methane steam reforming. The electrochemical properties of La(Sr)CrO_3–δ, either pure and doped with manganese, show that the perovskite films can be potential electrodes, depending on their doping, for hydrogen anodic oxidation in solid oxide fuel cells.     

Synthesis,Characterization, and Computational Study of New Ferrocene-Based Schiff Bases as Potential Nonionic Surfactants

Ferrocene-based nonionic surfactants were synthesized by reacting ferrocenylcarboxyaldehyde with different long-chain amines. Nonionic surfactants were characterized using Fourier transform infrared spectra (FT-IR), ¹HNMR, and ¹³CNMR spectroscopy. The ferrocene-based surfactants were characterized using ultraviolet (UV)–visible spectroscopy and surface tension measurements to determine the critical micelle concentration (CMC). The CMC values indicate high aggregation ability of the synthesized surfactants in ethanol. Dominance of their hydrophilic character was ensured from hydrophilic–lipophilic balance in the 10–15 range. Voltammetric response of all surfactants showed well-defined and stable redox signals. Computational studies further revealed their physicochemical characteristics. Results of the study confirm the multifunctionality of the surfactants and suggest utilization in various fields.     

Molten Salt Synthesis of a Complex Perovskite, Pb(Fe0.5Nb0.5)O3

Pure, single-phase stoichiometric Pb(Fe_0.5Nb_0.5)O₃ (PFN) powders were successfully formed by molten salt synthesis using mixtures of NaCl and KCl salts. Lower temperatures and shorter times (1/2 h at 800°C) were needed for singlephase PFN formation from molten salts relative to those required for solid-phase methods (4 h at 1000°C). A systematic study indicating the effects of process parameters, such as temperature, time, and amount of flux with respect to starting oxides, on the PFN formation mechanism and its resulting powder characteristics is reported. The particle size increased with increasing synthesis temperature; the rate of increase was greatest above 900°C, which is close to the melting point of PbO. PFN powders formed by molten salt synthesis are spheroidal, free from aggregates, and sintered to good densities at temperatures as low as 1000°C.     

Barium Rare-Earth Hafnates: Synthesis, Characterization, and Potential Use as Substrates for YBa2Cu3O7-delta Superconductor

A new group of complex perovskites Ba₂REHfO_5.5 (where RE = La, Pr, Nd, and Eu) has been synthesized and sintered as single-phase materials with high sintered density and stability using a solid-state reaction method for the first time. The structure of Ba₂REHfO_5.5 has been studied by X-ray diffactometry (XRD) and all of the perovskites are isostructural and have a cubic structure. The dielectric constant and loss factor values of these materials are in a range suitable for their use as substrates for YBa₂Cu₃O_7-delta superconductors. XRD and resistivity measurements show that there is no detectable reaction between YBa₂Cu₃O_7-delta and Ba₂REHfO_5.5, even when the two substances are mixed thoroughly and sintered at 950°C for 15 h. The addition of Ba₂REHfO_5.5 up to 20 vol% in YBa₂Cu₃O_7-delta-Ba₂REHfO_5.5 composite shows no detrimental effect on the superconducting transition temperature of YBa₂Cu₃O_7-delta. Thick films of YBa₂Cu₃O_7-delta fabricated on polycrystalline Ba₂REHfO_5.5 substrate have a superconducting zero resistivity transition of 92 K, indicating the suitability of these new materials as substrates for YBa₂Cu₃O_7-delta films.     

A Fluorescent Silver(I) Carbene Complex with Anticancer Properties: Synthesis,Characterization, and Biological Studies

The silver(I) N-heterocyclic carbene (NHC) complex bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) silver chloride ([Ag(EIA)₂]Cl), bearing two anthracenyl fluorescent probes, has been synthesized and characterized. [Ag(EIA)₂]Cl is stable in organic solvents and under physiological conditions, and shows potent cytotoxic effects in vitro toward human SH-SY5Y neuroblastoma cells. The interactions of [Ag(EIA)₂]Cl with a few model biological targets have been studied as well as its ability to be internalized in cells. The in vitro anticancer activity is apparently related to the level of drug internalization. Notably, [Ag(EIA)₂]Cl does not react with a few model proteins, but is capable of binding the C-terminal dodecapeptide of thioredoxin reductase hTrxR(488–499) and to strongly inhibit the activity of this enzyme. Binding occurs through an unconventional process leading to covalent binding of one or two carbene ligands to the C-terminal dodecapeptide with concomitant release of the silver cation. To the best of our knowledge, this mode of interaction is reported here for the first time for Ag(NHC)₂ complexes.     

Gas-Phase Flame Synthesis and Characterization of Iron Oxide Nanoparticles for Use in a Health Effects Study

Iron oxide nanoparticles, to be used in a health effects study, were synthesized in a H₂/air diffusion flame and characterized by transmission electron microscopy, X-ray diffraction, surface area measurement, inductively coupled plasma mass spectrometry, and a spectrophotometric speciation method. The nanoparticles exhibited the maghemite (γ -Fe₂O₃) crystal structure and contained only trivalent iron. There were two size modes in the particles. The large size mode contained crystalline, non-agglomerated particles with a median diameter of approximately 45 nm; the small size mode contained particles that were in the size range of 3–8 nm and were mostly amorphous. Depending on the value taken for the small particle size, the small mode accounted for 73–82% of the particle surface area. The particles in the small size mode were likely formed from the vapor of FeO and Fe.     

Rare-Earth Barium Stannates: Synthesis, Characterization, and Potential Use as Substrates for YBa2Cu3O7-δ Superconductor

A new group of complex perovskites, REBa₂SnO_5.5 (where RE = Pr, Sm, Eu, and Gd) have been synthesized and sintered as single-phase materials with high sintered density and stability by the solid-state reaction method. The structure of REBa₂SnO_5.5 was studied by the X-ray diffraction technique, and all of them were found to be isostructural and have a cubic perovskite structure. The dielectric constant and loss factor values of these materials are in a range suitable for substrate applications. The X-ray diffraction and resistivity measurements have shown that there is no detectable reaction between YBa₂Cu₃O_7-δ and REBa₂SnO_5.5, even when the substances are mixed thoroughly and sintered at 950°C for 15 h. Thick films of YBa₂Cu₃O_7-δ fabricated on polycrystalline REBa₂SnO_5.5 substrates gave superconducting zero resistivity transition T _C(0)= 92 K, indicating the suitability of these new materials as substrates for YBa₂Cu₃O_7-δ films.     

Novel Nanosized Aluminium Carboxylates: Synthesis,Characterization and Use as Nanofillers for Protective Polymeric Coatings

A mixture of novel aluminium carboxylate nanoparticles and aluminium hydroxide ultrafine powder was prepared via precipitation reaction between Al(2‐PrO)₃ and maleic acid. In this mixture both free primary particles occur (mean geometrical size around 40 nm) together with a secondary agglomerated particle fraction of sizes in the low micrometer region. However, centrifugation processes allowed for the removal of the latter and resulted in the formation of size stable nanopowders. Up to 30 wt.‐% of these particles were incorporated into acrylate matrices resulting in low‐viscosity formulations with [η] < 1 000 mPa · s, which allowed for roller application and even spray coating of these nanocomposites at room temperature. Radiation curing of such coatings was accomplished via UV irradiation. In comparison to the corresponding SiO₂‐based nanocomposites and carboxylate alumoxane fillers, the cured coatings revealed significantly improved surface mechanical properties.

     

Dependence of YBaCuO Superconductor Properties on Constituent Oxide Preparation: I, CuO and BaCO3 Pretreatment

A systematic study has been made of the influence of different solid-state decomposition preparations of copper oxide and barium carbonate on the synthesis of YBa₂Cu₃O_7−x superconductor. Considerable morphological control on the end product can be achieved through a monitored calcining of starting materials. The ceramic particle size is found to be primarily dependent on initial CuO morphology, whereas uniformity of the ceramic and the occurrence of an intergranular phase is sensitive to the form of the BaO precursor. The use of accoustic testing for characterizing the ceramic quality is suggested.     

一种铱磷光配合物的合成表征及性能研究

利用2-苯基吡啶(ppy)、三水合氯化铱(IrCl_3·3H_2O)和2-吡啶甲酸(pic)配位,得到铱配位物Ir(ppy)_2pic,合成产率9 0%,该方法适合于Ir(ppy)2pic的批量制备。通过元素分析、核磁共振(~1H-NMR、~(13)C-NMR)和质谱(MS)对产物分子结构进行了表征,此外结合紫外吸收光谱(UV-Vis)和荧光光谱(PL)对其光物理性能进行了研究。结果表明:该配合物在紫外谱图上的250~300 nm处出现了强的配体单重态π-π*自旋跃迁吸收峰,在400~500 nm处出现了铱(Ш)到配体的单重态和三重态(~1MLCT和~3MLCT)电子跃迁吸收峰,在荧光光谱的514 nm处有较强的金属配合物三重态的磷光发射峰,显示为一种高效的绿色磷光材料。     

皂化法合成硬脂酸钡,镉新工艺

将化学计量比的硬脂酸、氯化钡或硫酸镉溶液、部分烧碱溶液和适量水搅拌加热,然后慢慢加入余量的烧碱溶液,可合成得到高质量的硬脂酸钡或硬脂酸镉产品,与传统的复分解法工艺相比,新工艺显著提高了生产效率,降低了能耗。     

Synthesis,Characterization, and Biodistribution of a Dinuclear Gadolinium Complex with Improved Properties as a Blood Pool MRI Agent

A dinuclear gadolinium(III) chelate containing two moieties of diethylenetriaminepentaacetic acid (DTPA), covalently conjugated to an analogue of deoxycholic acid, was synthesized and thoroughly characterized. A full relaxometric analysis was carried out, consisting of 1) the acquisition of nuclear magnetic resonance dispersion (NMRD) profiles in various media; 2) the study of binding affinity to serum albumin; 3) the measurement of ¹⁷O transverse relaxation rate versus temperature, and 4) a transmetallation assay. In vivo biodistribution MRI studies at 1 T and blood pharmacokinetics assays were carried out in comparison with Gd‐DTPA (Magnevist) and gadocoletic acid trisodium salt (B22956/1), two well‐known Gd complexes that share the same chelating cage and the same deoxycholic acid residue of the Gd complex investigated herein ((GdDTPA)₂‐Chol). High affinity for plasma protein and, in particular, the availability of more than one binding site, allows the complex to reach a fairly high relaxivity value in plasma (～20 mm ^?1 s^?1, 20 MHz, 310 K) as well as to show unexpectedly enhanced properties of blood pooling, with an elimination half‐life in rats approximately seven times longer than that of B22956/1.     

Doped Perovskite Oxide, PrMnO3, as a New Cathode for Solid-Oxide Fuel Cells that Decreases the Operating Temperature

Cathodic overpotentials of Ln_0.6Sr_0.4MnO₃ (Ln is La, Pr, Nd, Sm, Gd, Yb, and Y) were studied for a new cathode for solid-oxide fuel cells (SOFCs) with low overpotentials in a relatively-low-temperature region. Cathodic overpotentials strongly depended on the rare-earth cations in the A sites of the perovskite oxide. In particular, overpotentials of a Sr-doped PrMnO₃ cathode maintained low values despite decreased operating temperature. Consequently, almost the same power density of a SOFC with Ln_0.6Sr_0.4MnO₃ cathode was obtained at about 100 K lower operating temperature by using Sr-doped PrMnO₃ as the cathode.     

Cytotoxic 1,2,3-Triazoles as Potential Leads Targeting the S100A2-p53 Complex: Synthesis and Cytotoxicity

In silico screening predicted 1 (N-(4-((4-(3-(4-(3-methoxyphenyl)-1H-1,2,3-triazol-1-yl)propyl)piperazin-1-yl) sulfonyl)-phenyl)acetamide) as an inhibitor of the S100A2-p53 protein-protein interaction. S100A2 is a validated pancreatic cancer drug target. In the MiaPaCa-2 pancreatic cell line, 1 was a ∼50 μM growth inhibitor. Synthesis of five focused compound libraries and cytotoxicity screening revealed increased activity from the presence of electron withdrawing moieties on the sulfonamide aromatic ring, with the 3,5-bis-CF₃ Library 3 analogues the most active, with GI₅₀ values of 0.91 (3-ClPh; 13 i ; BxPC-3, Pancreas) to 9.0 μM (4-CH₃; 13 d ; PANC-1, Pancreas). Activity was retained against an expanded pancreatic cancer cell line panel (MiaPaCa-2, BxPC-3, AsPC-1, Capan-2, PANC-1 and HPAC) and the normal cell line MCF10A (breast). Bulky 4-disposed substituents on the terminal phenyl ring enhanced broad spectrum activity with growth inhibition values spanning 1.1 to 3.1 μM (4-C(CH₃)₃; 13 e ; BxPC-3 and AsPC-1 (pancreas), respectively). Central alkyl spacer contraction from propyl to ethyl proved detrimental to activity with Library 4 and 5.5- to 10-fold less cytotoxic than the propyl linked Library 2 and Library 3. The data herein was consistent with the predicted binding poses of the compounds evaluated. The highest levels of cytotoxicity were observed with those analogues best capable of adopting a near identical pose to the p53-peptide in the S100A2-p53 binding groove.     

New Core-Shell Nanostructures for FRET Studies: Synthesis,Characterization, and Quantitative Analysis

This work describes the synthesis and characterization of new core-shell material designed for Förster resonance energy transfer (FRET) studies. Synthesis, structural and optical properties of core-shell nanostructures with a large number of two kinds of fluorophores bound to the shell are presented. As fluorophores, strongly fluorescent rhodamine 101 and rhodamine 110 chloride were selected. The dyes exhibit significant spectral overlap between acceptor absorption and donor emission spectra, which enables effective FRET. Core-shell nanoparticles strongly differing in the ratio of donors to acceptor numbers were prepared. This leads to two different interesting cases: typical single-step FRET or multistep energy migration preceding FRET. The single-step FRET model that was designed and presented by some of us recently for core-shell nanoparticles is herein experimentally verified. Very good agreement between the analytical expression for donor fluorescence intensity decay and experimental data was obtained, which confirmed the correctness of the model. Multistep energy migration between donors preceding the final transfer to the acceptor can also be successfully described. In this case, however, experimental data are compared with the results of Monte Carlo simulations, as there is no respective analytical expression. Excellent agreement in this more general case evidences the usefulness of this numerical method in the design and prediction of the properties of the synthesized core-shell nanoparticles labelled with multiple and chemically different fluorophores.