利用Raman光谱计算铌酸锂晶体中Li的含量

根据商群对称性分析法对LiNbO3(简称LN)晶体的Raman光谱做了理论计算.测量了LN不同配置下的室温Raman光谱.利用155cm-1处的峰的半波宽计算了LN中Li的含量.结果证明我们所用LN样品是近化学计量比晶体.     

A Proton NMR Study of the Stoichiometry and Stability of 18-Crown-6 Complexes with K+, Rb+ and Tl+ Ions in Binary Dimethyl Sulfoxide-Nitrobenzene Mixtures

Proton NMR spectroscopy was used to study the complexation reaction of 18-crown-6 (18C6) with K⁺, Rb⁺ and Tl⁺ ions in a number of binary dimethyl sulfoxide-nitrobenzene mixtures. In all cases, the exchange between free and complexed crowns was fast on the NMR time scale and only a single population average ¹H signal was observed. Formation constants of the resulting 1:1 complexes in different solvent mixtures were determined by computer fitting of the chemical shift-mole ratio data. There is an inverse relationship between the complex stability and the amount of dimethyl sulfoxide in the mixed solvent. It was found that, in all solvent mixtures used, Rb⁺ ion forms the most stable complex with 18-crown-6 in the series.     

Spectroscopic investigations and crystal structure from synchrotron powder data of the inclusion complex of beta-cyclodextrin with atenolol

Inclusion complexes of atenolol with beta-cyclodextrin (beta-CD) in aqueous solution have been investigated with (1)H NMR and UV-vis spectroscopy. The stoichiometry of this inclusion complex was established to be equimolar (1:1) and its stability constant was determined by UV-vis spectroscopy. The crystal structure of the beta-CD-atenolol (1:1) inclusion compound has been solved from synchrotron powder diffraction data using direct-space search techniques. The crystal structure model and (1)H NMR data are in good agreement and, with support of Hyperchem MM+ molecular dynamics results, suggest which protons are likely to be involved in the inclusion process that leads to the supramolecular architecture of this guest-host complex.     

Study of Complex Formation between 5,7‐Diiodo‐8‐hydroxyquinoline and Zn2+, Cd2+, Pb2+ and Tl+ Cations in Binary Non‐Aqueous Solvents Using Square Wave Polarography Technique (SWP)

The complexation reaction between Zn²⁺, Pb²⁺, Cd²⁺ and Tl⁺ cations by 5,7‐diiodo‐8‐hydroxyquinoline (IQN) was studied in the Dimethylformamide /Acetonitril (DMF‐AN) binary system using square wave polarography technique. The stoichiometry and stability of the complexes were determined by monitoring the shifts in half‐wave or peak potential of the polarographic waves of metal ions against the ligand concentration. The stoichiometry of the complexes was found to be 1:1. The results obtained show that there is an inverse relationship between the formation constant of the complexes and the donor number of solvent base on the Guttmann donocity scale. In all cases the formation constants increased with increasing amounts of AN in these binary systems. The selectivity order for IQN complexes with the cations is Zn²⁺ > Pb²⁺ > Cd²⁺ > Tl⁺.     

Li4Mn5O12Cathode for Both 3 V and 4 V Lithium-ion Batteries

Spinel Li₄Mn₅O₁₂ has been of economical and academic interest as cathode material for 3 V lithium-ion batteries(LIBs) since the 1990s. Recent studies also demonstrate that the increase of upper cut-off voltage to 5.0 V can significantly promote the specific capacity and the average operating voltage thus enabling its possibility to be used in 4 V LIBs. It is cost-effective and environmentally benign, shows structural stability without suffering from Jahn-Teller distortion due to the tetravalent oxidation state of Mn ion. However, the undesirable decomposition reactions during high-temperature calcination result in the difficulty of fabricating stoichiometric Li₄Mn₅O₁₂ compounds. Meanwhile, the high capacity led by the enlarged voltage window is combined with fast capacity fading due to the poor reversibility of oxygen redox. In this review, the understanding of the relationship between structure and stochiometric chemistry of Li₄Mn₅O₁₂ is discussed and the ways to improving its electrochemical performance are summarized. Our focus is its recent developments of being used as high voltage cathode or "additive" for layered cathodes. At last, we also provide our perspectives on this material regarding to the target of enabling its application in 4 V LIBs.     

Application of the Generalized Molar‐Ratio Method to the Determination of the Stoichiometry and Apparent Binding Constant of Nanoparticle‐Organic Capping Systems

A generalization of the molar‐ratio method is applied to the determination of the stoichiometry and apparent binding constant of metal nanoparticle‐organic capping complexes (M_mL_x) using voltammetric data for the oxygen reduction reaction (ORR) in air‐saturated aqueous phosphate buffer solutions. The method is applied to the formation of binary nanohybrids consisting of gold nanoparticles (AuNPs) capped with a rigid spacer, cucurbit[7]uril (CB), termed AuNP@CB, as well as to the formation of their ternary complexes (M_mL_xB_z) with methylene blue (MB), termed AuNP@CB@MB. The obtained stoichiometries correspond to binding of four Au surface atoms for each CB unit.     

Validation of a novel LC-MS/MS method for the quantitation of colistin A and B in human plasma

A liquid chromatography/tandem mass spectrometry (LC-MS/MS) method, characterized by complete automation and high-throughput, was developed for the determination of colistin A and B in human plasma. All sample preparation procedures were performed by using 2.2 mL 96-deep-well plates, whereas robotic liquid-handling workstations were utilized for all liquid transfer steps, including solid-phase extraction (SPE). The whole preparation procedure was very rapid, whereas the method had a very short chromatographic run time of just 2 min. Sample analysis was performed by reversed phase LC-MS/MS, with positive electrospray ionization, using multiple reaction monitoring. The absence of available purified colistin A and B standards led to the development of a novel LC method with evaporative light-scattering detector for the determination of their stoichiometries in the standard mixture, along with its purity. The proposed bioanalytical method was fully validated and it was proven to be selective, accurate, precise, reproducible and suitable for the determination of colistin A and B in human plasma. It was applied successfully to a pharmacokinetic study for the determination of both analytes in samples of patients.     

Structural and compositional investigations of Zr4Pt2O: A filled-cubic Ti2Ni-type phase

Syntheses, structural and compositional analyses of the filled cubic Ti₂Ni-type phase in Zr-Pt-O system have been studied, largely for the platinum-richer compositions. Diffraction quality crystals were grown by annealing an arc-melted composition Zr₄Pt₂O_0.66 at 1600 °C under Ar. The refined composition Zr_4.0Pt_1.95(1)O_0.93(6) (a=12.5063(6) Å, , Z=16) is close to the idealized composition Zr₄Pt₂O known in several other Zr-T-O systems (T=late 4d or 5d transition element). (This composition has been erroneously reported by ICDD for years as Zr₆Pt₃O (No. 00-017-0557) and referred to as ε-Zr₆Pt₃O.) The product is only marginally poor in platinum and oxygen, in contrast to the 1960 reports of metallographic studies (∼Zr₄Pt_1.62O_0.44). Under arc-melting conditions, high yields of the cubic phase are obtained from samples with lower platinum concentrations (Zr₄Pt_1.74O_1.04), whereas samples near the refined cubic composition contain hexagonal Zr₅Pt₃O_x as well (Mn₅Si₃-type). The hexagonal structure of binary Zr₅Pt₃ was also refined (Mn₅Si₃ type, P6₃/mcm, a=8.210(1) Å, c=5.385(2) Å) and shown to be non-stoichiometric to at least Zr₅Pt_2.5.     

Dual purpose laser ablation-inductively coupled plasma mass spectrometry for pulsed laser deposition and diagnostics of thin film fabrication: Preliminary study

PLD (pulsed laser deposition) is an attractive technique to fabricate thin films with a stoichiometry reflecting that of the target material. Conventional PLD instruments are more or less black boxes in which PLD is performed virtually “blind”, i.e. without having great control on the important PLD parameters. In this preliminary study, for the first time, a 213 nm Nd-YAG commercial laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS) intended for microanalysis work was used for PLD under atmospheric pressure and in and ex situ ICPMS analysis for diagnostics of the thin film fabrication process.A PLD demonstration experiment in a He atmosphere was performed with a Sm_13.8Fe_82.2Ta_4.0 target-Ta-coated silicon wafer substrate (contraption with defined geometry in the laser ablation chamber) to transfer the permanent magnetic properties of the target to the film. Although this paper is not dealing with the magnetic properties of the film, elemental analysis was applied as a means of depicting the PLD process. It was shown that in situ ICPMS monitoring of the ablation plume as a function of the laser fluence, beam diameter and repetition rate may be used to ensure the absence of large particles (normally having a stoichiometry somewhat different from the target). Furthermore, ex situ microanalysis of the deposited particles on the substrate, using the LA-ICPMS as an elemental mapping tool, allowed for the investigation of PLD parameters critical in the fabrication of a thin film with appropriate density, homogeneity and stoichiometry.     

Stoichiometry of superconducting YBa2Cu3Oy. Determination of Cu(III)/Cu(II) ratio and oxygen content

The electrical properties of the high T_c superconductor YBa₂Cu₃O_y depend on its oxygen content. The oxygen content is indirectly determined by iodimetric measurement of the oxidation state of copper. A combination of two titrations, with and without addition of KI, prior to dissolving the sample permits the determination of the two species Cu(II) and Cu(III). A simplified automatic titration with potentiometric detection of the end-point is described. The method is suitable for rapid and reliable determinations of the Cu(III)/Cu(II) ratio and total copper content and for controlling the stoichiometry of the compound.Samples of the superconductor were analysed and the stoichiometric coefficient y for oxygen was determined with excellent results. Typically, y=6.811 ± 0.0063 (s.d.) (n=5). A comparison of the total copper content (found by direct analytical determination) with the copper concentration calculated from the stoichiometric formula gives an evaluation of possible deterioration of the sample.