Ein Beitrag zur Struktur geschmolzener Mischungen aus Alkalimetall- und Erdalkalimetallhalogeniden,dargestellt an ihren thermodynamischen Eigenschaften

Thermodynamics and Structure of Molten Mixtures Alkali Halide-Alkaline Earth Halide Thermodynamic quantities a_i, f_i, G^E, and S^E were calculated on the basis of vapour pressures of molten mixtures of the type alkali halide-alkaline earth halide. Negative deviations from ideality were found in all systems. The influence of cations or anions on the properties of mixtures is discussed. There is a good correlation between G^E and the change of polarization energy δE_p. Strong ionic interactions were found in molten mixtures, especially in the system RbBr—CaBr₂. The existence of stable complex ions in melts could not be shown by Raman spectroscopy.     

Simultaneous determination of halide and thiocyanate ions by potentiometric precipitation titration and multivariate calibration

Halide and thiocyanate ions can be determined by a precipitation titration with silver nitrate as the titrant, and the end-point can be evaluated by a potentiometric method, in which generally a silver indicator electrode is used as the indicator electrode and a double-junction Ag–AgCl electrode as the reference electrode. However, when mixtures of halide and thiocyanate are titrated, it is difficult to determine these components individually for there are overlapping steps in the potentiometric titration curves, especially in the case that there are obvious differences between concentrations of the components. In this paper, the linear equation for the potentiometric precipitation titration of a mixture of halide and thiocyanate ions was developed and it was then used for determining the components in the mixtures simultaneously with the aid of multivariate calibration methods. By application of this model, 27 synthetic mixtures with three- and four-component combinations of chloride, bromide, iodide and thiocyanate with low concentration levels from 1.8×10⁻⁴ to 6.2×10⁻⁴ mol l⁻¹ were analyzed and acceptable results were obtained.     

卤离子对Al-Sn-Ga合金阳极的活化作用

铝阳极;卤素离子;卤离子对Al-Sn-Ga合金阳极的活化作用     

Structure and conformation properties of 1-alkyl-3-methylimidazolium halide ionic liquids: a density-functional theory study

The structures and conformational properties of 1-alkyl-3-methylimidazolium halide ionic liquids have been studied with a Becke's 3 Parameter functional method. The interaction mechanisms between the cation and the anion in 1-ethyl-3-methylimidazolium (Emim+) halide and 1-butyl-3-methylimidazolium (Bmim+) halide ionic liquids were investigated using 6-31G*, 6-31++G**, and 6-311++G** basis sets. Forty structures of different ion pairs were optimized and geometrical parameters of them have been discussed in details. Halide ions (Cl- or Br-) have been gradually placed in different regions around imidazolium cation and the interaction energies between the anion and the cation have been calculated. Theoretical results indicate that there are four activity regions in the vicinity of the imidazolium cations, in these regions the imidazolium cations and the halide anions formed stable ion pairs. Imidazolium cations can form hydrogen bond interactions with one, two or three but no more than three nearest halide anions. The halide ions are situated in hydrogen bond positions rather than at random.     

Dual effect of halides in the Stille reaction: in situ halide metathesis and catalyst stabilization

Halide anions can increase or decrease the transmetallation rate of the Stille reaction through in situ halide metathesis. Although the influence of the halogen present in oxidative addition complexes on the transmetallation rate with organostannanes was already known, the application of in situ halide metathesis to accelerate cross-coupling reactions with organometallic reagents is not described in the literature yet. In addition a second unprecedented role of halides was discovered. Halide anions stabilize the [Pd(0)(L)(2)] catalyst in Stille reactions, by means of [Pd(0)X(L)(2)](-) formation (X=Cl, I), hereby preventing its leaching from the catalytic cycle. Both arene (iodobenzene) and azaheteroarene (2-halopyridine, halopyrazine, 2-halopyrimidine) substrates were used.     

A special reactor coupled with a high‐temperature mass spectrometer for the investigation of the vaporization and cracking of organometallic compounds

A special reactor coupled to a high‐temperature mass spectrometer was specifically designed for the study of vaporization and thermal cracking of organometallic precursors. This reactor has two kinds of settings. One is a single Knudsen effusion cell which enables the analysis of the composition of saturated vapors and the determination of the partial pressure of each gaseous molecule in equilibrium with its condensed phase. This cell is an evaporation/sublimation cell (operating from 243 to 473 K), which can be tightly closed – like a vacuum chamber – in order to protect organometallic compounds against moisture and atmospheric components. This cell can be independently weighed usefully to evaluate the equilibrium vapor pressures of the sample using the mass‐loss method. During experiments, the effusion aperture is externally opened for direct mass spectrometric measurements. The other setting dedicated to the study of thermal decomposition of gaseous molecules consists of a set of tandem cells: the previously described Knudsen cell and a cracking cell (operating from 293 to 973 K). Copyright © 2009 John Wiley & Sons, Ltd.     

Indirect detection of halide ions via fluorescence quenching of quinine sulfate in microcolumn ion chromatography.

Halide ions could be visualized via fluorescence quenching in microcolumn ion chromatography. The fluorescence of quinine sulfate, which was contained in an acidic eluent, was quenched by halide ions. The observed fluorescence quenching values increased in this order: iodide, bromide, and chloride. The present detection system was relatively sensitive to halide ions except for fluoride: other anions gave smaller signals than halide ions. The present detection system provided quantitative information, so it could be applied to the determination of chloride in water samples.     

钙钛矿二维纳米材料的合成和发光研究进展

钙钛矿纳米材料的研究取得了飞速发展:一方面,合成方法不断涌现,已经可以实现从零维纳米晶、一维纳米线到二维纳米片的形貌精确控制,对其尺寸和维度依赖的光学性质认识也不断深入;另一方面,钙钛矿纳米材料的光学和光电子应用也得到了快速发展,其中,基于钙钛矿量子点的光致发光和电致发光技术最受关注。 由于钙钛矿的天然层状结构,通过配体调控很容易制备出二维纳米材料,其发光性能可以通过层数和组分进行调节,最高量子产率超过85%,且具有偏振发光特性,有望成为一类新型发光材料。 本文从制备方法、光致发光和电致发光应用等方面综述了基于钙钛矿二维纳米材料的进展,并对其未来的发展方向进行讨论。     

Effect of nonvolatile solute on vapor–liquid equilibrium at fixed liquid composition

The influence of some nonvolatile solutes on boiling points of two azeotropic mixtures (1-propanol–water and methanol–tetrahydrofuran systems) was determined by means of isobaric vapor–liquid equilibrium experiments. A basic thermodynamic equation of nonvolatile solute effect on vapor–liquid equilibrium at fixed liquid composition was derived. Based on the theoretical analysis about the equation, two criterions of universal significance were obtained: (1) when a little nonvolatile solute dissolves in a binary liquid mixture with constant composition, if the vapor composition of less volatile component is increased the boiling point must be elevated at given pressure or the vapor pressure must be depressed at given temperature; (2) when a little nonvolatile solute dissolves in an azeotropic mixture, any kind of nonvolatile solute always causes the elevation of boiling point at given pressure or the depression of vapor pressure at given temperature irrespective of the variation of vapor composition. Verifying through the experiments of this paper and lot of the relevant experimental data in the literature, all of the experimental results were in agreement with both criterions without exception.     

Cracking study of pentakis(dimethylamino)tantalum vapors by Knudsen cell mass spectrometry

Organometallic molecules are commonly used as gaseous precursors in Atomic Layer Deposition/Chemical Vapor Deposition (ALD/CVD) processes. However, the use of these molecules, which are generally thermally unstable at temperatures close to the deposition temperature, requires an understanding of their gas‐phase chemical behavior. The thermal cracking of the gaseous precursor, pentakis(dimethylamino) tantalum (PDMAT), generally adopted in the ALD/CVD TaN deposition processes, has been studied in the temperature range from 343 to 723K using a specific reactor coupled with a high‐temperature mass spectrometer. This reactor – built as tandem Knudsen cells – consists of two superimposed cells. The first stage reactor – an evaporation cell – provides an input saturated vapor flow operating from room temperature to 333K. The second stage cell, named the cracking cell, operated from 333 to 723K in the present study. Experiments showed the appearance of many gaseous species when the cracking temperature increased and, in particular, dimethylamine, corresponding to the saturated organic branches of PDMAT. Decomposition products of the HNC₂H₆ branch were observed at relatively high temperature, namely above 633K. This gas‐phase study – as for the preceding saturated one – shows the presence of oxygen‐containing molecules in PDMAT cracked vapor. Thus, it explains the systematic presence of oxygen contamination in the deposited TaN films observed in ALD/CVD industrial processes. Copyright © 2010 John Wiley & Sons, Ltd.     

Activity coefficients of the binary mixtures of o-cresol or p-cresol with C1–C4 aliphatic alcohols near ambient pressure

Bubble point temperatures near ambient pressure, for the binary mixtures, formed by o-cresol or p-cresol with – methanol, ethanol, n- and iso-propanols and n-, iso-, sec- and tert-butanols – covering the whole composition range, are measured using a Swietoslawski-type ebulliometer. The liquid phase composition–bubble point temperature measurements are found to be well represented by the Wilson model. Values of the optimum Wilson parameters as well as the computed values of vapor phase mole fractions and activity coefficients are tabulated. The results are discussed in terms of isomerization with reference to the selected set of compounds, constituting the mixtures and the stearic effects in the cresols.     

A ‘clicked’ macrocyclic probe incorporating Binol as the signalling unit for the chiroptical sensing of anions

We describe a macrocyclic chiroptical sensor for the detection of halide anions, with the Binol moiety acting as the CD signalling unit. The macrocycle is conveniently synthesized using CuAAC ‘click’ reactions in the cyclization step; this methodology installs 1,2,3-triazole moieties within the macrocyclic backbone, able to directionally bind anions by means of CH?X^– hydrogen bonds. ¹H NMR complexation studies in CDCl₃ reveal weak binding to halide and aliphatic carboxylate anions. Halide anions, however, when held into the macrocyclic cavity, are able to trigger a large chiroptical response originating from the steric interaction with the Binol moiety, which changes its dihedral angle, thus modulating its characteristic CD signature.     

(Vapor + liquid) equilibrium of the binary mixtures formed by acetonitrile with selected compounds at 95.5 kPa

Bubble point temperatures at 95.5 kPa, over the entire composition range, are measured for the binary mixtures of acetonitrile with acetyl acetone, anisole, bromobenzene, isopropyl alcohol, methyl tertiary butyl ether, and tetra ethoxy silane – making use of a Swietoslawski type ebulliometer. The measured liquid phase composition versus bubble point temperature are found to be well represented by the Wilson model. Measured values of the liquid phase mole fraction versus bubble point temperature data are presented, along with the computed values of the vapor phase mole fractions and activity coefficients, and discussed.     

Über die Existenz von Verbindungen des Typs Hg2XA (X  Halogen,A  Anion ≠ Halogen) und Hg2XY (X und Y Halogen)

Existence of Hg₂XA (X ? Halide, A ? Anion ≠ Halide) and Hg₂XY Compounds (X and Y Halide) Investigations in molten mercuric bromide HgBr₂ [1, 2] and comparing considerations between mercuric and mercurous chemistry lead to the till now unknown or less investigated compounds Hg₂XA and Hg₂XY (X, Y halide; A anion ≠ halide). Using TGA and DTA measurements in order to improve the reaction conditions Hg₂XClO₄ salts could be synthesized, whereas the hydrogene sulfates Hg₂XHSO₄ are formed in concentrated sulfuric acid (crystalline, instable by solvent removing). Powder diagrams and spectrochemical investigations point our that the lattices of the isolated mixed halides Hg₂BrCl, Hg₂BrI, and Hg₂ClI contain not only the pure molecules Hg₂X₂ and Hg₂Y₂ but also the mixed molecules Hg₂XY. Final statements need X-ray investigations.     

Alkylation of Crystalline Salts of 1,3-Thiazolidine-2,4-diones with Alkyl Halide Vapors

Alkylation of 1,3-thiazolidine-2,4-diones with alkyl halide vapors was performed. The composition of the reaction mixtures was determined by thin-layer chromatography.     

Extending Carrier Lifetimes in Lead Halide Perovskites with Alkali Metals by Passivating and Eliminating Halide Interstitial Defects

Defects, such as halide interstitials, act as charge recombination centers, induce degradation of halide perovskites, and create major obstacles to applications of these materials. Alkali metal dopants greatly improve perovskite performance. Using ab initio nonadiabatic molecular dynamics, it is demonstrated that alkalis bring favorable effects. The formation energy of halide interstitials increases by up to a factor of four in the presence of alkali dopants, and therefore, defect concentration decreases. When defects are present, alkali metals strongly bind to them. Halide interstitials introduce mid‐gap states that rapidly trap charge carriers. Alkalis eliminate the trap states, helping to maintain high current density. Further to charge trapping, the interstitials accelerate charge recombination. By passivating the interstitials, alkalis make carrier lifetimes up to seven times longer than in defect‐free perovskites and up to thirty times longer than in defective perovskites.     

Evaluation of the responses of a semiconductor gas sensor to gaseous mixtures under the application of temperature modulation

A novel gas-sensing system based on a dynamic nonlinear response is reported to evaluate the effect of gaseous mixtures on the sensor response. A sinusoidal temperature perturbation was applied to a semiconductor gas sensor and the resulting conductance of the sensor was analyzed by fast Fourier transformation (FFT). The sensor response, which changed characteristically depending on the composition of the gaseous mixture, could be classified into three types (enhanced, suppressed, and preferential responses) by the mixture. To monitor the progress of the reaction of gases, the sample gas was analyzed by gas chromatography. The coexistent effect on the response to gaseous mixtures was theoretically simulated by considering the kinetics of gas molecules on the semiconductor surface.     

Rapid removal of selected volatile organic compounds from gaseous mixtures using a new dispersive vapor extraction technique: A feasibility study

A new dispersive vapor extraction (DVE) technique for rapid removal of selected volatile organic compounds (VOCs) from gaseous mixtures was investigated. In this technique, less than 1.0 mL of a volatile solvent was vaporized for 8 min in a 250-mL flask containing a gaseous mixture. The flask was then cooled under running tap water for 2-3 min to induce condensation of the vapor and co-extraction of the VOCs from the headspace. The technique was tested over a concentration range of 4-23 ppb, and resulted in extraction efficiencies ranging from 80 to 97% for the VOCs tested. Because of its simplicity and the relatively short sampling time, DVE could potentially lead to high sample throughput and rapid air analysis.