Performance of the High Resolution,Multi-collector Helix MC <Emphasis Type="Italic">Plus</Emphasis> Noble Gas Mass Spectrometer at the Australian National University

Performance of the Helix MC Plus noble gas mass spectrometer installed at the Australian National University (ANU) is reported. Results for sensitivity, mass discrimination and their linearity against partial pressure of noble gases, and mass resolution of the mass spectrometer are presented, and the results are compared with those of conventional noble gas mass spectrometers. The application of the five detectors on the Helix MC Plus in measuring various noble gas isotopes in multi-collector modes and the integration of the software drivers of peripheral hardware devices into the controlling program Qtegra of the mass spectrometer are discussed. High mass resolution (>1800) and mass resolving power (>8000) make this mass spectrometer unique in noble gas cosmo-geochemistry. It provides the capability to measure isobaric interference-free noble gas isotopes in multi-collector mode, significantly improves the accuracy to determine isotopic ratios, and greatly increases the efficiency of data acquisition.

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A Self‐Binding,Melt‐Castable,Crystalline Organic Electrolyte for Sodium Ion Conduction

The preparation and characterization of the cocrystalline solid–organic sodium ion electrolyte NaClO₄(DMF)₃ (DMF=dimethylformamide) is described. The crystal structure of NaClO₄(DMF)₃ reveals parallel channels of Na⁺ and ClO₄⁻ ions. Pressed pellets of microcrystalline NaClO₄(DMF)₃ exhibit a conductivity of 3×10⁻⁴ S cm⁻¹ at room temperature with a low activation barrier to conduction of 25 kJ mol⁻¹. SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55–65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO₄(DMF)₃, permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles.     

Few‐Layer Antimonene by Liquid‐Phase Exfoliation

We report on a fast and simple method to produce highly stable isopropanol/water (4:1) suspensions of few‐layer antimonene by liquid‐phase exfoliation of antimony crystals in a process that is assisted by sonication but does not require the addition of any surfactant. This straightforward method generates dispersions of few‐layer antimonene suitable for on‐surface isolation. Analysis by atomic force microscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy confirmed the formation of high‐quality few‐layer antimonene nanosheets with large lateral dimensions. These nanolayers are extremely stable under ambient conditions. Their Raman signals are strongly thickness‐dependent, which was rationalized by means of density functional theory calculations.     

A mild, one-pot synthesis of disubstituted benzimidazoles from 2-nitroanilines

A one-pot synthesis of disubstituted benzimidazoles from 2-nitroanilines is described. Hydrogenation of N-substituted 2-nitroanilines with palladium on carbon as catalyst in the presence of trimethyl orthoformate and catalytic pyridinium p-toluenesulfonate (PPTS) at room temperature provided good to excellent yields of the corresponding disubstituted benzimidazoles.     

Asymptotic distribution theory of statistical functionals: The compact derivative approach for robust estimators

Summary Derivatives of statistical functionals have been used to derive the asymptotic distributions ofL-,M- andR-estimators. This approach is often heuristic because the types of derivatives chosen have serious limitations. The Gateaux derivative is too weak and the Fréchet derivative is too strong. In between lies the compact derivative. This paper obtains strong results in a rigorous manner using the compact derivative onC ₀(R). This choice of space allows results for a broader class of functionals than previous choices, and the fact that is often tight provides the compact set required. A major result is the derivation of the compact derivative of the inverse c.d.f. when the range space is endowed with the uniform norm. It has applications to the asymptotic theory ofL-,M- andR-estimators. We illustrate the power of this result by applications toL-estimators in settings including the one sample problem, data grouped by quantiles, and censored survival time data.     

Determination of arsenic and antimony in electrolytic copper by anodic stripping voltammetry at a gold film electrode

A simple procedure is described for the determination of arsenic and antimony in electrolytic copper. The copper is digested with nitric acid and copper is separated from arsenic and antimony by passing an ammoniacal solution of the sample through a column of Chelex-100 resin. After digestion with sulphuric acid and reduction to arsenic(III) and antimony(III) with sodium sulphite in 7 M sulphuric acid at 80°C, both arsenic and antimony are deposited at-0.30V and their total is determined by anodic stripping; antimony is then selectively deposited at -0.05 V for anodic stripping. The lower limits of determination are 56 ng As and 28 ng Sb per gram of copper; relative standard deviations (n = 5) are in the ranges 6.1–15.0% for 5.5—0.5 ppm arsenic in copper and 4.1–6.8% for 2.6—0.6 ppm antimony.     

A convenient scalable one-pot conversion of esters and Weinreb amides to terminal alkynes

Esters and amides undergo reduction to the corresponding aldehydes using DIBAL-H followed by same pot conversion to terminal alkynes utilizing the Bestmann-Ohira reagent in good to excellent yields. Additionally chiral nonracemic substrates undergo this transformation with complete preservation of stereochemical integrity.     

Photo-cured polymers in ion-selective electrode membranes: Part 2: A Calcium Electrode for Flow Injection Analysis

The preparation of a calcium-selective electrode based on a photo-cured polymer membrane containing a neutral carrier is described. This electrode is suitable for use in flow injection analysis because of its fast initial response and the harness and mechanical strength of the membrane.     

Cooperative self-assembly of dendrimers via pseudorotaxane formation from a homotritopic guest molecule and complementary monotopic host dendrons

Interaction of the homotritopic guest 1,3,5-tris[p-(benzylammoniomethyl)phenyl]benzene tris(hexafluorophosphate) (1a) with dibenzo-24-crown-8 (DB24C8) leads to the sequential self-assembly of [2]-, [3]-, and [4]-pseudorotaxanes 7a, 8a, and 9a, respectively. The self-assembly processes were studied using NMR spectroscopy. In CD(3)CN and CD(3)COCD(3) the individual association constants K(1), K(2), and K(3) for 1:1, 1:2, and 1:3 complexes were determined by several methods. Via Scatchard plots, the three NH(2)(+) sites of 1a were shown to behave independently in binding DB24C8. K values (4.4 x 10(2), 1.4 x 10(2), and 41 M(-)(1), respectively, in CD(3)CN) directly determined from signals for the individual complexes (7a, 8a, and 9a) were somewhat higher than those estimated from the Scatchard plot because of concentration dependence, but the ratios of association constants followed the expected statistical order (K(1):K(2):K(3) = 3:1:(1)/(3)). These are believed to be the first evaluations of association constants leading to a [4]-pseudorotaxane. In the less polar CDCl(3), association constants could not be determined because approximately 90% of the dissolved tritopic guest, which by itself is insoluble, was present as the fully loaded [4]pseudorotaxane 9a! Self-assembly of homotritopic guest 1a with benzyl ether dendrons of the first, second, and third generations functionalized at the "focal point" with DB24C8 moieties (3-5) produces pseudorotaxane dendrimers. The self-assembly processes were studied using (1)H NMR spectroscopy. In CD(3)COCD(3) for all three generations the individual association constants K(1), K(2), and K(3) for [2]-, [3]-, and [4]-pseudorotaxane complexes 7c-e, 8c-e, and 9c-e indicated that the self-assembly was cooperative; that is, the ratios of the individual association constants exceeded the expected statistical ratios. Scatchard plots confirmed this behavior. Self-assembly processes in the less polar CDCl(3) were kinetically slow, requiring ca. 1, 2, and 3 days, respectively, for the first, second, and third generation systems to reach equilibrium with 1a; the slow rate is attributed to the insolubility of the homotritopic guest 1a in this medium and the steric demands of the resulting dendrimers. However, only dendrimers of 1:3 stoichiometry, that is, the nanoscopic [4]pseudorotaxanes 9, were formed! Moreover, it is noteworthy that the extent of dissolution of 1a (reflective of the overall association constant which is too high to measure) increases with generation number, presumably because of the more effective screening of the ionic guest by the larger dendrons and perhaps favorable pi-pi and CH-pi interactions. Such cooperative effects suggest a number of applications that can take advantage of the pH-switchable nature of these self-assembly processes.