Revised δ34S reference values for IAEA sulfur isotope reference materials S‐2 and S‐3

Revised δ³⁴S reference values with associated expanded uncertainties (95% confidence interval (C.I.)) are presented for the sulfur isotope reference materials IAEA‐S‐2 (22.62 ± 0.16‰) and IAEA‐S‐3 (−32.49 ± 0.16‰). These revised values are determined using two relative‐difference measurement techniques, gas source isotope ratio mass spectrometry (GIRMS) and double‐spike multi‐collector thermal ionization mass spectrometry (MC‐TIMS). Gas analyses have traditionally been considered the most robust for relative isotopic difference measurements of sulfur. The double‐spike MC‐TIMS technique provides an independent method for value‐assignment validation and produces revised values that are both unbiased and more precise than previous value assignments. Unbiased δ³⁴S values are required to anchor the positive and negative end members of the sulfur delta (δ) scale because they are the basis for reporting both δ³⁴S values and the derived mass‐independent Δ³³S and Δ³⁶S values. Published in 2009 by John Wiley & Sons, Ltd.     

Measurement of sulfur isotope composition (δ34S) by multiple‐collector thermal ionization mass spectrometry using a 33S‐36S double spike

A new analytical technique is described for the determination of δ³⁴S that is comparable to or better than modern gas source mass spectrometry in precision and accuracy, but requires about a factor of 10 less sample. The technique is based on the production of singularly charged arsenic sulfide molecular ions (AsS⁺) by thermal ionization using silica gel as an emitter and combines multiple‐collector thermal ionization mass spectrometry (MC‐TIMS) with a ³³S‐³⁶S double spike to correct instrumental fractionation. Three international sulfur standards (IAEA‐S‐1, IAEA‐S‐2, and IAEA‐S‐3) were measured to evaluate the precision and accuracy of the new technique and to evaluate the consensus values for these standards. Two different double spike preparations were used. The δ³⁴S values (reported relative to Vienna Canyon Diablo Troilite (VCDT), (δ³⁴S (‰) = ([((³⁴S/³²S)_sample/(³⁴S/³²S)_VCDT ? 1) × 1000]), ³⁴S/³²S_VCDT = 0.0441626) determined were ?0.32 ± 0.04‰ (1σ, n = 4) and ?0.31 ± 0.13‰ (1σ, n = 8) for IAEA‐S‐1, 22.65 ± 0.04‰ (1σ, n = 7) and 22.60 ± 0.06‰ (1σ, n = 5) for IAEA‐S‐2, and ?32.47 ± 0.07‰ (1σ, n = 8) for IAEA‐S‐3. The amount of natural sample used for these analyses ranged from 0.40 to 2.35 µmol. Replicate determinations of each standard showed less than 0.5‰ variability (IAEA‐S‐1 <0.4‰, IAEA‐S‐2 <0.2‰, and IAEA‐S‐3 <0.2‰). Because the technique is based on thermal ionization of AsS⁺, and As is mononuclidic, corrections for interferences or for scale contraction/expansion are not required. The availability of MC‐TIMS instruments in laboratories around the world makes this technique immediately available to a much larger scientific community who require highly accurate and precise measurements of sulfur. Published in 2005 by John Wiley & Sons, Ltd.     

δ34S for tracing the origin of cheese and detecting its authenticity

Casein δ³⁴S of 725 samples of cheese from all over the world were measured using IRMS. δ³⁴S alone made it possible to establish characteristic ranges of values for two types of Italian cheese (Grana Padano PDO and Parmigiano Reggiano PDO) and for the different regions and provinces of both the Grana Padano PDO and the Parmigiano Reggiano PDO zones. Moreover, δ³⁴S of PDO Italian samples were compared to both Italian (not PDO) and foreign competitive cheese samples. In all the cases, sulfur isotopic ratio analysis was a powerful tool to fix characteristic ranges of values for cheeses coming from different countries and to improve the information given by other isotopic parameters.     

Sulfur isotope analysis of cinnabar from Roman wall paintings by elemental analysis/isotope ratio mass spectrometry – tracking the origin of archaeological red pigments and their authenticity

The most valuable pigment of the Roman wall paintings was the red color obtained from powdered cinnabar (Minium Cinnabaris pigment), the red mercury sulfide (HgS), which was brought from mercury (Hg) deposits in the Roman Empire. To address the question of whether sulfur isotope signatures can serve as a rapid method to establish the provenance of the red pigment in Roman frescoes, we have measured the sulfur isotope composition (δ³⁴S value in ‰ VCDT) in samples of wall painting from the Roman city Aventicum (Avenches, Vaud, Switzerland) and compared them with values from cinnabar from European mercury deposits (Almadén in Spain, Idria in Slovenia, Monte Amiata in Italy, Moschellandsberg in Germany, and Genepy in France). Our study shows that the δ³⁴S values of cinnabar from the studied Roman wall paintings fall within or near to the composition of Almadén cinnabar; thus, the provenance of the raw material may be deduced. This approach may provide information on provenance and authenticity in archaeological, restoration and forensic studies of Roman and Greek frescoes. Copyright © 2010 John Wiley & Sons, Ltd.     

Sulphur isotopes in animal hair track distance to sea

Stable sulphur isotope ratios (³⁴S/³²S) in animal tissues have been suggested as a tracer of coastal residency of terrestrial animals, but data are lacking that quantify the inland range of the sulphur coastal signal and the effects of seasonality. Here, we present δ³⁴S measurements of sheep wool collected seasonally on eight farms across Ireland and wool samples collected opportunistically along the west and east coasts. We observed large (>10‰) δ³⁴S differences across the island and we show that wool δ³⁴S values were negatively correlated with distance to the west coast. We propose that this is due to the predominantly (south‐)westerly airflow, possibly combined with the influence of anthropogenic sulphur deposited from the east. While essentially all the sulphur contained in west‐coast wool is of marine origin, relatively high δ³⁴S values were still measured >100 km inland, suggesting that marine sulphur can be carried over long distances. Seasonal variations are small at the individual level for sedentary grazing animals. We conclude that sulphur isotopes ratios measured in archival keratinous tissues can be used to describe regional δ³⁴S isoscapes primarily defined by distance to coasts and thus provide a tool to detect short‐term movements of domestic, feral and wild animals within such isoscapes. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of phthalate esters in bottled water using dispersive liquid–liquid microextraction coupled with GC–MS

Dispersive liquid–liquid microextraction method was developed for the determination of the amount of phthalate esters in bottled drinking water samples and dispersive liquid–liquid microextraction samples were analyzed by GC–MS. Various experimental conditions influencing the extraction were optimized. Under the optimized conditions, very good linearity was observed for all analytes in a range between 0.05 and 150 μg/L with coefficient of determination (R²) between 0.995 and 0.999. The LODs based on S/N = 3 were 0.005–0.22 μg/L. The reproducibility of dispersive liquid–liquid microextraction was evaluated. The RSDs were 1.3–5.2% (n = 3). The concentrations of phthalates were determined in bottled samples available in half shell. To understand the leaching profile of these phthalates from bottled water, bottles were exposed to direct sunlight during summer (temperature from 34–57°C) and sampled at different intervals. Result showed that the proposed dispersive liquid–liquid microextraction is suitable for rapid determination of phthalates in bottled water and di‐n‐butyl, butyl benzyl, and bis‐2‐ethylhexyl phthalate compounds leaching from bottles up to 36 h. Thereafter, degradation of phthalates was observed.     

Concentration effects on laser-based δ18 O and δ2 H measurements and implications for the calibration of vapour measurements with liquid standards

Recently available isotope ratio infrared spectroscopy can directly measure the isotopic composition of atmospheric water vapour (δ¹⁸O, δ²H), overcoming one of the main limitations of isotope ratio mass spectrometry (IRMS) methods. Calibrating these gas‐phase instruments requires the vapourisation of liquid standards since primary standards in principle are liquids. Here we test the viability of calibrating a wavelength‐scanned cavity ring‐down spectroscopy (CRDS) instrument with vapourised liquid standards. We also quantify the dependency of the measured isotope values on the water concentration for a range of isotopic compositions. In both liquid and vapour samples, we found an increase in δ¹⁸O and δ²H with water vapour concentration. For δ¹⁸O, the slope of this increase was similar for liquid and vapour, with a slight positive relationship with sample δ‐value. For δ²H, we found diverging patterns for liquid and vapour samples, with no dependence on δ‐value for vapour, but a decreasing slope for liquid samples. We also quantified tubing memory effects to step changes in isotopic composition, avoiding concurrent changes in the water vapour concentration. Dekabon tubing exhibited much stronger, concentration‐dependent, memory effects for δ²H than stainless steel or perfluoroalkoxy (PFA) tubing. Direct vapour measurements with CRDS in a controlled experimental chamber agreed well with results obtained from vapour simultaneously collected in cold traps analysed by CRDS and IRMS. We conclude that vapour measurements can be calibrated reliably with liquid standards. We demonstrate how to take the concentration dependencies of the δ‐values into account. Copyright © 2010 John Wiley & Sons, Ltd.     

On‐line photodecomposition for the determination of antimony species

On‐line UV photooxidation by peroxodisulfate was coupled to ion chromatography hydride generation atomic fluorescence spectroscopy (IC‐UV‐HG‐AFS) for the speciation of inorganic antimony [Sb(III) and Sb(V)] and methylated species. Several parameters (UV lamp, irradiation time and peroxodisulfate concentration) that greatly influence the sensitivity of these three antimony species were investigated in depth. Under optimized conditions, photodecomposition resulted in an improvement in methylantimony species sensitivity. Dilution in di‐ammonium tartrate medium was necessary in order to ensure short‐term stability of Sb(III) at the µg l^?1 concentration level. Furthermore, the efficiency of irradiation was strongly dependent on the chemical composition of the measured solution. Detection limits of 0.04 µg l^?1 for Sb(V), 0.03 µg l^?1 for Me₃SbCl₂ and 0.03 µg l^?1 for Sb(III) as well as repeatability and reproducibility better than 4 and 8% RSD, respectively, were obtained. The proposed methodology was applied for antimony speciation in terrestrial plant sample extracts. Copyright © 2005 John Wiley & Sons, Ltd.     

Metal Derivatives of Heterocyclic Thioamides: Synthesis and Crystal Structures of Copper Complexes with 1‐Methyl‐1,3‐imidazoline‐2‐thione and 1,3‐Imidazoline‐2‐thione

Reactions of copper(I) halides (Cl, Br, I) with 1‐methyl‐1, 3‐imidazoline‐2‐thione (mimzSH) in 1 : 2 molar ratio yielded sulfur‐bridged dinuclear [Cu₂X₂(μ‐S‐mimzSH)₂(η¹‐S‐mimzSH)₂] (X = I, 1 , Br, 2 ; Cl, 3 ) complexes. Copper(I) iodide with 1,3‐imidazoline‐2‐thione (imzSH₂) and Ph₃P in 1 : 1 : 1 molar ratio has also formed a sulfur‐bridged dinuclear [Cu₂I₂(μ‐S‐imzSH₂)₂(PPh₃)₂] ( 4 ) complex. The central Cu(μ‐S)₂Cu cores form parallelograms with unequal Cu–S bond distances {2.324(2), 2.454(3) Å} ( 1 ); {2.3118(6), 2.5098(6) Å} ( 2 ); {2.3075(4), 2.5218(4) Å} ( 3 ); {2.3711(8), 2.4473(8) Å} ( 4 ). The Cu···Cu separations, 2.759–2.877Å in complexes 1 – 3 are much shorter than 3.3446Å in complex 4 . The weak intermolecular interactions {H₂CH···S^# ( 2 ); CH···Cl^# ( 3 ); NH···I^# ( 4 )} between dimeric units in complexes 2 – 4 lead to the formation of linear 1D polymers.     

Biodistribution study of free and microencapsulated 6‐methylcoumarin in Wistar rats by HPLC

A sensitive, specific and reproducible HPLC method has been developed and validated for the quantitative determination of 6‐methylcoumarin (6MC) in plasma and other tissues in Wistar rats. A C₁₈ column was used with UV detection at 321 nm and a gradient system consisting of methanol‐deionized water was used as mobile phase. The retention time for 6MC was 14.921 min and no interfering peaks were observed for any of the matrices. Linear relationships (r² > 0.997) were obtained between the peak height ratios and the corresponding biological sample concentrations over the range 0.4–12.8 µg/mL. Precision and accuracy were evaluated; the coefficient of variation and the relative error for all of the organs were <2 and 7%, respectively. The limit of quantitation was 0.20 µg/mL for the heart and 0.30 µg/mL for the other tissues evaluated. This HPLC method was successfully used in the determination of 6MC in the biodistribution study after administration of 200 mg/kg of both 6MC‐free and 6MC‐loaded polymeric microparticles. In this study, extensive 6MC was found, in both free and microencapsulated forms, in all the organs tested. The 6MC‐free showed a range of between 1.7 and 11.5 µg/g, while the microencapsulated 6MC showed concentrations of between 6.35 and 17.7 µg/g, suggesting that 6MC improved absorption rate. Copyright © 2014 John Wiley & Sons, Ltd.     

A novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry based on sample mixing with a non-enriched standard

In this work, a novel approach to measure isotope ratios via multi-collector—inductively coupled plasma—mass spectrometry (MC-ICP-MS) for low amounts of target element is proposed. The methodology is based on mixing of the sample (target element isolate) with a non-enriched in-house standard, previously characterized for its isotopic composition. This methodology has been applied to isotopic analysis of Cu and of Fe in whole blood samples. For this purpose, different mixtures of sample + in-house standard were prepared and adjusted to a final concentration of 500 μg/L of the target elements for isotopic analysis. δ⁶⁵Cu, δ⁵⁶Fe, and δ⁵⁷Fe varied linearly as a function of the amount of in-house standard (or of sample) present in the mixture. The isotopic composition of the sample was calculated considering the isotope ratios measured for (i) the mixture and (ii) the in-house standard and (iii) the relative concentrations of target element contributed by the sample and the standard to the mixture, respectively. For validation purposes, the isotopic analysis of whole blood Cu was carried out using both the conventional (using 2 mL of whole blood) and the newly developed approach (using 500 μL of whole blood). The δ⁶⁵Cu values obtained using mixtures containing 40 % (200 μg/L) of Cu from the blood samples and 60 % (300 μg/L) of Cu from the in-house standard were in good agreement with the δ⁶⁵Cu value obtained using the conventional approach (bias ≤0.15?‰).     

Isolable Boron Persulfide: Activation of Elemental Sulfur with a 2‐Chloro‐Azaborolyl Anion

The novel boron persulfide 2 LB(η²‐S₂) (L=[ArNC(R)CHC(R)]^?; Ar=2,6‐Me₂C₆H₃, R=tBu) was obtained by the reaction of the 2‐chloro‐azaborolyl anion 1 (LBCl)K(THF) with 0.25 equiv of elemental sulfur (S₈). Persulfide 2 is labile in solution and could be converted to the cyclic tetrasulfide LBS₄ ( 3 ) and hexasulfide LBS₆ ( 4 ) in the presence of sulfur at room temperature and 50 °C, respectively. Desulfination of 2 with triphenylphosphine resulted in the formation of the thioxoborane LB=S ( 5) . Alternatively, 3 and 4 could be obtained by the reaction of 1 with an excess of sulfur. Structural analysis of 2 disclosed the relatively long S?S bond of 2.1004(8) Å due to the lone‐pair repulsions of the two sulfur atoms, as disclosed by DFT calculations.     

A new method for calibrating the current gain of 1013 Ω amplifiers in thermal ionization mass spectrometry

We report a new method for calibrating the current gain of 10¹³ Ω amplifiers in both positive and negative mode used in thermal ionisation mass spectrometry (TIMS). This method uses any isotopic standard or sample to calibrate the gain factor as long as it can produce a stable current signal. It is simpler and more flexible than that recommended by Thermo‐Fisher (the manufacture of the TIMS). In these analyses, the gains of five 10¹³ Ω amplifiers were assessed. The precision of gain factors was better than 100 ppm (2 RSD) in a day, and the long‐term reproducibility was better than 300 ppm (2 RSD) within 2 to 8 months. After a gain was calibrated, the ratio accuracy and precision in the positive mode for ⁸⁷Sr/⁸⁸Sr of NIST 987 Sr and ¹⁴³Nd/¹⁴⁴Nd of La Jolla Nd were 0.710242 ± 60 (2 SD, n = 14) and 0.511842 ± 10 (2 SD, n = 22), respectively, at intensities of ⁸⁸Sr 0.3 V and ¹⁴²Nd 0.4 V, while in the negative mode for ¹⁸⁷Os/¹⁸⁸Os of Merck Os was 0.120229 ± 34 (2 SD, n = 23) at an intensity of ¹⁸⁷OsO₃ 0.01 mV. In addition, a difference in the gain factors between the negative mode TIMS (NTIMS) and positive mode TIMS (PTIMS) has been recognized. The values of the gain factor for NTIMS and PTIMS show a deviation of 0.54% on the Triton and 0.31% on the Triton Plus TIMS in this study; therefore, gain calibration should be carried out on both NTIMS and PTIMS. Moreover, a bias of ~ 1.5 × 10⁻⁵ between H and L Faraday cups for the same 10¹³ Ω amplifier has been detected, hinting that the efficiency of different Faraday cups may affect the gain factors, which can be eliminated through the new method of “cross‐calibration” discribed in this study.     

Simultaneous δ2H and δ18O analyses of water inclusions in halite with off‐axis integrated cavity output spectroscopy

Stable isotope compositions of ancient halite fluid inclusions have been recognized to be valuable tools for reconstructing past environments. Nevertheless, in order to better understand the genesis of halite deposits, it could be of great interest to combine both δ²H and δ¹⁸O measurements of the water trapped as inclusions in the defects of the mineral lattice. We developed a method combining off‐axis integrated cavity output spectroscopy (OA‐ICOS) connected on line with a modified elemental analyzer (EA‐OA‐ICOS) to perform those measurements. The first step was to test the method with synthetic halite crystals precipitated in the laboratory from isotopically calibrated waters. Water isotopic signatures have been measured with conventional techniques, equilibration for δ¹⁸O and chromium reduction for δ²H. Then, we modified and optimized a conventional EA to connect it online with an OA‐ICOS instrument for H₂O measurements. The technique is first evaluated for calibrated free water samples. The technique is also evaluated for salt matrix effect, accuracy, and linearity for both isotopic signatures. Then, the technique is used to measure simultaneously δ²H and δ¹⁸O values of halite water inclusions precipitated from the evaporation experiments. Data generated with this new technique appeared to be comparable with those inferred from prior off‐line technique studies. The advantages offered by the OA‐ICOS technique are the simultaneous acquisition of both isotopic ratios and the substantial reduction of data acquisition time and sample aliquot size. Natural halite samples have been analyzed with this method. Natural halite samples as old as Precambrian have also been analyzed with this method.     

Does natural weathering change the stable isotope composition (2H, 13C, 15N, 18O and 34S) of cattle hair?

Stable isotope analysis of hair has found applications in many fields of science because it provides a temporally resolved, fairly stable isotopic archive of mammalian individuals. We investigated whether this hair archive is modified by natural weathering while attached to a living animal. We analyzed the tail switch hairs of one suckler cow, sampled seven times over a period of four annual summer pasture–winter stall feeding cycles. We compared relative isotope ratios (δ²H, δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S) of sections of hair that grew simultaneously but were exposed to natural weathering conditions over different periods of time. Natural wear caused a loss of mass of approx. 0.13% day^–1, with no apparent effect of environmental conditions. Changes in δ²H, δ¹³C, δ¹⁵N and δ¹⁸O were below the detection limit, indicating that hair is a reliable archive for the isotopes of these elements. In contrast, δ³⁴S values increased during the grazing period by about 1 ‰, with exposure to UV radiation appearing to have a major influence on this result. The δ³⁴S values decreased during the subsequent stall period, probably due to abrasion. Seasonal variation in δ³⁴S may indicate alternating environments that differ in their weathering conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Continuous analysis of δ18O and δD values of water by diffusion sampling cavity ring‐down spectrometry: a novel sampling device for unattended field monitoring of precipitation,ground and surface waters

A novel sampling device suitable for continuous, unattended field monitoring of rapid isotopic changes in environmental waters is described. The device utilises diffusion through porous PTFE tubing to deliver water vapour continuously from a liquid water source for analysis of δ¹⁸O and δD values by Cavity Ring‐Down Spectrometry (CRDS). Separation of the analysed water vapour from non‐volatile dissolved and particulate contaminants in the liquid sample minimises spectral interferences associated with CRDS analyses of many aqueous samples. Comparison of isotopic data for a range of water samples analysed by Diffusion Sampling‐CRDS (DS‐CRDS) and Isotope Ratio Mass Spectrometry (IRMS) shows significant linear correlations between the two methods allowing for accurate standardisation of DS‐CRDS data. The internal precision for an integration period of 3 min (standard deviation (SD) = 0.1 ‰ and 0.3 ‰ for δ¹⁸O and δD values, respectively) is similar to analysis of water by CRDS using an autosampler to inject and evaporate discrete water samples. The isotopic effects of variable air temperature, water vapour concentration, water pumping rate and dissolved organic content were found to be either negligible or correctable by analysis of water standards. The DS‐CRDS system was used to analyse the O and H isotope composition in short‐lived rain events. Other applications where finely time resolved water isotope data may be of benefit include recharge/discharge in groundwater/river systems and infiltration‐related changes in cave drip water. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetics and mechanism of the gas‐phase OH hydrogen abstraction reaction from methionine: A quantum mechanical approach

Unrestricted density functional theory (BHandHLYP) calculations have been performed, using the 6‐311G(d,p) basis sets, to study the gas‐phase OH hydrogen abstraction reaction from methionine. The structures of the different stationary points are discussed. Ring‐like structures are found for all the transition states. Reaction profiles are modeled including the formation of prereactive complexes, and negative net activation energy is obtained for the gamma H‐abstraction channel. A complex mechanism is proposed, and the rate coefficients are calculated using transition state theory over the temperature range 250–350 K. The rate coefficients are proposed for the first time and it was found that in gas phase the hydrogen abstraction occurs almost exclusively from the gamma site. The large overall rate coefficient for the methionine + OH reaction compared to other free amino acids could explain the significant role of methionine in the oxidative processes. The following expressions in [L/(mol s)] are obtained for the alpha, beta, and gamma H‐abstraction channels, and for the overall temperature‐dependent rate constants, respectively: k_α = (3.42 ± 0.11) × 10⁸ exp[(?1118 ± 9)/T], k_β = (1.13 ± 0.03) × 10⁸ exp[(?1070 ± 8)/T], k_γ = (2.11 ± 0.26) × 10⁷ exp[(2049 ± 34)/T], and k_tot = (2.12 ± 0.26) × 10⁷ exp[(2047 ± 34)/T]. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 212–221, 2003     

High‐precision determination of lithium and magnesium isotopes utilising single column separation and multi‐collector inductively coupled plasma mass spectrometry

Rationale

Li and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single‐step cation‐exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices.

Methods

The column method utilises the macro‐porous AGMP‐50 resin and a high‐aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High‐precision isotope determination was conducted by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICPMS) on the Thermo Scientific™ NEPTUNE Plus™ fitted with 10¹³ Ω amplifiers which allow accurate and precise measurements at ion beams ≤0.51 V.

Results

Sub‐nanogram Li samples (0.3–0.5 ng) were regularly separated (yielding Mg masses of 1–70 μg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long‐term external 2σ precisions of ±0.39‰ for δ⁷Li and ±0.07‰ for δ²⁶Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption.

Conclusions

The possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.

     

NaZr2N2SCl: Ein flußmittelstabilisiertes Derivat von Zirconium(IV)–Nitridsulfid (Zr2N2S)

NaZr₂N₂SCl: A Flux‐Stabilized Derivative of Zirconium(IV) Nitride Sulfide (Zr₂N₂S) The oxidation of zirconium metal with elemental sulfur and sodium azide (NaN₃) should give access to zirconium(IV) nitride sulfide, Zr₂N₂S, which could crystallize isotypically with the trigonal rare‐earth(III) oxide sulfides M₂O₂S (M = Y, La–Lu). Appropriate molar admixtures of these reactants together with NaCl added as flux were heated for seven days at 850 °C in torch‐sealed evacuated silica tubes. As main product, however, pale yellow platelets with the composition NaZr₂N₂SCl (trigonal, R 3 m; a = 363.56(3), c = 2951.2(4) pm; Z = 3) emerged as single crystals. This pseudo‐quaternary compound crystallizes isotypically with e. g. Li_xEr₂H_yCl₂ (x ≤ 1, y ≤ 2) in a (doubly) stuffed ZrBr‐type structure and contains at least structural domains of the hypothetical Ce₂O₂S‐analogous Zr₂N₂S. Zr⁴⁺ resides in monocapped trigonal anti‐prismatic sevenfold coordination of the anions (d(Zr–N) = 218 (3 ×) and 220 pm (1 ×), d(Zr–S/Cl) = 266 pm, 3 ×). Closest packed double‐layers of Zr⁴⁺ with all tetrahedral interstices occupied with N^3– are sandwiched by layers of isoelectronic S^2– and Cl^– anions. These anionic six‐layer slabs (S/Cl–Zr–N–N–Zr–S/Cl) pile up parallel (001) in a cubic closest packed fashion. Charge balance and structural consistence occurs between these layers by intercalation of Na⁺ within octahedral voids (d(Na–S/Cl) = 282 pm, 6 ×) of double‐layers of the indistinguishable heavy anions (S^2– and Cl^–).     

Long‐Life Room‐Temperature Sodium–Sulfur Batteries by Virtue of Transition‐Metal‐Nanocluster–Sulfur Interactions

Room‐temperature sodium–sulfur (RT‐Na/S) batteries hold significant promise for large‐scale application because of low cost of both sodium and sulfur. However, the dissolution of polysulfides into the electrolyte limits practical application. Now, the design and testing of a new class of sulfur hosts as transition‐metal (Fe, Cu, and Ni) nanoclusters (ca. 1.2 nm) wreathed on hollow carbon nanospheres (S@M‐HC) for RT‐Na/S batteries is reported. A chemical couple between the metal nanoclusters and sulfur is hypothesized to assist in immobilization of sulfur and to enhance conductivity and activity. S@Fe‐HC exhibited an unprecedented reversible capacity of 394 mAh g^?1 despite 1000 cycles at 100 mA g^?1, together with a rate capability of 220 mAh g^?1 at a high current density of 5 A g^?1. DFT calculations underscore that these metal nanoclusters serve as electrocatalysts to rapidly reduce Na₂S₄ into short‐chain sulfides and thereby obviate the shuttle effect.