Analysis of Ir in Köfelsit rocks by inductively coupled plasma–sector-field mass spectrometry (ICP–SFMS)

Three different analytical strategies have been evaluated for the quantification of Ir in geological samples. Glassy rock samples from Köfels and reference material WGB-1 were analyzed directly by inductively coupled plasma sector field mass spectrometry (ICP–SFMS) at mass resolution 400 using membrane desolvation and at mass resolution 9500 without membrane desolvation. Matrix separation by anion-exchange pre-concentration was also investigated. The ultrasonic nebulizer USN6000AT⁺ (Cetac Technologies, Omaha, NE, USA) incorporating a membrane desolvation unit was used as the sample-introduction system. Sample preparation involved complete microwave-assisted acid digestion of the silicate matrix with HNO₃–HCl–HF. The results obtained by the three methods of quantification were in good agreement, showing that oxide-type interferences were effectively eliminated solely by membrane desolvation. The limits of detection were 6 pg g^–1 for low resolution measurement with use of the membrane, 15 pg g^–1 at a mass resolution of 9500, and 59 pg g^–1 for the ion-exchange procedure. The ultimate precision obtained for the Köfelsit Ir data was, however, compromised by the small sample intake (0.3 g), because of the inhomogeneous distribution of Ir in geological samples.     

Spinelle mit substituierten Nichtmetallteilgittern. VII. Röntgenographische und elektronische Eigenschaften,Mößbauer- und IR-Spektren des Spinellsystems AgCrSn(S1−xSex)4

Spinels with Substituted Nonmetal Sublattices. VII. X-Ray Investigations, Electronic Properties, Mössbauer, and I.R. Spectra of the Spinel System AgCrSn(S_1?xSe_x)₄ Polycrystalline samples of the spinel system AgCrSn(S_1?xSe_x)₄ have been prepared in the range 0 ? x ? 1. The lattice constants linearly increase with x by 50 pm, the chalcogen parameter has the mean value 0.384. The Mössbauer spectra consist of a weakly split doublet, they are in agreement with Sn(IV) and covalent bonding. The substances are n type semiconductors. I.R. spectra have been measured from 50 cm^?1 to 600 cm^?1.     

Preparation of source and sealed absorber holder for237Np and238U Mössbauer measurements

Preparation of source and sample holder is described for the Mössbauer studies of²³⁷Np and²³⁸U. For the Mössbauer measurement of²³⁷Np, a source assembly with small sources of²⁴¹Am metal was developed taking account of the transport regulations for radioactive substances. The source assembly of²⁴¹Am showed a sufficient activity enough to measure the Mössbauer spectra of²³⁷Np. In order to handle²³⁷Np compounds safely, trebly sealed holders were designed which could encapsulate²³⁷Np samples without the seepage of liquid helium. A source for²³⁸U Mössbauer measurement was also developed from a highly pure²⁴²PuO₂.     

Lattice temperature and hyperfine interactions of Pb1−xSnxTe (0.21 ≤ x ≤ 0.75)

Thin (<15 μm) samples of lead tin telluride, Pb_1?xSn_xTe (x = 0.21, 0.25, 0.55, and 0.75) have been studied by temperature dependent Mössbauer spectroscopy using the 23.8 keV gamma radiation of ^119mSn. The tin atom occupies a lattice site having cubic symmetry (QS = 0 ± 0.020 mm sec^?1) over the temperature range 78 ≤ T ≤ 240 K, and there is no evidence for a rhombic (low temperature) to cubic (high temperature) phase transition such as that reported for SnTe in this temperature interval. The lattice temperature as probed by the Sn atom is independent of the compositional parameter x and is similar to that reported for SnTe from Mössbauer studies and for Pb_0.63Sn_0.37Te from X-ray powder diffraction data. Radiation damage produced by 2-MeV proton irradiation to a total fluence of ～10¹⁷ cm^?2 at liquid nitrogen temperature does not have any effect on the Mössbauer parameters, possibly because the major damage is annealed at temperatures below 150 K.     

57Fe Mössbauer spectroscopic and magnetic study of a spin-crossover polymer complex, Fe(3-chloropyridine)2Ni(CN)4

The coordination polymer Fe(3-chloropyridine)₂Ni(CN)₄ (2) has been prepared by a method similar to that for Fe(pyridine)₂Ni(CN)₄ (1). The complex (2) has been characterized by⁵⁷Fe Mössbauer spectroscopy and a SQUID technique.⁵⁷Fe Mössbauer and magnetic susceptibility data show that complex (2) exhibits spin-crossover behavior. The spin transition of (2) occurs between 120 and 80 K with very small hysteresis or without hysteresis. The temperature range of the spin transition in (2) is lower than that in (1). A residual high spin iron(II) fraction is observed at low temperatures in (2), being different from (1). SQUID data also show that samples treated differently yield different spin transition curves.     

Investigation of clinoptilolite rich natural zeolites from Turkey: a combined XRF,TG/DTG,DTA and DSC study

Turkey clinoptilolite-rich tuffs from Gördes and Bigadiç regions of western of Anatolia and their exchanged forms (K⁺, Na⁺, Mg²⁺ and Ca²⁺) were characterized by TG/DTG-DTA, DSC and XRF methods and the surface areas were also determined for both tuffs. TG-DTG and DTA curves of all clinoptilolite samples were measured in the temperature range 30–1000 °C. All clinoptilolite samples had major, rapid mass losses between 30 and 200 °C, with slower and less significant mass losses at higher temperatures. The mass loss of the Natural-G is 9.54% while that of the Natural-B sample is 10.50%. Water content increases in the order of K < Na < Ca < Mg for Bigadiç clinoptilolite samples and in the following sequence K < Na < Mg < Ca for Gördes clinoptilolite samples. One mass loss step for all clinoptilolite samples was observed using differential scanning calorimeter (DSC) in the range of 30–550 °C.     

Vertical distribution of the natural and artificial radionuclides in various soil profiles to investigate soil erosion

Vertical distributions of ¹³⁷Cs and ²¹⁰Pb in soil profiles were examined to study their availability in soil erosion at Gökova region where there exists intensive agricultural activities on sloppy fields. Since the mobility of these radionuclides depend on soil characteristics, soil samples were analyzed also for their physical and chemical properties. From ¹³⁷Cs inventories measured, erosion rates for cultivated and disturbed (no cultivation) soils were calculated to range from 79.1 to 6.5 t^.ha^-1.y^-1 and from 79.9 to 3.5 t^.ha^-1.y^-1, respectively. The ²¹⁰Pb technique is found to be not suitable for erosion determination for this area, presumably due to the coal-fired power plants operating in the region.     

Mössbauer and thermogravimetric study of ferrous gluconate

Ferrous gluconate Fe(C₆H₁₁O₇)₂·2H₂O was investigated by means of⁵⁷Fe (14.4 keV)-Mössbauer spectroscopy and thermogravimetry. The Mössbauer study was performed in the temperature range 80 to 423 K. It was found that Fe²⁺ occupies two distinctly different Mössbauer sites in the hydrated phase and a single site in the product of the thermal treatment. All samples were contaminated by some amount of Fe³⁺. A significant oxidation occurs during thermal treatment (about 378 K) at least for the samples exposed to the air. No Goldanskii-Karyagin effect has been detected, in contrast to the previous claim. It has to be noted that the ferrous gluconate is often used as the iron containing component of drugs used in the treatment of anaemia.     

Spinelle mit substituierten Nichtmetallteilgittern. VI. Röntgenographische und elektronische Eigenschaften,Mößbauer- und IR-Spektren des Spinellsystems CuCrSn(S1−xSex)4

Spinels with Substituted Nonmetal Sublattices. VI. X-Ray Investigation, Electronic Properties, Mössbauer and I.R. Spectra of the Spinel System CuCrSn(S_1?xSe_x)₄ Polycrystalline samples of the spinel system CuCrSn(S_1?xSe_x)₄ have been prepared in the range 0 ≤ x ≤ 1. The lattice constants linearly increase with x while chalcogen parameters remain constant. The calculated distances copper-chalcogen are in agreement with Cu(I). From the Mössbauer spectra we conclude that the bonding is mostly covalent and that Sn is in the oxidation state +4. The substances are p type semiconductors. Resistivities, Seebeck coefficients, and activation energies decrease with increasing x. The electrical properties are compared to those of the system ZnCr₂(S_1?xSe_x)₄. I.R. spectra have been measured from 50 cm^?1 to 600 cm^?1.     

Beiträge zum 121Sb-Mößbauer-Effekt. VI. 121Sb-Mößbauer-Spektrum und Schwingungsspektrum von Sb2O5

Contributions to the ¹²¹Sb-Mössbauer Effect. VI. ¹²¹Sb-Mössbauer Spectrum and Vibrational Spectrum of Sb₂O₅ The results of ¹²¹Sb-Mössbauer spectroscopy at 4.2 K on pure Sb₂O₅, obtained by hydrothermal synthesis, are reported. The vibrational spectrum (i.r., raman) is correlated with the expectations of factor group analysis. The findings are compared to measurements carried out on samples hitherto regarded as Sb₂O₅.     

Comparison of Different Analytical Techniques for the Determination of Organic Mercury

Abstract

Methods for the determination of (1) total organic mercury (Hg) using an extraction +neutron activation analysis, (2) the sum of methyl-Hg+phenyl-Hg using ¹³¹I^?-Cl^? exchange and (3) methyl-Hg using two different Westöö modifications, have been compared. Sample materials were 8 falcon livers, 5 pike livers and 2 pike muscles. Although differences were found between the methods, interaction effects caused by either sample inhomogeneity or bad performance of the analytical methods impeded a clear interpretation of the comparison. Total Hg in the samples was determined by neutron activation analysis (NAA) and atomic absorption spectrometry. The accuracy of the total Hg determination using NAA was verified by the analysis of certified reference material.

In addition to the other organic Hg determinations phenyl-Hg was determined separately in some of the samples by an isotope exchange method using ²⁰³Hg²⁺.

The main conclusion of the study was that there is a demand for reference materials certified for at least total organic Hg and methyl-Hg.     

A facile carbothermal preparation of Sn–Co–C composite electrodes for Li-ion batteries using low-cost carbons

Sn–Co–C composites were prepared by carbothermal reaction of ball-milled precursors. X-ray diffraction and ¹¹⁹Sn Mössbauer spectroscopy of the original composites revealed the predominance of Sn and CoSn₂ phases for those samples prepared with a high Sn/Co ratio. Electron microscopy images showed a homogeneous dispersion of sub-micrometric metallic particles in the carbon matrix. Galvanostatic cycling at several kinetic rates revealed that Sn₇Co₁C₉₂ and Sn₈Co₄C₈₈ are able to maintain 400 mA h g^?1 after 40 cycles at 35 mA g^?1. The large CoSn₂ contribution revealed by Mössbauer spectroscopy in the original and cycled electrodes is responsible for the good electrochemical performance. This interpretation is also supported by impedance spectroscopy measurements.     

Viability of Möbius Topologies in [26]‐ and [28]Hexaphyrins

Recently, hexaphyrins have emerged as a promising class of π‐conjugated molecules that display a range of interesting electronic, optical, and conformational properties, including the formation of stable Möbius aromatic systems. Besides the Möbius topology, hexaphyrins can adopt a variety of conformations with Hückel and twisted Hückel topologies, which can be interconverted under certain conditions. To determine the optimum conditions for viable Möbius topologies, the conformational preferences of [26]‐ and [28]hexaphyrins and the dynamic interconversion between the Möbius and Hückel topologies were investigated by density functional calculations. In the absence of meso substituents, [26]hexaphyrin prefers a planar dumbbell conformation, strongly aromatic and relatively strain free. The Möbius topology is highly improbable: the most stable tautomer is 33 kcal mol^?1 higher in energy than the global minimum. On the other hand, the Möbius conformer of [28]hexaphyrin is only 6.5 kcal mol^?1 higher in energy than the most stable dumbbell conformation. This marked difference is due to aromatic stabilization in the Möbius 4n electron macrocycle as opposed to antiaromatic destabilization in the 4n+2 electron system, as revealed by several energetic, magnetic, structural, and reactivity indices of aromaticity. For [28]hexaphyrins, the computed activation barrier for interconversion between the Möbius aromatic and Hückel antiaromatic conformers ranges from 7.2 to 10.2 kcal mol^?1, in very good agreement with the available experimental data. The conformation of the hexaphyrin macrocycle is strongly dependent on oxidation state and solvent, and this feature creates a promising platform for the development of molecular switches.     

Facile,single-pot preparation of nanoporous SiO2 particles (carrier) with AgNPs at core and crust for controlled disinfectant release

This study demonstrates a novel, facile and one-pot approach to synthesize silica nanoparticles with silver at core and crust (SiNP-AgCC). A modified Stöber method was used to make SiNP-AgCC. A significant reduction in the size of SiO₂ nanoparticles was seen, with 2–5 nm AgNPs being uniformly distributed on the surface and 10–20 nm AgNPs in the center. A typical mesoporous SiO₂ particle (SiNP) produced using the Stöber method was transformed to nanoporous SiO₂ by this modified Stöber method. Nanoporous SiO₂ particles with silver in the center are advantageous for slow and consistent Ag⁺ release, which was confirmed by Ag⁺ ion release test. Antibacterial activities of the samples were tested to evaluate the disinfection performance of the samples on gram-negative bacteria (Escherichia coli) using disk diffusion and the LB-agar method. SiNP-AgCC showed prolonged silver release for more than 20 days and improved antibacterial properties even after five days of incubation.     

The FeSe system. II. Mössbauer diffusional line-broadening studies of Fe1 + xSe2 (x ∼ 0.5, i.e., Fe∼3Se4)

Diffusional line broadening of the ⁵⁷Fe Mössbauer resonance has been observed in samples of Fe_{1 + x}Se₂ (x = 0.50 and 0.55) in the temperature range 820 to 980°K. The lineshapes could not be fitted to a single Lorentzian peak and indicated non-Lorentzian behavior. The lattice, which has the NiAsCdI₂ structure, contains jump pathways in one, two, and three dimensions, each of which is predicted to give a different line shape when the jump frequency approaches the mean life of the Mössbauer excited state (～100 nsec). The observed shapes were not consistent with only one-dimensional diffusion or only three-dimensional diffusion, but could be interpreted as arising from a mixture of several of the jump types.     

Rapid cooling experiments and use of an anionic nuclear probe to sense the spin transition of the 1D coordination polymers [Fe(NH2trz)3]SnF6n x H2O (NH2trz=4-amino-1,2,4-triazole)

[Fe(NH₂trz)₃]SnF₆ ? n H₂O (NH₂trz=4‐amino‐1,2,4‐triazole; n=1 ( 1 ), n=0.5 ( 2 )) are new 1D spin‐crossover coordination polymers. Compound 2 exhibits an incomplete spin transition centred at around 210 K with a thermal hysteresis loop approximately 16 K wide. The spin transition of 2 was detected by the Mössbauer resonance of the ¹¹⁹Sn atom in the SnF₆^2? anion primarily on the basis of the evolution of its local distortion. Rapid‐cooling ⁵⁷Fe Mössbauer and superconducting quantum interference device experiments allow dramatic widening of the hysteresis width of 2 from 16 K up to 82 K and also shift the spin‐transition curve into the room temperature region. This unusual behaviour of quenched samples on warming is attributed to activation of the molecular motion of the anions from a frozen distorted form towards a regular form at temperatures well above approximately 210 K. Potential applications of this new family of materials are discussed.     

Oxygen consumption by conserved archaeological wood

Rates of oxygen consumption have been measured over extended time periods for 29 whole samples of conserved, archaeological wood and four samples of fresh, unconserved wood, at 50 % relative humidity and room temperature. Samples from the Swedish Warship Vasa and the Danish Skuldelev Viking ships are included. Most rates were close to 1 μg O₂ (g wood)^?1 day^?1 and the process persisted for several years at least. Consumption of oxygen is related to change in chemical composition, which is, in turn, related to degradation. It is thus demonstrated that despite conservation, waterlogged archaeological wood continues to degrade in a museum climate.

Preliminary analyses of natural radionuclides in selected Turkish power plant lignites

This preliminary study presents the experimental results concerning the concentrations of selected radionuclides (²³⁸U, ²³²K, ²²⁶Ra, ²³²Th) in Af?in-Elbistan, Çan, Çay?rhan, Erzurum, Göynük, Kangal, Orhaneli, Saray, Seyitömer, Soma, Tunçbilek, Yata?an and Yeniköy lignites, which are primarily utilized as fuel for thermal power plants in Turkey. Gamma-spectrometry of 39 representative lignite samples gave results with the following concentration ranges: 8 to 296 Bq/kg for ²³⁸U, 3 to 79 Bq/kg for ²³²Th, 17 to 360 Bq/kg for 40K, and 5 to 130 Bq/kg for ²²⁶Ra. The ²³⁸U results reported here are higher than other literature values for various world coals, earth's crust and world average.     

Effect of powder dispersion on the1 A 1 ⇄5 T 2 spin transition in Fe(II) complexes with 4-amino-l,2,4-triazole

A series of Fe(II) complexes with 4-amino-1,2,4-triazole ground in an agate mortar for 10 min is studied by Mössbauer spectroscopy. Strong effects of powder dispersion both on the¹ A ₁ ?⁵ T ₂ spin transition and on the structure dynamic characteristics of the complexes are found. Thus at 295 K the high-spin form of Fe(II) appears in the samples or its fraction increases; the ionicity of Fe-N bonds and the extent of distortion of the octahedral environment of iron atoms for the low-spin phases of the complexes also increase. It is established that powder dispersion markedly affects the probability of the Mössbauer effect and the vibrational spectrum of the lattice of coordination compounds. For both the low- and high-spin phases of the complexes, it is reported that the vibrational spectrum is “softened.” The main reason for these effects is supposed to be defectiveness rather than the size of the particles due to mechanical activation of the powder.     

Aspects of the Chemistry of Diarylditellurides and Related Compounds containing Telurium to Tin Bonds

The examination mixtures of two ditellurides by mass and ¹H nmr spectroscopies provides the first evidence for the existence of unsymmetrical diarylditellurides, RTeTeR′. Possible mechanisms for the redistribution reaction are discussed and it is noted that no positive support for a radical mechanism is obtained. Appearance potential measurements on the ion (aryl)Te⁺ derived from a number of organotellurium compounds suggest that tellurium extrusion may be a low energy pathway for the decomposition of diarylditellurides. A new series of compounds, Ph₃SnTe(aryl) is reported and they are examined by ¹¹⁹Sn and ¹²⁵Te Mösabauer spectroscopies. Attempts are made to interpret the Mösabauer data in terms of orbital populations, and it is demonstrated that only an sp bonding model gives a self-consistent interpretation of the combined tin and tellurium Mösabauer data.