Analysis of the chromite inclusions found in nephrite minerals obtained from different deposits using SEM‐EDS and LRS

Scanning electron microscopy with energy dispersive spectrometer (SEM‐EDS) and laser Raman spectroscopy (LRS) were used to analyse the chromite inclusions found in four samples of the mineral nephrite that were obtained from Taiwan (one), Manasi in China (two) and New Zealand (one). The chromite inclusions found in sample HL‐1 (Taiwan) contain low contents of Mg and Al, as well as a characteristically high Zn content. The most significant finding, however, was that HL‐1 could also be distinguished from the other samples by the lower wavenumbers of the positions of the peaks that belong to the A_1g, F_2g⁽¹⁾ and E_g modes. Compared to the difference in compositions, the difference in the positions of the peaks in the Raman spectra of the chromite inclusions, as revealed by LRS, can more easily be used to distinguish between samples of nephrite that have been obtained from different deposits, and in particular to identify the provenance of the raw material used in ancient nephrite artefacts, in view of the fact that LRS is non‐destructive and easy to apply. Copyright © 2011 John Wiley & Sons, Ltd.     

Ageing of calcium silicate cements for endodontic use in simulated body fluids: a micro‐Raman study

To evaluate bioactivity properties, a calcium silicate experimental cement (wTC) and a phosphate‐doped wTC cement (wTC‐TCP) were aged for different times (1–180 days) at 37 °C in two simulated body fluids, i.e. Dulbecco's phosphate buffered saline (DPBS) and Hank's balanced salt solution (HBSS). The cements were analyzed by micro‐Raman spectroscopy to investigate the presence of calcium phosphate deposits and the composition changes as a function of the storage time (hydration of anhydrite/gypsum and formation of ettringite; hydration of belite/alite and formation of hydrated silicates). After 1 day of ageing in DPBS, the two cements already showed a different behavior: only the surface of wTC‐TCP cement showed the band at 965 cm⁻¹, suggesting the formation of a detectably thick calcium phosphate deposit. The trend of the I₉₆₅/I₉₉₀ Raman intensity ratio indicated the formation of a meanly thicker apatite deposit on the wTC‐TCP cement until 90 days. After 60 days of ageing in DPBS, the thickness of the apatite deposit on wTC and wTC‐TCP was about 200 and 500 µm, respectively, whereas at 180 days, the two cements did not appear significantly different (thickness of about 900 µm). The bioactivity of both cements in HBSS was less pronounced than in DPBS, according to the lower phosphate concentration of HBSS; at the same time, higher amounts of calcite were found on the surface of both cements. The wTC‐TCP cement showed a higher bioactivity in this medium also; after 180 days, the thickness of the apatite deposit on wTC and wTC‐TCP was < 50 µm and about 100 µm, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Real‐time measurement of H/D exchange in a microdialysis Raman quartz cell

We present here a novel quartz cell for monitoring H/D exchange in biomolecules using Raman spectroscopy. This cell is combined with a syringe to pump heavy water through a hollow microdialysis fibre, which is inserted into the cell. The deuterium efflux into the sample has been studied as a function of the molecular weight cut‐off of the microdialysis fibre and compared with other microcell systems comprising conventional glass capillaries. The fastest D₂O efflux that we have obtained (k_d = 0.38 ± 0.008 min⁻¹) permits to measure exchange rates of 2.5 min⁻¹ or less. Application of this cell to deuterium exchange in glyceraldehyde‐3‐phosphate dehydrogenase reveals a class of H‐atoms highly resistant to deuteration, which is consistent with a previous infrared study on this protein. Copyright © 2009 John Wiley & Sons, Ltd.     

Anomalous concentration dependence of the coordination behavior of Cl− ion to Ln3+ ion (Ln3+ = rare‐earth ion) in anhydrous LnCl3 alcohol solutions

Raman spectroscopic measurements were carried out for the anhydrous LnCl₃·20ROH·XLiCl solutions (Ln³⁺ = La³⁺− Lu³⁺, X = 0–3; ROH = MeOH, EtOH, n‐PrOH) in the liquid state. The salt concentration (X) dependence of the wavenumber for the Ln–Cl stretching Raman band (ν_Ln–Cl) is examined in conjunction with the formation of chloro‐rare‐earth complexes. We have obtained very intriguing results including the fact that the chloro complexations of the middle rare‐earth ions (e.g. gadolinium, holmium ions, etc.) in the MeOH and EtOH solutions show peculiar behavior with regard to the salt concentration dependence: the ν_Ln–Cl wavenumber increases with the increasing chloride concentration. However, the ν_Ln–Cl wavenumbers of the light and heavy rare‐earth (e.g. lanthanum, lutetium, etc.) salt solutions show normal behavior; i.e. ν_Ln–Cl decreases with the increasing chloride concentration. On the other hand, in the n‐PrOH solutions, the ν_Ln–Cl frequency in the solutions of all the rare‐earth elements exhibits a normal behavior. We now present a possible mechanism for this anomalous concentration dependence of coordination of Cl⁻ ions to Ln³⁺ ions in anhydrous LnCl₃ alcohol solutions. Copyright © 2007 John Wiley & Sons, Ltd.     

Evolution of excess electron binding motifs under both internal‐push (from exo C–F bonds) and external‐push (from endo C–F bonds) electron effects in endohedral metallofullerenes with endo C–F bonds

How does the endo C–F bond influence the excess electron binding motif? For lithium‐doped endohedral perfluorofullerenes with endo C–F bonds, under both internal‐push (from exo C–F bonds) and external‐push (from endo C–F bonds) electron effects, the singly occupied molecular orbital electron cloud of the sphere‐like Li···F₈@C₆₀F₅₂ (D₂) is partially dispersed within the σ_p–s antibonding orbital of endo C–F bonds and the space between C^δ+–F_endo^δ– double electric layers, which makes Li···F₈@C₆₀F₅₂ have partial excess electron (electride characteristics) and partial lithium salt characteristics, while in the tube‐like Li···F₂@C₆₀F₅₈ (C_s), as the Li is changing from approaching F to keeping away from F and to approaching another one, the singly occupied molecular orbital electron cloud is mainly dispersed from within the p orbital of the short endo C–F bond to within the middle of the two F atoms and again to within the p orbital of the short endo C–F bond, which indicates an evolution from lithium salt characteristic to excess electron characteristic, and again to lithium salt characteristic. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrogen abstraction from H‐donor substrates by the 6‐CF3‐benzotriazol‐N‐oxyl radical (TFNO)

The aminoxyl radical 6‐trifluoromethyl‐benzotriazol‐N‐oxyl (TFNO) has been generated from the parent hydroxylamine 6‐CF₃‐1‐hydroxy‐benzotriazole (TFBT) by one‐electron oxidation with a Ce^IV salt and characterized by spectrophotometry and cyclic voltammetry (CV). Rate constants of H‐abstraction (k_H) by TFNO from a number of H‐donor benzylic substrates have been determined spectrophotometrically in MeCN solution at 25 °C. A radical H‐atom transfer (HAT) route of oxidation is substantiated for TFNO by several pieces of evidence. The kinetic data also testify the relevance of stereoelectronic effects upon the HAT reactivity of TFNO. Copyright © 2010 John Wiley & Sons, Ltd.     

Exchange‐Biased Fe3−xO4‐CoO Granular Composites of Different Morphologies Prepared by Seed‐Mediated Growth in Polyol: From Core–Shell to Multicore Embedded Structures

Magnetically contrasted granular hetero‐nanostructures are prepared by seed‐mediated growth in polyol, properly combining two oxide phases with different magnetic order, ferrimagnetic (F) partially oxidized magnetite Fe_3−xO₄ and antiferromagnetic (AF) cobalt oxide. Spinel Fe_3−xO₄ nanoparticles are first synthesized and then used as seeds for rock salt CoO nanocrystals growth. Three different hetero‐nanostructure designs are realized, acting on the content ratio between the seeds and the deposit's precursors during the synthesis. For all of them, the spinel and the rock salt phases are confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. Both phases are obtained in high‐crystalline quality with a net epitaxial relationship between the two crystallographic lattices. Mössbauer spectrometry confirms the cobalt cation diffusion into the spinel seeds, giving favorable chemical interfacing with the rock salt deposit, thus prevailing its heterogeneous nucleation and consequently offering the best condition for exchange‐bias (EB) onset. Magnetic measurements confirm EB features. The overall magnetic properties are found to be a complex interplay between dipolar interactions, exchange anisotropy at the F/AF interface, and magnetocrystalline anisotropy enhancement in the F phase, due to Co²⁺ diffusion into iron oxide's crystalline lattice. These results underline the powerfulness of colloidal chemistry for functional granular hetero‐nanostructured material processing.     

X‐ray absorption spectroscopy at the Ni?K edge in Stackhousia tryonii Bailey hyperaccumulator

Young plants of Stackhousia tryonii Bailey were exposed to 34 mM Ni kg^?1 in the form of NiSO₄· 6H₂O solution and grown under controlled glasshouse conditions for a period of 20 days. Fresh leaf, stem and root samples were analysed in vivo by micro x‐ray absorption spectroscopy (XAS) at the Ni? K edge. Both x‐ray absorption near edge structure and extended x‐ray absorption fine structure spectra were analysed, and the resulting spectra were compared with spectra obtained from nine biologically important Ni‐containing model compounds. The results revealed that the majority of leaf, stem and root Ni in the hyperaccumulator was chelated by citrate. Our results also suggest that in leaves Ni is complexed by phosphate and histidine, and in stems and roots, phytate and histidine. The XAS results provide an important physiological insight into transport, detoxification and storage of Ni in S. tryonii plants. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman and ab initio study of the conformational isomerism in the 1‐ethyl‐3‐methyl‐imidazolium bis(trifluoromethanesulfonyl)imide ionic liquid

The calculated and experimental Raman spectra of the (EMI⁺)TFSI⁻ ionic liquid, where EMI⁺ is the 1‐ethyl‐3‐methylimidazolium cation and TFSI⁻ the bis(trifluoromethanesulfonyl)imide anion, have been investigated for a better understanding of the EMI⁺ and TFSI⁻ conformational isomerism as a function of temperature. Characteristic Raman lines of the planar (p) and non‐planar (np) EMI⁺ conformers are identified using the reference (EMI⁺)Br⁻ salt. The anion conformer of C₂ symmetry is confirmed to be more stable than the cis (C₁) one by 4.5 ± 0.2 kJ mol⁻¹. At room temperature, the population of trans (C₂) anions and np cations is 75 ± 2% and 87 ± 4%, respectively. Fast cooling quenches a metastable glassy phase composed of mainly C₂ anion conformers and p cation conformers, whereas slow cooling gives a crystalline phase composed of C₁ anion conformers and of np cation conformers. Copyright © 2006 John Wiley & Sons, Ltd.     

X‐ray fluorescence analysis of Co,Ni, Pd,Ag, and Au in the scrapped printed‐circuit‐board ash

A method for the quantitative analysis of Co, Ni, Pd, Ag, and Au in the scrapped printed‐circuit‐board ash by X‐ray fluorescence (XRF) spectrometry using loose powder was developed. The printed‐circuit‐board samples were converted to ash pyrolytically in porcelain crucibles by sequential heating using a gas burner and electric furnace, and then were ground with a ball mill. The calibrating standards were prepared by adding the appropriate amounts of NiO powder and aqueous standard solutions containing Co, Pd, Ag, and Au to the base mixtures of Al₂O₃ (5.0 mass%), SiO₂ (49 mass%), CaCO₃ (11 mass%), Fe₂O₃ (3.3 mass%), and CuO (30 mass%) as a matrix. Then, 10 g of the resulting mixtures were dried and homogenized for 90 min with a V‐type mixing machine. Specimens for XRF analysis were prepared from the so‐called loose‐powder method in which powder samples were compacted into a hole (12.0‐mm diameter and 5.0‐mm height) in an acrylic plate and covered with a 6‐µm thickness of polypropylene film. Matrix effects were corrected using the intensity value of Compton scattering for PdKα, AgKα, and AuLβ₂, and that of background scattering at 35.8° (2θ) for CoKα and NiKα. The detection limits corresponding to three times the standard deviation of the blank intensity were 2.5–45 µg g^?1. The proposed method was validated against the pressed‐powder‐pellet method by comparing the calibration curves. Moreover, the concentrations of Co, Ni, Pd, and Ag determined using the proposed XRF method were approximately the same as those resulting from an atomic‐absorption‐spectrometric analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

Scattering processes and electrical conductivity of partially ionized hydrogen plasma

We consider partially ionized hydrogen plasma for the density region n_e = (10¹⁸ ÷ 10²²) cm^—3. The cross sections for scattering processes between the particles are calculated within the partial wave method. Charged particles in the system (electrons, protons) interact via an effective potential that takes into account threeparticle correlations. The Buckingham polarization potential is used to describe electron‐atom and proton‐atom interactions. The electrical conductivity is determined using the Chapman‐Enskog method. The results are compared with other available data.     

Flow‐Injection Chemiluminescence Study of Luminol–Hydrogen Peroxide–Carbendazim System

Abstract

A new flow‐injection chemiluminescence (CL) method is described for the determination of carbendazim. The method is based on the CL reaction of luminol and hydrogen peroxide (H₂O₂). Carbendazim can greatly enhance the chemiluminescence intensity in sodium hydroxide–sodium dihydrogen phosphate (NaOH–NaH₂PO₄) medium (pH=12.6). Under the optimum conditions, the linear range for the determination of carbendazim is 2.00×10^?8 to 2.00×10^?6 g mL^?1 with a detection limit (S/N=3) of 7.24×10^?9 g mL^?1. The relative standard deviation is 1.8% for 1.0×10^?7 g mL^?1 carbendazim (n=8). The proposed method has been applied to the determination of carbendazim in tap‐water samples. Furthermore, the possible enhanced CL mechanism is discussed by examining the CL spectra and fluorescence spectra.     

Protonic conductivity of solid UO2HPO4·3H2O

The electrical and electrochemical properties of the solid ionic conductor UO₂HPO₄·3H₂O were investigated within the temperature range from room temperature up to 673 K. The conductivity of a nondehydrated sample within the temperature range from 303 K (6.5 × 10^-3 S/m) to 350 K (2.5 × 10^-2 S/m), with the activation energy of 23 kJ/mol, is a consequence of the presence of crystal water, and originates, mostly, from the fast movement of protons across the network of molecules of water in a tunneling mechanism pattern. When heated, the conductor loses crystal water, which leads to a final change in the nature of the conductor and in the conductivity mechanism. The conductivity of the dehydrated salt UO₂HPO₄ (2.5 × 10^-4 S/m at 488 K), with the activation energy 44.04 kJ/mol, is considerably lower than the one mentioned above and can be attributed, to a great extent, to the movement of protons, most likely by a tunneling mechanism, through the less favourable structure formed by phosphate groups of the dehydrated salt. On being heated above 623 K for a certain time, the acid phosphate transforms into pyrophosphate, the conductivity of which is lower than that mentioned above. By means of electrochemical methods, the electrode processes were studied. It has been shown that H⁺ and UO²⁺ ions are reduced at the cathode, while the phosphate groups oxidize at the anode and O₂ is evolved.     

Two salts and the salt cocrystal of ciprofloxacin with thiobarbituric and barbituric acids: The structure and properties

Ciprofloxacin (CfH, C₁₇H₁₈FN₃O₃) crystallizes with 2‐thiobarbituric (H₂tba) and barbituric acid (H₂ba) in the aqueous solution to yield salt CfH₂(Htba)·3H₂O ( 1 ), salt cocrystal CfH₂(Hba)(H₂ba)·3H₂O ( 2 ), and salt CfH₂(Hba)·H₂O ( 3 ). The compounds are structurally characterized by the X‐ray single‐crystal diffraction. The numerous intermolecular hydrogen bonds N–H?O and O–H?O formed by water molecules, Htba^?/Hba^? and CfH₂⁺ ions, and H₂ba molecules stabilize the crystal structures of 1 to 3 . Hydrogen bonds form a 2D plane network in the salts of 1 and 3 and a 3D network in the salt cocrystal of 2 . There are different π‐π interactions in 1 to 3 . The compounds have been characterized by powder X‐ray diffraction, thermogravimetry/differential scanning calorimetry, and Fourier transform infrared spectroscopy. The compounds dehydration ends at 130°C to 150°C, and their oxidative decomposition is observed in the range of 250°C to 275°C.     

Influence of Ag2O on crystallisation and structural modifications of phosphate glasses

A series of phosphate glasses of composition 45P₂O₅–(40???x)CaO–15Na₂O–xAg₂O (x?=?0, 3, 6, 8, 10 and 12?mol%) with different Ag₂O contents were prepared using the melt-quenching technique. The incorporated Ag₂O highly influenced the increase of its transition tendency towards crystallisation and, on contrary, reduced the degree of glassification of phosphate glasses. The lowering of glass transition temperature and increase in thermal expansion were observed in glasses against Ag₂O inclusions. The crystalline phase transitions of amorphous material during thermal treatment were confirmed by employing X-ray diffraction studies. As revealed by X-ray photoelectron spectroscopy, the incorporated silver oxide into phosphate glass exists in two different oxidation states, Ag₂O and AgO. The pyrophosphate and metaphosphate units were predominantly occupied in glass and glass ceramics. The elastic moduli and Vicker's hardness values exhibited the decrease in phosphate glass structural compactness due to Ag₂O-incorporation and these values were found to improve because of crystalline transitions.     

Effect of the humidity on the uptake of NO<Subscript>3</Subscript> on coatings composed of MgCl<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O and MgBr<Subscript>2</Subscript> · 6H<Subscript>2</Subscript>O and mixtures thereof with NaCl

The reactive uptake of NO₃ radicals on the surface of wetted individual X salts and of wetted X-NaCl salts (X = MgCl₂ · 6H₂O and MgBr₂ · 6H₂O) at [H₂O] = 2 × 10¹²−2 × 10¹⁵ cm⁻³ and NO₃ (4.8 × 10¹² cm⁻³) was studied using a reactor with a movable insert covered with a salt coating in combination with a mass spectrometer for monitoring the initial reactant and products. The probabilities of NO₃ uptake γ on X-NaCl binary salts as functions of the content of doping salt were determined. A parametric approximation of the experimental data was proposed, which makes it possible to quantitatively predict the extent of surface enrichment of a wetted binary salt coating in doping salt and its dependence on the humidity and the content of this salt in the binary mixture. It was established that the relative surface density σ_X of X doping salt depends on its mole fraction μ_X in the X-NaCl binary salt as σ_X = aμ_X (a = 2.2 for MgBr₂ and 13.1 for MgCl₂) over the entire humidity range covered. The contributions of the X salts to the overall uptake of NO₃ at NO₃ concentration typical of the tropospheric conditions ([NO₃] ∼ 10⁷ cm⁻³ and relative humidities of RH ≤ 20%) were estimated.     

Neutron scattering from PEEK

An alkali‐soluble polysaccharide, GM5‐1, from the mycelium of Ganoderma tsugae, was fractionated by the nonsolvent addition method. The weight‐average molecular mass (M _w) and intrinsic viscosity ([η]) of fractions were studied by laser light scattering and viscometry with dimethylsulfoxide (DMSO) containing 0.25M LiCl (0.25M LiCl/DMSO) as the solvent at 30°C. The dependences of [η] and the radius of gyration (?S ²?_z ^1/2) on M _w were found to be [η]=9.8×10^?2 M _w ^0.57 (cm³g^?1) and ?S ²?_z ^1/2=1.65×10^?2 M _w ^0.58 (nm) in the M _w range from 8.6×10⁵ to 2.6×10⁶. The analysis based on current theories for a wormlike chain showed that the chain conformational parameters of GM5‐1 were 4.2 nm for persistence length (q) and 833 nm^?1 for linear mass density (M_L) with an obvious excluded volume effect. The results suggested the alkali‐soluble polysaccharide behaves like a semiflexible chain in 0.25M LiCl/DMSO at 30°C.     

Synthesis and characterization of proton-conducting polymer electrolyte based on polyacrylonitrile (PAN)

Solid polymer electrolytes based on polyacrylonitrile (PAN) doped with ammonium iodide (NH₄I) have been prepared by solution casting method with different molar ratios of polymer and salt using DMF as solvent. The XRD pattern confirms the dissociation of salt. The FTIR analysis confirms the complex formation between the polymer and the salt. A shift in glass transition temperature (T _g ) of the PAN/NH₄I electrolytes has been observed from the DSC thermograms, which indicates the interaction between the polymer and the salt. The conductivity analysis shows that the polymer electrolyte with 20 mol% NH₄I has the highest conductivity equal to 1.106 × 10⁻³ S cm⁻¹ at room temperature. The activation energy (E _a ) has been found to be low for the highest conductivity sample. The dielectric permittivity (ε*) and modulus (M*) have been calculated from the alternating current (AC) impedance spectroscopy in the frequency range 42 Hz–1 MHz. The DC polarization measurement shows that the conductivity is mainly due to ions.

     

Catalysis by hydrogen chloride in the gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐buten‐3‐ol

A homogeneous, molecular, gas‐phase elimination kinetics of 2‐phenyl‐2‐propanol and 3‐methyl‐1‐ buten‐3‐ol catalyzed by hydrogen chloride in the temperature range 325–386 °C and pressure range 34–149 torr are described. The rate coefficients are given by the following Arrhenius equations: for 2‐phenyl‐2‐propanol log k₁ (s^?1) = (11.01 ± 0.31) ? (109.5 ± 2.8) kJ mol^?1 (2.303 RT)^?1 and for 3‐methyl‐1‐buten‐3‐ol log k₁ (s^?1) = (11.50 ± 0.18) ? (116.5 ± 1.4) kJ mol^?1 (2.303 RT)^?1. Electron delocalization of the CH₂?CH and C₆H₅ appears to be an important effect in the rate enhancement of acid catalyzed tertiary alcohols in the gas phase. A concerted six‐member cyclic transition state type of mechanism appears to be, as described before, a rational interpretation for the dehydration process of these substrates. Copyright © 2007 John Wiley & Sons, Ltd.     

Selectivity of nitro versus fluoro substitution in arenes in their reactions with charged O‐ and S‐nucleophiles

The relative mobility of nitro and fluoro substituents in 1,3‐dinitro‐ and 1‐fluoro‐3‐nitrobenzenes, 3,5‐dinitro‐ and 3‐fluoro‐5‐nitrobenzotrifluorides under the action of the nucleophiles (2ArYH)·K₂CO₃ and ArY^?K⁺ in solution and the nucleophiles ArYH·K₂CO₃ (Y = O, S) under heterogeneous conditions was studied by a competitive method in DMF at 40–140 °C. The unique dependences of ΔΔH^≠ on ΔΔS^≠ and ΔΔH^≠ on ΔΔG^≠ were determined for all the substrates and nucleophiles. The dependence of the mechanistic pathway on the nucleophile is discussed. Two results are relevant to the reactions studied: (i) substituent effects in the nucleophiles (2ArYH)·K₂CO₃ and ArYH·K₂CO₃ on the activation entropies suggest that the entropy favours the displacement of nitro group; (ii) the negative signs of ΔΔH^≠ and ΔΔS^≠ for the reactions of the nucleophiles ArY^?K⁺ indicate that the enthalpy determines the displacement of nitro group. It is concluded that the selectivity of the reactions with aryloxide and arylthioxide ions cannot be explained by the hard–soft acid–base principle only. Copyright © 2007 John Wiley & Sons, Ltd.