Structure Of Sulfide Research Articles

BLUE-GREEN LUMINESCENCE OF CHEMICALLY SYNTHESIZED MWCNT/CdS NANOHYBRID STRUCTURE

A simple inexpensive wet chemical technique at room temperature to prepare hybrid structure of multiwalled carbon nanotubes (MWCNT) and cadmium sulfide ( CdS ) nanoparticles has been reported in this paper. Cadmium sulfide nanocrystals of average size 5 nm have been synthesized and attached with the surfaces of MWCNTs. The hybrid material is characterized by high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and Raman spectroscopy. Interesting optical properties of the composite are revealed through UV–visible and photoluminescence (PL) spectroscopy. Significant blue-green PL emission covering a region from 450–600 nm wavelength has been observed when excited by UV radiation of 220–240 nm wavelength. Sharp emission peak has been obtained and this may find wide applications in optical sensors and optoelectronic devices.

Lanthanide Sensitization in II−VI Semiconductor Materials: A Case Study with Terbium(III) and Europium(III) in Zinc Sulfide Nanoparticles

This work explores the sensitization of luminescent lanthanide Tb(3+) and Eu(3+) cations by the electronic structure of zinc sulfide (ZnS) semiconductor nanoparticles. Excitation spectra collected while monitoring the lanthanide emission bands reveal that the ZnS nanoparticles act as an antenna for the sensitization of Tb(3+) and Eu(3+). The mechanism of lanthanide ion luminescence sensitization is rationalized in terms of an energy and charge transfer between trap sites and is based on a semiempirical model, proposed by Dorenbos and co-workers (Dorenbos, P. J. Phys.: Condens. Matter 2003, 15, 8417-8434; J. Lumin. 2004, 108, 301-305; J. Lumin. 2005, 111, 89-104. Dorenbos, P.; van der Kolk, E. Appl. Phys. Lett. 2006, 89, 061122-1-061122-3; Opt. Mater. 2008, 30, 1052-1057. Dorenbos, P. J. Alloys Compd. 2009, 488, 568-573; references 1-6.) to describe the energy level scheme. This model implies that the mechanisms of luminescence sensitization of Tb(3+) and Eu(3+) in ZnS nanoparticles are different; namely, Tb(3+) acts as a hole trap, whereas Eu(3+) acts as an electron trap. Further testing of this model is made by extending the studies from ZnS nanoparticles to other II-VI semiconductor materials; namely, CdSe, CdS, and ZnSe.

The structure and optical properties of nanocrytalline lead sulfide films

The crystal structure of lead sulfide (PbS) films produced by chemical deposition onto a glass sub� strate is studied by Xray diffraction analysis. The th ickness of the synthesized films is ~120 nm, the dimen� sions of the regions of coherent scattering are 70-80 nm, and the magnitude of microstrains is ~0.20%. It is established that the crystal structure of the synthesized PbS films and of the same films annealed at the tem� perature 293-423 K is cubic (space group Fm m) and corresponds to the D0 3 type that differs from the B1 type typical of coarsegrained PbS. In the cubic stru cture of the PbS nanofilms, there is a latent nonsto� ichiometric distribution of S atoms and vacancies among octahedral sites 4(b) and tetrahedral positions 8(c). The optical transmittance of the nanocrystalline PbS films is measured in the wavelength range from 200 to 3270 nm. The most pronounced variations in the transmittance is observed in the wavelength range from 700-800 to 1600-2000 nm (corresponding to the photon energy range from ~1.8 to ~0.7 eV). It is established that the band gap Eg is 0.83-0.85 eV, i.e., it is larger than the band gap of singlecrystal PbS, 0.41 eV.

Crystal Structure of Sulfide:Quinone Oxidoreductase from Acidithiobacillus ferrooxidans: Insights into Sulfidotrophic Respiration and Detoxification

Sulfide:quinone oxidoreductase from the acidophilic and chemolithotrophic bacterium Acidithiobacillus ferrooxidans was expressed in Escherichia coli and crystallized, and its X-ray molecular structure was determined to 2.3 Å resolution for native unbound protein in space group P4 22 12 . The decylubiquinone-bound structure and the Cys160Ala variant structure were subsequently determined to 2.3 Å and 2.05 Å resolutions, respectively, in space group P6 222 . The enzymatic reaction catalyzed by sulfide:quinone oxidoreductase includes the oxidation of sulfide compounds H 2S, HS −, and S 2− to soluble polysulfide chains or to elemental sulfur in the form of octasulfur rings; these oxidations are coupled to the reduction of ubiquinone or menaquinone. The enzyme comprises two tandem Rossmann fold domains and a flexible C-terminal domain encompassing two amphipathic helices that are thought to provide for membrane anchoring. The second amphipathic helix unwinds and changes its orientation in the hexagonal crystal form. The protein forms a dimer that could be inserted into the membrane to a depth of approximately 20 Å. It has an endogenous flavin adenine dinucleotide (FAD) cofactor that is noncovalently bound in the N-terminal domain. Several wide channels connect the FAD cofactor to the exterior of the protein molecule; some of the channels would provide access to the membrane. The ubiquinone molecule is bound in one of these channels; its benzoquinone ring is stacked between the aromatic rings of two conserved Phe residues, and it closely approaches the isoalloxazine moiety of the FAD cofactor. Two active-site cysteine residues situated on the re side of the FAD cofactor form a branched polysulfide bridge. Cys356 disulfide acts as a nucleophile that attacks the C4A atom of the FAD cofactor in electron transfer reaction. The third essential cysteine Cys128 is not modified in these structures; its role is likely confined to the release of the polysulfur product.

Pressure-induced orthorhombic structure of PbS

The pressure-induced crystal structure of lead sulfide (PbS) above 2.2 GPa hasbeen studied with single-crystal x-ray diffraction in a diamond anvil cell atroom temperature. It has been found to be twinned and of the TlI type (Cmcm,Z = 4), in which the Pb atoms are surrounded by seven S atoms in a capped trigonal prismcoordination. The twin laws in relation to the parent B1 (NaCl) type structure (, Z = 4) at atmospheric pressure have been discussed.

Structural defects in CVD ZnS

The structure of polycrystalline zinc sulfide grown by chemical vapor deposition has been studied, and stacking faults have been revealed in the cubic matrix of crystals, which lead to a striated subgranular structure. During synthesis, mixed-phase crystals are formed as a result of the characteristic polymorphism. The effect of structural inhomogeneities on the optical loss in the material in the visible range is analyzed.

Bismuth Sulfide (Bi2S3) as the Active Species in Extreme Pressure Lubricants Containing Bismuth Carboxylates and Sulfur Compounds

A series of bismuth carboxylates were tested with active and inactive sulfur compounds as extreme pressure (EP) lubricant additives. Wear and load measurements from four-ball tests are reported. Bismuth 2-ethylhexanoate (Bi 2EH), bismuth neodecanoate (Bi NDA) and bismuth naphthenate (Bi Nap) showed excellent EP activity with both active and inactive sulfur compounds (≥ 620 kg four-ball weld load). The mechanism of the EP lubricity was studied using thermogravimetric analysis (TGA), high-temperature X-ray diffraction (HTXRD), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The results of these studies support the formation of bismuth sulfide during thermolysis of the bismuth carboxylate-polysulfide mixtures. The structure of bismuth sulfide suggests that interlayer shear occurs and provides lubricity.

Diallyl Trisulfide Protects Rats from Carbon Tetrachloride-Induced Liver Injury

Alk(en)yl sulfides have been found to be responsible for the anticancer, antithrombotic, and antioxidant effects of garlic. We sought to identify the most potent structure of sulfides that exhibits a hepatoprotective effect against carbon tetrachloride (CCl4)-induced acute liver injury in rats. Rats were pretreated with diallyl trisulfide (DATS) i.g. at a dose of 500 μmol/kg body weight for 5 d. On d 6, CCl4 was administered i.g. at a dose of 2.5 mL/kg body weight. Twenty-four hours after CCl4 administration, rats were killed and plasma and liver samples collected. DATS pretreatment significantly suppressed the CCl4-induced elevation of plasma aspartate aminotransferase and alanine aminotransferase activities (P < 0.05). Histological observations supported the hepatoprotective effects. Western blot and spectrophotometric analyses indicated that DATS suppressed cytochrome P450 2E1 activity and its protein level and elevated those of glutathione S-transferase. Dipropyl trisulfide (DPTS), which is a saturated alkyl chain analogue of DATS, did not affect CCl4-induced liver toxicity or drug-metabolizing enzymes. These results suggest that hepatoprotective activity of trisulfides is due to their regulation of drug-metabolizing enzymes. Furthermore, the effects of 6 kinds of alk(en)yl trisulfides, including DATS and DPTS, on phase II enzyme activity were examined in rats. Alk(en)yl trisulfides were administered i.g. (500 μmol/kg body weight) to rats for 5 d. Only the allyl group-containing DATS and allyl methyl trisulfide enhanced these activities.

&lt;I&gt;In-Situ&lt;/I&gt; TEM Observations of the Crystallization Process of Solution-Prepared MoS&lt;SUB&gt;2&lt;/SUB&gt; Amorphous Particles

The crystallization of polymer-mixed amorphous molybdenum sulfide was observed in-situ by a TEM equipped with a heated specimen holder. High electron beam irradiation induced the formation of a crystal structure with a lattice spacing of 0.62 nm, which corresponds to the layer spacing of MoS2. With a lower electron dose, a possible new crystal structure of molybdenum sulfide with several fringe spacings was identified at room temperature. An ordered layered structure of MoS2 appeared after annealing at 600 degrees C. The completely different crystal phase found here might be responsible for the high temperature required for the formation of the MoS2 layered structure.

Effect of Diluent Mixture on Porous Structure of Polyphenylene Sulfide via Thermally Induced Phase Separation

Polyphenylene sulfide (PPS) microporous membranes were prepared via the thermally induced phase separation process using diluent mixtures of diphenyl ether (DPE) and diphenyl ketone (DPK). The effects of DPE ratio to DPK in the diluent mixture on the microstructure were investigated. The results showed that the pore morphology of the membranes prepared from the diluent mixture was different from those of fabricated from pure diluents. Moreover, the pore structures of the membranes were changed along with the variation of the diluent composition.

Electron states and bonding in titanium sulfide

The electronic structure of titanium sulfide is studied in a series of molecular orbital and band structure calculations using the first-principles Hartree-Fock-Slater model. The results are correlated with optical data and with X-ray emission and absorption, and compared with recent semiempirical tight binding models.

Identification of a sulfide derivative with a bicyclic hydrocarbon skeleton related to squalene. Part I: synthesis of a dithiane triterpenoid

In order to confirm the tentative structure of a dithiane sulfide with a bicyclic squalene hydrocarbon skeleton representing the predominant alkyl sulfide in Shell Beach samples from the Monterey Formation (Miocene, CA) and also occurring in various immature sulphur-rich sediments [Schouten, S., Sinninghe Damsté, J.S., de Leeuw, J.W., 1995. A novel triterpenoid carbon skeleton in immature sulphur-rich sediments. Geochimica et Cosmochimica Acta 59, 953–958], synthesis of a reference compound bearing two thiochromane moieties has been carried out. The product was obtained as a diastereomeric mixture appearing in the form of five peaks (partly) resolved in gas chromatography (GC). This is in sharp contrast with the geochemical compound, which appears as a single broad peak in GC. Co-elution experiments showed that none of the peaks from the synthetic mixture coelute in GC with that of the geochemical sulfide. Furthermore, the different synthetic isomers have identical mass spectra, which are clearly distinct from that of the naturally-occurring compound. The results unambiguously indicate that the natural compound is not the dithiane triterpenoid originally envisaged. Instead, we propose that the compound has a structure of a bicyclic squalene derivative bearing two “S-spiro”-type moieties as is the case for other sulfides related to regular polycyclic polyprenoids and hopanoids in Monterey sediments.

New crystalline phase in thin lead sulfide films

The crystal structure of thin lead sulfide (PbS) films fabricated by hydrochemical deposition is studied by X-ray diffraction analysis. It is established that both the synthesized PbS films and the same films annealed in the temperature interval of 293–423 K have a cubic (space group Fm\( \bar 3 \)m) crystal structure different from the B1-type structure. In this structure, sulfur (S) atoms are located not only in positions 4(b) (octahedral interstices of the face-centered sublattice of lead (Pb) atoms) but also in positions 8(c), i.e., in tetrahedral interstices. The occupations of positions 4(b) and 8(c) by S atoms are ∼0.84 and ∼0.08, respectively. Long-range order in the location of S atoms in positions of each type is absent, but correlations may be present. The new revealed structure of PbS films remains stable under a prolonged annealing in the temperature interval from 293 to 423 K.

Synthesis of rare earth sulfides and their UV-vis absorption spectra

Rare earth sulfides were systematically synthesized via the sulfurization of their commercial oxide powders using CS 2 gas to shorten sulfurization time, and their UV-vis absorption spectra were investigated. The appropriate sulfurization conditions were studied. For the rare earth sulfides with the same crystal structure, the sulfurization temperature showed increasing tendency with the decrease of rare earth element atomic radii. The UV-vis absorption spectra of rare earth sulfides did not depend on the crystal structure of rare earth sulfides, but on the 4f electronic structure of rare earth element. The data showed that the optical band gaps of rare earth sulfides were irregular, and the values ranged from 1.65 to 3.75 eV.

Synthesis, Structure, and Reactivity of Intramolecularly Coordinated Organoantimony and Organobismuth Sulfides

Organoantimony(III) and organobismuth(III) sulfides, containing O,C,O-chelating ligands (L1−3 = 2,6-(ROCH2)2C6H3−, where R = Me (L1), t-Bu (L2), or mesityl (L3)), [L1−3MS]2, where M = Sb (L1 (5), L2 (6), L3 (7)) or M = Bi (L2 (8)), were prepared by the reaction of parent organoantimony and organobismuth chlorides with Na2S·9H2O in toluene/water. All sulfides 5−8 were characterized by elemental analysis, electrospray ionization mass spectrometry, 1H and 13C NMR spectroscopy, and X-ray diffraction techniques. Organoantimony sulfides 5−7 are stable both in solution and in the solid state in contrast to the organobismuth congener, which is stable at −30 °C but decomposes at ambient temperature. While the reaction of 5 and 7 with I2 yielded the expected organoantimony iodides L1,3SbI2 (L1 (9), L3 (10)), compound 6 containing ligand L2 gives the unexpected oxastibol 12 besides the intended diiodide L2SbI2 (11). The molecular structure of 12 in the solid state was determined by X-ray diffraction techniques and showed formation of an Sb−O covalent bond as a result of C−O ether bond cleavage.

Mineralogy, Fluid Inclusion, and Stable Isotope Constraints on the Genesis of the Roudny Au-Ag Deposit, Bohemian Massif

Orogenic gold deposits with gold of low-fineness are relatively rare in the Bohemian Massif but occur locally within the late Variscan Blanice graben structure in the Moldanubian zone. Among them, the Roudný deposit has been the most important, with total production of about 6 t of gold between 1895 and 1930. The ore is related to an irregular quartz stockwork and is represented by sulfide and electrum impregnations within the quartz gangue and the altered host rocks. Ore grade varies from 4 to 25 g/t Au. The gold is present as macro-and microscopic electrum (fineness 658–665) and also as “invisible gold” in the crystal structure of early sulfides (As-rich pyrite and Sb-rich arsenopyrite). Three mineralization stages have been distinguished: (1) the largely barren pre-ore stage, (2) the main-ore stage with economic Au-Ag mineralization, (3) the late stage with subeconomic Ag-Pb-Zn mineralization. Fluid inclusion and mineral thermometry indicate that the three stages were formed at about 400° to 330°, 350° to 250°, and 250° to 70°C, respectively. Early mineralization stages are related to complex H2O-CO2 ± CH4-N2 low salinity (<3.9 wt % NaCl equiv) fluids with isotopic signatures consistent with a metamorphic origin (δ18Ofluid = 4.7–2.9‰ SMOW). Most of the main ore-stage minerals, including the electrum, precipitated from aqueous fluids (2–4 wt % NaCl equiv). During the late mineralization stage, the salinity of aqueous fluid was higher (7–9 wt % NaCl equiv). The isotopic composition of the late fluid, however, also records gradually increasing proportions of meteoric water (δ18Ofluid = +2 to −1‰ SMOW). Elevated arsenic contents (120–210 ppm As) were found in aqueous-carbonic fluids by the LA-ICP-MS technique. Models of fluid mixing at the transition of the main to late mineralization stages are used to estimate the temperature and paleogeothermal gradient. Possible ages of electrum mineralization (~300 to ~ 275 Ma) and Ag-Pb-Zn vein-type mineralization (~275 to ~265 Ma) are discussed. Overall, the Roudný deposit shows striking similarities with ~300 Ma gold deposits of the French Massif Central.

Biosynthesis of cadmium sulfide nanoparticles by photosynthetic bacteria Rhodopseudomonas palustris

A simple route for the synthesis of cadmium sulfide nanoparticles by photosynthetic bacteria Rhodopseudomonas palustris has been demonstrated in this work. The cadmium sulfate solution incubated with R. palustris biomass changed to a yellow color from 48 h onward, indicating the formation of cadmium sulfide nanoparticles. The purified solution yielded the maximum absorbance peak at 425 nm due to CdS particles in the quantum size regime. Also, X-ray analysis of the purified nanoparticles confirmed the formation of cadmium sulfide. Transmission electron microscopic analysis of the samples showed a uniform distribution of nanoparticles, having an average size of 8.01 ± 0.25 nm, and its corresponding electron diffraction pattern confirmed the face-centered cubic (fcc) crystalline structure of cadmium sulfide. Furthermore, it was observed that the cysteine desulfhydrase producing S 2− in the R. palustris was located in cytoplasm, and the content of cysteine desulfhydrase depending on the growth phase of cells was responsible for the formation of CdS nanocrystal, while protein secreted by the R. palustris stabilized the cadmium sulfide nanoparticles. In addition, R. palustris was able to efficiently transport CdS nanoparticles out of the cell.

High-energy heavy-ion induced physical and surface-chemical modifications in polycrystalline cadmium sulfide thin films

The effect of high electronic energy deposition on the structure, surface topography, optical properties, and electronic structure of cadmium sulfide (CdS) thin films have been investigated by irradiating the films with 100 MeV Ag+7 ions at different ion fluences in the range of 1012–1013 ions/cm2. The CdS films were deposited on glass substrate by thermal evaporation, and the films studied in the present work are polycrystalline with crystallites preferentially oriented along (002)-H direction. It is shown that swift heavy ion (SHI) irradiation leads to grain agglomeration and hence an increase in the grain size at low ion fluences. The observed lattice compaction was related to irradiation induced polygonization. The optical band gap energy decreased after irradiation, possibly due to the combined effect of change in the grain size and in the creation of intermediate energy levels. Enhanced nonradiative recombination via additional deep levels, introduced by SHI irradiation was noticed from photoluminescence (PL) analysis. A shift in the core levels associated with the change in Fermi level position was realized from XPS analysis. The chemistry of CdS film surface was studied which showed profound chemisorption of oxygen on the surface of CdS.

The electronic structure and catalytic properties of molybdenum sulfides in the coal hydrogenation process

Comparative analysis of the electronic structure of molybdenum sulfides and their catalytic activity in hydrogenation reactions was performed from the results of Hartree-Fock ab initio quantum-chemical calculations using the STO 3-21G* and 6-311G basis sets with geometry optimization. The model reactions of hydrogenation of aromatic and saturated hydrocarbons with hydrogen and hydrogen sulfide were studied. It was shown that the hydrogenation reactions of aromatic hydrocarbons with hydrogen sulfide must occur at a higher rate (with lower activation energy) as compared to those with molecular hydrogen.

The Effect of Morphology and Distribution of Sulfides on Mechanical Properties and Fatigue Life of Non-Quenched and Tempered Steel

The effect of morphology and distribution of sulfides on tensile, impact and bending fatigue properties of non-quenched and tempered steel 49MnVS3 has been investigated in this paper. Microscopic structure and morphology of sulfides are observed, and impact fracture and fatigue fracture have been analyzed by SEM. The results show that the morphology of sulfides is mostly strip and distributes in ferrite, which affects mechanical properties and fatigue life. The length direction of sulfide strip is parallel to the rolling direction of steel. When the length of sulfide is short relatively and is approximate to the shape of particles. The impact properties and bending fatigue performance of 49MnVS3 are higher. Under those conditions, there are more ductile characteristics in their impact fracture and the fatigue fracture. The reasons for the effect of sulfide morphology on the mechanical and fatigue properties are explained.