Formation Of S2 Research Articles

Soot and PAH formation in laminar diffusion flames of RP-3 jet kerosene and its surrogates at preheat temperature

For investigating the effects of preheat temperature on the soot/PAH formation of RP-3 kerosene surrogates, planar laser-induced incandescence (PLII), planar laser-induced fluorescence of PAH (PAH-PLIF) and chemical kinetic simulation are conducted in several laminar diffusion flames. The goal is to provide a surrogate that matches well with the soot formation characteristics of RP-3 kerosene and to investigate the mechanism behind the temperature sensitivity of different surrogates. Firstly, surrogate S1 (30.3% n-hexadecane, 39.8% iso-cetane, 29.8% o-xylene, in mole fraction) is formulated to obtain a surrogate with good reproducibility of soot formation characteristics corresponding to the RP-3 jet kerosene. Compared with another reported surrogate S2, S1 presents a higher soot yield due to its higher PAH formation and a stronger soot formation propensity. With elevated preheat temperature, soot yield of all the studied flames gets higher, and the temperature sensitivities for soot formation of S1 and S2 are shown with little difference. By further analyzing the PAH results experimentally and numerically, the temperature sensitivity for soot yield of S2 is more closely related to the temperature sensitivity of PAH precursors, while the subsequent processes after soot inception may be more important to the temperature dependence of S1.

Hydrothermal reduction of sulfates by ferrous carbonate: Implications for the origin of reduced sulfur in carbonate-hosted Pb-Zn deposits associated spatially with basalts

Reduced sulfur derived from thermochemical sulfate reduction (TSR) in Pb-Zn deposits is one of the long-debated issues in economic geology. The formation of - 2 valent sulfur (S2-) in Pb-Zn deposits associated spatially with basalts, may be related to the thermal reduction of SO42- by ferrous ions (Fe2+). In the present study, hydrothermal experiments on the reduction of magnesium sulfate (MgSO4) by ferrous carbonate (FeCO3) were carried out to investigate the thermodynamics feasibility, kinetic characteristics and reaction mechanisms for the inorganic reduction of sulfates. The results show that the reduction of MgSO4 by FeCO3 is thermodynamically stronger than TSR of oil, gaseous hydrocarbons and solid bitumen. Moreover, this reduction reaction occurs at threshold temperatures below 300 °C under hydrothermal conditions, yielding the main products of magnetite (Fe3O4), pyrite (FeS2) and pyrrhotite (Fe7S8). The reaction mechanism for the studied multiphase system at 400 − 525 °C involves at least nine elementary steps. The chemical kinetics for the FeCO3 −MgSO4 − H2O system is in accordance with the phase boundary control reaction model with apparent activation energy of 70 kJ/mol. The formation of S2- in carbonate-hosted Pb-Zn deposits associated spatially with basalts is most likely a two-stage sulfate reduction process involving Fe2+ (90 −140 °C) and organic matters (>140 °C) in series. The new findings from the inorganic reduction of sulfates would contribute to clarification of the genesis of Pb-Zn deposits and help to reconceptualize some of the long-standing controversial issues in this field.

Experimental Study of Secondary Flow in Narrow and Sharp Open-Channel Bends

Secondary flow is a prominent feature of channel bends; it alters the streamwise velocity and bed shear stress distributions. Experiments were conducted to investigate the complex pattern of secondary flow in a narrow and sharp open-channel bend and the underlying mechanism of generation of multiple circulation cells. Compared with the moderate bends, the sharp bends are characteristic of multiple circulation cells from the 90° section. In addition to the curvature-induced circulation cell (S1) and turbulence-induced counter-rotation circulation cell (C1) near the outer bank, another circulation cell (S2) was observed near the inner bank and was attributed to flow separation. A term-by-term analysis of the vorticity equations indicates that the centrifugal term favours S1 and C1 while opposing S2. The turbulence-related term accounts for the formation of C1 and S2. The advective transport term redistributes vorticity and maintains the existence of S2. The dependence of secondary flow structure on Reynolds number and aspect ratio was also explored. With an increase in the Reynolds number from 23000 to 37000, both the strength and size of C1 are reduced by 50%, whereas the size of S2 increases by 20%, and its strength slightly decreases. With a decrease in the aspect ratio from 3.3 to 2, the strengths of S1, S2, and C1 are doubled, and the sizes of C1 and S2 increase by 90% and 20%, respectively.

SKI-1/S1P Facilitates SARS-CoV-2 Spike Induced Cell-to-Cell Fusion via Activation of SREBP-2 and Metalloproteases, Whereas PCSK9 Enhances the Degradation of ACE2.

Proprotein convertases activate various envelope glycoproteins and participate in cellular entry of many viruses. We recently showed that the convertase furin is critical for the infectivity of SARS-CoV-2, which requires cleavage of its spike protein (S) at two sites: S1/S2 and S2'. This study investigates the implication of the two cholesterol-regulating convertases SKI-1 and PCSK9 in SARS-CoV-2 entry. The assays used were cell-to-cell fusion in HeLa cells and pseudoparticle entry into Calu-3 cells. SKI-1 increased cell-to-cell fusion by enhancing the activation of SREBP-2, whereas PCSK9 reduced cell-to-cell fusion by promoting the cellular degradation of ACE2. SKI-1 activity led to enhanced S2' formation, which was attributed to increased metalloprotease activity as a response to enhanced cholesterol levels via activated SREBP-2. However, high metalloprotease activity resulted in the shedding of S2' into a new C-terminal fragment (S2″), leading to reduced cell-to-cell fusion. Indeed, S-mutants that increase S2″ formation abolished S2' and cell-to-cell fusion, as well as pseudoparticle entry, indicating that the formation of S2″ prevents SARS-CoV-2 cell-to-cell fusion and entry. We next demonstrated that PCSK9 enhanced the cellular degradation of ACE2, thereby reducing cell-to-cell fusion. However, different from the LDLR, a canonical target of PCSK9, the C-terminal CHRD domain of PCSK9 is dispensable for the PCSK9-induced degradation of ACE2. Molecular modeling suggested the binding of ACE2 to the Pro/Catalytic domains of mature PCSK9. Thus, both cholesterol-regulating convertases SKI-1 and PCSK9 can modulate SARS-CoV-2 entry via two independent mechanisms.

Influence of ferrous ions on surface properties of malachite and its response to sulfidization xanthate flotation

Sulfidization flotation is the principal method used for recovering malachite. There are some unavoidable metal ions appear in the solution during enrichment, and the existence of ferrous ions has a certain impact on the surface sulfidization and xanthate adsorption on surface of malachite. In this work, the influence of the ferrous species on the sulfidization flotation of malachite were investigated, and it showed that the ferrous species could be adsorbed on the mineral surface before and after sulfidization. Meanwhile, the hydroxyl species increased due to the addition of ferrous ions adsorbed as Fe–hydroxyl species, and depressed the formation of S2– and Sn2–species. However, the SOn2–species with excessive oxidation increased significantly. The content of the Cu(I) species decreased, implying that the addition of ferrous ions was not conducive to the sulfidization process of malachite and the reactivity of sulfidization products with subsequent reagents decreased. In addition, the S and Fe species adsorption layer on malachite surface were visually characterised using time–of–flight secondary ion mass spectrometry analysis, and verifies the above experimental results. After ferrous ions was introduced into flotation system, the adsorption of collector decreased and the consumption of collector in solution increased. Therefore, the flotation recovery of malachite was reduced by the addition of ferrous ions before and after sulfidization.

Modular Synthesis of Tetraurea and Octaurea Macrocycles Encoded with Specific Monomer Sequences

Modular Synthesis of Tetraurea and Octaurea Macrocycles Encoded with Specific Monomer Sequences

Behavior of S, SO, and SO3 on Pt (001), (011), and (111) surfaces: A DFT study.

In the hybrid sulfur (HyS) cycle, the reaction between SO2 and H2O is manipulated to produce hydrogen with water and sulfuric acid as by-products. However, sulfur poisoning of the catalyst has been widely reported to occur in this cycle, which is due to strong chemisorption of sulfur on the metal surface. The catalysts may deactivate as a result of these impurities present in the reactants or incorporated in the catalyst during its preparation and operation of the HyS cycle. Here, we report a density functional theory investigation of the interaction between S, SO, and SO3 with the Pt (001), (011), and (111) surfaces. First, we have investigated the adsorption of single gas phase molecules on the three Pt surfaces. During adsorption, the 4F hollow sites on the (001) and (011) surfaces and the fcc hollow site on the (111) surface were preferred. S adsorption followed the trend of (001)4F > (011)4F > (111)fcc, while SO adsorption showed (001)4F > (011)bridge/4F > (111)fcc and SO3 adsorption was most stable in a S,O,O bound configuration on the (001)4F > (011)4F > (111)fcc sites. The surface coverage was increased on all the surfaces until a monolayer was obtained. The highest surface coverage for S shows the trend (001)S = (111)S > (011)S, and for SO it is (001)SO > (011)SO > (111)SO, similar to SO3 where we found (001)SO3 > (011)SO3 > (111)SO3. These trends indicate that the (001) surface is more susceptible to S species poisoning. It is also evident that both the (001) and (111) surfaces were reactive toward S, leading to the formation of S2. The high coverage of SO3 showed the formation of SO2 and SO4, especially on the (011) surface. The thermodynamics indicated that an increased temperature of up to 2000K resulted in Pt surfaces fully covered with elemental S. The SO coverage showed θ ≥ 1.00 on both the (001) and (011) surfaces and θ = 0.78 for the (111) surface in the experimental region where the HyS cycle is operated. Lower coverages of SO3 were observed due to the size of the molecule.

Synthesis, Characterization, Molecular Docking, In Vitro Biological Evaluation and In Vitro Cytotoxicity Study of Novel Thiazolidine-4-One Derivatives as Anti-Breast Cancer Agents

Thiazolidine-4-one is a promising class of heterocyclic compounds with interesting pharmacological and biological activities, such as anticancer and antibacterial. Therefore, many researchers have synthesized thiazolidine-4-ones and evaluated their biological potential for developing new drugs. In this study, two novel thiazolidine-4-one derivatives (T1 and T2) were synthesized and evaluated for their antibacterial activity toward Staphylococcus aureus, Escherichia coli, and Proteus mirabilis. Also, the cytotoxic activities of compounds T1 and T2 were estimated against MCF-7 (HER2+, ER+, and ER+) and MDAMB- 231 (triple-negative) human breast cancer cell lines. The chemical structures of the compounds T1 and T2 were proven using spectral techniques (FT-IR, 1HNMR, and 13CNMR) and CHN elemental analysis. The synthesis of thiazolidine-4-one compounds was performed in two steps. The first step consisted of the formation of Schiff bases S1 and S2. In the second step, the synthesized Schiff bases were reacted with thioglycolic acid to prepare thiazolidine-4-one compounds. Hemolysis assay, molecular docking, cytotoxicity activity (MTT assay), and antibacterial activity (disc diffusion assay) were studied. The hemolysis study demonstrated that the hemolytic ratio of compounds T1 and T2 at (1, 2, and 3) mg/ml was less than 4%. MTT assay showed that 100 μg/ml of compounds T1 and T2 diminish the MCF-7 cell growth up to 80.05 ± 1.72 and 69.85 ± 3.26 respectively after 72hr., while the same concentration of compounds T1 and T2 reduces the MDA-MB-231 cell growth up 70.28 ± 2.31 and 57.15 ± 1.49, respectively. The inhibition zones of T1 and T2 were 12 mm at 50 mg/ml and 10 mm at 5 mg/ml in E. coli bacteria. Furthermore, a docking study was carried out to investigate the affinity and binding mode of compounds T1 and T2 towards the ERα, VEGF, and HER2 protein receptors in breast cancer cells. Data obtained from the docking study were exactly identical to that obtained from in vitro cytotoxicity assay. The results proved that T1 is an optimal anticancer agent toward breast cancer cells and the hemolysis study indicates the use of safety inside the body for compound T1. Synthesized compound T1 was most effective against MCF-7 cells compared to MDA-MB-231 cells and more effective than the reference drug tamoxifen in breast cell lines. The high cytotoxicity of T1 on the growth of MCF-7 cells because T1 binds with a high degree of affinity to the estrogen and HER2 receptors, which in turn inhibits cell proliferation and induces apoptosis.

Enhancement of Chemiluminescence Intensity of S2* in Non-premixed Hydrogen Microjet Flame in the Photometric Detector for Sulfur Detection.

A transparent quartz rod (q) placed vertically on top of a non-premixed hydrogen microjet flame in a flame photometric detector (qFPD) was developed and evaluated for sulfur detection. The microjet flame burned around the quartz rod because of Coanda effect, forming an extended downstream flame zone with a relatively low temperature between 550 and 650 °C, which is favorable to the formation of S2*. The emission intensity of S2* and the signal-to-noise ratio (SNR) of sulfur response were enhanced 2.6- and 2.1-fold, respectively. It was found that the quartz rod of diameter 4 mm with a tip shape of semicircle placed 6 mm above the nozzle yielded the highest SNR. The limits of detection (LOD) for seven kinds of tested sulfur-containing compounds of qFPD were 0.3-0.5 pg S s-1, which is 5-7 times better than that of commercially available FPD detectors (LOD: 1.6-2.8 pg S s-1). The selectivity of sulfur over carbon was 105 on qFPD when the SNR for the mass flow rate of S and C atoms was ∼3 times. It was the first time that a quartz rod was used vertically on top of a microjet hydrogen-rich flame in FPD to enhance the chemiluminescence of S2* and improve the LOD down to 0.3-0.5 pg S s-1.

A new whole-cell biocatalyst for sulfur dioxide filtering and degradation

In this study, the interaction of the magnetotactic bacterium with sulfite compounds and their potential to degrade SO2 was investigated using cyclic voltammetry (CV), molecular emission cavity analysis (MECA) and ion-exchange chromatography (IEC). This biofilter was able to degrade SO2 up to 22281 mg m−3 by disproportionation reaction and the formation of S2− and SO42− with ≥99% efficiency. Designed biofilter was able to restart the initial performance at least after seven cycles if it was used at 14-day intervals. According to theoretical studies, the value of mean free energy (E) obtained using the Dubinin-Radushkevich isotherm model was 0.02 kJ mol−1, which is in the range expected for physical adsorption. Designed biofilter can be considered as a powerful tool to degrade SO2 in diverse urban and industrial centers.

Photodissociation dynamics of the tert-butyl perthiyl radical.

The photodissociation dynamics of the tert-butyl perthiyl (t-BuSS) radical are investigated by fast-beam coincidence translational spectroscopy. A fast (6 keV-8 keV) beam of neutral t-BuSS radicals is produced via photodetachment of the corresponding anion, followed by photodissociation at 248 nm (5.00 eV) or 193 nm (6.42 eV) and coincident detection of the neutral products. Photofragment mass and translational energy distributions are obtained at both wavelengths. At 248 nm, the dominant product channel (90%) is found to be S loss, with a product translational energy distribution that peaks close to the maximum available energy and an anisotropic photofragment angular distribution, indicating dissociation along a repulsive excited state. A minor channel (10%) leading to the formation of S2 + t-Bu is also observed. At 193 nm, both two- and three-body dissociation are observed. The formation of S2 + t-Bu is the dominant two-body product channel, with multiple electronic states of the S2 molecule produced via excited-state dissociation processes. The formation of S + t-BuS is a minor two-body channel at this dissociation energy. The three-body channels are S2 + H + isobutene, S2 + CH3 + propene, and S + SH + isobutene. The first two of these channels result from a sequential dissociation process in which the loss of S2 from t-BuSS results in ground-state t-Bu with sufficient internal energy to undergo secondary fragmentation. The third three-body channel, S + SH + isobutene, is attributed to the loss of internally excited HS2 from t-BuSS, which then rapidly dissociates to form S + SH in an asynchronous concerted dissociation process.

(Invited) A New Family of Lithium-Rich Layered Sulfides (Li[LitTi1-t]S2, 0 < t ≤ 0.33) Belonging to the LiTiS2 – Li2TiS3 System

Li-rich layered oxide (Li[LixM1-x]O2, (M = Mn, Ni, Co,...) positive electrode materials are considered as a key component for next generation lithium ion batteries, as they display outstanding specific energy originating from a combination of additional lithium de-intercalation and the unusual oxidation of oxygen anions.Recently we have extended these studies to the homologous titanium sulfides belonging to the LiTiS2 – Li2TiS3 system. Layered Li2TiS3 was obtained for the first time by direct reaction of Li2S on TiS2. Its structure is similar to the Li2MnO3 one, with a small amount of stacking faults. Overlithiated compositions (Li[LitTi1-t]S2, (0 < t ≤ 0.33)) were synthesized by direct synthesis from Li2TiS3 and LiTiS2 and structurally characterized. While LiTiS2 exhibits the O1 type sulfur packing, all compositions with ~0.08 < t ≤ 0.33 exhibit the O3 type sulfur packing like the homologous oxides.High resolution HAADF images recorded for the Li2TiS3 end-member reveal that lithium and titanium are fully ordered within the [Li1/3Ti2/3]S2 slabs of the typical honeycomb lattice usually observed for Li-rich layered oxides. Nevertheless, stacking faults are observed along the hexagonal C axis. In the Li[LitTi1-t]S2, (0.08 < t ≤ 0.33) solid solution the honeycomb ordering is observed only in some domains thank to the departure from the ideal ratio required for the ordering.The electrochemical studies shows that up to 1.1 Li per Li[LitTi1-t]S2 can be reversibly cycled with a negligible irreversibility. The high capacity (≈240 mAh/g) and the shape of the charge curves suggest that Ti3+ ions are oxidized in a first step and the S2- ions in a second step to form S2 2- ions. The very small irreversibility results from the easy oxidation of S2- ions, which does not induce any sulfur release from the particle surface and subsequent structural densification. The XPS study of the deintercalated material confirms the formation of S2 2- species.Contrary to oxides, there is a very small fading and voltage decay upon cycling. This behavior suggests that there is no significant structure modification as it is observed in lithium-rich oxides. In a particular composition range, they exhibit high electrochemical performance with a reversible capacity and an energy density exceeding respectively 265 mAh·g-1 and 600 Wh·kg-1, a very low irreversible capacity in the first cycle, fast activation and a limited voltage decay.Their operation potential within the electrochemical stability window of sulfide-based fast ionic conductors makes them promising cathode materials for all-solid-state lithium and Li-ion batteries.

New insights into the multi-layer metallogenesis of carbonated-hosted epigenetic Pb-Zn deposits: A case study of the Maoping Pb-Zn deposit, South China

The Maoping Devonian and Carboniferous carbonate-hosted epigenetic Pb-Zn deposit, a typical representative of multi-layer (two or more than two ore-bearing strata) Pb-Zn metallogenesis, is located in the central Upper Yangtze Pb-Zn metallogenic province, which consists of >400 carbonate-hosted Pb-Zn deposits (spots) accounting for at least a quarter of total Pb and Zn reserves in China. The Maoping deposit is the second largest one in the province and contains ~30 Mt ores with grades of Pb + Zn ranging from 15 wt% to 35 wt%. A total of three ore bodies (groups) as layers, lens or veinlets are distributed in the NW-trending inverted wing of the Maomaoshan anticline and its secondary NE-trending bedding fracture. Nos. I, II and III ore bodies (groups) are hosted by dolostone of the late Devonian Zaige Fm., early Carboniferous Baizuo Fm., and late Carboniferous Weining Fm., respectively. Sphalerite, galena and pyrite are the most abundant sulfide minerals, while dolomite, calcite, quartz and barite are gangue minerals. These minerals have a massive, disseminated or veined structure, and a granular, metasomatic, co-edge, colloidal, aggregate or fragmentation texture, suggesting an epigenetic origin. NanoSIMS in-situ sulfur isotope analysis shows that the δ34S values of sulfides ranging from −20.4‰ to +25.7‰, of which the pyrite framboid and colloidal sphalerite have δ34S values ranging from −20.4‰ to −8.7‰, and the δ34S values of euhedral granular pyrite and xenomorphic granular sphalerite vary from +22.1‰ to +25.7‰. Such sulfur isotope signatures indicate that the formation of S2- in ore-forming fluids has undergone both marine bacterial sulfate reduction (BSR) and thermochemical sulfate reduction (TSR) processes. The processes of BSR and TSR are chiefly temperature depended, so the reduction of sulfate in the Maoping deposit is most likely to occur at the local and may first undergo a relatively low temperature’s BSR process, then goes through a relatively high temperature’s TSR process. LA-MC-ICPMS in-situ Pb isotope analysis shows that the Pb isotopic ratios of galena are relatively uniform and 206Pb/204Pb = 18.707–18.773, 207Pb/204Pb = 15.780–15.802 and 208Pb/204Pb = 39.375–39.530. Such Pb isotope signatures indicate that the source of Pb is single or well-mixed. After comparing with all the potential metal source rocks, we implied that the metals in the Maoping deposit were mainly derived from wall rocks with a certain contribution from basements and basalts. In addition, the in-situ Pb isotopic ratios increase as altitude increases (from 720 to 760 m), which suggests that the migration of metal-bearing fluids is most likely to go upward, and with the evolution of hydrothermal system, the contribution of radiogenic Pb-depleted basements and basalts was declining. This paper proposed that (i) Pb-Zn ores do not select strata, but are selective for lithology, (ii) various processes are responsible for the ore formation at Maoping, including BSR and TSR, fluids mixing and sulfide rapid precipitation, and (iii) the multi-layer metallogenesis of the Maoping carbonated-hosted epigenetic Pb-Zn deposit is a coupling mineralization of ore-forming fluids, trapped structure systems and favorable lithological combinations, which is different from that of typical Mississippi Valley-type (MVT) deposits.

Highly efficient S2−-adsorbed MoSx-modified TiO2 photocatalysts: A general grafting strategy and boosted interfacial charge transfer

Exploiting efficient and low-cost cocatalyst with a facile grafting strategy is of critical importance for significantly boosting the photocatalytic H2-evolution activity. In this study, S2−-adsorbed MoSx nanoparticle as a superior H2-evolutoin cocatalyst was successfully grafted on the TiO2 surface to greatly boost its photocatalytic activity via one-step lactic acid-induced synthesis strategy. Herein, the lactic acid can induce the homogeneous production of amorphous MoSx (a-MoSx) nanoparticles from MoS42− precursor, while the symbiotic S2- ions can be easily and availably self-adsorbed on the a-MoSx surface, resulting in the formation of S2--adsorbed a-MoSx nanoparticles with a small size of 0.5−3 nm. Photocatalytic results manifested that the S2−-adsorbed MoSx nanoparticles could dramatically facilitate the H2-generation rate of TiO2 photocatalysts (3452 μmol h-1 g-1, AQE = 16.5 %). In situ irradiated XPS in conjunction with transient-state PL and photoelectrochemical tests reveal that the improved H2-generation activity can be ascribed to the synergistic effect of boosted interfacial charge transfer from TiO2 to S2−-adsorbed MoSx and the superior H2-evolution reaction on self-adsorbed S2− ions. In addition, the S2−-adsorbed MoSx nanoparticles can also act as the general H2-generation cocatalyst to obviously promote the activity of other typical host photocatalysts such as g-C3N4 and CdS. This work provides an innovative approach to develop high-efficiency MoSx-based cocatalyst with boosted interfacial charge transfer toward highly efficient photocatalytic materials.

New insights into the evolution of Mississippi Valley-Type hydrothermal system: A case study of the Wusihe Pb-Zn deposit, South China, using quartz in-situ trace elements and sulfides in situ S-Pb isotopes

AbstractUnraveling the evolution of Mississippi Valley-type (MVT) hydrothermal system is crucial for understanding ore genesis and exploration. In this paper, we take the Wusihe Pb-Zn deposit in the western Yangtze Block (South China) as a case study, using detailed ore deposit geology, quartz in situ trace elements, and sulfides in situ S-Pb isotopes, to propose a new integrated model for the evolution of MVT hydrothermal system. Four hydrothermal stages were identified in the Wusihe ore district: (I) lamellar pyrite-sphalerite; (II) disseminated, stock-work, and brecciated sphalerite-galena; (III) massive galena, and (IV) veined calcite-bitumen. Within the most representative stage (stage II), Al concentrations in quartz (Q) increase from 8.46–354 ppm (mean 134 ppm) of Q1 to 171–3049 ppm (mean 1062 ppm) of Q2, and then decrease to 3.18–149 ppm (mean 25.4 ppm) of Q3. This trend indicates the role of acid-producing processes that resulted from sulfide precipitation and acid consumption by carbonate buffering. The occurrence of authigenic non-altered K-feldspar provides further evidence that the ore-forming fluids were weakly acidic with pH values of &amp;gt; ~5.5. Moreover, new bulk δ34S values of sulfides (+1.8 to +14.3‰) are overall lower than those previously reported (+7.1 to +20.9‰), implying that in addition to thermochemical sulfate reduction (TSR), bacterial sulfate reduction (BSR) may play an important role in the formation of S2–. In situ δ34S values show a larger range (–4.3 to +26.6‰), and significantly, varies within single grains (up to +12.3‰), suggesting mixing of two isotopically distinct S2– end-members produced by TSR and BSR. The diagenetic and hydrothermal early phase (stage I) sulfides were formed within a nearly closed system of BSR, whereas the formation of late phase (stage II and stage III) sulfides was caused by the input of hydrothermal fluids that promoted TSR. New galena in situ Pb isotopic ratios (206Pb/204Pb = 18.02–18.19, 207Pb/204Pb = 15.66–15.69, and 208Pb/204Pb = 38.14–38.39) suggest that the sources of mineralizing metals in the Wusihe deposit are mainly Proterozoic basement rocks. Hence, a multi-process model (i.e., basin-mountain coupling, fluid mixing, local sulfate reduction, in situ acid-producing and involvement of black shales and carbonate sequences) was responsible for the formation of the Wusihe deposit, while S2– was produced by both TSR and BSR, providing new insights into the evolution of MVT hydrothermal system.

Efficient Electrogenerated Chemiluminescence of Pyrrolopyrrole Aza-BODIPYs in the Near-Infrared Region with Tripropylamine: Involving Formation of S2 and T2 States.

Efficient electrogenerated chemiluminescences (ECLs) of three pyrrolopyrrole aza-BODIPYs in the near-infrared region by using tripropylamine as a coreactant are reported. Kinetic analysis based on Marcus theory indicates the direct formation of S2 and T2 states through the electron transfer reaction, which affects the ECL efficiencies.

One-step electrosynthesis of CdS quantum dots stabilized by babassu oil and luminescent films deposited by DoD technology

The electrochemical synthesis of CdS quantum-dots was carried out in a one-step electrochemical procedure using babassu oil (BO) as stabilizer. The electrochemical reduction of elemental sulfur in DMSO was investigated by cyclic voltammetry, showing the formation of polysulfides and S2−, such results are in agreement to literature. Thus, the CdS-BO electrosynthesis was realized in DMSO solvent and 30 mA constant current in cavity cell. The cadmium and sulfide ions were locally generated by simultaneous oxidation of a cadmium bar (sacrificial anode), and reduction of elemental sulfur in a graphite powder macroelectrode. The CdS-BO quantum-dots showed a UV–Vis absorption band at λmax = 387 nm with symmetrical emission band at λem = 547 nm, with a full width at half maximum (FWHM) of 124 nm. Lauric (C12H24O2, 48.9%) and myristic (C14H28O2, 20.4%) acids were identified as major components of the BO, in addition, 2.4% of free fatty acids were identified in the BO composition by titration, which explains the good stabilization of CdS QDs synthesized. The CdS-BO colloidal system was used as photonic ink and deposited on silica sheets by inkjet printing by drop on demand technology, without waste generation at all stages. The nanoparticles preserved luminescence after printing and drying, showing that the BO promotes an effective stabilization of the quantum dots.

Direct Detection of S(3P) and S(1D) Generated in the O(1D) + OCS Reaction: Mechanism of the Formation of S2(X3Σg- and a1Δg).

Highly vibrationally excited disulfur S2 in the X3Σg- and a1Δg states has been detected in the gaseous mixture of O3 and OCS irradiated with light at 266 nm. Generation of CO2 in the reaction system has been reported; however, no direct detection of sulfur atoms (S(3P) and S(1D)) has been made. In the present study, we have employed the two-photon laser-induced fluorescence (2P-LIF) technique to detect S(3P) and S(1D) directly and recorded the time profiles of the atoms at varying pressures of OCS. Kinetic analyses of the profiles show that (i) S(1D) is generated in the O(1D) + OCS reaction and consumed by the S(1D) + OCS reaction, and (ii) S(3P) is mainly generated in the O(1D) + OCS reaction instead of quenching of S(1D) by collisions with OCS and ambient gases. The vibrational levels v = 19 and 10 of the respective electronic states X3Σg- and a1Δg of S2 were detected in the O3/OCS/266 nm system. The two vibrational levels cannot be generated by the available energy of the S(3P) + OCS reaction, giving evidence that S2 in the X3Σg- and a1Δg states are generated by the S(1D) + OCS reaction.

Ore genesis of the Fule Pb[sbnd]Zn deposit and its relationship with the Emeishan Large Igneous Province: Evidence from mineralogy, bulk C[sbnd]O[sbnd]S and in situ S[sbnd]Pb isotopes

Magmatic activity plays an important role in mineralization, but little is understood of its role with respect to carbonate-hosted stratabound epigenetic PbZn deposits. The Fule PbZn deposit (~10 Mt of sulfide ore with mean grades of 15–20wt% Zn+Pb), is stratigraphically placed in middle Permian strata and spatially (~1m) associated with late Permian continental flood basalts of the Emeishan Large Igneous Province (ELIP). It thus provides an ideal case to investigate its genetic relationship with the ELIP. In addition, the Fule deposit is characterized by high concentrations of Ag, Cd, Ge and Ga, and contains a variety of Cu and Ni sulfide minerals. Syn-ore calcite (δ13C=+2.57–+3.01‰) and associated fluids (δ13C=+2.96–+3.40‰) have δ13C values similar to those of fresh limestone (δ13C=+1.58–+2.63‰), but the δ18O values of calcite (+16.83–+19.92‰) and associated fluids (+7.80–+10.89‰) are distinctly lower than those of limestone (δ18O=+21.85–+23.61‰). This means that C is mainly derived from limestone, whereas the O isotope signature may be related to water/rock (W/R) interaction between mantle and/or metamorphic fluids and limestone. δ34S values of sulfide minerals obtained by in situ NanoSIMS and conventional bulk techniques record a range of +9.8–+23.1‰ and +10.04–+16.43‰, respectively, reflecting the enrichment of heavy S isotopes in the ore-forming fluids and thermochemical sulfate reduction (TSR) is the principal mechanism for the formation of S2−. Cores of sulfide crystals have much higher δ34S values than their rims, indicating a probable mixture of multiple S reservoirs and/or a dynamic fractionation of S isotopes occurred during sulfide precipitation. The uniform femtosecond (fs) LA-MC-ICPMS in situ Pb isotopic data for galena plot in the field that differs from any of the three potential sources in the region. Such signatures demonstrate that metal Pb was most likely derived from a well-mixed source of basalts, sedimentary rocks and basement rocks. We propose that (a) the enrichment in Ag, Cu, Ni, Cd, Ge and Ga, and the isotope signatures of hydrothermal minerals in the Fule region are related to fluids derived from or flowed through multiple reservoirs; (b) Emeishan magmatism provided heat, elements and associated fluids, and its basalts acted as an impermeable and protective layer; and (c) fluid mixing caused TSR, and then resulted in W/R interaction and CO2 degassing, all of which played a key role in the precipitation of hydrothermal minerals.

Bis(aryl) Tetrasulfides as Cathode Materials for Rechargeable Lithium Batteries.

An organotetrasulfide consists of a linear chain of four sulfur atoms that could accept up to 6 e- in reduction reactions, thus providing a promising high-capacity electrode material. Herein, we study three bis(aryl) tetrasulfides as cathode materials in lithium batteries. Each tetrasulfide exhibits two major voltage regions in the discharge. The high voltage slope region is governed by the formation of persulfides and thiolates, and the low voltage plateau region is due to the formation of Li2 S2 /Li2 S. Based on theoretical calculations and spectroscopic analysis, three reduction reaction processes are revealed, and the discharge products are identified. Lithium half cells with tetrasulfide catholytes deliver high specific capacities over 200 cycles. The effects of the functional groups on the electrochemical characteristics of tetrasulfides are investigated, which provides guidance for developing optimum aryl polysulfides as cathode materials for high energy lithium batteries.