Sulfide Bonds Research Articles

Study on the Reaction Mechanism of Oxidative Microbial Desulfurization of Organic Sulfur-Rich Coal

The present work deals with the use of iron/sulfur-oxidizing bacterium Acidithiobacillus ferrooxidans for the desulfurization of a coal sample from Assam, India. The coal sample contains 3.87% w/w of organic sulfur, 1.4% w/w pyritic sulfur, and 1.29% w/w of sulfate sulfur which altogether are contributing to its total sulfur content of 6.56% w/w. The microbial process followed the oxidative-desulfurization mechanism for the removal of sulfur from the coal sample. The bacterium performed cleavage of the sulfide bonds in pyrite to release the inorganic sulfur. Mass spectroscopic analysis revealed that the bacterial strain A. ferrooxidans performed oxidative desulfurization of a model sulfur-containing organic compound dibenzothiophene to 2-hydroxy biphenyl through the formation of dioxy-dibenzothiophene. A. ferrooxidans cells played the catalytic role to release the sulfur present in organic and inorganic form in the coal sample. The microbial desulfurization process conducted in a shake flask scale (500 mL) removed about 79% of total sulfur from the coal sample in 14 days.

Efficient passivation of n-type and p-type silicon surface defects by hydrogen sulfide gas reaction

An efficient surface defect passivation is observed by reacting clean Si in a dilute hydrogen sulfide–argon gas mixture (<5% H2S in Ar) for both n-type and p-type Si wafers with planar and textured surfaces. Surface recombination velocities of 1.5 and 8 cm s−1 are achieved on n-type and p-type Si wafers, respectively, at an optimum reaction temperature of 550 °C that are comparable to the best surface passivation quality used in high efficiency Si solar cells. Surface chemical analysis using x-ray photoelectron spectroscopy shows that sulfur is primarily bonded in a sulfide environment, and synchrotron-based soft x-ray emission spectroscopy of the adsorbed sulfur atoms suggests the formation of S–Si bonds. The sulfur surface passivation layer is unstable in air, attributed to surface oxide formation and a simultaneous decrease of sulfide bonds. However, the passivation can be stabilized by a low-temperature (300 °C) deposited amorphous silicon nitride (a-Si:N X :H) capping layer.

Diffusible signal factor signaling controls bioleaching activity and niche protection in the acidophilic, mineral-oxidizing leptospirilli

Bioleaching of metal sulfide ores involves acidophilic microbes that catalyze the chemical dissolution of the metal sulfide bond that is enhanced by attached and planktonic cell mediated oxidation of iron(II)-ions and inorganic sulfur compounds. Leptospirillum spp. often predominate in sulfide mineral-containing environments, including bioheaps for copper recovery from chalcopyrite, as they are effective primary mineral colonizers and oxidize iron(II)-ions efficiently. In this study, we demonstrated a functional diffusible signal factor interspecies quorum sensing signaling mechanism in Leptospirillum ferriphilum and Leptospirillum ferrooxidans that produces (Z)-11-methyl-2-dodecenoic acid when grown with pyrite as energy source. In addition, pure diffusible signal factor and extracts from supernatants of pyrite grown Leptospirillum spp. inhibited biological iron oxidation in various species, and that pyrite grown Leptospirillum cells were less affected than iron grown cells to self inhibition. Finally, transcriptional analyses for the inhibition of iron-grown L. ferriphilum cells due to diffusible signal factor was compared with the response to exposure of cells to N- acyl-homoserine-lactone type quorum sensing signal compounds. The data suggested that Leptospirillum spp. diffusible signal factor production is a strategy for niche protection and defense against other microbes and it is proposed that this may be exploited to inhibit unwanted acidophile species.

Ultra-deep desulfurization of model diesel fuel over Pr/Ce–N–TiO2 assisted by visible light

The removal of thiophene sulfides was considered as one of the major steps for producing clean diesel fuel. We prepared a defect-rich Pr/Ce–N–TiO2 for breaking carbon-sulfur bonds of thiophene sulfides aided by visible light. Prepared photocatalysts of Pr/Ce–N–TiO2-2 had a large specific surface area of 114 m2/g and a pore diameter of 20–30 nm. The experimental results displayed the Turnover Frequency of thiophene, benzothiophene, dibenzothiophene, and 4, 6-dimethyl-dibenzothiophene was 50, 48, 45, and 49, respectively. Interestingly, the proper content of defects on the surface distinctly improved the activity of the oxidation and in situ hydrogenation of dibenzothiophenes. And desulfurization ratios were 100% when the composition of Pr3+, Ce3+, Ti3+, and Oads on the surface of the catalyst was 10.6, 6.6, 18.9, and 12.3%. The consequences of Photoluminescence emission spectra, Ultraviolet and visible spectrophotometry, and Electron paramagnetic resonance spectroscopy showed the co-doping of N, Pr, and Ce extended the photo-absorption range and increased the hole-electron separation of TiO2, which might be because the synergy of N, Pr, and Ce increased oxygen vacancies and defects on the catalytic surface, and formed lower gap energy leading to transfer and reserve electrons quickly under visible light. Also, we speculated the mechanism of photocatalytic desulfurization over Pr/Ce–N–TiO2 depending on the experimental results.

Change in the Structure of Asphaltene Macromolecules of the Krapivinskoye Oil Field During Biological Oxidation

Using physico-chemical methods of research (elemental analysis, infrared spectroscopy, selective chemical destruction of sulfide and ester bonds, chromatomass spectrometry) the influence of biodegradation processes on the composition and structure of asphaltenes of light oil at the Krapivinskoye deposit was studied. The results of comparative characteristics of initial asphaltenes and asphaltenes after biodestruction are presented. Attention is paid to studying their structural parameters and composition of fragments bound in asphaltene molecules through ester and sulfide bridges. It has been shown that microbial oxidation of asphaltenes of light oil by aboriginal soil microflora (laboratory experiment) occurs through a series of catalytic processes with formation of intermediate products of transformation – alcohols, aldehydes, ketones and fatty acids. It has been established that “grey and ether-bound” fragments in asphaltene molecules of biodegradable oil differ from “bound” compounds in the structure of the original asphaltenes with the qualitative composition of saturated and aromatic hydrocarbons and heteroatomic components

Effect of Production Technology of Hydrin T6000 Elastomers on Their Properties and Structure

The influence of the technology for producing elastomer materials based on epichlorohydrin rubber of Hydrin T6000 brand on physical-mechanical properties, structure formation, and frost resistance is studied. Differences in the properties of vulcanizates are revealed due to the formation of various sulfide bonds in a vulcanization network with different densities. The use of rubber swelling technology in a plasticizer leads to a screening effect, which reduces the interaction of the filler with the polymer. On the plus side, this effect improves low-temperature properties, and on the minus side, deteriorates physical-mechanical properties of the material.

Surfactant-free synthesis of monodispersed organosilica particles with pure sulfide-bridged silsesquioxane framework chemistry via extension of Stöber method

Sulfide bond incorporated organosilica particles have been broadly applied to versatile biomedical applications, wherein the uniformity of particles and the sulfur content significantly dictate the ultimate performance. Unfortunately, due to the difficulty in controlling the chemical behavior of organosilica precursors in a sol–gel process, challenges still exist in developing a facile and green synthetic approach to fabricate organosilica particles with good dispersity and high sulfur content. In the present work, by extending the classic Stöber method, a surfactant-free synthesis of monodispersed organosilica particles with pure sulfide-bridged silsesquioxane framework chemistry is reported for the first time. By simply tailoring the ethanol-to-water ratio and amount of catalyst, the size of disulfide-bridged organosilica particles can be tuned from ~0.50 to ~1.20 µm. Moreover, this approach can be employed to prepare tetra-sulfide bridged silica nanoparticles with an extremely high sulfur content of 30.7 wt% and negligible cytotoxicity. Notably, taking advantage of this extended Stöber method, both hydrophilic (methylene blue) and hydrophobic (curcumin) molecules can be in-situ encapsulated into tetra-sulfide bridged silica nanoparticles, whose glutathione-triggered biodegradability is also demonstrated. Collectively, the innovative synthetic approach and organosilica particles developed in this work are expected to open up new opportunities in hybrid materials fabrication and bio-applications.

Application and Analysis of 6-Mercaptopurine Nanomedicine in the Treatment of Leukemia.

As a first-line drug widely used in the treatment of leukemia, 6-MP has obvious effects on leukemia. However, 6-MP disadvantages such as poor solubility in water, easy binding with serum proteins, short circulation time, and large toxic and side effects greatly limit the application of 6-MP. For this reason, various 6-MP nano drug-loading systems have been designed to increase the water solubility of 6-MP, extend the circulation time, and increase the bioavailability of 6-MP to a certain extent, reducing its toxic and side effects. However, its therapeutic effect in vivo and in vitro is still far from expectations, and there is a lot of room for improvement. In order to solve the above problems encountered in the clinical application of 6-MP, we have tried two ways of polymer prodrugs and drug-loaded vesicles to achieve efficient targeted delivery and treatment of 6-MP. We designed hyaluronic acid (HA)-based gluteal-skin-responsive 6-MP polymer prodrug (HA-GS-MP) for highly effective targeted therapy of acute myeloid leukemia. Hyaluronic acid is a natural polysaccharide, which has excellent biocompatibility and biodegradability, and has a good ability to actively target malignant tumor cells overexpressing the CD44 receptor. 6-MP is connected to the HA chain through a vinyl sulfide bond, which is stable under physiological conditions (no drug release), and under intracellular reducing conditions, the connection bond is broken and 6-MP is quickly released. HA-GS-MP has a simple preparation process, good water solubility, long cycle time, and strong targeting ability. This GSH-responsive CD44 targeted 6-MP polymer prodrug is expected to improve the therapeutic effect on acute myeloid leukemia cells.

Электропроводящая резина с эффектом положительного температурного коэффициента сопротивления из шинного регенерата

The possibility of developing conductive rubber based on tire regenerate and conductive carbon black OMCARB CH85 is shown. The vulcanizing characteristics of the regenerates obtained by thermomechanical devulcanization using a curing group and conductive carbon black were studied. It is shown that after thermomechanical devulcanization, preservation of sulfide bonds, re-vulcanization occurs only in the presence of sulfur and vulcanization accelerators. A flocculation effect was detected upon the introduction of OMCARB CH85 into the regenerate.It is shown that tensile strength and Shore A hardness are increase with an increase in the content of conductive carbon black in the regenerate. However, there is insufficient dispersion of carbon black, a decrease in elongation at break and resistance to abrasion is observed. The study of volume resistivity showed that the resulting rubbers belong to semiconductor materials. The dependence of resistivity on temperature in the range from 10 to 80 °C is constructed. It is shown that the effect of a positive thermal coefficient is observed in all samples. The values of the positive temperature coefficient of resistance in the temperature range of 10 – 80 °C are 0.054 – 0.285 deg–1.

Calcined Co(II)-Triethylenetetramine, Co(II)- Polyaniline-Thiourea as the Cathode Catalyst of Proton Exchanged Membrane Fuel Cell.

Triethylenetetramine (TETA) and thiourea complexed Cobalt(II) (Co(II)) ions are used as cathode catalysts for proton exchanged membrane fuel cells (PEMFCs) under the protection of polyaniline (PANI) which can become a conducting medium after calcination. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra clearly reveal the presence of typical carbon nitride and sulfide bonds of the calcined Nitrogen (N)- or Sulfur (S)-doped co-catalysts. Clear (002) and (100) planes of carbon-related X-ray diffraction patterns are found for co-catalysts after calcination, related to the formation of a conducting medium after the calcination of PANI. An increasing intensity ratio of the D to G band of the Raman spectra reveal the doping of N and S elements. More porous surfaces of co-catalysts are found in scanning electronic microscopy (SEM) micropictures when prepared in the presence of both TETA and thiourea (CoNxSyC). Linear sweep voltammetry (LSV) curves show the highest reducing current to be 4 mAcm−2 at 1600 rpm for CoNxSyC, indicating the necessity for both N- and S-doping. The membrane electrode assemblies (MEA) prepared with the cathode made of CoNxSyC produces the highest maximum power density, close to 180 mW cm−2.

Effect of high pressure and setting condition on physico-chemical, structural and functional characteristics of transglutaminase mediated fish gels.

Application of High pressure and low temperature setting condition on microbial transglutaminase (MTGase) mediated gelation was studied against conventional cooking in pink perch mince. A high pressure of 250 MPa was given to pink perch mince samples added with and without MTGase enzyme, for a holding time of 12 min and a setting condition of 25 °C for 30 min was given prior and after the treatments. Nine random experiments (T1 to T9) were made against high pressure and cooking and analysed its textural and functional properties. Addition of MTGase and setting conditions had significant effect on the textural properties of the both samples especially in inducing the gel strength. Reduction in total and reactive sulfhydryl groups observed was due to the formation of disulfide linkages, which was found more in T6 to T9. Setting condition had significant effect on protein hydrophobicity in both pressure and heat induced gels. No significant variation in the Ca2+-ATPase enzyme activity was observed among treatments. SEM images revealed more closed and dense fibrous network in samples with enzyme (T6 to T9), due to more protein polymerisation. So MTGase enzyme along with pressure treatment enhanced the conformational stability and produce stronger networks through the formation of non sulfide bonds between proteins and setting reinforced these networks. Hence the synergistic effect of high pressure and MTGase can enhance the textural and functional properties of fish gels, when compared with the conventional cooking.

Exploring the binding interactions of structurally diverse dichalcogenoimidodiphosphinate ligands with α-amylase: Spectroscopic approach coupled with molecular docking

Postprandial hyperglycemia has orchestrated untimely death among diabetic patients over the decades and regulation of α-amylase activity is now becoming a promising management option for type 2 diabetes. The present study investigated the binding interactions of three structurally diverse dichalcogenoimidodiphosphinate ligands with α-amylase to ascertain the affinity of the ligands for α-amylase using spectroscopic and molecular docking methods. The ligands were characterized using 1H and 31P NMR spectroscopy and CHN analysis. Diselenoimidodiphosphinate ligand (DY300), dithioimidodiphosphinate ligand (DY301), and thioselenoimidodiphosphinate ligand (DY302) quenched the intrinsic fluorescence intensity of α-amylase via a static quenching mechanism with bimolecular quenching constant (Kq) values in the order of x1011 M-1s-1, indicating formation of enzyme-ligand complexes. A binding stoichiometry of n≈1 was observed for α-amylase, with high binding constants (Ka). α-Amylase inhibition was as follow: Acarbose > DY301>DY300>DY302. Values of thermodynamic parameters obtained at temperatures investigated (298, 304 and 310 K) revealed spontaneous complex formation (ΔG<0) between the ligands and α-amylase; the main driving forces were hydrophobic interactions (with DY300, DY301, except DY302). UV–visible spectroscopy and Förster resonance energy transfer (FRET) affirmed change in enzyme conformation and binding occurrence. Molecular docking revealed ligands interaction with α-amylase via some key catalytic site amino acid residues (Asp197, Glu233 and Asp300). DY301 perhaps showed highest α-amylase inhibition (IC50, 268.11 ± 0.74 μM) due to its moderately high affinity and composition of two sulphide bonds unlike the others. This study might provide theoretical basis for development of novel α-amylase inhibitors from dichalcogenoimidodiphosphinate ligands for management of postprandial hyperglycemia.

Bio-inspired, Multifunctional Metal-Thiolate Motif: From Electron Transfer to Sulfur Reactivity and Small-Molecule Activation.

Sulfur-rich metalloproteins and metalloenzymes, containing strongly covalent metal-thiolate (cysteinate) or metal-sulfide bonds in their active site, are ubiquitous in nature. The metal-sulfur motif is a highly versatile tool involved in various biological processes: (i) metal storage, transport, and detoxification; (ii) electron transfer; (iii) activation of the sulfur atom to promote different types of S-based reactions including S-alkylation, S-oxygenation, S-nitrosylation, or disulfide or thiyl radicals formation; (iv) activation of small earth-abundant molecules (such as water, dioxygen, superoxide radical anion, carbon oxides, nitrous oxide, and dinitrogen).This Account describes our investigations carried out during the past 10 years on bio-inspired and biomimetic low-nuclearity complexes containing metal-thiolate bonds. The general objective of these structural, spectroscopic, electrochemical, and catalytic studies was to determine structure-properties-function correlations useful to (i) understanding the peculiar features or the mechanism of the mimicked natural systems and/or (ii) reproducing enzymatic reactivities for specific catalytic applications.By employing a unique highly preorganized N2S2-donor ligand with two thiolate functions, in combination with different first-row transition metals (Mn, Fe, Co, Ni, Cu, Zn, or V), we got access to a series of bio-inspired sulfur-rich complexes displaying a widespread spectrum of structures, properties, and functions. We isolated a dicopper(I) complex that, for the first time, mimicked concomitantly the key structural, spectroscopic, and redox features of the biological CuA center, a highly efficient electron transfer agent involved in the respiratory enzyme cytochrome c oxidase. In the field of sulfur activation, we explored (i) sulfur methylation promoted by a Zn-dithiolate complex that mimics Zn-dependent thiolate alkylation proteins and shows different selectivity compared to the Ni and Co congeners and (ii) a series of Co, Fe, and Mn complexes as the first copper-free systems able to promote thiolate/disulfide interconversion mediated by (de)coordination of halides. Concerning metal-centered reactivity, we investigated two families of metal-thiolate catalysts for small-molecule activation, especially relevant in the fields of sustainable fuel production and energy conversion: (i) two isostructural Mn and Fe dinuclear complexes that activate and reduce dioxygen selectively, either to hydrogen peroxide or water as a function of the experimental conditions; (ii) a family of dinuclear MFe (M = Ni or Fe) hydrogenase mimics active for catalytic H2 evolution both in organic solution and on modified electrodes in water.This Account thus illustrates how the versatility of thiolate ligation can support selected functions for transition metal complexes, depending on the nature of the metal, the nuclearity of the complex, the presence and type of co-ligands, the second coordination sphere effects, and the experimental conditions.

Structural, functional and phylogenetic analysis of a beta defensin gene from the Whipfin silverbiddy, Gerres filamentosus (Cuvier, 1829)

Beta defensins have been considered as a major class of Antimicrobial peptides (AMPs) that play an important role in the innate immunity of fishes. In this study, we have identified and characterized a β-defensin gene sequence from the Whipfin silverbiddy, Gerres filamentosus which was termed as Gf-Def. The Gf-Def open reading frame (ORF) consists of 192 bp that encodes 63 amino acid residues. It includes a signal peptide region of 20 amino acids followed by a mature peptide sequence of 43 amino acids. Gerres filamentosus beta defensin (Gf-Def) has a molecular weight of 5.2 KDa and an isoelectric point of 8.90 with a GRAVY score of −0.872. Also, the characteristic six cysteine residues involved in pattern specific formation of intramolecular disulfide bridges could be deduced from the peptide sequence using Cys_Rec software. Three-dimensional modeling of Gf-Def carried out using DNASTAR protean software revealed β strands stabilized by cysteine sulfide bonds along with a short N-terminal α helix spanning the signal peptide sequence. Four Conserved motifs were identified in Gf-Def, all of which were unexceptionally and extensively shared by other fish defensins suggesting a possible functional similarity and evolutionary selection of the sequence. Phylogenetic analysis revealed that Gf-Def was close to Oplegnathus fasciatus, Siniperca chautsi, Trachinotus ovatus and Lates calcarifer defensins which probably suggests that Gf-Def peptide sequence is quite similar to β-defensin sequences of other Perciformes. This being the first report of a beta defensin from whipfin silverbiddy, G. filamentosus and the comparative analysis shall provide a background data for the functional and evolutionary studies on fish beta defensins.

Highly Stable Membranes of Poly(phenylene sulfide benzimidazole) Cross-Linked with Polyhedral Oligomeric Silsesquioxanes for High-Temperature Proton Transport

Poly(phenylene sulfide benzimidazole) has been synthesized and tested as a potential material for high-temperature proton transport. A high content of sulfide bonds has been implemented in the polymer chains to endow a high antioxidant capacity and, in combination with bulky benzimidazole pendant units, to significantly suppress crystallinity and thereby improve the solubility in highly polar aprotic solvents. The amorphous polymer has high thermal stability and high glass transition temperature (Tg). Freestanding, insoluble, and robust membranes were obtained via thermal cross-linking of the benzimidazole moieties with octa-glycidyl polyhedral oligomeric silsesquioxane (g-POSS). The series of hybrid networks (cPPSBi_X, with X being the g-POSS content wt %) showed excellent oxidative stability, with cPPSBi_15 having weight loss lower than 5% after 264 h in Fenton’s reagent at 80 °C. Elastic moduli as high as 868 MPa with reduced strain at break (1.8%) were obtained. After doping the membranes with phosphoric acid, proton conductivity in the range of 2.3 × 10–2 S cm–1 at 180 °C was obtained, and the membranes show a stress at break of 2.3 MPa. Dimensional and mechanical stability were maintained also at high doping levels thanks to the inclusion of g-POSS which provides the resulting hybrid networks with increased free volume and high cross-link density.

Preparation and in vitro study of stromal cell-derived factor 1-targeted Fe3O4/poly(lactic-co-glycolic acid)/perfluorohexane nanoparticles.

Compared with traditional imaging techniques, multimodal imaging obtains more accurate images that may increase disease detection rates. The present study prepared stromal cell-derived factor 1 (SDF-1)-loaded, targeted nanoparticles coated with iron (II,III) oxide and perfluorohexane (PFH) to be used as polymer-shelled contrast agents with multimodal imaging functions, with the aim of improving tongue cancer and lymph node metastasis diagnosis. The multifunctional, targeted, polymeric nanoparticles were prepared using a double emulsion method and chemokine SDF-1 was conjugated to nanoparticles by a sulfide bond. The nanoparticles were spherical, uniform size and well dispersed. The results of the in vitro photoacoustic and ultrasonic imaging experiments demonstrated that the multifunctional nanoparticles displayed excellent multimodal imaging functions, as even small concentrations of nanoparticles presented clear ultrasound and photoacoustic imaging. When the temperature reached the boiling point of PFH (56˚C), a liquid-gas phase change occurred and the microsphere volume and acoustic impedance increased, leading to enhanced ultrasonic development. The nanoparticles were automatically targeted to tongue squamous carcinoma cells in vitro via SDF-1-CXC chemokine receptor 4 interactions. The targeted experiment and flow cytometry results indicated that the nanoparticles underwent strong targeted binding to human tongue squamous cell carcinoma (SCC-15) cells. In summary, the nanoparticles were automatically targeted to SCC-15 cells and displayed promising characteristics for ultrasound and photoacoustic imaging. Higher concentrations of nanoparticles was associated with clearer imaged and greater echo intensity value and photoacoustic value. The present study established a foundation for the development of procedures for primary tongue cancer and lymph node metastasis diagnosis.

Evaluation on the microwave-assisted chemical desulfurization for organic sulfur removal

Coal desulfurization is imperative to create clean coal and reducing harmful emissions during the combustion process. However, organic sulfur in coal is more difficult to remove than inorganic sulfur. Therefore, in this paper, a method of coal sample desulfurization using citric acid with microwave assisted was proposed, and experimental investigation was carried out. The influences of the particle size, reaction temperature, irradiation time, microwave power, and concentration of citric acid on desulfurization effect were studied and the corresponding optimal value was determined. The desulfurization effect was improved; the remove efficiencies of the total sulfur, organic sulfur and inorganic sulfur were 34.25%, 59.86% and 20.23%, respectively. In addition, XRD and FTIR were used to test and compare the coal samples before and after the experiment, and it was found that pyrite was transformed into H2S, S and the Fe2+ which was combined with citric acid to form a complex; The carbon-sulfur bond of sulfonate and the iron-sulfur bond of ferrous sulfide are both broken; Clean coal has a smoother surface. In general, microwave-assisted citric acid could potentially remove organic sulfur without any significant interference of the calorific value on coal. And compared with other desulfurizers, citric acid has the advantages of good desulfurization effect (especially organic sulfur), non-toxic, low corrosion and low cost, etc. The current research work may provide new routes and meaningful guidelines to pre-combustion desulfurization of coal.

Ultrasmall aqueous starch-capped CuS quantum dots with tunable localized surface plasmon resonance and composition for the selective and sensitive detection of mercury(ii) ions.

Ultrasmall starch-capped CuS quantum dots (QDs) with controllable size were chemically fabricated in an aqueous medium. The phase of the CuS QDs was confirmed via X-ray diffraction (XRD), whereas the characteristic localized surface plasmon resonance (LSPR) peak in the near-infrared (NIR) region was measured using UV-Vis spectroscopy. Transmission electron microscopy and high bandgap analysis confirmed the formation of ultrasmall CuS QDs in the size range of 4–8 nm. CuS QDs have been used for the selective and sensitive detection of Hg2+ ions through colorimetric and spectroscopic techniques. The selective sensing of Hg2+ ions from various metal ions was detected via a remarkable change in color, damping in LSPR intensity, significant change in the Fourier-transform infrared spectra and X-ray photoelectron spectroscopic measurements. The mechanism of interaction between the CuS QDs and Hg2+ ions has been deeply explored in terms of the role played by the starch and the reorganization of sulfide and disulfide bonds to facilitate the access of Hg2+ ions into the CuS lattice. Finally, an intermediate Cu2−xHgxS nanostructure resulted in the leaching of Cu+ ions into the solution, which were further recovered and reused for the formation of fluorescent Cu2S nanoparticles. Thus, the entire process of synthesis, sensing and reuse paves the way for sustainable nanotechnology.

Short-Chain Polyselenosulfide Copolymers as Cathode Materials for Lithium-Sulfur Batteries.

Copolymerization of sulfur, which forms sulfur-rich polymers, has recently opened a new era in the lithium-sulfur (Li-S) battery research as improved battery performances could be achieved compared to pure sulfur (S8). By means of organic chemistry, sulfur copolymers with desired features and chemical structures could be rationally designed and synthesized. In this study, sulfur-rich polymers consisting of short-chain tetrasulfide (R-S4-R) (PTS) and selenotrisulfide (R-SeS3-R) (PTSeS) bonds are suggested as cathode materials for Li-S batteries. Intrinsically short poly(seleno)sulfide bonds along with covalent anchoring effect effectively suppress the parasitic shuttle effect originating from soluble long-chain lithium polysulfides formed from pure S8. Furthermore, a comparative study demonstrates the indisputable advantage of the selenium doping, which enhances the electrical conductivity of the polymer and following battery performances. In terms of cycling performance, both PTSeS and PTS with ∼2 mg cm-2 polymer loading exhibit small capacity decays of 0.078 and 0.052% per cycle until 500 cycles at 0.5C, respectively. However, active material utilization and high rate performance are substantially superior in PTSeS due to the enhanced electron transfer kinetics. This work would provide useful design principles for fabrication of sulfur-based polymers with even greater applicability in future Li-S batteries.

СОСТАВ И СТРУКТУРА СМОЛИСТЫХ КОМПОНЕНТОВ ЛЕГКОЙ И ТЯЖЕЛЫХ НЕФТЕЙ

Актуальность работы обусловлена отсутствием сравнительной характеристики состава и строения смол нефтей различной химической природы, так как особенности структуры смолистых компонентов оказывают существенное влияние на глубину их превращения в легкие углеводороды для производства светлых нефтепродуктов. Особое значение работы в этом направлении получили в последнее время из-за неуклонного роста в составе разведанных и извлекаемых запасов тяжелых высоковязких нефтей, которые отличаются от традиционных нефтей высоким содержанием высокомолекулярных гетероатомных соединений. Цель: сравнительное изучение состава, структуры и особенностей строения основных структурных блоков молекул и химического состава азоторганических оснований смолистых компонентов легкой и тяжелых нефтей. Методы: селективная химическая деструкция сульфидных и эфирных связей, элементный и структурно-групповой анализы, жидкостно-адсорбционная хроматография, криоскопия в бензоле, ЯМР 1Н-спектроскопия, хроматомасс-спектрометрия. Результаты. Проведен сравнительный анализ состава и структуры смолистых компонентов легкой и тяжелых нефтей. Определены сходства и различия их структурно-группового состава, строения азотистых соединений основного характера и структурных блоков, связанных в молекулах смол C-O и C-S связями. Установлено, что смолистые компоненты тяжелых нефтей отличаются большими общими размерами средних молекул за счет числа связанных воедино структурных единиц (1,79–1,86 против 1,25), имеющих более крупные средние размеры полиареновых ядер (число ароматических циклов 2,36–2,43 против 1,57); большее число алициклических фрагментов, сконденсированных с ароматическим ядром молекул (количество атомов С, находящихся в α-положении к ароматическим циклам 4,56–4,75 против 3,42), и большую распространенность длинных алкильных заместителей (2,42–2,59 против 1,97). К наиболее распространенным «связанным» фрагментам макромолекул исследуемых смол относятся н-алканы, циклогексаны, прегнаны, холестаны, хейлантаны и гопаны. Особенностью молекул смол тяжелых нефтей является присутствие в составе их «эфиросвязанных» фрагментов полициклических ароматических углеводородов и гетероорганических соединений, а особенностью смол легкой нефти – присутствие в составе «серосвязанных» фрагментов полициклоалканов, этиловых эфиров н-алкановых кислот, алифатических спиртов и бициклических сульфидов. Смолы тяжелых нефтей характеризуются более высоким суммарным выходом азоторганических оснований (38,4–40,8 против 26,0 %), в составе которых доминируют соединения, осаждаемые в виде нерастворимых хлористоводородных солей (36,5–37,6 против 10,9 %).