Sulfide Bonds Research Articles

Developing sustainable chalcogenide for energy storage: Investigating the semiconducting MnS2: CuS: CoS2: Ni2S3 quaternary complexes as supercapacitor electrode material

Electrochemical energy storage is crucial in today’s urbanized world to achieve energy sustainability. Using a single source precursor technique, a unique and energy-efficient semiconducting [manganese: copper: cobalt: nickel] sulphide (MnS2: CuS: CoS2: Ni2S3) composite chalcogenide system has been synthesized for the first time. The resulting dithiocarbamate metallic sulfide exhibits a median crystallite size of 36.55 nm as well as a relatively small band gap of 2.61 eV. Many bonds, including the metal sulfide bond, were found, according to a functional group analysis. MnS2: CuS: CoS2: Ni2S3 was morphologically manifested as irregularly shaped particles that tended to form sphere-like shapes. MnS2: CuS: CoS2: Ni2S3 based electrode was measured for electrochemical charge-storing behaviour. With an excellent capacitance spanning around 956.76F g−1, the tetra-chalcogenide-decorated electrode demonstrated a favourable capacity for charge storage, according to the results of cyclic voltammetry conducted in 1 M potassium hydroxide. This suggests that there is a lot of potential for long-term energy storage using the electrode. This electrode elucidated the particular power density of 10020.12 W kg−1 in addition to a lowered series resistance of (Rs) = 1.98 Ω based on the impedance investigations.

Atomistic insights into salicylic acid treatment on human keratinized skin by XPS combined with argon gas cluster sputtering: A pilot study

Stratum corneum is the skin's outermost layer, whose main constituent is keratin. The treatment of dermatological diseases showing hyperkeratosis is a serious problem in dermatology and cosmetics seriously affecting the population showing increasing prevalence. One of the treatment is a peeling agent like salicylic acid (SA), categorized as a keratolytic agent, however its mode of action is not fully understood. X-ray photoelectron spectroscopy (XPS) is a method for monitoring the changes of surface composition at atomistic level in 5–10 nm depth. The development of argon cluster sputtering enabled the investigation of deeper regions (nanometric level) even for biomaterials. In this pilot study, the mode of action of SA has been studied at atomistic level for the first time. Different concentrations of SA (3, 5, 10 wt%) in different time frames (1 day, 1 week, 1 month) was applied on human keratinized skin. The carbon, nitrogen and oxygen peak have not shown changes during the treatment, not showing the suggested desmolytic mechanism of SA. However, significant changes were observed in the sulfur peak, with increasing time and concentration the rate of sulfonate and sulfate was increased compared to thiol group indicating the break of sulfide bonds between the polypeptide chains in keratin, indicating that keratolysis happens at nanometric level. Already a 1 week-10 wt% SA treatment resulted in higher rate of sulfate compared to sulfonate indicating further oxidation of the keratolytic product. However, 1 month-10 wt% treatment resulted in the same surface composition as 3 wt%-1-month treatment indicating that enough time with low concentration can exert the same effect as higher concentrations. These findings have relevance in the design of future SA-based dermatologic therapies.

Biodegradable cobalt and tin doped chitosan nanocomposites from structure tailoring to solar-driven photocatalytic degradation of toxic organic dyes

The primary concern is the large amounts of emitted organic dyes through wastewater from numerous sectors. One of the most hazardous dyes commonly used in the industrial sector is methyl violet. It has been known to cause skin, gastric, and respiratory disorders. Therefore, a novel photocatalyst based on cobalt‑tin sulfide (Co3Sn2S2) was prepared using the solvothermal process. The photocatalyst was supplemented with Chitosan to prepare the cobalt tin sulfide-chitosan composite (Co3Sn2S2/Chi) for the photocatalytic degradation of methyl violet dye. Based on EDX analysis, a definite ratio of tin, cobalt, and sulfide was found. The FTIR of Co3Sn2S2/Chi revealed the characteristic bands of chitosan and metal sulfide bonds. SEM results showed that the particle had an irregular shape. The composite's crystalline structure was identified by XRD analysis as being 56 nm in crystalline size. The photocatalyst had a narrow band gap of 1.02 eV. At ideal conditions, the developed photocatalyst demonstrated greater degradation efficiency of methyl violet dye under solar light irradiation. The photocatalyst successfully decomposed 95 % of the methyl violet dye (40 ppm) within 70 min, operating at a pH of 9.0. This remarkable degradation was achieved by employing 0.25 g of the photocatalyst. The photocatalyst is more appealing and can be reused for up to three successive cycles. The photocatalyst is well-suited for “pseudo-first-order kinetics” to decontaminate methyl violet dye. The novel photocatalyst showed the most robust ability to decolorize methyl violet when exposed to sunlight and was a viable substitute for dye detoxification of organic dyes from wastewater.

The Use of Rubber-Polymer Composites in Bitumen Modification for the Disposal of Rubber and Polymer Waste.

The use of rubber-polymer composites ELTC (End of Life Tire Compound) for bitumen modification was investigated. ELTC contains not only devulcanized rubber from used car tires, but also used plastics (polymers) such as polyethylene (PE) and polypropylene (PP). ELTC is obtained using the method of rubber devulcanization using a selective catalyst that allows selectively decomposing sulfide bonds at relatively low temperatures, while preserving most of the macromolecular chains. The characteristics of the asphalt binder improved after the modification of ELTC. After modification, the base asphalt binder became more homogeneous, and the thermal stability of the base asphalt binder increased. ELTC is evenly distributed, the compatibility between the components of the modified asphalt binder is good, which proves the uniformity of the modified asphalt binders. The results show that all ELTC formulations improve the softening temperature and increase their resistance to plastic deformation in the summer.

Effects of wheat gluten-soy protein ratios and moisture levels on high-moisture extruded meat analogues for burger patties.

In response to the growing demand for plant-based meat alternatives, this study explores the impact of incorporating wheat gluten (WG) into soy protein isolate (SPI) on both the proximate and functional properties of protein blends. The research also examines the effects of high moisture extrusion processing, varying feed moisture levels (60%, 65%, and 70%), and WG-SPI blends on extruder response, as well as the textural, rheological, and solubility characteristics of the resulting extruded meat analogues. Moreover, the prime objective was to gain insights into the impact of using HMMA made at different ratios and feed moisture levels on plant-based burgers. As the WG incorporation level increased in SPI, the RVA viscosity, water absorption, and oil absorption capacities, and foaming stability exhibited a decrease while foaming capacity increased. As feed moisture and WG incorporation levels in SPI increased, the system parameters, rheological, and textural parameters of high moisture extruded meat analogs decreased. WG25-SPI75 showed the highest degree of texturization or sulfide bonds, and its extruded meat analogues at 60% feed moisture level burger patties resemble a similar textural to a chicken burger patty. This study is pivotal in understanding how wheat gluten in SPIs and feeding moisture level influence the textural and rheology properties of HMMA.

Synthesis of CuCo2S4 nanosheets and its application in dye-sensitized solar cells

CuCo2S4, a ternary sulfide and an eco-friendly thiospinel that occurs naturally as a mineral named Carrollite, has been synthesized successfully in ambient conditions at low temperatures using ultrasonication. It has yet to be reported, but the nanosheet structure obtained from the ultrasonication synthesis method employed as a counter electrode in the dye-sensitized solar cells (DSSCs) has been demonstrated. The purity, crystallinity, morphology, and structure were explored thoroughly through the medium of XRD, SEM, TEM, SAED, and EDAX, and along with this, the presence of metal sulfide bond was investigated with the FT-IR and Raman spectra, which altogether confirmed the formation of CuCo2S4 nanosheet. The as-prepared nanosheets of CuCo2S4 have shown excellent homogeneity, as expected. Also, the presence of sulfur in the synthesized CuCo2S4, which is a highly polarizable atom and of a smaller size exhibiting a higher surface area, demonstrates higher electrocatalytic activity when fabricated as a counter-electrode in DSSCs by providing an incredible short circuit current density of 31.05 mA cm−2, open circuit potential of 735 mV with good fill factor value which altogether resulted in the power conversion efficiency of 10.21 % nearer to DSSC fabricated with Platinum counter electrode under the same conditions.

Exploring a facile preparation method for Co-Ni/MoS2-derived nanohybrid from wheat straw extract and its physicochemical properties.

This study presents a novel approach for the fabrication of a Co,Ni/MoS2-derived nanohybrid material using wheat straw extract. The facile synthesis method involves a sol-gel process, followed by calcination, showcasing the potential of agricultural waste as a sustainable reducing and chelating reagent. The as-prepared nanohybrid has been characterized using different techniques to analyse its physicochemical properties. X-ray diffraction analysis confirmed the successful synthesis of the nanohybrid material, identifying the presence of NiMoO4, CoSO4 and Mo17O47 as its components. Fourier-transform infrared spectroscopy differentiated the functional groups present in the wheat straw biomass and those in the nanohybrid material, highlighting the formation of metal-oxide and sulphide bonds. Scanning electron microscopy revealed a heterogeneous morphology with agglomerated structures and a grain size of around 70 nm in the nanohybrid. Energy-dispersive X-ray spectroscopy analysis shows the composition of elements with weight percentages of (Mo) 9.17%, (S) 6.21%, (Co) 12.48%, (Ni) 12.18% and (O) 50.46% contributing to its composition. Electrochemical analysis performed through cyclic voltammetry showcased the exceptional performance of the nanohybrid material as compared with MoS2, suggesting its possible applications for designing biosensors and related technologies. Thus, the research study presented herein underscores the efficient utilization of natural resources for the development of functional nanomaterials with promising applications in various fields. This study paves a way for manufacturing innovation along with advancement of novel synthesis method for sustainable nanomaterial for future technological developments.

Sustainable in-situ synthesis of BaS2:Cu8S5:LaS tri-metal chalcogenide via diethyldithiocarbamate precursors for high-performing energy storage systems

Current work, for the first time, reports the synthesis of the novel BaS2:Cu8S5:LaS ternary chalcogenide for utilization in the energy storage devices owing to its superior capacitive performance. BaS2:Cu8S5:LaS was marked by remarkable optical behavior with the narrowed band gap energy i.e. 2.55 eV. Crystallographic analysis is indicative of the 16.77 nm average crystallite size. The presence of the metal sulphide bonds was confirmed by the vibrational stretches between 420 – 890 cm−1. Rod shaped particles with the suspended spheres was the predominant morphology. With the augmented redox behavior and charging-discharging behavior, fabricated electrode attained the auspicious specific capacitance of 1299F/g. Furthermore, the specific power density obtained for this electrode was 11166 W kg−1. The enhanced electrochemical performance was also exhibited by the elevated electrical conductivity showing the equivalent series resistance (Rs) = 0.48 Ω.

Deciphering the energy storage and electro‐catalytic potential of the BaLa2MnS5 ternary metallic sulfide prepared via single source precursor route

AbstractThe present work elucidates the first report on the synthesis and energy applications of the novel BaLa2MnS5 prepared from single source precursor route. This metal chalcogenide expressed a tuned band gap of 3.84 eV and an average crystallite size of 20.52 nm. Functional groups explored for BaLa2MnS5 expressed strong signals for presence of the metal sulfide bonds. The thermal decomposition pattern of BaLa2MnS5 followed a two‐phased mechanism. Synthesized metal sulfide possessed an irregular morphology with particles arranged in random manner. An assessment of the chalcogenide BaLa2MnS5 for energy applications has been carried out. When employed as an electrode material in 1 M KOH, which acted as the background electrolyte, BaLa2MnS5 chalcogenide showed a specific capacitance of 597 F g−1. Furthermore, this BaLa2MnS5 chalcogenide decorated electrode has a low resistance, as shown by the Rs of 1.35 Ω, and a specific power density of 7366 W kg−1, according to the impedance investigations. The electrochemical results for the OER activity are indicative of the OER overpotential and Tafel slope values as 388 mV and 108 mV/dec. This electrode achieved the HER overpotential value of 241 mV while the obtained Tafel slope was 194 mV/dec.

A rapid strategy to develop personalized cancer nanovaccines for different immunogenic tumors.

e14670 Background: Therapeutic cancer vaccines aim to train the immune system and elicit antitumor immune responses, which are expected to fill the unmet medical need of immune checkpoint inhibitors. Despite tremendous efforts over the past decades, it remains challenging to prepare personalized cancer vaccines using a facile and rapid approach due to tumor diversity. CpG-ODN is a promising immunoadjuvant in cancer immunotherapy, and many clinical trials have been performed or are ongoing. However, commonly used phosphorothioate-modified CpG ODN easily induces protein aggregation and its long-term side effects are concerned. Here, we designed hollow large-pore mesoporous organosilica with sulfide bond to simultaneously load unmodified CpG-ODN with guanine-quadruplex (G4) structures and different tumor antigens to prepare personalized cancer vaccines in a simple, fast, and effective way. Methods: High-immunogenicE.G7-OVA lymphoma or low-immunogenic Lewis lung carcinoma (LLC) cells were subcutaneously inoculated into the left flanks to establish tumor-bearing mice. On days 4, 7, and 10 post tumor inoculation, cancer vaccines prepared using model antigen (OVA) or autologous tumor antigen (LLC tumor cell lysate) were subcutaneously injected into the right flanks of mice, respectively. Saline group, free tumor antigen group, free tumor antigen + CpG-ODN group, tumor antigen + organosilica group were used as controls. The size of tumors was monitored. Results: Cancer vaccines against E.G7-OVA showed high loading efficiencies of >95% for both CpG-ODN and OVA, triggered antitumor immune response with high percentages of CD4+, CD8+, tetramer+CD8+ T cells in splenocytes, and effectively inhibited the growth of established tumor, compared with free OVA, free OVA + CpG-ODN, free OVA + organosilica groups. Cancer vaccines against LLC exhibited high loading efficiencies of >95% and >80% for CpG-ODN and LLC tumor cell lysate, activated antitumor immune response with high percentages of CD4+ and CD8+ T cells in splenocytes and CD8+ T, NK and M1 cells in tumor sites, and effectively inhibited the growth of established tumor, compared with control groups. Conclusions: Codelivery of CpG-ODN and different tumor antigens using hollow large-pore mesoporous organosilica elicits antitumor immunity against both high-immunogenic and low-immunogenic tumors.

Mo3S13 Chalcogel: A High-Capacity Electrode for Conversion-Based Li-Ion Batteries.

Despite large theoretical energy densities, metal-sulfide electrodes for energy storage systems face several limitations that impact the practical realization. Here, we present the solution-processable, room temperature (RT) synthesis, local structures, and application of a sulfur-rich Mo3S13 chalcogel as a conversion-based electrode for lithium-sulfide batteries (LiSBs). The structure of the amorphous Mo3S13 chalcogel is derived through operando Raman spectroscopy, synchrotron X-ray pair distribution function (PDF), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) analysis, along with ab initio molecular dynamics (AIMD) simulations. A key feature of the three-dimensional (3D) network is the connection of Mo3S13 units through S-S bonds. Li/Mo3S13 half-cells deliver initial capacity of 1013 mAh g-1 during the first discharge. After the activation cycles, the capacity stabilizes and maintains 312 mAh g-1 at a C/3 rate after 140 cycles, demonstrating sustained performance over subsequent cycling. Such high-capacity and stability are attributed to the high density of (poly)sulfide bonds and the stable Mo-S coordination in Mo3S13 chalcogel. These findings showcase the potential of Mo3S13 chalcogels as metal-sulfide electrode materials for LiSBs.

Organic Electrochemical Transistor Aptasensor for Interleukin-6 Detection.

We demonstrate an organic electrochemical transistor (OECT) biosensor for the detection of interleukin 6 (IL6), an important biomarker associated with various pathological processes, including chronic inflammation, inflammaging, cancer, and severe COVID-19 infection. The biosensor is functionalized with oligonucleotide aptamers engineered to bind specifically IL6. We developed an easy functionalization strategy based on gold nanoparticles deposited onto a poly(3,4-ethylenedioxythiophene) doped with polystyrenesulfonate (PEDOT:PSS) gate electrode for the subsequent electrodeposition of thiolated aptamers. During this functionalization step, the reduction of sulfide bonds allows for simultaneous deposition of a blocking agent. A detection range from picomolar to nanomolar concentrations for IL6 was achieved, and the selectivity of the device was assessed against Tumor Necrosis Factor (TNF), another cytokine involved in the inflammatory processes.

Potential of single and designed mixed cultures to enhance the bioleaching of chalcopyrite by oxidation-reduction potential control

Biomining is the extraction of target metals from ores or wastes such as the dissolution of chalcopyrite for copper recovery. A key outstanding topic of study is to improve the rate and total copper released from chalcopyrite that can become ‘passivated’ by surface layers, which hinders oxidative attack on the metal sulfide bond. One strategy to increase chalcopyrite bioleaching is to control of the oxidation-reduction potential in the desired range by using ‘weak’ iron oxidizers. In this study, 15 acidophilic species were evaluated for their ability to catalyze chalcopyrite dissolution that resulted in the addition of Acidithiobacillus ferrianus, Sulfobacillus thermotolerans, and Metallosphaera sedula to the known ‘weak’ iron oxidizing species. Based upon these data, four microbial consortia were designed including mesophiles (25° and 37 °C), moderate thermophiles (49 °C), and thermophiles (70 °C) that increased copper recoveries by up to 32% compared to abiotic controls. The best performing consortium was the moderate thermophiles Sulfobacillus thermotolerans, Sulfobacillus acidophilus, and Ferroplasma acidiphilum that maintained the oxidation-reduction potential in the desired range. However, the consortia also showed evidence of synergistic interactions between ‘weak’ iron oxidizers that increased the efficiency of ferrous iron oxidation that resulted in oxidation-reduction potentials above the desired range and lower copper release. Therefore, while designing microbial consortia is a promising strategy to improve the performance of chalcopyrite bioleaching, care must be taken to ensure synergistic effects do not result in high oxidation-reduction potentials.

Organic halide salts and PbI2 in improving the efficiency of perovskite solar cells

First developed in 2012, perovskite solar cells (PSC) have been attracting enormous attention for their high-power conversion efficiency, low manufacturing cost, easy annealing and fabricating techniques, good stability in ambient environments, and excellent overall performance. Skyrocketing from a PCE of 2.8% to 25.2%, PSCs are deemed as one of the most promising solar energy harvesters in the near future. However, due to the grain boundaries and some poor interface connections, there appear several defects that affect the efficiency and stability of PSCs. In this case, two primary methods are discussed in this review to minimize such limitations: the introduction of (1) PbI2 and (2) organic halide salts as additives to the perovskite film. By filling the vacancies at the grain boundary, promoting spatial electron–hole separation, generating Lewis acid–base reaction, and forming intermolecular interactions like hydrogen bonding, sulfide bonds, pi-conjunctions, etc., these additives serve as promising candidates for reducing the surface recombination of PSCs. Moreover, because of the hydrophobic characteristics of organic halide-based compounds and the thermal annealing process, the stability of PSCs can also be improved in both high-temperature and -humidity environments. Through presenting and compiling the results of recent studies on various additives, this review also proposes further development and next-generation strategies for minimizing the limitations and challenges in the future.

Facile and dynamic cleavage of every iron–sulfide bond in cuboidal iron–sulfur clusters

Nature employs weak-field metalloclusters to support a wide range of biological processes. The most ubiquitous metalloclusters are the cuboidal Fe-S clusters, which are comprised of Fe sites with locally high-spin electronic configurations. Such configurations enhance rates of ligand exchange and imbue the clusters with a degree of structural plasticity that is increasingly thought to be functionally relevant. Here, we examine this phenomenon using isotope tracing experiments. Specifically, we demonstrate that synthetic [Fe4S4] and [MoFe3S4] clusters exchange their Fe atoms with Fe2+ ions dissolved in solution, a process that involves the reversible cleavage and reformation of every Fe-S bond in the cluster core. This exchange is facile-in most cases occurring at room temperature on the timescale of minutes-and documented over a range of cluster core oxidation states and terminal ligation patterns. In addition to suggesting a highly dynamic picture of cluster structure, these results provide a method for isotopically labeling pre-formed clusters with spin-active nuclei, such as 57Fe. Such a protocol is demonstrated for the radical S-adenosyl-l-methionine enzyme, RlmN.

N-acetyl cysteine inhibits IL-1α release from murine keratinocytes induced by 2-hydroxyethyl methacrylate.

The hydrophilic compound 2-hydroxyethyl methacrylate (HEMA) is a major component of dental bonding materials, and it enhances the binding of resin-composites to biomolecules. However, HEMA is a well-known contact sensitizer. We reported previously that intradermal injection of HEMA induces the production of IL-1 locally in the skin. Keratinocytes are the first barrier against chemical insults and constitutively express IL-1α. In this study, we analyzed whether HEMA induces the production of inflammatory cytokines from murine keratinocyte cell line Pam212 cells. We demonstrated that HEMA induced the release of 17-kDa mature IL-1α and caused cytotoxicity. The activity of calpain, an IL-1α processing enzyme, was significantly higher in HEMA-treated cells. The thiol-containing antioxidant N-acetyl cysteine (NAC) inhibited HEMA-induced IL-1α release but not cytotoxicity. NAC inhibited intracellular calpain activity and reactive oxygen species (ROS) production induced by HEMA. NAC post-treatment also inhibited IL-1α release and intracellular ROS production induced by HEMA. Furthermore, HEMA-induced in vivo inflammation also inhibited by NAC. NAC inhibited polymerization of HEMA through adduct formation via sulfide bonds between the thiol group of NAC and the reactive double bond of HEMA. HEMA-induced IL-1α release and cytotoxicity were also inhibited if HEMA and NAC were pre-incubated before adding to the cells. These results suggested that NAC inhibited IL-1α release through decreases in intracellular ROS and the adduct formation with HEMA. We concluded that HEMA induces IL-1α release from skin keratinocytes, and NAC may be a promising candidate as a therapeutic agent against inflammation induced by HEMA.

Synthesis of Pyridine Heterocyclic Low-Melting-Point Phthalonitrile Monomer and the Effects of Different Curing Agents on Resin Properties.

A phthalonitrile monomer (DPTP) containing pyridine with sulfide bonds was prepared and cured into polymers using different curing agents under the same temperature-programmed process. We characterized and comprehensively evaluated the effects of different curing agents on the thermal and thermomechanical properties of phthalonitrile resin, showing that the DPTP monomer cured with naphthalene-containing curing agent exhibited the best performance among the three polymers. Differential scanning calorimetric (DSC) investigation manifested that the melting point of the DPTP monomer was 61 °C, with a processing window of about 170 °C, suggesting the presence of a wide processing range. Thermogravimetric analysis (TGA) demonstrated the outstanding heat resistance, T5%, of 460 °C in nitrogen, at the same time demonstrating superior long-term stability compared with other commonly used polymer materials, which proves the long-term usage under high temperatures of 300 °C. Dynamic mechanical analysis (DMA) revealed that the storage modulus at 50 °C was 3315 MPa, and the glass transition temperature (Tg) of the polymer was more than 350 °C. Therefore, DPTP resins have favorable thermal stability as well as prominent thermomechanical properties.

Comparative study on the reductive immobilization of Se(IV) by Beishan granite and Tamusu claystone

Understanding the retardation of 79Se by the host rock is essential for the safety assessment of the high-level radioactive waste (HLRW) repository and thus the final site-selection process. In this work, we performed a comparative study on the interaction of Se(IV) with Beishan granite and Tamusu claystone, and multiple characterization techniques were used to identify the speciation of Se and to unravel the underlying mechanism. Results showed that Se(IV) can be reduced to Se(0) by the Beishan granite from borehole 16 that contains Fe(II)-bearing fluorannite, and the removal efficiency of Se(IV) is more favorable at acidic condition. We proposed that release of the structure Fe2+ in granite, followed by surface adsorption and reaction could be responsible for the Se(IV) reduction by this granite. In addition to Se(0) product, FeSe2 was also observed for Se(IV) reacted with the granite from borehole 28. This is the first time observed the formation of FeSe2 on natural Fe(II)-containing minerals, which is mainly ascribed to the simultaneous occurrence of aqueous sulfide dissolved from the ground granite powder. The reactive sulfide might be generated from the breakage of Fe(S)–S bonds of iron sulfides (e.g., pyrite) contained in the granite during the anoxic grinding process, and it could mainly account for the Se(IV) reduction by the granite from borehole 28. Due to the presence of pyrite, the Tamusu claystone from borehole Tzk2 was effective to remove aqueous Se(IV) via the formation of Se(0). Conversely, the Se(IV) removal efficiency was much lower for the claystone from borehole Tzk1 that did not contain pyrite, although there was a considerable amount of Fe(II)-bearing fluorannite. Hence, the Fe2+ contained in Tamusu claystone was less active for Se(IV) reduction in comparison with that in Beishan granite from borehole 16. The findings of this study provide important data for the safety assessment of China's future HLRW repository, but also improve our understanding of the geochemical behavior of selenium in the presence of Fe(II)- and sulfide-bearing minerals in the relevant anoxic environments.

Mechanistic Investigation of the Nickel-Catalyzed Metathesis between Aryl Thioethers and Aryl Nitriles

Functional group metathesis is an emerging field in organic chemistry with promising synthetic applications. However, no complete mechanistic studies of these reactions have been reported to date, particularly regarding the nature of the key functional group transfer mechanism. Unraveling the mechanism of these transformations would not only allow for their further improvement but would also lead to the design of novel reactions. Herein, we describe our detailed mechanistic studies of the nickel-catalyzed functional group metathesis reaction between aryl methyl sulfides and aryl nitriles, combining experimental and computational results. These studies did not support a mechanism proceeding through reversible migratory insertion of the nitrile into a Ni-Ar bond and provided strong support for an alternative mechanism involving a key transmetalation step between two independently generated oxidative addition complexes. Extensive kinetic analysis, including rate law determination and Eyring analysis, indicated the oxidative addition complex of aryl nitrile as the resting state of the catalytic reaction. Depending on the concentration of aryl methyl sulfide, either the reductive elimination of aryl nitrile or the oxidative addition into the C(sp2)-S bond of aryl methyl sulfide is the turnover-limiting step of the reaction. NMR studies, including an unusual 31P-2H HMBC experiment using deuterium-labeled complexes, unambiguously demonstrated that the sulfide and cyanide groups exchange during the transmetalation step, rather than the two aryl moieties. In addition, Eyring and Hammett analyses of the transmetalation between two Ni(II) complexes revealed that this central step proceeds via an associative mechanism. Organometallic studies involving the synthesis, isolation, and characterization of all putative intermediates and possible deactivation complexes have further shed light on the reaction mechanism, including the identification of a key deactivation pathway, which has led to an improved catalytic protocol.

Rapid internal conversion harvested in Co/Mo dichalcogenides hollow nanocages of polysulfides for stable Lithium-Sulfur batteries

The sluggish conversion kinetics of the lithium polysulfide (LiPS) intermediates are hindering the practical application of lithium sulfur batteries (LSB) by their low efficiency and low cycle stability. To tackle these challenges, a rapid internal conversion (RIC) mechanism is proposed for the first time to accelerate the liquid–solid conversion in the sulfur reduction reaction (SRR) kinetics. It is reaveled that the reaction energy barrier in the SRR lies in the liquid–solid conversion, from Li2S4 to LiS2* to Li2S2. To accelerate the liquid–solid conversion, the CoS2@MoS2 hollow nanocage, a novel sulfur cathode, with the rational synergistic active site configuration is specifically designed toward a well-managed reaction path and sulfurphilic structure to regulate and modulate Li(LiPS)-S(sulfide) and S(LiPS)-M(sulfide) bonds prominently, affecting on activating reactants and stablizing transition states. Based on the RIC mechanism in the SRR, the stronger S-Co bonds between CoS2 and LiPS traps Li2S4 and catalytically facilitates S-S bond scission while the MoS2 is conducive to the migration of Li2S4 by weaker Li-S bonds. The unique synergetic conversion and catalytic functions is confirmed by density functional theory (DFT) calculations. The RIC mechanism could provide a new idea for exploring the conversion-catalysis material of Li-S batteries in the specific material design.