Sulfur Anions Research Articles

Construction of a low-valent thiolate-bridged dicobalt platform and its reactivity toward hydrogen activation and evolution

Low-valence transition metallic complexes have drawn longstanding attention due to their high reactivity toward catalytic transformation of various small molecules. Among these known complexes, the low-valence metal centres are commonly stabilized by neutral bulky ligands with strong electron-donating capacity. However, low-valence bimetallic complexes supported by anionic sulfur and cyclopentadienyl ligands are still difficult to obtain in high isolated yield. Herein, we report the synthesis and characterization of two scarce thiolate-bridged CoICoII and CoICoI complexes bearing sterically demanding ligands through two stepwise one-electron reduction processes. Interestingly, the CoICoII complex can facilely promote the homolytic cleavage of dihydrogen across the short Co−Co metallic bond to give a CoIICoIII dihydride bridged complex, which is capable of serving as a competent hydrogen atom transfer agent. Moreover, the anionic CoICoI complex can trigger a stepwise hydrogen generation cycle involving several isolated and structurally well-characterized intermediates.

Construction of Thioamide Peptide via Sulfur-Involved Amino Acids/Amino Aldehydes Coupling.

A sulfur-involved ligation for thioamide quasi-peptides was developed via amino acids and amino aldehydes coupling. The key to the transformation was the chelation of copper with imines for chiral activation and fixation. In this environment, linear polysulfur decreased the alkalinity of single sulfur anions to prevent racemization caused by the interaction between sulfur and sodium sulfide. Dipeptides, tripeptides, tetrapeptides, and the linkage between the drug and amino acids were successfully obtained.

Leveraging of Sulfur Anions in Photoinduced Molecular Transformations.

This perspective describes recent advances in the use of sulfur anions to promote molecular transformations under irradiation with visible light. The topics are classified by the following reaction modes performed by the key sulfur anions: (1) C–S coupling via electron donor–acceptor (EDA) interactions, (2) photoinduced molecular transformation via sulfur anion EDA catalysis, (3) sulfur anions as photoredox and hydrogen atom transfer (HAT) catalysts, and 4) dithiocarbamate and xanthate as nucleophilic catalysts for photoinduced radical cascade reactions.

Computational Investigation on the Role of Aliovalent Cation Dopants to the Na+ Ion Superionic Conductivity of Na3SbS4 Solid Electrolytes By Density Functional Theory Methods

Na+ ion batteries are regarded as one of the most promising alternative to Li+ ion batteries especially from the viewpoint of applications wherein the form factor is not a major issue, such as in large-scale smart grids and stationary back up power sources. Similar to all-solid-state Li+ ion batteries (Li-ASSBs), all-solid-state Na+ ion batteries (Na-ASSBs) with a solid electrolyte are considered to be highly promising for realizing high safety. Amongst the solid electrolyte types, sulfide-based ones are especially known to demonstrate high ionic conductivity owing to the high polarizability of sulfur anions. In addition, sulfide-based solid electrolyte materials can be prepared under mild processing conditions for crystallization. They are also highly elastic, enabling for a good interfacial contact with the electrodes and other components.Recently, a sulfide-type Na+ superionic conductor, Na2.88Sb0.88W0.12S4, was reported with an unprecedented conductivity on the order of 10-2 S/cm.1 Although it appears trivial that the W6+ aliovalent dopant cation directly modifies the Na vacancy concentration and thus the ionic conductivity, it is still unclear why the it reached a one-order-of-magnitude enhancement. This in contrast to other reported aliovalent doping strategies which used other dopant elements but failed to obtain such conductivity improvement. In this work, we employed density functional theory methods (e.g., geometry optimization, molecular dynamics) in order to study the role of aliovalent cation dopants (e.g., W6+, Mo6+) in Na3SbS4 for realizing superionic ionic conductivity.2 It was determined that the transport process in Na3SbS4 is governed by a concerted migration behavior of Na+ ions. The modulation of Na vacancy concentration by cation doping was confirmed to play a role, but it cannot solely account for the observed order of magnitude rise in conductivity. To find the crucial factors, the pathway channels and phonon density of states were investigated together with the effects of doping to the jump frequency (conductivity prefactor) and activation energy (conductivity Boltzmann factor). In particular, correlations were analyzed between conductivity and the sizes of Na Wyckoff site cage and site-to-site jump bottleneck in the pathway channel. Our results provide new useful insights towards the rational design of solid electrolytes in general in ASSBs.This work was supported in part by MEXT as Elements Strategy Initiative (Grant Number JPMXP0112101003), the Program for Promoting Researches on the Supercomputer Fugaku (Fugaku Battery & Fuel Cell Project, Grant Number JPMXP1020200301), and the Materials Processing Science project (“Materealize”, Grant Number JPMXP0219207397). The work was also supported by JSPS KAKENHI (Grant Numbers JP19H05815 and JP19H05816). References A. Hayashi, N. Masuzawa, S. Yubuchi, F. Tsuji, C. Hotehama, A. Sakuda, M. Tatsumisago, Nat. Commun. 2019, 10, 5266. R. Jalem, A. Hayashi, F. Tsuji, A. Sakuda, Y. Tateyama, Chem. Mater. 2020, 32, 8373-8381.

TECHNOLOGY OF COMPLEX SORPTION TREATMENT OF INDUSTRIAL WASTEWATER FROM SULPHIDE AND COPPER(II)–IONES

Complex processing of industrial waste of individual industries, including wastewater treatment, containing sulfur anions and cations of heavy metals, in order to obtain both purified water and finished industrial products is an urgent task for today. The possibility of efficient use of regenerated mixed sorbent (AC+K), containing activated carbon (AC) and diatomaceous earth (K), for wastewater treatment of certain technological processes of chemical (petrochemical) industry and galvanic industries has been shown. The sorbent with the removed contaminants was offered to be utilized as a part of plastic lubricants of special purpose. The technological process of complex sorption treatment of industrial wastewater from sulfide and copper (II) ions includes the following main stages: sorbent regeneration; purification of sulfide-alkaline solutions; purification of washing waters of galvanic productions; obtaining plastic oils. The basic technological scheme of the site of regeneration of the spent mixed sorbent (AC+K) and purification of water-sugar solutions from organic impurities was developed. The material balance of regeneration of the spent mixed sorbent was calculated. The basic technological scheme of the site of combined treatment of industrial wastewater from sulfide and copper (II) ions, regeneration of spent industrial oils with regenerated sorbent (AC+K) and production of plastic oils has been developed. It was shown that the technology of complex sorption wastewater treatment is based on the most common technological processes - heating, cooling, adsorption and filtration and does not require complex schemes of automatic process control, and chemical equipment is typical for chemical enterprises in Ukraine. The economic effect of production of special purpose plastic oils was calculated.

Light-Induced Single-Electron Transfer Processes involving Sulfur Anions as Catalysts

Photoredox catalysis has evolved as an attractive approach to enable a wide variety of chemical reactions with high selectivity under mild conditions. The development of novel photocatalytic systems is key to obtaining new reactivity and improving their catalytic performances. In this context, cost-effective organic anion-based photocatalysts have recently attracted increasing interest. In particular, sulfur-based anionic catalysts are of interest due to their unique redox properties. This Perspective highlights and discusses recent advances in light-induced single-electron-transfer processes directly involving sulfur anions as catalysts. The content of this Perspective is organized along the different photoinduced electron-transfer pathways between catalysts and substrates.

Optical Aptasensors and the Challenge of Food Contamination With Lead

Contamination of heavy metals in food, especially drinking water and groundwater, has become a serious problem for human health. These metals are mainly the constituent elements of nature widely distributed in the earth's crust, but significant amounts of them are also found in everyday goods. These elements are usually found in combinations with oxygen, chlorine, sulfur, and other anions that generally contain inorganic and organic compounds. Lead is one of the heavy metals with high toxicity that poses serious risks to the environment and humans. Recent advances in nucleic acid research have led to the identification of oligonucleotide sequences that bind with high affinity specifically to target molecules, including proteins. Such single-stranded sequences are called "aptamer" nucleic acids. Aptamers are synthetic single-stranded DNA or RNA sequences of 30 to 100 nucleotides, and their secondary and tertiary structures are folded to make them highly specific for binding to targets. The binding of aptamers to different targets, from a single cell to large chemical and biological molecules, is done with high affinity. This aptamer feature is used to detect lead. In this review article, the designed optical aptasensors for the detection of lead will be reviewed.

High-pressure behavior of disordered kesterite-type Cu2ZnSnS4

We have investigated the high-pressure structural and vibrational behavior of the disordered kesterite-type Cu2ZnSnS4 compound at ambient temperature. Our experimental and theoretical investigations have revealed a clear structural transition to a GeSb-type phase close to 15 GPa, a tetragonally distorted variant of the NaCl-type phase. The latter transformation is accompanied by a cationic coordination increase from fourfold to sixfold with respect to the sulfur anions. In addition, a change in the compressibility rate was detected at about 8 GPa within the pressure stability range of the disordered kesterite-type phase. Upon decompression, a disordered zinc blende/sphalerite structure is recovered. We discuss our findings in close conjunction with our recent high-pressure work on the ordered Cu2ZnSnS4 modification.

Anisotropic optical properties of Cu2ZnSn(SxSe1−x)4 solid solutions: First-principles calculations with TB-mBJ+U

The main aim of this work is to determine and explain the relationships between optoelectronic properties and the sulfur anion content in Cu2ZnSn(SxSe1−x)4 solid solution. Band gap and absorption coefficient are of primary interest to the engineers and scientists researcher worked in optoelectronic field. Herein, the electronic and optical properties are calculated based on 128 conventional atoms within lattice parameters obtained at 300 K by using the FP-LAPW method combined with quasi-harmonic Debye model. The composition dependent band gaps of CZTSSe solid solutions are investigated by TB-mBJ+U. As results, all materials are semiconductors with a direct band gap ranging from 0.614 to 0.99 eV. The band gap variation increases as a function of sulfur anion content and showed a positive deviation from Vegard's law with a very small downward bowing parameter of + 0.079 eV. The density of state (DOS) calculations indicate that the energy bands of VBM involve Cu_d/anion(S/Se)_p hybridized antibonding-like states. Based on band alignment, the Ec offset between CZTS and CZTSe is larger than the Ev offset. These results are reported previously in other work and are confirmed in this study. Our work included a systematic comparison of the influence of S/(S+Se) atomic ratios on optical quantities. The dielectric function tensors show remarkable anisotropy. In addition, the static dielectric constants are found to decrease with sulfur anion content. The CZTSSe is proved to be suitable for good solar cells with high absorption coefficient (> 104 cm−1). Such deep optical studies would be helpful for future optoelectronic applications of these compounds with different S/(S+Se) atomic ratios.

Full-Spectrum Fluoromethyl Sulfonation via Modularized Multicomponent Coupling

Full-Spectrum Fluoromethyl Sulfonation via Modularized Multicomponent Coupling

Alternate routes to sustainable energy recovery from fossil fuels reservoirs. Part 1. Investigation of high-temperature reactions between sulfur oxy anions and crude oil

The world is undergoing a substantial transition in its energy supply. Examining the possibilities to recover and use fossil fuel energy without emitting carbon dioxide to the surface, H2S was considered as an alternative energy vector to deliver a carbon free fuel from petroleum reservoirs to the surface. In this study, we investigated the high P-T chemical oxidation of crude oil with a suite of inorganic sulfur compounds. Tested inorganic sulfur compounds can be ordered by their ability to promote chemical changes to the oil matrix with the concomitant production of hydrogen sulfide, with a reactivity series, listed in order of decreasing reactivity as: S0 > S2O32− ~ S4O62− > SO32− > SO42−. The reaction mechanisms proposed in the study also light on likely key intermediate reactants and the geological timescale process of thermochemical sulfate reduction. Polysulfide species (containing S-S bond structures), such as thiosulfate and tetrathionate, may be reactive intermediates during the redox reaction. However, the early stage of thermochemical sulfate reduction may also involve labile organic sulfur functional groups converting to more stable molecules with aromatic structural units, such as dibenzothiophenes (DBT) and benzonaphthothiophenes (BNT). The apparent formation of saturated fatty acids and O2, NO and NO2 aromatic heteroatom species indicates the oxidation of saturated and aromatic hydrocarbons or heteroatom compounds. The oxidation of aromatic species may lead to aromatic ring-opening, followed by decarboxylation forming CO2 as final products.

Lithium-Ion Conductivity of Mixed-Anion Chloride Solid Electrolyte

Lithium-ion batteries are required to have high energy density, high cycle characteristics, and safety to be used for electric vehicles. Current lithium-ion batteries use a flammable organic electrolyte as electrolyte suffers from safety issues. All-solid-state batteries using non-flammable solid electrolytes are attracting attention because they can improve safety and energy density. The practical use of all-solid-state batteries requires solid electrolytes having higher conductivity, atmospheric stability, electrochemical stability, and moldability than conventional liquid electrolytes. However, no material that combines everything has been found at present.Solid electrolytes are divided into two main types: oxide-based and sulfide-based materials. As oxide-based solid electrolytes, garnet-type Li7La3Zr2O12, which shows the room-temperature ionic conductivity is 5.1 × 10-4 S / cm, has been developed [1]. Generally, oxide-based materials have high atmospheric stability and are stable to oxide-based cathode materials, but the ionic conductivity is lower than sulfide-based materials, and a high-temperature process is required for synthesis. As sulfide-based solid electrolytes, crystalline Li10GeP2S12, which shows the room-temperature ionic conductivity is 1.2 × 10-2 S / cm, has been developed [2]. Sulfide-based materials have a relatively higher ionic conductivity than oxide-based materials. Moreover, sulfide-based materials have high moldability and can be synthesized at a lower temperature than oxide-based materials. However, sulfide-based materials have the disadvantages of low atmospheric stability, are at risk of reacting with water to generate H2S, and have low stability to oxide-based cathode materials.High ionic conductivity solid electrolytes have been discovered mainly in oxide-based and sulfide-based materials. In addition, recently, it has been reported that lithium conductive solid electrolytes of halide-based materials have high ionic conductivity, and the material-searching region is expanding. Halide-based materials are considered to have high ionic conductivity due to the properties of halogen anions. Since the monovalent halogen anion has a weaker interaction with lithium ions than the divalent sulfur and oxygen anions, high-speed transport of lithium ions can be expected. In addition, the ionic radius of the halogen anion is relatively large, and the halogen anion has high polarizability. Li3YCl6, Li3YBr6 and Li3InCl6, which show the room-temperature ionic conductivity is 10-3 S / cm have been reported as lithium halide solid electrolyte materials [3], [4].Most of these lithium halide solid electrolyte materials are single-anion compounds, and little research has been conducted on mixed-anion compounds as lithium-ion conductors. In this study, we focused on the chloride-based solid electrolyte Li3InCl6, which is reported to have high lithium-ion conductivity comparable to oxide and sulfide-based materials and is expected to have higher chemical stability than sulfide-based materials. The characteristics of the solid electrolyte when Li3InCl6 was doped with a group 16 element were investigated. A composite anion compound in which oxygen, sulfur, and selenium, which have higher polarizabilities than chlorine, were dissolved was synthesized, and the conductivity characteristics were analyzed by electrochemical measurement. Li3InCl6, Li3InCl5.4O0.3, Li3In0.9Cl5.4O0.15, Li3In0.82Cl5.4O0.03, Li3InCl5.4S0.3, Li3InCl5.4S0.6 and Li3InCl5.4Se0.6 samples were synthesized by mechanochemical method and solid-phase reaction in an argon atmosphere. The crystal structure of the synthesized samples was characterized by X-ray diffraction (XRD), and the ionic conductivity was measured by AC impedance measurements. Comparing the XRD patterns of the Li3InCl6 sample and each sample, a peak of impurities was confirmed for the oxygen solid solution sample, and a decrease in crystallinity was confirmed for the sulfur and selenium solid solution samples. The conductivity of each sample decreased in the order of Li3InCl6> Li3In0.82Cl5.4O0.03 > Li3In0.9Cl5.4O0.15 > Li3InCl5.4O0.3 > Li3InCl5.4S0.3 > Li3InCl5.4Se0.6 > Li3InCl5.4S0.6. In conclusion, addition of mixed anion to the chloride-based solid electrolytes causes negative effects for the lithium-ion conduction. From these results, it is considered that if a divalent anion is dissolved in a crystal constituting a sublattice by the monovalent anion, an increase in Coulomb interaction has a greater effect on lithium-ion conductivity than an action due to polarizability, decreasing conductivity.[1] R. Murugan, V. Thangadurai, W. Weppner, Angew. Chem 46, 7778(2007)[2] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, Nature Materials 10, 686(2011)[3] T. Asano, A. Sakai, S. Ouchi, M. Sakaida, A. Miyazaki, S. Hasegawa, Adv. Mater. 30, 1803075(2018)[4] X. L, J. Liang, J. Luo, M. N. Banis, C. Wang, W. Li, S. Deng, C. Yu, F. Zhao, Y. Hu, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, K. R. Adair, X. Sun, Energy Environ. Sci. 12, 2665(2019)

Unraveling H2O2-stimulated surface oxidation of non-magnetic pyrrhotite and pentlandite by underlying electronic structures

The selective flotation of pentlandite from non-magnetic pyrrhotite is a long-standing issue. To contribute to solving this issue, we report our fundamental understanding of the selective depression of non-magnetic pyrrhotite in pentlandite flotation using H2O2. Reactions of H2O2 were studied using chronopotentiometry (CP) tests and dissolved oxygen (DO) tests. Surface oxidations were studied with surface composition depth profiles of X-ray photoelectron spectrometry (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). It was found that H2O2 reduction stimulated the surface oxidation of non-magnetic pyrrhotite, meanwhile, H2O2 reduction on pentlandite was balanced by the oxidation of H2O2. The different responses to H2O2 conditioning were attributed to the distinct electronic structures of pyrrhotite and pentlandite, which were calculated based on density functional theory (DFT). For pyrrhotite, the higher S 3p band center than its Fe 3d band center suggests a strong interaction between surface sulfur anions and H2O2 redox reaction intermediates such as OH* and OOH*, resulting in easy sulfur oxidation. For pentlandite, the lower S 3p band center than its metal d band centers suggests a weak interaction between the sulfur anions and the H2O2 redox reaction intermediates, protecting sulfur from oxidation and rendering high catalysis effects to active metallic centers.

Copper Chalcogenide-Copper Tetrahedrite Composites-A New Concept for Stable Thermoelectric Materials Based on the Chalcogenide System.

For the first time, an alternative way of improving the stability of Cu-based thermoelectric materials is proposed, with the investigation of two different copper chalcogenide–copper tetrahedrite composites, rich in sulfur and selenium anions, respectively. Based on the preliminary DFT results, which indicate the instability of Sb-doped copper chalcogenide, the Cu1.97S–Cu12Sb4S13 and Cu2−xSe–Cu3SbSe3 composites are obtained using melt-solidification techniques, with the tetrahedrite phase concentration varying from 1 to 10 wt.%. Room temperature structural analysis (XRD, SEM) indicates the two-phase structure of the materials, with ternary phase precipitates embed within the copper chalcogenide matrix. The proposed solution allows for successful blocking of excessive Cu migration, with stable electrical conductivity and Seebeck coefficient values over subsequent thermal cycles. The materials exhibit a p-type, semimetallic character with high stability, represented by a near-constant power factor (PF)—temperature dependences between individual cycles. Finally, the thermoelectric figure-of-merit ZT parameter reaches about 0.26 (623 K) for the Cu1.97S–Cu12Sb4S13 system, in which case increasing content of tetrahedrite is a beneficial effect, and about 0.44 (623 K) for the Cu2−xSe–Cu3SbSe3 system, where increasing the content of Cu3SbSe3 negatively influences the thermoelectric performance.

Superficial state regulation in double-anion-coupled Ni nanostructure for efficient hydrogen evolution reaction

Because nickel-sulfide based electrode materials are regarded as appealing hydrogen evolution reaction (HER) electrocatalysts, various strategies have been designed to enhance their HER activity. Herein, we adopt a simple electrodeposition method to synthesize amorphous nickel sulfide electrocatalysts. Through altering the added amounts of electroplating bath consisting of NiCl2 and thiourea (TU), the HER electrocatalytic activity in alkaline electrolyte of these nickel sulfides can be optimized, and it exhibits a low overpotential of 130 mV at a current density of −10 mA cm−2, a small Tafel slope of 91 mV dec−1, and high electrochemical stability. The experimental analysis and density functional theory calculations suggest that the excellent electrochemical activity is ascribed to the coordination regulation of Ni nanostructures decorated with sulfur and oxygen anions. These findings demonstrate a simple and effective method to explore high efficiency electrocatalysts to HER.

Tuned single atom coordination structures mediated by polarization force and sulfur anions for photovoltaics

Impeding high temperature sintering is challengeable for synthesis of carbon-supported single-atom catalysts (C-SACs), which requires high-cost precursor and strictly-controlled procedures. Herein, by virtue of the ultrastrong polarity of salt melts, sintering of metal atoms is effectively suppressed. Meanwhile, doping with inorganic sulfur anions not only produces sufficient anchoring sites to achieve high loading of atomically dispersed Co up to 13.85 wt.%, but also enables their electronic and geometric structures to be well tuned. When served as a cathode catalyst in dye-sensitized solar cells, the C-SAC with Co-N4-S2 moieties exhibits high activity towards the iodide reduction reaction (IRR), achieving a higher power conversion efficiency than that of conventional Pt counterpart. Density function theory (DFT) calculations revealed that the superior IRR activity was ascribed to the unique structure of Co-N4-S2 moieties with lower reaction barriers and moderate binding energy of iodine on the Co center, which was beneficial to I2 dissociation.

Emulating Solar Spectral Reflectance of Natural Leaf with Bionic Leaf Prepared from 4A Zeolite-Derived Ultramarine Green Pigment.

The emulation of the reflectance of green leaf in the solar spectral band (300–2500 nm) has garnered increasing attention from researchers. Currently, various materials have been proposed and investigated as potential bionic leaves. However, the problems such as poor weather durability, heavy metal pollution, and complex preparation technology still persist. Herein, a bionic leaf is prepared from an ultramarine green pigment as the functional material, polyvinylidene fluoride (PVDF) as the film-forming material, and LiCl as the humidizer. To prepare the ultramarine green pigment, the sulfur anion is added into the β cage of the 4A zeolite. The mechanisms and properties were discussed based on X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and spectroscopic methods. The results show that the as-fabricated bionic leaf based on the 4A zeolite-derived ultramarine green pigment was able to demonstrate a high spectral similarity coefficient of 0.91 with the green leaf. Furthermore, the spectral similarity coefficient was increased to 0.94 after being subjected to a simulated rainforest environment for 48 h, which indicated its high weather durability.

One-step bulk and surface co-modification of LiNi0.8Co0.15Al0.05O2 cathode material towards excellent long-term cyclability

In order to improve the cycling stability of nickel-rich LiNi0.8Co0.15Al0.05O2 (NCA) cathode material for lithium-ion battery applications, a sulfur-modified NCA cathode material with bulk and surface co-modification is prepared by sol−gel method through addition of a very small amount of lithium sulfide (Li2S) as the sulfur-containing additive, and characterized in comparison with the pristine NCA material. Physical characterizations reveal that during the calcination process, some of the introduced S2− enter the layered oxide lattice to replace oxygen, while some of the introduced S2− are oxidized into a thin layer of Li2SO4 coated on the surface of the primary nanoparticles of the layered oxide. Doping of sulfur anion in bulk phase obviously reduces the content of Ni2+ and the degree of cation mixing. The electrochemical results demonstrate that the co-modified material has excellent long-term cycling stability and obviously improved storage stability. For example, when it is repeatedly cycled at 1C rate for 1100 cycles, its specific capacity is decreased from 145.0 to 102.1 mAh g−1, with capacity retention of 70.4%. The significantly improved cyclability is attributed to the enhanced structural stability owing to the reduced cation mixing and the improved electrode/electrolyte interfacial stability due to the surface modification.

Synthetic and mechanistic aspects of anionic polymerization of methyl methacrylate using tetrabutyl ammonium thioimidate

AbstractThe tetrabutylammonium salts of ionic organo‐initiator containing N,N'‐diisopropylthiourea (TUA‐1) or N,N'‐diethylthiourea (TUA‐2) serve as inexpensive initiators for the anionic polymerization of methyl methacrylate (MMA) at room temperature. The molecular weights of obtained polymers are in the range of 1500–22,700 g mol−1 and the molecular weight distributions are fairly broad (Đ = 1.9–2.5) in optimized cases. The molar ratio of monomer to initiator can be achieved up to 800. Side‐reactions, for example, backbiting, transfer reactions result in the polymerization being a non‐living manner, thus leading to broad molecular weight distributions of the resulting polymers. The effects of counterion nature were also studied from the polymerization of MMA using TUA‐1 anion with sodium or potassium salts as counterions under identical conditions. Detailed investigation indicates that the polymerization proceeds via a sulfur anion initiated repeated 1,4‐Machael addition. In general, thioimidate initiators induced MMA polymerization feature certain induction periods, which is ascribed to slow addition thioimidate to CC double bond of MMA as a result of low initiator efficiency.

Monolayer MoS2/WO3 Heterostructures with Sulfur Anion Reservoirs as Electronic Synapses for Neuromorphic Computing

Memristive devices based on two-dimensional (2D) semiconducting materials have emerged as highly promising neuromorphic devices due to their intrinsic atomic body and unique properties. However, th...