Polymerization of styrene with tetramethylthiuram disulfide as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy

The bulk polymerization of styrene was investigated with tetramethylthiuram disulfide (TMTD) as an initiator in the presence of 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) at 123 °C. The polymerization proceeded in a controlled/living way; that is, the polymerization rate was first‐order with respect to the monomer concentration, and the molecular weight increased linearly with conversion. The molecular weights of the polymers obtained were close to the theoretical values, and the molecular weight distributions were relatively low (weight‐average molecular weight/number‐average molecular weight = 1.1–1.3). The rate of polymerization with TMTD as an initiator was faster than that with benzoyl peroxide, and the rate was independent of the initial concentration of TMTD in the presence of TEMPO. The obtained polystyrene was functionalized with ultraviolet‐light‐sensitive ? SC(S)N(CH₃)₂ groups, which was characterized with ¹H NMR spectroscopy. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 543–551, 2005     

Mechanism of the gas-phase oxidation of carbon disulfide at elevated temperatures (the C-S-O system)

Machine modeling was used to investigate the kinetic mechanism of the gas-phase oxidation of carbon disulfide at elevated temperatures. The scheme of the process examined includes 70 elementary reactions. On the basis of the kinetic data on these reactions available in the literature the rates of the oxidation process, the concentrations of end products and intermediate particles were calculated as a function of the time under various conditions (composition, pressure, temperature). Comparison of the results obtained with the experimental data showed satisfactory agreement and also revealed some important elementary reactions.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow 117977. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 812–822, April, 1992.     

The formation of intercalation compounds of MoS2 with cations of alkali metals and alkylammonium from monolayer dispersion of molybdenum disulfide

Ion-exchange interaction of the monolayer aqueous dispersion obtained by hydration of crystalline LiMoS₂ with Li, Na, K salts and alkyiammoniiim halides is studied. Intercalation compounds of MoS₂ with hydrated inorganic cations as well as hitherto unattainable intercalation compounds of MoS₂ with alkylammonium cations are shown to be formed under these conditions. The composition and structure of these compounds are investigated.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 672–674, April, 1993.     

Ion-pair chromatography of bis (sodium-sulfopropyl) disulfide brightener in acidic copper plating baths

Quantitative analysis of the brightener component bis (sodium-sulfopropyl) disulfide (SPS) in acidic copper plating baths poses a real challenge due to the complex chemical matrix containing large amounts of Cu(II) ion and sulfuric acid together with other organic additives and additive decomposition products. We developed a new ion-pair chromatography method to analyze micro-molar amounts of SPS directly in plating bath samples without the need for sample pre-treatment. Addition of tetra-N-methylammonium cation as ion-pairing agent to a methanol-sulfuric acid-water eluent increases the retention time of the anionic SPS2- on a C18 column sufficiently to separate this compound from Cu(II) ion and additive by-products.     

花球状二硫化钒的制备及其储锂研究

采用一步水热法并添加表面活性剂聚乙二醇400制备出花球状二硫化钒,利用X射线粉末衍射仪、场发射扫描电子显微镜等方法对产物的物相和形貌进行了表征. 观测生长过程发现花球状二硫化钒由若干六边形二硫化钒纳米片堆叠穿插组成,该花球状结构使材料拥有较高的比表面积及出色的结构稳定性. 将花球状二硫化钒用于锂离子电池正极材料测试,结果表明花球状二硫化钒在电压区间为1 ~ 3 V,电流密度为200 mA·g^-1时具有出色的循环稳定性且循环50周之后容量可达450 mAh·g^-1.     

Direct visualization of structural defects in 2D semiconductors

Direct visualization of the structural defects in two-dimensional (2D) semiconductors at a large scale plays a significant role in understanding their electrical/optical/magnetic properties, but is challenging. Although traditional atomic resolution imaging techniques, such as transmission electron microscopy and scanning tunneling microscopy, can directly image the structural defects, they provide only local-scale information and require complex setups. Here, we develop a simple, non-invasive wet etching method to directly visualize the structural defects in 2D semiconductors at a large scale, including both point defects and grain boundaries. Utilizing this method, we extract successfully the defects density in several different types of monolayer molybdenum disulfide samples, providing key insights into the device functions. Furthermore, the etching method we developed is anisotropic and tunable, opening up opportunities to obtain exotic edge states on demand.     

Synthesis of the Antimicrobial S‐Linked Glycopeptide,Glycocin F

The first total synthesis of glycocin F, a uniquely diglycosylated antimicrobial peptide bearing a rare S‐linked N‐acetylglucosamine (GlcNAc) moiety in addition to an O‐linked GlcNAc, has been accomplished using a native chemical ligation strategy. The synthetic and naturally occurring peptides were compared by HPLC, mass spectrometry, NMR and CD spectroscopy, and their stability towards chymotrypsin digestion and antimicrobial activity were measured. This is the first comprehensive structural and functional comparison of a naturally occurring glycocin with an active synthetic analogue.     

Stability,Structure and Reconstruction of 1H-Edges in MoS2

Density functional studies of the edges of single-layer 1H-MoS₂ are presented. This phase presents a rich variability of edges that can influence the morphology and properties of MoS₂ nano-objects, play an important role in industrial chemical processes, and find future applications in energy storage, electronics and spintronics. The so-called Mo-100 %S edges vertical S-dimers were confirmed to be stable, however the authors also identified a family of metastable edges combining Mo atoms linked by two-electron donor symmetrical disulfide ligands and four-electron donor unsymmetrical disulfide ligands. These may be entropically favored, potentially stabilizing them at high temperatures as a “liquid edge” phase. For Mo-50 %S edges, S-bridge structures with 3× periodicity along the edge are the most stable, compatible with a Peierls’ distortion arising from the d-bands of the edge Mo atoms. An additional explanation for this periodicity is proposed through the formation of 3-center bonds.     

Thiol‐responsive micelles based on nonionic gemini surfactants with a cystine disulfide spacer

Thiol‐responsive micelles consisting of novel nonionic gemini surfactants with a cystine disulfide spacer are reported. The gemini surfactants, (C₁₈‐Cys‐mPEG)₂ and ((C₁₈)₂‐Lys‐Cys‐mPEG)₂, were synthesized from polyethylene glycol, cysteine, and stearic acid, and their structures were confirmed by ¹H NMR and gel permeation chromatography. (C₁₈‐Cys‐mPEG)₂ and ((C₁₈)₂‐Lys‐Cys‐mPEG)₂ formed micelles with average diameters of 13 and 22 nm above the critical micelle concentration of 6.5 and 4.7 µg mL^?1, respectively. The micelles of ((C₁₈)₂‐Lys‐Cys‐mPEG)₂ containing more stearoyl groups showed encapsulated more hydrophobic indomethacin (IMC) with higher entrapment efficiencies than those of (C₁₈‐Cys‐mPEG)₂. The gemini surfactant micelles exhibited an accelerated release of encapsulated IMC with the concentration of the reducing agent, glutathione (GSH), whereas they were unaffected by the presence of reduced GSH (GSSG). The 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)?2‐(4‐sulfophenyl)?2H‐tetrazolium studies revealed the noncytotoxic nature of the gemini surfactant micelles. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 582–589