微波辅助裂解离子液体制备硫氮共掺杂多孔碳材料

Sulfur and nitrogen co-doped porous carbon (SNDPC) was successfully synthesized using one-step microwave-assisted pyrolysis of ionic liquid. The structure and morphology of the pyrolysis products were characterized by Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), electron microscopy, and X-ray photoelectron spectroscopy (XPS). The pyrolysis mechanism of the ionic liquid 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide (EMImNTf₂) under microwave irradiation was discussed. Microwave irradiation was found to accelerate the pyrolysis of EMImNTf₂. The cation of EMImNTf₂ works as the precursor of the carbon backbone of the porous carbon, while the anion acts as sulfur source and porosity-directing regulator. The SNDPC was obtained at 320 ℃ and exhibited graphitic structure with numerous surface defects. The atomic percentages of N and S in SNDPC were 12.84% and 1.07%, respectively. The N atoms mainly substitute the C sites in the graphitic carbon matrix, whereas the S atoms mainly bond to the ledges and defects of the carbon matrix.     

硫粉为硫源,多元醇辅助合成硫化钼纳米片

MoS₂ nanosheets are prepared with sulfur powder and Na₂MoO₄ by a one-pot two-phase method at 170-200 ℃ for 8 h. In addition, a three-step growth mechanism based on the aggregation and coalescence model is proposed. The reassembly of sulfur powder ensures the transformation from sulfur powder to H₂S to reduce Na₂MoO₄ and plays a key role in the successful preparation of MoS₂ nanosheets. The as-prepared MoS₂ nanosheets are rich in unsaturated sulfur atoms, probably resulting from the dislocation cores of the MoS₂ nanosheets, which have been found to be beneficial for hydrogen evolution reaction catalysis. The method and growth mechanism adopted in this study may be applied to other transition metal dichalogenides for similar structures. The facile and green method provides an alternative for the preparation of MoS₂ nanosheets.     

O3 and SO2 sensing concept on extended surface of B12N12 nanocages modified by Nickel decoration: A comprehensive DFT study

Adsorption of SO₂ and O₃ molecules on pristine boron nitride (B₁₂N₁₂) and Ni-decorated B₁₂N₁₂ nano-cages has been systemically investigated through density functional theory (DFT) methods. Adsorption energies (thermodynamics), bond distances, charge analysis, dipole moments, orbital analysis and density of states are calculated by van der Waals DFT method (MPW1PW91) functional. The adsorption energies of O₃ and SO₂ on pristine B₁₂N₁₂ are about −143.8 and −14.0 kJ mol⁻¹, respectively. The interaction energies of O₃ and SO₂ with pristine B₁₂N₁₂ are indicative of chemisorption and physisorption, respectively. Ni-decorated B₁₂N₁₂ (Ni@BN) enhances adsorption of both O₃ and SO₂ species. The interaction energies for adsorption of SO₂ are about −166 and −277 kJ mol⁻¹ whereas the corresponding energies for O₃ are −362 and −396 kJ mol⁻¹ for configuration A and B, respectively. These observations show that functionalized B₁₂N₁₂ are highly sensitive toward SO₂ and O₃ molecules.     

Comparative study on the reactivity of propargyl and alkynyl sulfides in palladium-catalyzed domino reactions

Three types of sulfides bearing a propargyl or an alkynyl moiety have been studied in cyclocarbopalladation/cross-coupling domino palladium-catalyzed sequences. The reactivity of different types of sulfured starting materials has been compared as well as the difference in behavior of these compounds depending on the type of cross coupling ending the domino sequence. It appeared that these cascades were constantly more efficient on the propargyl benzyl thioether. In addition, it has been demonstrated that domino sequences ending with Stille, Suzuki–Miyaura, or Mizoroki–Heck lead efficiently and selectively to the desired cyclized products. Notably, when the introduction of an alkyne is targeted at the end of the cascade, it appeared that the Sonogashira coupling leads every time to the desired cyclic product in the mixture with the product resulting from the direct coupling between the aryl moiety of the substrate and the alkyne used as partner. Finishing the domino sequence with a Stille coupling instead of a Sonogashira one allowed improving significantly the ratio of the mixture in favor of the desired cyclized compound.     

Determination of trace sulfur in biodiesel and diesel standard reference materials by isotope dilution sector field inductively coupled plasma mass spectrometry

A method is described for quantification of sulfur at low concentrations on the order of mg kg⁻¹ in biodiesel and diesel fuels using isotope dilution and sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). Closed vessel microwave-assisted digestion was employed using a diluted nitric acid and hydrogen peroxide decomposition medium to reduce sample dilution volumes. Medium resolution mode was employed to eliminate isobaric interferences at ³²S and ³⁴S related to polyatomic phosphorus and oxygen species, and sulfur hydride species. The method outlined yielded respective limits of detection (LOD) and limits of quantification (LOQ) of 0.7 mg kg⁻¹ S and 2.5 mg kg⁻¹ S (in the sample). The LOD was constrained by instrument background counts at ³²S but was sufficient to facilitate value assignment of total S mass fraction in NIST SRM 2723b Sulfur in Diesel Fuel Oil at 9.06 ± 0.13 mg kg⁻¹. No statistically significant difference at a 95% confidence level was observed between the measured and certified values for certified reference materials NIST SRM 2773 B100 Biodiesel (Animal-Based), CENAM DRM 272b and NIST SRM 2723a Sulfur in Diesel Fuel Oil, validating method accuracy.     

Enantioselective Sulfur‐Michael Addition of Thioacetic Acid to Nitroalkenes Catalyzed by Bifunctional Amine‐Thiourea Catalysts

An enantioselective Michael addition of thioacetic acid (AcSH) to nitroalkenes, catalyzed by a leucine‐derived bifunctional amine? thiourea, was developed with high yields and moderate enantioselectivities. The thiourea‐ammonium salt formed in the reaction is identified as the active catalyst, and the multiple H‐bonding system is responsible for the stereocontrol. The resulting thioester products are useful intermediates for the synthesis of enantiomerically enriched S‐containing compounds.     

硅芯硅棒自动清洗设备的研制

通过分析硅芯硅棒清洗方式的现状,提出其自动清洗设备研制的必要,介绍了全自动硅芯硅棒清洗机的技术参数和工艺流程,详细分析了设备的结构设计,包括工艺清洗系统、传动系统、电气控制系统、排风系统、管路系统和设备主体等。     

Integrated analytical methodologies for the study of corrosion processes in archaeological bronzes

The investigations on structure and micro-chemical composition of archaeological metal alloys are needed in archaeometry. The aim of this study is devoted both to acquire information about their provenance and production technology, and to improve our understanding about the corrosion processes. In this paper we present the study of the corrosion phenomena of bronze samples, laboratory-made according to binary, ternary and quaternary alloys typical of Roman archaeometallurgical production through an integrated methodology based on the use of non or micro invasive physical techniques. Among the analysed samples, two were artificially aged through burial in the archaeological site of Tharros, along the west coast of Sardinia (Italy). The corrosion products, typical of the bronzes in archaeological sites near the sea, have been characterized by non invasive and micro-destructive measurements. In particular, the corrosion patinas were examined through optical microscopy, scanning electron microscopy and microanalysis, X-ray fluorescence and laser ablation spectroscopy. The use of integrated technologies allowed us to determine both the elemental composition and surface morphology of the patina, highlighting the correlation between patina nature and chemical composition of the burial context. Moreover, data obtained by the laser-induced breakdown spectroscopy along the depth profile on the samples, have yielded information about the stratigraphic layers of corrosion products and their growth. Finally, the depth profiles allowed us to verify both the chemical elements constituting the patina, the metal ions constituting the alloy and the occurrence of migration phenomena from bulk to the surface.     

dl‐Aspartic Acid‐Mediated Hydrothermal Synthesis of β‐ZnS Microspheres and Their Optical Properties

ZnS hollow microspheres were synthesized by a dl ‐aspartic acid mediated hydrothermal route. dl ‐aspartic acid plays an important role as crystal growth soft template, which regulates the release of Zn²⁺ ions for the formation of ZnS hollow spheres. The formation of these hollow spheres was mainly attributed to an Ostwald ripening process. The products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), electron diffraction (ED), UV/Vis spectroscopy (UV), and photoluminescence (PL). The shells of the microspheres were composed of ZnS quantum dots (QDs) with the average size of 2.31 nm. The average microspheres diameter is 0.5–3.5 μm. The shell thickness of the hollow sphere is ≈?300 nm. The optical bandgap energy increased significantly compared to the bulk ZnS material due to the strong quantum confinement effect. Two strong emissions at ≈?425 nm and ≈?472 nm in the photoluminescence (PL) spectrum of ZnS hollow microspheres indicate strong quantum confinement because of the presence of QDs.