Global Reactivity of Heterostructure Armchair BC2N‐(4,4) Nanotubes: A Density Functional Theory Investigation

Electronic structures of three types of heterostructure armchair BC₂N nanotube besides armchair (4,4)CNT and (4,4)BNNT were calculated by the B3LYP method of density functional theory. The reactivities of nanotubes were discussed by means of obtained vertical ionization potentials and electron affinity potentials. The corresponding electrophilicity values are well correlated with those obtained from the HOMO and LUMO energies of the nanotubes. The good linear correlation found between ω(I,A) and ω(H,L) allows to confirm the use of the easily available B3LYP/6‐31G(d) HOMO and LUMO energies to obtain reasonable values of the global electrophilicity index of nanotubes at a lower computational cost. © 2013 Wiley Periodicals, Inc. Heteroatom Chem 24:168–173, 2013; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.21078     

Synthesis of Tungsten Oxide Nanorods by the Controlling Precipitation Reaction: Application for Hydrogen Evolution Reaction on a WO3 Nanorods/Carbon Nanotubes Composite Film Modified Electrode

Tungsten trioxide nanorods (WO₃) were prepared by controlling the precipitation reaction of sodium tungstate dehydrates solution and hydrothermal process. The synthesized tungsten trioxide nanorods have been characterized by X‐ray diffraction (XRD), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), cyclic voltammetry (CV) and linear sweep voltammetry (LSV). Electrochemical activity for hydrogen evolution reaction (HER) on WO₃ nanorods / carbon nanotube (WO₃/CNT) composite electrocatalyst was first studied in acid solution (0.1 M H₂SO₄) at room temperature. The overall experimental results revealed that the electrocatalytic activity for HER on WO₃/CNT is two order magnitude higher than those obtained with WO₃ nanorods and is four times than in the case of commercial WO₃ in 0.1 M H₂SO₄. On the other hand, the kinetic reaction mechanisms were discussed on WO₃/CNT electrocatalysts in acid solution for HER. However, the rate‐determining step carries through Tafel reaction on commercial WO₃, CNT, WO₃ nanorods and WO₃/CNT electrocatalysts in acidic solution was introduced.     

New mono- and binuclear Pd(II) complexes containing 1,2,4-triazole moieties

The reaction of AMTT (AMTT = 4-amino-3-methyl-1,2,4-triazol-5-thione, HL1) with palladium(II) chloride and triphenylphosphane as a co-ligand in acetonitrile afforded the mononuclear Pd^II-complex [(PPh₃)Pd(HL1)Cl]Cl·2CH₃CN (1). The complex [(PPh₃)Pd(HL1)I]Cl·1/2H₂O (2) was prepared via halogen exchange between 1 and sodium iodide in methanol/acetonitrile. The first binuclear palladium(II) complex containing singly deprotonated HL1, [(PPh₃)₂ClPd(L1)Pd(PPh₃)Cl]Cl·1/3H₂O·CH₃OH (3), was prepared by the reaction of HL1 with palladium(II) chloride and triphenylphosphane in the presence of sodium acetate in methanol.     

Origin of dark-channel X-ray fluorescence from transition-metal ions in water

The nonradiative dark channels in the L-edge fluorescence spectra from transition-metal aqueous solution identify the ultrafast charge-transfer processes playing an important role in many biological and chemical systems. Yet, the exact origin of such spectral dips with respect to the X-ray transmission spectrum has remained unclear. In the present study we explore the nature of the underlying decay mechanism of 2p core-excited Co(2+) in water by probing the nonradiative Auger-type electron emission channel using photoelectron spectroscopy from a liquid microjet. Our measurements demonstrate unequivocally that metal-to-water charge transfer quenches fluorescence and will inevitably lead to a dip in the total-fluorescence-yield X-ray absorption spectrum. This is directly revealed from the resonant enhancement of valence signal intensity arising from the interference of two identical final states created by a direct and Auger-electron emission, respectively.     

In situ-generated N-thiocyanatosuccinimide (NTS) as a highly efficient reagent for the one-pot thiocyanation or isothiocyanation of alcohols

The first application of in situ-generated N-thiocyanatosuccinimide (NTS) for the thiocyanation of alcohols is described. This method can be easily applied for the facile conversion of primary, secondary and tertiary alcohols into the corresponding alkyl thiocyanates or alkyl isothiocyanates in good to excellent yields.     

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones

A multi-component synthesis of 3-aryl-1-(arylmethylideneamino)pyrrolidine-2,5-diones is described. A mixture of N-isocyaniminotriphenylphosphorane, an aldehyde, and Meldrum's acid undergo a 1:2:1 addition reaction under mild conditions to afford the title compounds in good to excellent yields.     

Synthesis of functionalized 5H-spiro[furan-2,2′-indene]-1′,3′,5-triones from primary amines, acetylenic esters and ninhydrin

An effective route to functionalized 5H-spiro[furan-2,2??-indene]-1??,3??,5-triones is described via tandem reaction of primary amines, acetylenic esters and ninhydrin.     

Enhancement of mechanical and thermal properties of oil palm empty fruit bunch fiber poly(butylene adipate-co-terephtalate) biocomposites by matrix esterification using succinic anhydride

In this work, the oil palm empty fruit bunch (EFB) fiber was used as a source of lignocellulosic filler to fabricate a novel type of cost effective biodegradable composite, based on the aliphatic aromatic co-polyester poly(butylene adipate-co-terephtalate) PBAT (Ecoflex?), as a fully biodegradable thermoplastic polymer matrix. The aim of this research was to improve the new biocomposites' performance by chemical modification using succinic anhydride (SAH) as a coupling agent in the presence and absence of dicumyl peroxide (DCP) and benzoyl peroxide (BPO) as initiators. For the composite preparation, several blends were prepared with varying ratios of filler and matrix using the melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 (wt %) and characterized. The effects of fiber loading and coupling agent loading on the thermal properties of biodegradable polymer composites were evaluated using thermal gravimetric analysis (TGA). Scanning Electron Microscopy (SEM) was used for morphological studies. The chemical structure of the new biocomposites was also analyzed using the Fourier Transform Infrared (FTIR) spectroscopy technique. The PBAT biocomposite reinforced with 40 (wt %) of EFB fiber showed the best mechanical properties compared to the other PBAT/EFB fiber biocomposites. Biocomposite treatment with 4 (wt %) succinic anhydride (SAH) and 1 (wt %) dicumyl peroxide (DCP) improved both tensile and flexural strength as well as tensile and flexural modulus. The FTIR analyses proved the mechanical test results by presenting the evidence of successful esterification using SAH/DCP in the biocomposites' spectra. The SEM micrograph of the tensile fractured surfaces showed the improvement of fiber-matrix adhesion after using SAH. The TGA results showed that chemical modification using SAH/DCP improved the thermal stability of the PBAT/EFB biocomposite.     

CO<Subscript>2</Subscript>/CH<Subscript>4</Subscript> separation using mixed matrix membrane-based polyurethane incorporated with ZIF-8 nanoparticles

This study presents using zeolitic imidazolate framework-8 (ZIF-8) as porous filler dispersed phase and polyurethane (PU) as continuous phase to synthesis mixed matrix membranes (MMMs). ZIF-8 nanoparticles were synthesized using centrifugal method. The synthesized nanoparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). In order to investigate the effect of ZIF-8 loading on the membrane performance in CO₂/CH₄ separation, different membranes were prepared with various amounts of ZIF-8 (0–50 wt%). Membranes properties were characterized by SEM, XRD, TGA, differential scanning calorimetry (DSC), and tensile analysis. SEM images exhibit that the ZIF-8 is dispersed uniformly in cross section of membrane. Thermal stability of membranes increases with addition of the ZIF-8 nanoparticles into the polymer matrix. Both tensile strength and strain at break in the MMMs increase with the ZIF-8 loading. To study the effect of feed pressure on CO₂ and CH₄ transport properties of the membranes, single gas experiments were conducted at 4, 8, and 12 bar feed pressures. Incorporation of ZIF-8 crystals into continuous PU matrix resulted in high-performance gas separation membranes. Increasing feed pressure, significantly, increased separation performances in all the membranes.     

Tyrosine sensing on phthalic anhydride functionalized chitosan and carbon nanotube film coated glassy carbon electrode

Phthaloylchitosan (PHCS) has been synthesized by a simple and low-cost method using chitosan and phthalic anhydride as organic precursors by microwave irradiation. Techniques of nuclear magnetic resonance (NMR), FT-IR spectroscopy and transmission electron microscope (TEM) were used to characterize the structure and properties of the Phthaloylchitosan. Moreover, glassy carbon electrode modified with Phthaloylchitosan and carbon nanotube (PHCS–CNT/GCE) was prepared by casting of the PHCS–CNT solution on GCE. The electrochemical behavior of PHCS–CNT/GCE was investigated and compared with the electrochemical behavior of Phthaloylchitosan modified GC (PHCS/GC), carbon nanotube modified GC (CNT/GC) and unmodified GC using cyclic voltammetry (CV). The Phthaloylchitosan film is electrochemically inactive; similar background charging currents are observed at bare GC. Electrochemical parameters, including apparent diffusion coefficient for the Fe(CN)₆^3-/4- redox probe at PHCS–CNT/GCE is comparable to values reported for GCE, CNT/GCE and PHCS/GCE. The PHCS–CNT/GCE sensor responded linearly to tyrosine (Tyr) in the concentration of 1.0 × 10^–6 to 8.0 × 10^–4 M with detection limit of 3.0 × 10^–7 M at 3σ using amperometry. In addition, the PHCS–CNT/GCE displayed good reproducibility, high sensitivity and good selectivity towards the determination of Tyr, making it suitable for the determination of Tyr in clinical and medicine.