The response of selected isomers of B80 buckyball toward NH3 adsorption: a density functional theory investigation

Density functional theory calculations at the B3LYP/6-31G(d) and B3LYP/6-31+G(d) levels were carried out for the adsorption of NH₃ on three symmetric isomers of B₈₀ {C ₁, T _h, I _h}. To investigate the binding features of B₈₀ isomers with NH₃, different studies including the structural and electronic parameters, the ¹⁴N electric field gradient tensors and the atoms in molecules (AIM) properties were considered. The calculated parameters by these investigations can be used as powerful tools to find out some of the unknown aspects of electronic structures of the boron buckyball and its isomers. According to previous studies, boron buckyball as an amphoteric and a hard molecule has two distinct reactive sites defined as cap and frame which act as an acid and a base, respectively. Regarding the obtained results in this study, all the isomers had the same exposure when NH₃ molecule reacted with the external wall of B₈₀. For instance, the stability of N–B bond in the cap site was significantly more than the stability of N–B bond in the frame. Moreover, the adsorption of NH₃ on frame site showed a considerable reduction in HOMO–LUMO energy gap. According to AIM theory, an electrostatic nature was observed for N–B interaction. Concerning the selected isomers of buckyball, the capability of the NH₃–B₈₀ complexes to localize electron at the N–B bond critical points depend on the reaction sites significantly. In general, ¹⁴N nuclear quadruple coupling constants and asymmetry parameter reveal a remarkable effect of NH₃ adsorption on electronic structure of the B₈₀.     

Theoretical prediction of proton and electron affinities,gas phase basicities,and ionization energies of sulfinamides

Structural Chemistry - Sulfinamides, as an asymmetric synthesizer, especially in drug synthesis, play critical roles in organic chemistry. In this study, the gas phase ion energetics data including...     

A simple graphical approach to predict local residue conformation using NMR chemical shifts and density functional theory

The dependency of amino acid chemical shifts on φ and ψ torsion angle is, independently, studied using a five‐residue fragment of ubiquitin and ONIOM(DFT:HF) approach. The variation of absolute deviation of ¹³C^α chemical shifts relative to φ dihedral angle is specifically dependent on secondary structure of protein not on amino acid type and fragment sequence. This dependency is observed neither on any of ¹³C^β, and ¹H^α chemical shifts nor on the variation of absolute deviation of ¹³C^α chemical shifts relative to ψ dihedral angle. The ¹³C^α absolute deviation chemical shifts (ADCC) plots are found as a suitable and simple tool to predict secondary structure of protein with no requirement of highly accurate calculations, priori knowledge of protein structure and structural refinement. Comparison of Full‐DFT and ONIOM(DFT:HF) approaches illustrates that the trend of ¹³C^α ADCC plots are independent of computational method but not of basis set valence shell type. © 2016 Wiley Periodicals, Inc.     

Simultaneous Determination of Nickel and Cadmium by Adsorptive Stripping Voltammetry

A sensitive and fast method for the simultaneous determination of trace amounts of nickel and cadmium in real samples has been described using differential pulse adsorptive stripping voltammetry (DPASV) by adsorptive accumulation of the N,N′‐bis(salicylaldehydo)4‐carboxyphenylenediamine (BSCPDA)–complex on the hanging mercury drop electrode (HMDE). As supporting electrolyte 0.02 mol L^?1 ammonia buffers containing ligand has been used. Optimal analytical conditions were found to be: BSCPDA concentration of 42 μM, pH 9.6 and adsorption potential at ?50 mV versus Ag/AgCl. With an accumulation time of 20 s, the peaks current are proportional to the concentration of nickel and cadmium over the 1–180, and 0.5–200 ng mL^?1 with detection limits of 0.06 and 0.03 ng mL^?1 respectively. The sensitivity of method for determination of nickel and cadmium were obtained 0.54 and 0.98 nA mL ng^?1, respectively. The procedure was applied to simultaneous determination of nickel and cadmium in some real and synthetic artificial samples with satisfactory results.     

Preparation and study of bi-supported Ziegler-Natta catalyst with nano graphene oxide and magnesium ethoxide supports for polymerization of polyethylene

In this study, we have reported the preparation of bi-supported Ziegler-Natta catalysts using magnesium ethoxide and graphene oxide as support. The polymerization process was carried out in slurry phase using triisobutylaluminum as a co-catalyst.The XRD analysis of TiCl₄/graphene oxide/Mg(OEt)₂ catalyst demonstrated that the space between the layers of graphene oxide had increased to 0.2 nm.The catalyst was characterized by XPS, BET, BJH, SEM, and TGA. The catalyst activity was studied for various Al/Ti molar ratios, and the catalyst activity was optimum at Al/Ti molar ratio of 315.     

(Triazinediyl)bis sulfamic acid-functionalized silica-coated magnetite nanoparticles: Preparation,characterization and application as an efficient catalyst for synthesis of mono-, bis-, tris- and spiro-perimidines

(Triazinediyl)bis sulfamic acid-functionalized silica-coated magnetite nanoparticles have been prepared and applicated as an efficient catalyst for synthesis of mono-, bis-, tris- and spiro-perimidines. The desired products have been synthesized in high purity and good yields. The workup procedure of reaction is simple. The catalyst was easily separated from the reaction mixture with the assistance of an external magnetic field and reused for several runs without deterioration in catalytic activity. The core/shell nanoparticles were characterized by transmission electron microscopy, scanning electron microscope, powder X-ray diffraction, energy dispersive spectrometer, Fourier transform infrared spectroscopy and vibrating sample magnetometer.     

Magnetic nanoparticles grafted <Emphasis Type="SmallCaps">l</Emphasis>-carnosine dipeptide: remarkable catalytic activity in water at room temperature

Modification of magnetic nanoparticle surface with l-carnosine dipeptide was developed using a simple chemical process. In order to synthesize this catalyst system, first, magnetic nanoparticles were modified with vinyl groups using trimethoxy(vinyl)silane. Next, the vinyl groups were oxidized with H₂O₂ to give the epoxy-functionalized MNPs. Reaction of l-carnosine with epoxide rings via amino group resulted in the functionalization of MNPs surface with l-carnosine, covalently. To explore high catalytic activity of this material, l-carnosine grafted on magnetic nanoparticles (Fe₃O₄@SiO₂@LCar; l-CarMNP) was used as a highly efficient heterogeneous nano-organocatalyst in a multicomponent reaction in aqueous medium at room temperature. It was reusable at least for eight times without a significant decrease in its catalytic activity. The catalytic activity of l-CarMNP was compared with other magnetic nano-organocatalyst, and results demonstrate that l-CarMNP has high catalytic activity related to others tested.     

Effects of nano graphene oxide as support on the product properties and performance of Ziegler–Natta catalyst in production of UHMWPE

The synthesis of mono‐ and bi‐supported Ziegler–Natta catalysts using magnesium etoxide Mg(OEt)₂ and graphene oxide (GO) as catalyst support for production of Ultra High Molecular Weight Polyethylene (UHMWPE) is reported in this investigation. Nano‐graphene oxide was prepared by the modified Hummer's method and its structure was analyzed by XRD and FTIR indicating the presence of hydroxyl groups on graphene oxide and the formation of an exfoliated structure. The activity of TiCl₄/Mg(OEt)₂, TiCl₄/Mg(OEt)₂‐GO, and TiCl₄/GO catalysts in terms of grams of PE produced per mmol of Ti per hour was experimentally obtained for catalysts with different ratios of co‐catalyst (triisobutylaluminium) to TiCl₄. For all three series of catalysts, the activity curve showed an optimum point at a specific Al/Ti molar ratio. Catalyst activity was highest for TiCl₄/Mg(OEt)₂ and lowest for TiCl₄/GO. The characterization of UHMWPE products indicated that the viscosity average molecular weight (Mv) was highest for the polymer produced by TiCl₄/Mg(OEt)₂ and lowest for the polymer produced by TiCl₄/GO. Furthermore, thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and mechanical tensile testing were conducted on the prepared polymers indicating that the polymer produced by TiCl₄/GO had the highest thermal and mechanical properties, while these properties were at their minimum for polymers produced by TiCl₄/Mg(OEt)₂. Copyright © 2015 John Wiley & Sons, Ltd.     

High-Efficiency Perovskite Solar Cells Enabled by Anatase TiO2 Nanopyramid Arrays with an Oriented Electric Field

One-dimensional (1D) nanostructured oxides are proposed as excellent electron transport materials (ETMs) for perovskite solar cells (PSCs); however, experimental evidence is lacking. A facile hydrothermal approach was employed to grow highly oriented anatase TiO₂ nanopyramid arrays and demonstrate their application in PSCs. The oriented TiO₂ nanopyramid arrays afford sufficient contact area for electron extraction and increase light transmission. Moreover, the nanopyramid array/perovskite system exhibits an oriented electric field that can increase charge separation and accelerate charge transport, thereby suppressing charge recombination. The anatase TiO₂ nanopyramid array-based PSCs deliver a champion power conversion efficiency of approximately 22.5 %, which is the highest power conversion efficiency reported to date for PSCs consisting of 1D ETMs. This work demonstrates that the rational design of 1D ETMs can achieve PSCs that perform as well as typical mesoscopic and planar PSCs.