Volume 231, Issue 9

We computationally investigated the structure and bonding situation of bis-gold chloride complexes, (AuCl) 2 , containing N-heterocyclic carbenes and analogues, called tetrylenes [(AuCl) 2 -NHE Me ] (Au2-NHE) with E=C to Pb, using density functional theory (DFT) at the BP86 level with the basis sets def2-SVP, def2-TZVPP, and TZ2P+. The nature of the (AuCl) 2 -NHE Me bond in the Au2-NHE complexes was analyzed using charge and energy decomposition methods. The calculated equilibrium structures of the Au2-NHE complexes showed that the tetrylene ligands, NHE Me (E=C to Ge), are bonded in a head-on fashion to the bis-gold chloride fragment, (AuCl) 2 , and that the structure of Au2-NHSn contains a distorted head-on NHSn ligand, and the NHPb ligand is bonded in a side-on mode to the bis-gold chloride fragment, (AuCl) 2 . The theoretical calculation of bond dissociation energy (BDE) suggests that the bis-gold chloride-NHE Me bond strength increases from Au2-NHC to Au2-NHSi and then significantly decreases from Au2-NHSi to Au2-NHSn, and the strongest bond is exhibited for Au2-NHPb. The EDA-NOCV results and NOCV pairs indicate that the NHE Me ligand in the Au2-NHE complexes is a strong σ-donor and a weak π-acceptor, as well as a very weak π-donor (AuCl) 2 ←{NHE Me }. The trend in the Au-E bond strength resulted from the increase in (AuCl) 2 ←NHE Me donation. The results of this study may establish an interesting class of compounds worthy of further study.

In this work the kinetics of the TiCl 4 ⇌ TiCl 3 + Cl reaction is studied theoretically. A variable-reaction coordinate transition-state theory (VRC-TST) is used to calculate the high-pressure limit rate coefficients. The interaction energy surface for the VRC-TST step is sampled directly at the CASPT2(6e,4o)/cc-pVDZ level of theory including an approximate treatment of the spin-orbit coupling. The pressure-dependence of the reaction in an argon bath gas is explored using the master equation in conjunction with the optimised VRC-TST transition-state number of states. The collisional energy transfer parameters for the TiCl 4 –Ar system are estimated via a “one-dimensional minimisation” method and classical trajectories. The Ti–Cl bond dissociation energy is computed using a complete basis set extrapolation technique with cc-pVQZ and cc-pV5Z basis sets. Good quantitative agreement between the estimated rate constants and available literature data is observed. However, the fall-off behaviour of the model results is not seen in the current experimental data. Sensitivity analysis shows that the fall-off effect is insensitive to the choice of model parameters and methods. More experimental work and development of higher-level theoretical methods are needed to further investigate this discrepancy.

The ultrasonic velocity, density and viscosity values of liquid mixture of aqueous polyvinyl pyrrolidone with aqueous zinc sulphate, manganese sulphate, zinc chloride and manganese chloride have been studied at 303.15 K, 308.15 K and 313.15 K. Relative association, surface tension, modified surface tension, adiabatic compressibility, acoustic impedance, intermolecular free length relaxation time and the nonlinearity parameter have been determined for various compositions. The variation observed in the results suggest that the presence of strong polymer-solvent interactions.

N-doped carbon xerogel (N-CX) is synthesized and used for adsorption removal of microcystin-LR (MC-LR) from aqueous solution. Characterizations including N 2 physisorption, TEM and XPS indicate that N atoms are doped into the N-CX and the material has porous structure. Adsorption tests show that the N-CX is efficient for MC-LR adsorption, with adsorption capacity of 1916.2 μg g −1 , which is higher than that of commercial activated carbon (1034.13 μg g −1 ) and graphene oxide (1700 μg g −1 ). The material is recyclable after desorption treatment by washing with NaOH solution, with no loss of uptake within five cycles. Effect of initial MC-LR concentration, temperature, and pH on the adsorption behavior is further investigated, to realize the adsorption process, showing that the adsorption process obeys the Langmuir isotherm and pseudo-second-order equation. Thermodynamical calculation indicates that the adsorption of MC-LR onto N-CX is a spontaneous and exothermic process, with the Gibbs free energy (ΔG) of −16.1 kJ mol −1 and enthalpy (ΔH) of −18.45 kJ mol −1 .

Diatomite platelets were employed to synthesize different polystyrene/diatomite composites. Mesoporous diatomite platelets were used for in situ polymerization of styrene by activators generated by electron transfer for atom transfer radical polymerization to synthesize tailor-made polystyrene nanocomposites. FTIR spectroscopy and thermogravimetric analysis were employed for evaluating some inherent properties of the pristine mesoporous diatomite platelets. Nitrogen adsorption/desorption isotherm is applied to examine surface area and structural characteristics of the diatomite platelets. Evaluation of pore size distribution and morphological studies were also performed by scanning and transmission electron microscopy. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Addition of 3 wt% pristine mesoporous diatomite leads to increase of conversion from 78 to 95%. Molecular weight of polystyrene chains increases from 15800 to 20000 g·mol −1 by addition of 3 wt% pristine mesoporous diatomite; however, polydispersity index values increases from 1.14 to 1.38. Increasing thermal stability of the nanocomposites is demonstrated by thermogravimetric analysis. Differential scanning calorimetry shows an increase in glass transition temperature from 93.8 to 97.4°C by adding 3 wt% of mesoporous diatomite platelets.

We herein report the synthesis of zinc oxide and evaluation of its catalytic performance for degradation of Rhodamine B dye in aqueous medium. Sodium hydroxide and zinc acetate dihydrate were used as precursor materials for synthesis of zinc oxide catalyst. X-ray difractometry, Fourier transform infer red spectroscopy, scanning electron microscopy, thermogravimetric and surface area analyses were used as characterization techniques. Catalytic performance of prepared zinc oxide was evaluated for degradation of Rhodamine B dye in aqueous medium. Catalytic degradation of dye was taking place according to Eley-Rideal mechanism which states that oxygen adsorbed at the surface of ZnO reacts with dye in fluid phase. During the reaction, reactive radicals are formed as a result of electron-hole pair formation between conduction and valence band of zinc oxide catalyst which degrade the dye into water and carbon dioxide.

The inhibiting behavior of polysorbate 80 on 6061 aluminum alloy corrosion was evaluated in 1.0 M Na 2 HPO 4 solution. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used in this study. The obtained results showed that the inhibition efficiency increases by increasing the concentration of polysorbate 80 reaching 85.8% at 500 ppm. Good agreement was found between the results obtained from the two techniques used. The inhibition process was found to be due to adsorption of the organic compound on the alloy surface obeying the Langmuir isotherm. Polarization curves indicate that the inhibition of polysorbate 80 has the mixed anodic–cathodic nature. EIS exhibits one capacitive loop which is attributed to the double layer charging and the charge transfer process. The inhibition efficiency of polysorbate 80 decreased by rising the temperature in the range of 303–333 K. These results confirm the physisorption of the inhibitor molecules on the metal surface. The thermodynamic functions for the dissolution and adsorption processes were calculated and discussed.

Abstract: The size effect of nanoscale silicon in both amorphous and porous silicon was investigated with micro-Raman spectroscopy. Silicon nanostructures in amorphous silicon were deposited on quartz substrates by plasma enhanced chemical vapor deposition (PECVD) with deposition powers of 15, 30 and 50 W. Micro-Raman spectra of the nanostructured silicon show the T 2g Raman active mode shifting from the 521 cm −1 crystalline Si Raman line to 494, 499 and 504 cm −1 as deposition power increased. Large Raman mode shifts, up to 27 cm −1 and broadening up to 23 cm −1 of the T 2g Raman-active mode is attributed to a phonon confinement effect. The analysis of micro-Raman scattering data is useful to understand the role of deposition condition of the silicon sample. In addition, micro-Raman scattering intensity of porous silicon prepared using various current densities such as 10, 50 and 125 mA/cm 2 has also been investigated. The effect of phonon confinement on the nanoscale porous silicon has been quantified. The relationship between Raman shift and stress on the porous silicon has been evaluated.