A theoretical study on the interaction of [Al(H2O)6] and [Mg(H2O)6] cations with fullerene (C60), coronene and benzene π-systems

Density functional theory (DFT), Bader’s theory of atoms in molecules (AIM) and natural bond orbital (NBO) calculations have been used to understand the nature of the interaction between M(H₂O)₆ⁿ⁺ (M = Mg²⁺, Al³⁺) complexes and fullerene, coronene and benzene π-systems. The interaction energies were calculated for all the compounds and corrected for the basis set superposition error (BSSE). The results showed that the above π-systems have larger interaction energies with Al(H₂O)₆³⁺ than Mg(H₂O)₆²⁺. Also the AIM topological parameters for the bond critical points (BCPs) between the M(H₂O)₆ⁿ⁺ cations and the fullerene, coronene and benzene π-systems confirmed that {[Al(H₂O)₆]³⁺?fullerene} has a much stronger bonding interaction than the other systems. The calculated interaction energies correlate well with both the Wiberg bond indices and the global value of charge transfers from π-systems to cations evaluated through natural population analysis. The calculations suggest that the ionic potential of the central metal ion in the M(H₂O)₆ⁿ⁺ cation and the nature of π-system are two influential factors that affect the strength and the nature of the interaction.     

A two‐scale approach to electron correlation in multiconfigurational perturbation theory

We present a new approach for the calculation of dynamic electron correlation effects in large molecular systems using multiconfigurational second‐order perturbation theory (CASPT2). The method is restricted to cases where partitioning of the molecular system into an active site and an environment is meaningful. Only dynamic correlation effects derived from orbitals extending over the active site are included at the CASPT2 level of theory, whereas the correlation effects of the environment are retrieved at lower computational costs. For sufficiently large systems, the small errors introduced by this approximation are contrasted by the substantial savings in both storage and computational demands compared to the full CASPT2 calculation. Provided that static correlation effects are correctly taken into account for the whole system, the proposed scheme represent a hierarchical approach to the electron correlation problem, where two molecular scales are treated each by means of the most suitable level of theory. © 2014 Wiley Periodicals, Inc.     

Physico-chemical characterisation of chitosan/halloysite composite membranes

Chitosan membranes reinforced by halloysite nanotubes (HNTs) at concentrations from 2 to 15 (w/w%) have been prepared by solution casting to investigate the optimal physico-chemical properties for biomedical applications. Tensile test data revealed that the membranes reinforced with 5 (w/w%) HNTs yielded the highest Young's modulus (0.52 ± 0.01 GPa) and strength (81.6 ± 4.4 MPa). Electron micrographs of the fractured surfaces implicated the interplay between individual HNTs and agglomerates of HNTs in the stress transfer mechanism. Infrared spectra revealed interaction between the HNT siloxane and chitosan functional groups. Thermogravimetric results demonstrated that the thermal stability of the membranes increased with HNT concentration.     

A method for solving fuzzy goal programming problems based on MINMAX approach

Narasimhan incorporated fuzzy set theory within goal programming formulation in 1980. Since then numerous research has been carried out in this field. One of the well-known models for solving fuzzy goal programming problems was proposed by Hannan in 1981. In this paper the conventional MINMAX approach in goal programming is applied to solve fuzzy goal programming problems. It is proved that the proposed model is an extension to Hannan model that deals with unbalanced triangular linear membership functions. In addition, it is shown that the new model is equivalent to a model proposed in 1991 by Yang et al. Moreover, a weighted model of the new approach is introduced and is compared with Kim and Whang’s model presented in 1998. A numerical example is given to demonstrate the validity and strengths of the new models.     

CABC–CSA: a new chaotic hybrid algorithm for solving optimization problems

Recently a lot of methods have been presented for solving optimization problems. In this paper, we are trying to propose a new hybrid algorithm for solving these kinds of problem. The proposed algorithm is based on chaotic artificial bee colony and chaotic simulated annealing, CABC–CSA. The chaotic artificial bee colony finds new locations chaotically. Actually, the proposed algorithm provides a combination of local search accuracy of simulated annealing and the ability of global search of artificial bee colony. Furthermore, we used a different method for generating the initial population. The proposed algorithm is validated using 12 benchmark functions. The results are compared with those of the artificial bees’ algorithm, the hybrid algorithm of artificial bee colony and simulated annealing and particle swarm optimization. Simulation results show the efficiency of the proposed algorithm.     

Using modified maximum regret for finding a necessarily efficient solution in an interval MOLP problem

The current research concerns multiobjective linear programming problems with interval objective functions coefficients. It is known that the most credible solutions to these problems are necessarily efficient ones. To solve the problems, this paper attempts to propose a new model with interesting properties by considering the minimax regret criterion. The most important property of the new model is attaining a necessarily efficient solution as an optimal one whenever the set of necessarily efficient solutions is nonempty. In order to obtain an optimal solution of the new model, an algorithm is suggested. To show the performance of the proposed algorithm, numerical examples are given. Finally, some special cases are considered and their characteristic features are highlighted.     

Electrocatalytic determination of hydroquinone with Mn+ modified gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer electrodes

Application of immobilized metal cations on the topside of gold-5-amino-2-mercaptobenzimidazole self-assembled monolayer (Au-5A2MBI-Mⁿ⁺ SAM, Mⁿ⁺:Cu²⁺ or Ag⁺) for electrocatalytic determination of hydroquinone (H₂Q) is described by voltammetric method. Several parameters were investigated to evaluate the performance of the sensors. Calibration curves for H₂Q concentrations were linear from 1.0 × 10^-5 to 4.0 × 10^-4 M (r = 0.998) for Au-5A2MBI, from 1.0 × 10^-5 to 6.0 × 10^-4 M (r = 0.998) for Au-5A2MBI-Cu²⁺, and from 2.0 × 10^-6 to 2.0 × 10^-5 M (r = 0.996) and 1.0 × 10^-4 to 1.0 × 10^-3 M (r = 0.991) for Au-5A2MBI-Ag⁺ SAM modified electrode. The respective detection limits were found as 6.5 × 10^-6, 4.6 × 10^-6 and 1.8 × 10^-7 M. Both Cu²⁺ and Ag⁺ ions were found to have a good electrocatalytic effect on the oxidation of H₂Q; however, Ag⁺ was a more effective catalyst and showed better sensitivity and lower detection limit than all other tested electrodes. Au-5A2MBI-Ag⁺ SAM electrode was used as a suitable sensor for determination of H₂Q in a radiolysis developing agent as real sample. The results obtained by using proposed sensor and that obtained by an ASTM reference method were in good agreement at the 95% confidence level.     

A green and chemoselective synthesis of coumarins via Pechmann condensation using recoverable heterogeneous catalyst (Au@pSiO2)

Nano Au@porous SiO₂ as a heterogeneous catalyst was prepared and characterized by Fourier transform infrared, X-ray powder diffraction, transmission electron microscopy, thermogravimetric analysis and inductively coupled plasma–atomic emission spectroscopy techniques and then used as an efficient catalyst in the condensation of various phenols with ethyl acetoacetate for the preparation of coumarin derivatives through the Pechmann reaction. The combined merits of chemoselective and solvent free reaction conditions and the recyclability of the nanostructured catalyst make the condensation a safe operation, with low pollution, rapid access to products and simple workup.     

Facile and green synthesis of Cu3V2O8 nanostructures via Moringa peregrina natural extract as a high performance photo catalyst

In this paper Cu₃V₂O₈ nanoparicles were synthesized with a low-cost and green method with using the extract of Moringa peregrine. This novel synthesized material was characterized by using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDS) analysis. The analysis showed the produced nanoparticles have high purity and well crystalline structure. Moreover, the capability of the nanostructures for the removal of dye pollutants was evaluated. For this purpose, methylene blue was selected as a model of organic dye. The experiments showed Cu₃V₂O₈ nanoparticles have high efficiency for removing of dye molecules. Photocatalytic decolorization of methyl blue was optimized with varying the experiment conditions. With 0.02 g of catalyst, pH 6 and concentration of dye 30 mg/l removal efficiency was obtained about 90% in a short time 20 min. Also a kinetic study showed this photodegradation process obeys a first-order kinetic with rate constant about 0.07 min⁻¹.