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  • Articles  (201)
  • 2010-2014  (201)
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  • Articles  (201)
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  • 1
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    Preparation of Zirconium Oxide Powder Using Zirconium Carboxylate Precursors (2014)
    Hindawi
    Details
    Publication Date: 2014-12-31
    Description: Zirconia was prepared at low temperatures (
    Print ISSN: 1687-7985
    Electronic ISSN: 1687-7993
    Topics: Chemistry and Pharmacology , Physics
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  • 2
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    Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface (2014)
    Hindawi
    Details
    Publication Date: 2014-12-16
    Description: Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.
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  • 3
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    Adsorption of Polyanion onto Large Alpha Alumina Beads with Variably Charged Surface (2014)
    Hindawi
    Details
    Publication Date: 2014-12-15
    Description: Adsorption of strong polyelectrolyte, poly(styrenesulfonate), PSS, of different molecular weights onto large α-Al2O3 beads was systematically investigated as functions of pH and NaCl concentrations. The ultraviolet (UV) absorption spectra of PSS at different pH and salt concentrations confirmed that the structure of PSS is independent of pH. With the change of molecular weight from 70 kg/mol (PSS 70) to 1000 kg/mol (PSS 1000), adsorption amount of PSS increases and proton coadsorption on the surface of α-Al2O3 decreases at given pH and salt concentration. It suggests that higher molecular weight of PSS was less flat conformation than lower one. The adsorption density of PSS 70 and PSS 1000 decreases with decreasing salt concentrations, indicating that both electrostatic and nonelectrostatic interactions are involved. Experimental results of both PSS 70 and PSS 1000 adsorption isotherms onto α-Al2O3 at different pH and salt concentrations can be represented well by two-step adsorption model. The effects of molecular weight and salt concentration are explained by structure of adsorbed PSS onto α-Al2O3. The influence of added SDS on the isotherms is evaluated from the sequential adsorption. The SDS uptake onto α-Al2O3 in the presence of hemimicelles can prevent the adsorption of PSS at low concentration so that adsorption of PSS reduces with preadsorbed SDS.
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  • 4
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    Evaluation of Density Matrix and Helmholtz Free Energy for Harmonic Oscillator Asymmetric Potential via Feynmans Approach (2014)
    Hindawi
    Details
    Publication Date: 2014-11-03
    Description: We apply a Feynmans technique for calculation of a canonical density matrix of a single particle under harmonic oscillator asymmetric potential and solving the Bloch equation of the statistical mechanics system. The density matrix and kinetic energy per unit length can be directly evaluated from the solving solutions. From the evaluation, it was found that both of the density matrix and kinetic energy per unit length depended on the parameter of the value of asymmetric potential , the value of axes-shift potential , and temperature (T). Comparison of the Helmholtz free energy was derived by the Feynmans technique and the path-integral method. The results illustrated are slightly different.
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  • 5
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    Evaluation of Density Matrix and Helmholtz Free Energy for Harmonic Oscillator Asymmetric Potential via Feynmans Approach (2014)
    Hindawi
    Details
    Publication Date: 2014-11-02
    Description: We apply a Feynmans technique for calculation of a canonical density matrix of a single particle under harmonic oscillator asymmetric potential and solving the Bloch equation of the statistical mechanics system. The density matrix (P^u) and kinetic energy per unit length (τ^L) can be directly evaluated from the solving solutions. From the evaluation, it was found that both of the density matrix and kinetic energy per unit length depended on the parameter of the value of asymmetric potential (λ), the value of axes-shift potential (g), and temperature (T). Comparison of the Helmholtz free energy was derived by the Feynmans technique and the path-integral method. The results illustrated are slightly different.
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  • 6
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    Effect of Concentration on Isomerization of Rhodanine Derivatives of Merocyanine Dyes in Polar Solvents (2014)
    Hindawi
    Details
    Publication Date: 2014-08-28
    Description: Rhodanine derivatives of merocyanine dyes with residues of 1,3,3-trimethyl-3H-indole and 3-ethylbenzothiazoline have been found to possess two molecular forms in diluted solutions of polar solvents such as dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidinone. The first molecular form was observed to prevail at low concentrations of the dyes, normally up to 10−5 M. The second one prevails at higher concentrations and is displayed through a new band in the electronic absorption spectrum, which is red-shifted with respect to the absorption band of the first form. No similar effect was found for these dyes by use of nonpolar solvents or upon alkyl-substitution of the molecules at nitrogen atom in the rhodanine moiety. We assign the above two forms to different molecular isomers and the analogous spectral changes were shown to take place by light or heat influence which correspond to a typical isomerization effect for the related merocyanine dyes. It is discussed that the isomer transformation is facilitated by the increased mobility of the proton bonded to the nitrogen atom of the rhodanine moiety in the polar environment and the increased amount of dye-dye collisions.
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  • 7
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    Effect of Concentration on Isomerization of Rhodanine Derivatives of Merocyanine Dyes in Polar Solvents (2014)
    Hindawi
    Details
    Publication Date: 2014-08-27
    Description: Rhodanine derivatives of merocyanine dyes with residues of 1,3,3-trimethyl-3H-indole and 3-ethylbenzothiazoline have been found to possess two molecular forms in diluted solutions of polar solvents such as dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidinone. The first molecular form was observed to prevail at low concentrations of the dyes, normally up to 10−5 M. The second one prevails at higher concentrations and is displayed through a new band in the electronic absorption spectrum, which is red-shifted with respect to the absorption band of the first form. No similar effect was found for these dyes by use of nonpolar solvents or upon alkyl-substitution of the molecules at nitrogen atom in the rhodanine moiety. We assign the above two forms to different molecular isomers and the analogous spectral changes were shown to take place by light or heat influence which correspond to a typical isomerization effect for the related merocyanine dyes. It is discussed that the isomer transformation is facilitated by the increased mobility of the proton bonded to the nitrogen atom of the rhodanine moiety in the polar environment and the increased amount of dye-dye collisions.
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  • 8
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    Ruthenium(III) Catalysis in Perborate Oxidation of 5-Oxoacids (2014)
    Hindawi
    Details
    Publication Date: 2014-08-25
    Description: Ruthenium(III) catalyzes perborate oxidation of substituted 5-oxoacids in acidic solution. The catalyzed oxidation is first order with respect to the oxidant and catalyst. The rate of ruthenium(III) catalyzed oxidation displays the Michaelis-Menten kinetics on the reductant and is independent of [H+] of the medium. Hydrogen peroxide is the reactive species of perborate and the kinetic results reveal formation of ruthenium(III) peroxo species-5-oxoacid complex. Electron-releasing substituents accelerate the reaction rate and electron-withdrawing substituents retard it. The order of reactivity among the studied 5-oxoacids is p-methoxy   p-methyl 〉 p-phenyl 〉 −H 〉 p-chloro 〉 p-bromo 〉 m-nitro. Activation parameters are evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data is proposed and discussed. A suitable rate law is derived based on the mechanism.
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  • 9
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    Ruthenium(III) Catalysis in Perborate Oxidation of 5-Oxoacids (2014)
    Hindawi
    Details
    Publication Date: 2014-08-24
    Description: Ruthenium(III) catalyzes perborate oxidation of substituted 5-oxoacids in acidic solution. The catalyzed oxidation is first order with respect to the oxidant and catalyst. The rate of ruthenium(III) catalyzed oxidation displays the Michaelis-Menten kinetics on the reductant and is independent of [H+] of the medium. Hydrogen peroxide is the reactive species of perborate and the kinetic results reveal formation of ruthenium(III) peroxo species-5-oxoacid complex. Electron-releasing substituents accelerate the reaction rate and electron-withdrawing substituents retard it. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫  p-methyl 〉 p-phenyl 〉 −H 〉 p-chloro 〉 p-bromo 〉 m-nitro. Activation parameters are evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data is proposed and discussed. A suitable rate law is derived based on the mechanism.
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  • 10
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    Full Kinetics and a Mechanistic Investigation of the Green Protocol for Synthesis of β-Aminoketone in the Presence of Saccharose as a Catalyst by a One-Pot Three-Component Reaction (2014)
    Hindawi
    Details
    Publication Date: 2014-06-17
    Description: For the first time, in a green protocol, an investigation of the kinetics and mechanism of the reaction between benzaldehyde 1, 4-chloroanilinne 2, and acetophenone 3 compounds in the presence of saccharose as a catalyst was performed for generating β-aminoketone. For determining the kinetic parameters, the reaction was monitored by using the UV/Vis spectrophotometry technique. The second order rate constant () was automatically calculated by the standard equations contained within the program. In the studied temperature range, the second order rate constant (, ) depended on reciprocal temperature that was in good consistent with Arrhenius and Eyring equations, respectively. These data provided the suitable plots for calculating the activation energy and parameters (Ea, , , and ) of the reaction. Furthermore, useful information was obtained from studying the effects of solvent, concentration, and catalyst on the reaction mechanism. The results showed that the first step of the reaction mechanism is a rate determining step (RDS). The obtained experimental data and also the steady state assumption confirmed the proposed mechanism.
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