The Scientific World Journal: Physical Chemistry The latest articles from Hindawi © 2017 , Hindawi Limited . All rights reserved. Kinetics and Mechanism of Nanoparticles-Catalyzed Piperidinolysis of Anionic Phenyl Salicylate Thu, 13 Nov 2014 11:21:22 +0000 The values of the relative counterion () binding constant (=, where and represent cetyltrimethylammonium bromide, CTABr, micellar binding constants of (in non-spherical micelles), , and Br− (in spherical micelles)) are 58, 68, 127, and 125 for , and , respectively. The values of 15 mM CTABr/[] nanoparticles-catalyzed apparent second-order rate constants for piperidinolysis of ionized phenyl salicylate at 35°C are 0.417, 0.488, 0.926, and 0.891 M−1 s−1 for = Na1, Na21, Na2, and Na22, respectively. Almost entire catalytic effect of nanoparticles catalyst is due to the ability of nonreactive counterions, , to expel reactive counterions, 3−, from nanoparticles to the bulk water phase. Norazizah Abd. Razak and M. Niyaz Khan Copyright © 2014 Norazizah Abd. Razak and M. Niyaz Khan. All rights reserved. Modeling and Assessment of Long Afterglow Decay Curves Sun, 14 Sep 2014 00:00:00 +0000 Multiple exponential equations have been successfully fitted to experimental long afterglow decay curve data for some phosphor materials by previous researchers. The calculated decay constants in such equations are used to assess the phosphorescence characteristics of an object. This study generates decay constants from experimental test data and from existing literature for comparison. It shows that the decay constants of an object may not be invariant and that they are dependent on phosphor material, temperature, irradiation intensity, sample thickness, and phosphor density for samples. In addition, the use of different numbers of exponential components in interpretation leads to different numerical results for decay constants. The relationship between the calculated decay constants and the afterglow characteristics of an object is studied and discussed in this paper. The appearance of the luminescence intensity is less correlated to the decay constants than to the time-invariant constants in an equation. Chi-Yang Tsai, Jeng-Wen Lin, Yih-Ping Huang, and Yung-Chieh Huang Copyright © 2014 Chi-Yang Tsai et al. All rights reserved. Thermodynamic and Spectroscopic Investigation of Interactions between Reactive Red 223 and Reactive Orange 122 Anionic Dyes and Cetyltrimethyl Ammonium Bromide (CTAB) Cationic Surfactant in Aqueous Solution Thu, 28 Aug 2014 00:00:00 +0000 The present study describes the conductometric and spectroscopic study of the interaction of reactive anionic dyes, namely, reactive red 223 and reactive orange 122 with the cationic surfactant cetyltrimethyl ammonium bromide (CTAB). In a systematic investigation, the electrical conductivity data was used to calculate various thermodynamic parameters such as free energy , enthalpy , and the entropy of solubilization. The trend of change in these thermodynamic quantities indicates toward the entropy driven solubilization process. Moreover, the results from spectroscopic data reveal high degree of solubilization, with strong interactions observed in the cases of both dyes and the CTAB. The spontaneous nature of solubilization and binding was evident from the observed negative values of free energies ( and ). Muhammad Irfan, Muhammad Usman, Asim Mansha, Nasir Rasool, Muhammad Ibrahim, Usman Ali Rana, Mohammad Siddiq, Muhammad Zia-Ul-Haq, Hawa Z. E. Jaafar, and Salah Ud-Din Khan Copyright © 2014 Muhammad Irfan et al. All rights reserved. Model of Close Packing for Determination of the Major Characteristics of the Liquid Dispersions Components Thu, 17 Jul 2014 11:55:35 +0000 We introduce a close packing model of the particles from the disperse phase of a liquid dispersion. With this model, we find the sediment volumes, the emergent, and the bound dispersion medium. We formulate a new approach for determining the equivalent radii of the particles from the sediment and the emergent (different from the Stokes method). We also describe an easy manner to apply algebraic method for determining the average volumetric mass densities of the ultimate sediment and emergent, as well as the free dispersion medium (without using any pycnometers or densitometers). The masses of the different components and the density of the dispersion phase in the investigated liquid dispersion are also determined by means of the established densities. We introduce for the first time a dimensionless scale for numeric characterization and therefore an index for predicting the sedimentation stability of liquid dispersions in case of straight and/or reverse sedimentation. We also find the quantity of the pure substance (without pouring out or drying) in the dispersion phase of the liquid dispersions. Kiril Hristov Kolikov, Dimo Donchev Hristozov, Radka Paskova Koleva, and Georgi Aleksandrov Krustev Copyright © 2014 Kiril Hristov Kolikov et al. All rights reserved. Effects of the Offset Term in Experimental Simulation on Afterglow Decay Curve Thu, 26 Jun 2014 12:21:25 +0000 This study examines the effect of the offset term in a multiple single exponential equation that fits into experimental afterglow decay curve data for material applications. For afterglow materials applied and attached to structures, the inclusion of this offset term may reduce the values of the calculated decay times, , and enlarge the time invariant constants, , in the associated equation compared to theoretically perfect test conditions. Using a set of experimental data obtained from a lab under dim light, adjustments can be made to calculate the required parameters for an equation without the offset term. This study uses mathematical simulations and lab tests to support our thesis and crosslink test results generated from different ambient light conditions. This paper defines the offset ratio as the ratio of the offset value, , versus the initial light intensity in an equation. This ratio can be used to evaluate possible effects on the calculated parameters of an equation in an associated numerical simulation. The most reliable parameters will have consistent results from the use of multiple single exponential equations, with and without the offset term, in simulations to obtain them in an equation to model a set of data. Chi-Yang Tsai, Jeng-Wen Lin, Yih-Ping Huang, and Yung-Chieh Huang Copyright © 2014 Chi-Yang Tsai et al. All rights reserved. Solvent Extraction of Tellurium from Chloride Solutions Using Tri-n-butyl Phosphate: Conditions and Thermodynamic Data Sun, 16 Mar 2014 00:00:00 +0000 The extractive separation of tellurium (IV) from hydrochloric acid media with tri-n-butyl phosphate (TBP) in kerosene was investigated. The dependence on the extraction of tellurium species, concentrations of tellurium and TBP, extraction time and stage, organic/aqueous ratio, and interferences from coexist metallic ions were examined and are discussed. Besides, the stripping agent and stripping time were also studied. It was found that the extraction reaction corresponds to the neutral complex formation mechanism and the extracted species is TeCl4·3TBP and that the extraction process is exothermic. The thermodynamic parameters of enthalpy , entropy , and free energy of the extraction process were evaluated at −26.2 kJ·mol−1, −65.6 J·mol−1·K−1, and −7.0 kJ·mol−1, respectively at 293 K. Dongchan Li, Yafei Guo, Tianlong Deng, Yu-Wei Chen, and Nelson Belzile Copyright © 2014 Dongchan Li et al. All rights reserved. In the Search of Fundamental Inner Bond Strength of Solid Elements Sun, 02 Mar 2014 08:13:48 +0000 In order to understand the physics behind the surface properties and nano-scale phenomena, we are motivated first to investigate the inner bond strengths as well as the effect of number of neighboring atoms and their relative distance in addition to space positions (crystallography). Therefore, in order to study the effect of the nature of metallic bond on their physico-chemical properties, we first tried to investigate and introduce a mathematical model for transforming the bulk molar cohesion energy into microscopic bond strengths between atoms. Then an algorithm for estimating the nature of bond type including the materials properties and lattice scale “cutoff” has been proposed. This leads to a new fundamental energy scale free from the crystallography and number of atoms. The results of our model in case of fundamental energy scale of metals not only perfectly describe the inter relation between binding and melting phenomena but also adequately reproduce the bond strength for different bond types with respect to other estimations reported in literatures. The generalized algorithm and calculation methodology introduced here by us are suggested to be used for developing energy scale of bulk crystal materials to explain or predict any particular materials properties related to bond strengths of metallic elements. Maziar Sahba Yaghmaee and Reza Riahifar Copyright © 2014 Maziar Sahba Yaghmaee and Reza Riahifar. All rights reserved. Kinetic Study on the Isothermal and Nonisothermal Crystallization of Monoglyceride Organogels Wed, 19 Feb 2014 00:00:00 +0000 The isothermal and nonisothermal crystallization kinetics of monoglyceride (MAG) organogels were studied by pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), respectively. The Avrami equation was used to describe the isothermal crystallization kinetics and experimental data fitted the equation fairly well. Results showed that the crystal growth of MAG organogels was a rod-like growth of instantaneous nuclei at higher degrees of supercooling and a plate-like form with high nucleation rate at lower degrees of supercooling. The exothermic peak in nonisothermal DSC curves for the MAG organogels became wider and shifted to lower temperature when the cooling rate increased, and nonisothermal crystallization was analyzed by Mo equation. Results indicated that at the same crystallization time, to get a higher degree of relative crystallinity, a higher cooling rate was necessary. The activation energy of nonisothermal crystallization was calculated as 739.59 kJ/mol according to the Kissinger method. Therefore, as the results of the isothermal and nonisothermal crystallization kinetics for the MAG organogels obtained, the crystallization rate, crystal nucleation, and growth during the crystallization process could be preliminarily monitored through temperature and cooling rate regulation, which laid the foundation for the real industrial manufacture and application of the MAG organogels. Zong Meng, Lijun Yang, Wenxin Geng, Yubo Yao, Xingguo Wang, and Yuanfa Liu Copyright © 2014 Zong Meng et al. All rights reserved. Fabrication of ZnS-Bi-TiO2 Composites and Investigation of Their Sunlight Photocatalytic Performance Tue, 11 Feb 2014 15:58:05 +0000 The ZnS-Bi-TiO2 composites were prepared by the sol-gel method and were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS). It is found that the doped Bi as Bi4+/Bi3+ species existed in composites, and the introducing of ZnS enhanced further the light absorption ability of TiO2 in visible region and reduced the recombination of photogenerated electrons and holes. As compared to pure TiO2, the ZnS-Bi-TiO2 exhibited enhanced photodegradation efficiency under xenon lamp irradiation, and the kinetic constant of methyl orange removal with ZnS-Bi-Ti-0.005 (0.0141 min−1) was 3.9 times greater than that of pure TiO2 (0.0029 min−1), which could be attributed to the existence of Bi4+/Bi3+ species, the ZnS/TiO2 heterostructure. Xuewei Dong, Fan Zhang, Chuan Rong, and Hongchao Ma Copyright © 2014 Xuewei Dong et al. All rights reserved. Development of Simple Designs of Multitip Probe Diagnostic Systems for RF Plasma Characterization Wed, 05 Feb 2014 06:07:02 +0000 Multitip probes are very useful diagnostics for analyzing and controlling the physical phenomena occurring in low temperature discharge plasmas. However, DC biased probes often fail to perform well in processing plasmas. The objective of the work was to deduce simple designs of DC biased multitip probes for parametric study of radio frequency plasmas. For this purpose, symmetric double probe, asymmetric double probe, and symmetric triple probe diagnostic systems and their driving circuits were designed and tested in an inductively coupled plasma (ICP) generated by a 13.56 MHz radio frequency (RF) source. Using characteristics of these probes, electron temperature, electron number density, and ion saturation current was measured as a function of input power and filling gas pressure. An increasing trend was noticed in electron temperature and electron number density for increasing input RF power whilst a decreasing trend was evident in these parameters when measured against filling gas pressure. In addition, the electron energy probability function (EEPF) was also studied by using an asymmetric double probe. These studies confirmed the non-Maxwellian nature of the EEPF and the presence of two groups of the energetic electrons at low filling gas pressures. M. Y. Naz, S. Shukrullah, A. Ghaffar, and N. U. Rehman Copyright © 2014 M. Y. Naz et al. All rights reserved. Comparison of Solubilization Capacity of Resveratrol in Sodium 3α,12α-Dihydroxy-7-oxo-5β-cholanoate and Sodium Dodecyl Sulfate Wed, 29 Jan 2014 06:57:19 +0000 In this study we investigated resveratrol (trans-3,5,4′-trihydroxystilbene) solubilization with sodium 3α,12α-dihydroxy-7-oxo-5β-cholanoate (S7-OD) and sodium dodecyl sulfate (SDS). The investigation was aimed at determining whether large spherical micelles (SDS) or small longitudinal micelles (S7-OD) are more convenient for incorporation of resveratrol. Also, we studied resveratrol behavior in mixed micelles with mentioned surfactants using spectroflourimetric method as well as the effects of sodium chloride and urea on resveratrol solubilization capacity in the applied surfactants. Resveratrol solubilization curve was different in the investigated surfactants. Resveratrol solubilization curve for sodium 3α,12α-dihydroxy-7-oxo-5β-cholanoate at concentration 0.9 CMC reached saturation level of 60% dissolved resveratrol. The curve for sodium dodecyl sulfate was linear within the whole range of the investigated concentration; resveratrol solubilization rate reached 13% at 2 CMC. In S7-OD, NaCl increased capacity of resveratrol solubilization up to 1.4 CMC surfactant concentration, whilst maximum level of dissolved resveratrol (90%) was observed at 0.9 CMC. In SDS, NaCl decreased resveratrol solubilization capacity. Urea reduced resveratrol solubilization rate in sodium 3α,12α-dihydroxy-7-oxo-5β-cholanoate, whereas it had inverse effect in sodium dodecyl sulfate. The obtained results strongly suggest that structure, that is, shape, of the surfactant micelles significantly affects their capacity of resveratrol solubilization. Also, presence of NaCl and urea influences solubilization capacities of investigated surfactants. Jelena Cvejić, Mihalj Poša, Ana Sebenji, and Milica Atanacković Copyright © 2014 Jelena Cvejić et al. All rights reserved. Why Do Tetrapropylammonium Chloride and Sulphate Salts Destabilize the Native State of Globular Proteins? Mon, 27 Jan 2014 18:25:22 +0000 It has recently been shown that aqueous solutions of tetrapropylammonium chloride and sulphate salts destabilize the folded conformation of Trp-peptides (Dempsey et al., 2011). This result is rationalized by the application of a statistical thermodynamic approach (Graziano, 2010). It is shown that the magnitude of the solvent-excluded volume effect, the main contribution for the native state stability, decreases in both aqueous 2 M TPACl solution and aqueous 1 M TPA2SO4 solution. This happens because TPA+ ions are so large in size and interact so weakly with water molecules, due to their very low charge density, to be able to counteract the electrostrictive effect of chloride and sulphate ions on the water structure, so that the density of their aqueous solutions is smaller or only slightly larger than that of water. Giuseppe Graziano Copyright © 2014 Giuseppe Graziano. All rights reserved. Prediction of Tetraoxygen Reaction Mechanism with Sulfur Atom on the Singlet Potential Energy Surface Thu, 23 Jan 2014 12:41:21 +0000 The mechanism of S+O4 () reaction has been investigated at the B3LYP/6-311+G(3df) and CCSD levels on the singlet potential energy surface. One stable complex has been found for the S+O4 () reaction, IN1, on the singlet potential energy surface. For the title reaction, we obtained four kinds of products at the B3LYP level, which have enough thermodynamic stability. The results reveal that the product P3 is spontaneous and exothermic with −188.042 and −179.147 kcal/mol in Gibbs free energy and enthalpy of reaction, respectively. Because P1 adduct is produced after passing two low energy level transition states, kinetically, it is the most favorable adduct in the 1S+1O4 () atmospheric reactions. Ashraf Khademzadeh, Morteza Vahedpour, and Fereshte Karami Copyright © 2014 Ashraf Khademzadeh et al. All rights reserved. Noncovalent Interactions of Tiopronin-Protected Gold Nanoparticles with DNA: Two Methods to Quantify Free Energy of Binding Wed, 22 Jan 2014 09:15:49 +0000 The binding of gold nanoparticles capped with N-(2-mercaptopropionyl)glycine (Au@tiopronin) with double-stranded DNA has been investigated and quantified in terms of free energies by using two different approaches. The first approach follows the DNA conformational changes induced by gold nanoparticles using the CD technique. The second methodology consists in the use of pyrene-1-carboxaldehyde as a fluorescent probe. This second procedure implies the determination of the “true” free energy of binding of the probe with DNA, after corrections through solubility measurements. Working at different salt concentrations, the nonelectrostatic and electrostatic components of the binding free energy have been separated. The results obtained revealed that the binding is of nonelectrostatic character, fundamentally. The procedure used in this work could be extended to quantify the binding affinity of other AuNPs/DNA systems. R. Prado-Gotor and E. Grueso Copyright © 2014 R. Prado-Gotor and E. Grueso. All rights reserved. Carbyne Polysulfide as a Novel Cathode Material for Rechargeable Magnesium Batteries Tue, 21 Jan 2014 07:31:29 +0000 We report the formation of carbyne polysulfide by coheating carbon containing carbyne moieties and elemental sulfur. The product is proved to have a sp2 hybrid carbon skeleton with polysulfide attached on it. The electrochemical performance of carbyne polysulfide as a novel cathode material for rechargeable magnesium batteries is firstly investigated. The material exhibits a high discharge capacity of 327.7 mAh g−1 at 3.9 mA g−1. These studies show that carbyne polysulfide is a promising candidate as cathode material for rechargeable Mg batteries if the capacity retention can be significantly improved. Yanna NuLi, Qiang Chen, Weikun Wang, Ying Wang, Jun Yang, and Jiulin Wang Copyright © 2014 Yanna NuLi et al. All rights reserved. Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment of N-(2′-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions Thu, 16 Jan 2014 15:10:24 +0000 The values of pseudo-first-order rate constants () for alkaline hydrolysis of 1, obtained at 1.0 mM NaOH and within (total concentration of ) range of 3.0–5.0 mM for and 10–20 mM for , fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversible micellar trapped 1 molecules () vary in the range ~0–0.75 for and ~0–0.83 for under such conditions. The values of become 1.0 at ≥10 mM and 50 mM . Kinetic analysis of the observed data at ≥10 mM shows near irreversible micellar entrapment of 1 molecules under such conditions. M. Niyaz Khan, Yoke-Leng Sim, and Azhar Ariffin Copyright © 2014 M. Niyaz Khan et al. All rights reserved. Interaction between DNA and Trimethyl-Ammonium Bromides with Different Alkyl Chain Lengths Thu, 16 Jan 2014 12:05:45 +0000 The interaction between λ—DNA and cationic surfactants with varying alkyl chain lengths was investigated. By dynamic light scattering method, the trimethyl-ammonium bromides-DNA complex formation was shown to be dependent on the length of the surfactant’s alkyl chain. For surfactants with sufficient long alkyl chain (CTAB, TTAB, DTAB), the compacted particles exist with a size of ~60–110 nm at low surfactant concentrations. In contrast, high concentration of surfactants leads to aggregates with increased sizes. Atomic force microscope scanning also supports the above observation. Zeta potential measurements show that the potential of the particles decreases with the increase of surfactant concentration (CTAB, TTAB, DTAB), which contributes much to the coagulation of the particles. For OTAB, the surfactant with the shortest chain in this study, it cannot fully neutralize the charges of DNA molecules; consequently, the complex is looser than other surfactant-DNA structures. Chao Cheng and Shi-Yong Ran Copyright © 2014 Chao Cheng and Shi-Yong Ran. All rights reserved. Equilibrium and Dynamic Osmotic Behaviour of Aqueous Solutions with Varied Concentration at Constant and Variable Volume Thu, 26 Dec 2013 15:58:19 +0000 Osmosis is essential for the living organisms. In biological systems the process usually occurs in confined volumes and may express specific features. The osmotic pressure in aqueous solutions was studied here experimentally as a function of solute concentration (0.05–0.5 M) in two different regimes: of constant and variable solution volume. Sucrose, a biologically active substance, was chosen as a reference solute for the complex tests. A custom made osmotic cell was used. A novel operative experimental approach, employing limited variation of the solution volume, was developed and applied for the purpose. The established equilibrium values of the osmotic pressure are in agreement with the theoretical expectations and do not exhibit any evident differences for both regimes. In contrast, the obtained kinetic dependences reveal striking divergence in the rates of the process at constant and varied solution volume for the respective solute concentrations. The rise of pressure is much faster at constant solution volume, while the solvent influx is many times greater in the regime of variable volume. The results obtained suggest a feasible mechanism for the way in which the living cells rapidly achieve osmotic equilibrium upon changes in the environment. Ivan L. Minkov, Emil D. Manev, Svetla V. Sazdanova, and Kiril H. Kolikov Copyright © 2013 Ivan L. Minkov et al. All rights reserved. Solvation Effects on the Static and Dynamic First-Order Electronic and Vibrational Hyperpolarizabilities of Uracil: A Polarized Continuum Model Investigation Sun, 22 Dec 2013 16:01:36 +0000 Electronic () and vibrational () first-order hyperpolarizabilities of uracil were determined in gas and water solution using the Coulomb-attenuating Density Functional Theory level with the Dunning’s correlation-consistent aug-cc-pVDZ basis set. Frequency-dependent values were computed for the Second Harmonic Generation (SHG) and Electric Optical Pockels Effect (EOPE) nonlinear optical phenomena. The Polarized Continuum Model was employed to study the solvent effects on the electronic and vibrational properties. The introduction of solvation contributions increases the (static) value by ca. 110%. In comparison, smaller enhancements are found for the (EOPE) and (SHG) data evaluated at the typical wavelength of 694 nm (by 40–50%). The gas-water hyperpolarizability difference was rationalised through a density analysis study. The magnitudes of the vibrational first-order hyperpolarizabilities are comparable to their electronic counterparts and noticeably increase in solution: (EOPE) ~ (EOPE) in aqueous phase at  nm. Analysis of the IR and Raman spectra is useful to elucidate the most important contributing modes to the vibrational first-order hyperpolarizabilities. Andrea Alparone Copyright © 2013 Andrea Alparone. All rights reserved. Fragmentation of Chitosan by Acids Sat, 02 Nov 2013 11:50:32 +0000 Fragmentation of chitosan in aqueous solution by hydrochloric acid was investigated. The kinetics of fragmentation, the number of chain scissions, and polydispersity of the fragments were followed by viscometry and size exclusion chromatography. The chemical structure and the degree of N-acetylation (DA) of the original chitosan and its fragments were examined by 1H NMR spectroscopy and elemental analysis. The kinetic data indicates that the reaction was of first order. The results of polydispersity and the DA suggest that the selected experimental conditions (temperature and concentration of acid) were appropriate to obtain the fragments having the polydispersity and the DA similar to or slightly different from those of the original one. A procedure to estimate molecular weight of fragments as well as the number of chain scissions of the fragments under the experimental conditions was also proposed. Mohammad Reza Kasaai, Joseph Arul, and Gérard Charlet Copyright © 2013 Mohammad Reza Kasaai et al. All rights reserved. Static and Dynamic Electronic (Hyper)polarizabilities of Dimethylnaphthalene Isomers: Characterization of Spatial Contributions by Density Analysis Mon, 28 Oct 2013 17:48:37 +0000 Static and frequency-dependent electronic (hyper)polarizabilities of the dimethylnaphthalene (DMN) isomers were computed in vacuum using the Coulomb-attenuating Density Functional Theory method. The nonlinear optical Second Harmonic Generation (SHG) and Electro-Optical Pockels Effect (EOPE) were investigated at the characteristic Nd:YAG laser wavelength of 1064 nm. The response electric properties especially the longitudinal polarizability, polarizability anisotropy, and first-order hyperpolarizability are significantly affected by the position of the methyl groups. The SHG and EOPE techniques can be potentially useful to discriminate the ,-DMN isomers (2,6-DMN < 2,7-DMN < 2,3-DMN) as well as the ,-DMN isomers (1,5-DMN < 1,4-DMN < 1,8-DMN). The (hyper)polarizability differences among the investigated DMNs were elucidated through density analysis calculations. The predicted polarizabilities exhibit good linear relationships with the experimental first-order biomass-normalized rate coefficient, a physicochemical property connected to the rates of biodegradation processes of polycyclic aromatic hydrocarbons. Andrea Alparone Copyright © 2013 Andrea Alparone. All rights reserved. Effects of Water Solutions on Extracting Green Tea Leaves Wed, 07 Aug 2013 11:12:51 +0000 This study investigates the effects of water solutions on the antioxidant content of green tea leaf extracts. Green teas prepared with tap water and distilled water were compared with respect to four antioxidant assays: total phenol content, reducing power, DMPD assay, and trolox equivalent antioxidant capacity assay. The results indicate that green tea prepared with distilled water exhibits higher antioxidant activity than that made with tap water. The high performance liquid chromatography showed that major constituents of green tea were found in higher concentrations in tea made with distilled water than in that made with tap water. This could be due to less calcium fixation in leaves and small water clusters. Water solutions composed of less mineralisation are more effective in promoting the quality of green tea leaf extracts. Wen-Ying Huang, Yu-Ru Lin, Ruei-Fen Ho, Ho-Yen Liu, and Yung-Sheng Lin Copyright © 2013 Wen-Ying Huang et al. All rights reserved. Koopmans' Analysis of Chemical Hardness with Spectral-Like Resolution Thu, 18 Jul 2013 11:20:08 +0000 Three approximation levels of Koopmans' theorem are explored and applied: the first referring to the inner quantum behavior of the orbitalic energies that depart from the genuine ones in Fock space when the wave-functions' Hilbert-Banach basis set is specified to solve the many-electronic spectra of spin-orbitals' eigenstates; it is the most subtle issue regarding Koopmans' theorem as it brings many critics and refutation in the last decades, yet it is shown here as an irrefutable “observational” effect through computation, specific to any in silico spectra of an eigenproblem; the second level assumes the “frozen spin-orbitals” approximation during the extracting or adding of electrons to the frontier of the chemical system through the ionization and affinity processes, respectively; this approximation is nevertheless workable for great deal of chemical compounds, especially organic systems, and is justified for chemical reactivity and aromaticity hierarchies in an homologue series; the third and the most severe approximation regards the extension of the second one to superior orders of ionization and affinities, here studied at the level of chemical hardness compact-finite expressions up to spectral-like resolution for a paradigmatic set of aromatic carbohydrates. Mihai V. Putz Copyright © 2013 Mihai V. Putz. All rights reserved. Adsorption Properties of Low-Cost Biomaterial Derived from Prunus amygdalus L. for Dye Removal from Water Tue, 09 Jul 2013 09:48:35 +0000 The capability of Prunus amygdalus L. (almond) shell for dye removal from aqueous solutions was investigated and methyl orange was used as a model compound. The effects of operational parameters including pH, ionic strength, adsorbent concentration and mesh size, dye concentration, contact time, and temperature on the removal of dye were evaluated. The adsorption kinetics conformed to the pseudo-second-order kinetic model. The equilibrium data pointed out excellent fit to the Langmuir isotherm model with maximum monolayer adsorption capacity of 41.34 mg g−1 at 293 K. Thermodynamic analysis proved a spontaneous, favorable, and exothermic process. It can be concluded that almond shell might be a potential low-cost adsorbent for methyl orange removal from aqueous media. Fatih Deniz Copyright © 2013 Fatih Deniz. All rights reserved. The Importance of the Solids Loading on Confirming the Dielectric Nanosize Dependence of BaTiO3 Powders by Slurry Method Thu, 06 Jun 2013 17:25:37 +0000 The dielectric nanosize dependence of BaTiO3 powders was investigated by the slurry method, where two series of BaTiO3 slurries with 10 vol% and 30 vol% solids loadings were prepared as model samples. Applying the Bruggeman-Hanai equation, the high-frequency limiting permittivity () of the slurries was extracted from the dielectric spectra. The of the 10 vol% slurry showed abnormal size independence in the range from 100 nm to 700 nm, and the of the 30 vol% slurry exhibited good agreement with the previous prediction. Through analysing quantitatively the response of to the changing permittivity of the powders under different solids loading, it was found that the of the slurry with lower solids loading is more inclined to be interfered by the systematic and random errors. Furthermore, a high permittivity value was found in the BaTiO3 powders with 50 nm particle size. Wei Zhou, Yi Mei Nie, Shu Jing Li, and Hai Yan Liang Copyright © 2013 Wei Zhou et al. All rights reserved. Study of the Counter Anions in the Host-Guest Chemistry of Cucurbit[8]uril and 1-Ethyl-1′-benzyl-4,4′-bipyridinium Mon, 27 May 2013 13:55:54 +0000 A series of 1-ethyl-1′-benzyl-4,4′-bipyridinium compounds with different counter anions (BEV-X2, where the X is Cl, Br, I, PF6, ClO4) were synthesized. By using of NMR, MS, electrochemistry, Na2S2O4-induced redox chemistry, and UV-Vis, the role of the different counter anions in the host-guest chemistry of cucurbit[8]uril (CB[8]) was studied for the first time. The result demonstrated that BEV-X2 can form a 1 : 1 host-guest complex with CB[8] in water. Theoretical calculation further suggested that the viologen region was threaded through the cavity of CB[8], while the corresponding counter anions were located outside the cavity. Some difference can be observed on UV-Vis titration and Na2S2O4-induced redox chemistry, which showed that the counter anions have some effect on the host-guest chemistry. All these provide new insights into CB[8] host-guest system. Hailong Ji, Fengyu Liu, and Shiguo Sun Copyright © 2013 Hailong Ji et al. All rights reserved. Methods of Calculating Ionization Energies of Multielectron (Five or More) Isoelectronic Atomic Ions Thu, 16 May 2013 09:55:49 +0000 We have previously used simple empirical equations to reproduce the literature values of the ionization energies of isoelectronic sequences of up to four electrons which gave very good agreement. We reproduce here a kinetic energy expression with corrections for relativity and Lamb shift effects which give excellent agreement with the literature values. These equations become more complex as the number of electrons in the system increases. Alternative simple quadratic expressions for calculating ionization energies of multielectron ions are discussed. A set of coefficients when substituted into a simple expression produces very good agreement with the literature values. Our work shows that Slater's rules are not appropriate for predicting trends or screening constants. This work provides very strong evidence that ionization energies are not functions of complete squares, and when calculating ionization energies electron transition/relaxation has to be taken into account. We demonstrate clearly that for particular isoelectronic sequences, the ionizing electrons may occupy different orbitals and in such cases more than one set of constants are needed to calculate the ionization energies. Peter F. Lang and Barry C. Smith Copyright © 2013 Peter F. Lang and Barry C. Smith. All rights reserved. Preparation of PEO/Clay Nanocomposites Using Organoclay Produced via Micellar Adsorption of CTAB Mon, 10 Dec 2012 14:52:53 +0000 The aim of this study was the preparation of polyethylene oxide (PEO)/clay nanocomposites using organoclay produced via micellar adsorption of cethyltrimethyl ammonium bromide (CTAB) and their characterisation by X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectra, and the investigation of certain mechanical properties of the composites. The results show that the basal distance between the layers increased with the increasing CTAB/clay ratio as parallel with the zeta potential values of particles. By considering the aggregation number of CTAB micelles and interlayer distances of organo-clay, it could be suggested that the predominant micelle geometry at lower CTAB/clay ratios is an ellipsoidal oblate, whereas, at higher CTAB/clay ratios, sphere-ellipsoid transition occurs. The increasing tendency of the exfoliation degree with an increase in clay content may be attributed to easier diffusion of PEO chains to interlayer regions. FT-IR spectra show that the intensity of Si-O stretching vibrations of the organoclays (1050 cm−1) increased, especially in the ratios of 1.0 g/g clay and 1.5 g/g clay with the increasing CTAB content. It was observed that the mechanical properties of the composites are dependent on both the CTAB/clay ratios and clay content of the composites. Ahmet Gürses, Mehtap Ejder-Korucu, and Çetin Doğar Copyright © 2012 Ahmet Gürses et al. All rights reserved. A Model Study on the Possible Effects of an External Electrical Field on Enzymes Having Dinuclear Iron Cluster [2Fe-2S] Tue, 01 May 2012 19:06:44 +0000 Hydrogenases which catalyze the H2 ↔ 2H+ + 2e− reaction are metalloenzymes that can be divided into two classes, the NiFe and Fe enzymes, on the basis of their metal content. Iron-sulfur clusters [2Fe-2S] and [4Fe-4S] are common in ironhydrogenases. In the present model study, [2Fe-2S] cluster has been considered to visualize the effect of external electric field on various quantum chemical properties of it. In the model, all the cysteinyl residues are in the amide form. The PM3 type semiempirical calculations have been performed for the geometry optimization of the model structure in the absence and presence of the external field. Then, single point DFT calculations (B3LYP/6-31+G(d)) have been carried out. Depending on the direction of the field, the chemical reactivity of the model enzyme varies which suggests that an external electric field could, under proper conditions, improve the enzymatic hydrogen production. Lemi Türker Copyright © 2012 Lemi Türker. All rights reserved. Electrochemically Pretreated Carbon Microfiber Electrodes as Sensitive HPLC-EC Detectors Mon, 30 Apr 2012 11:06:44 +0000 The paper focuses on the analysis and detection of electroactive compounds using high-performance liquid chromatography (HPLC) combined with electrochemical detection (EC). The fabrication and utilization of electrochemically treated carbon fiber microelectrodes (CFMs) as highly sensitive amperometric detectors in HPLC are described. The applied pretreatment procedure is beneficial for analytical characteristics of the sensor as demonstrated by analysis of the model set of phenolic acids. The combination of CFM with separation power of HPLC technique allows for improved detection limits due to unique electrochemical properties of carbon fibers. The CFM proved to be a promising tool for amperometric detection in liquid chromatography. Zdenka Bartosova, Daniel Riman, Petr Jakubec, Vladimir Halouzka, Jan Hrbac, and David Jirovsky Copyright © 2012 Zdenka Bartosova et al. All rights reserved. Preparation and Characterization of Ni-Doped TiO2 Materials for Photocurrent and Photocatalytic Applications Tue, 24 Apr 2012 11:41:59 +0000 Different amounts of Ni-doped TiO2 (Ni=0.1 to 10%) powders and thin films were prepared by following a conventional coprecipitation and sol-gel dip coating techniques, respectively, at 400 to 800°C, and were thoroughly characterized by means of XRD, FT-IR, FT-Raman, DRS, UV-visible, BET surface area, zeta potential, flat band potential, and photocurrent measurement techniques. Photocatalytic abilities of Ni-doped TiO2 powders were evaluated by means of methylene blue (MB) degradation reaction under simulated solar light. Characterization results suggest that as a dopant, Ni stabilizes TiO2 in the form of anatase phase, reduces its bandgap energy, and adjusts its flat band potentials such that this material can be employed for photoelectrochemical (PEC) oxidation of water reaction. The photocatalytic activity and photocurrent ability of TiO2 have been enhanced by doping of Ni in TiO2. The kinetic studies revealed that the MB degradation reaction follows the Langmuir-Hinshelwood first-order reaction relationship. Ibram Ganesh, A. K. Gupta, P. P. Kumar, P. S. C. Sekhar, K. Radha, G. Padmanabham, and G. Sundararajan Copyright © 2012 Ibram Ganesh et al. All rights reserved.