http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Thu, 06 Jun 2013 13:43:22 +0000 http://www.hindawi.com/isrn/physchem/2013/171865/ Biosorption of Pb(II) ions from aqueous solution by cow hooves (CHs) was investigated as a function of initial pH, contact time, and biosorbent dosage through batch studies. Equilibrium experiments were performed at three different temperatures (298, 308, and 318 K) using initial Pb2+ concentration ranging from 15 to 100 mgg−1. This study revealed that maximum uptake (96.2% removal) of Pb2+ took place within 30 minutes of agitation, and the process was brought to equilibrium within 60 minutes of equilibration. The equilibrium data were modelled using Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir isotherm model fitted the data best at all temperatures considered. The Lagergren second-order kinetic model fitted the biosorption process better than the first-order model. The negative values obtained for both Gibb’s free energy change and enthalpy change are an indication of the spontaneous and exothermic nature of the sorption of Pb2+ onto CH. A study of the FTIR spectral obtained before and after Pb2+ sorption showed that carbonyl, hydroxyl, amino, and carboxyl groups were involved in the sorption process. I. Osasona, A. O. Adebayo, and O. O. Ajayi Copyright © 2013 I. Osasona et al. All rights reserved. Sun, 02 Jun 2013 11:43:35 +0000 http://www.hindawi.com/isrn/physchem/2013/547378/ The silver nanoparticles were fabricated by the focused laser irradiation to silver rod immersed in various kinds of surfactant aqueous solutions. It was found that anionic and cationic surfactants showed different roles on the silver nanoparticle growth during the focused laser irradiation processes. Silver nanoparticle synthesis in an amphoteric surfactant aqueous solution was also carried out using the same techniques, and it was found that the spectral shifts for these surface plasmon bands showed complicated behaviors against the concentration of amphoteric surfactants as well as pH. Furthermore, the influence of the gas dissolved in a solution on the silver nanoparticle growth during the focused laser irradiation processes was investigated. With increasing the gas pressure of CO2, the surface plasmon bands of silver nanoparticles were shifted to longer wavelength, suggesting that the dissolved gas of CO2 in a solution enhances the silver nanoparticle growth. The plausible mechanism was proposed to understand the reason of such enhancement of silver nanoparticle growth by increasing the dissolved gas in a solution. Ming Jing Chua and Yoshinori Murakami Copyright © 2013 Ming Jing Chua and Yoshinori Murakami. All rights reserved. Mon, 20 May 2013 08:31:01 +0000 http://www.hindawi.com/isrn/physchem/2013/738932/ Cephalosporins are β-lactam antibiotics, and the important drugs of this group are cephalexin, cefadroxil and cephradine. In the present research, the kinetics and mechanism of oxidation of cephalexin (CEX), cefadroxil (CFL), and cephradine (CPD) with chloramine-T (CAT) in alkaline medium were investigated at 301 K. All the three oxidation reactions follow identical kinetics with a first-order dependence each on [CAT]o and [substrate]o. The reaction is catalyzed by hydroxide ions, and the order is found to be fractional. The dielectric effect is negative. Proton inventory studies in H2O-D2O mixtures with CEX as a probe have been made. Activation parameters and reaction constants have been evaluated. Oxidation products were identified by mass spectral analysis. An isokinetic relation was observed with β = 378 K, indicating that enthalpy factors control the rate. The rate increases in the following order: CPD > CFL > CEX. The proposed mechanism and the derived rate law are consistent with the observed kinetics. Anu Sukhdev, A. S. Manjunatha, and Puttaswamy Puttaswamy Copyright © 2013 Anu Sukhdev et al. All rights reserved. Sun, 28 Apr 2013 11:05:25 +0000 http://www.hindawi.com/isrn/physchem/2013/475296/ Room temperature ionic liquids (RTILs) are the environment-friendly alternatives for organic volatile solvents in a host of synthetic, catalytic, and electrochemical applications. These are also being used for various R&D works in nuclear fuel cycle research such as the recovery and purification of nuclides of interest from spent nuclear fuel matrices. In this work, density, refractive index () at sodium line, and thermodynamic water activity of the aqueous solution of 1-hexyl-3-methyl imidazolium bromide were determined in dilute aqueous solutions at 298.15 K. These results were used to calculate the apparent molal volumes of each solute over various concentration ranges. The measurements were performed as per ASTM procedures. Vapour pressure was derived using water activity values. Information on excess properties and structural interaction was also reported. Debasmita Dash, Shekhar Kumar, C. Mallika, and U. Kamachi Mudali Copyright © 2013 Debasmita Dash et al. All rights reserved. Tue, 09 Apr 2013 11:16:26 +0000 http://www.hindawi.com/isrn/physchem/2013/175910/ Quantum chemical calculations based on density functional theory (DFT) methods were performed on indigo blue (IB), methylene blue (MB), and crystal violet (CV) molecules as inhibitors for iron corrosion in acid media. DFT calculations were performed on the molecular structures to describe electronic parameters which are associated with inhibition efficiency such as the values −4.981 eV, −4.518 eV, and −3.872 eV which increased in the order IB > MB > CV while values were −3.73 eV, −3.63 eV, and −2.87 eV for IB, MB, and CV, respectively. Quench molecular dynamics simulations performed at metal/vacuum interface were applied to find the equilibrium adsorption configurations and calculate the minima interaction energy between inhibitor molecules and iron surface Fe(110). The theoretical order of inhibition efficiency of these dye molecules had a linear relationship with experimentally observed inhibition efficiency on iron corrosion in acid media. The electronic structures as well as reactivity elucidate parameters which could be practical in designing novel high-efficiency, cheap, and eco-friendly inhibitors by quantitative structure-activity relationship (QSAR) method. R. S. Oguike, A. M. Kolo, A. M. Shibdawa, and H. A. Gyenna Copyright © 2013 R. S. Oguike et al. All rights reserved. Wed, 03 Apr 2013 09:02:11 +0000 http://www.hindawi.com/isrn/physchem/2013/208087/ The effectiveness of alkali-acid modification in enhancement the adsorption capacity of rice straw (RS) for removing a basic dye was studied. The obtained adsorbents were characterized by slurry pH, pHPZC, iodine number, methylene blue number, FTIR, and SEM analyses. Adsorption of methylene blue (MB) was described by the Langmuir, Freundlich, Tempkin, and Redlich-Peterson isotherm models. Effects of contact time, initial concentration of MB dye, pH of solution, adsorbent dose, salt concentration of NaCl, and desorbing agents on the removal of MB were reported. Kinetic studies were analyzed using the pseudo-first-order, pseudo-second-order, and the intraparticle diffusion models and were found to follow closely the pseudo-second-order model. Equilibrium data were best represented by the Langmuir and Redlich-Peterson isotherms. The adsorption capacities were varied between 32.6 and 131.5 mg/g for untreated and treated RS samples with NaOH-1M citric acid (ARS-1C), respectively. Adsorption behavior of the ARS-1C sample was experimented in a binary mixture containing methylene blue (basic) and reactive blue 19 (acidic) dyes which showed its ability to remove MB higher than RB19. Overall, the results indicate that the alkali-acid treatment proved to be potential modification for producing effective low-cost adsorbents for the removal of the basic dyes from wastewater. Nady A. Fathy, Ola I. El-Shafey, and Laila B. Khalil Copyright © 2013 Nady A. Fathy et al. All rights reserved. Tue, 05 Mar 2013 11:48:46 +0000 http://www.hindawi.com/isrn/physchem/2013/804576/ In this work, the modified linear isotherm regularity (LIR) equation of state parameter table is extended in order to represent volumetric behaviour of primary alkylamines. In addition, the isothermal compressibility and thermal expansion coefficient of these compounds have been predicted. To do so, we consider each of primary alkylamine as a hypothetical mixture of methyl, methylene and a primary amine functional group, in which the interaction potential of each pair is assumed to be the average effective pair potential. Then, the LIR equation of state has been extended to such a hypothetical mixture. Furthermore, three basic compounds, namely, propane, -butane, and cyclohexane are used to obtain the contribution of methyl and methylene groups in the EOS parameters, and also other appropriate compounds are used to obtain the contribution of the primary amine functional groups, such as 1-pentylamine for the contribution of −CH2NH2 and 2-aminopentane for the contribution of groups. The calculated EOS parameters along with the modified EOS are then used to calculate the density and its derivatives for alkylamines at different pressures and temperatures. The obtained results for different properties are compared with the experimental values. Zahra Kalantar, Hossein Nikoofard, and Faezeh Javadi Copyright © 2013 Zahra Kalantar et al. All rights reserved. Thu, 28 Feb 2013 11:49:56 +0000 http://www.hindawi.com/isrn/physchem/2013/164868/ The syntheses of nitrobenzene and p-nitrotoluene directly from benzene, toluene, and NO2 within the pore network of the initially acid-free zeolite NaZSM-5 are reported for the first time. The active species , formed by the interaction of NO2 with the Na+ cations present on the internal surface, results in the acid-free electrophilic substitution of the aromatic ring. There are two distinct reservoirs for the reagents: one associated with close proximity to the cation sites and the other associated with the siliceous areas of the pore network. Up to 34% of the hydrocarbon and 70% of the available NO2 are reacted at 50°C. Only the cation associated sites are reactive at low temperature, and there appears to be little mobility between the sites under the reaction conditions. There is no evidence of a second nitration occurring. This represents a novel route to the single nitration of benzene and toluene and for toluene, the generation of the para isomer exclusively. The pore network of the NaZSM-5 restricts the available reaction volume and transition state geometry allowing only the para-substituted product. Scott J. Kirkby Copyright © 2013 Scott J. Kirkby. All rights reserved. Tue, 26 Feb 2013 17:58:14 +0000 http://www.hindawi.com/isrn/physchem/2013/279463/ The present paper reviews the investigation of ambient water structure and focusses in particular on the determination of the radial distribution functions of water from total experimental radiation scattering experiments. A novel method for removing the inelastic scattering from neutron data is introduced, and the effect of Compton scattering on X-ray data is discussed. In addition the extent to which quantum effects can be discerned between heavy and light water is analysed against these more recent data. It is concluded that, with the help of modern data analysis and computer simulation tools to interrogate the scattering data, a considerable degree of consistency can be obtained between recent and past scattering experiments on water. That consistency also gives a realistic estimate of the likely uncertainties in the extracted radial distribution functions, as well as offering a benchmark against which future experiments can be judged. A. K. Soper Copyright © 2013 A. K. Soper. All rights reserved. Mon, 25 Feb 2013 07:22:45 +0000 http://www.hindawi.com/isrn/physchem/2013/146401/ We studied for the first time 16 tautomers/rotamers of diphosphocytosine by four computational methods. Some of these tautomers/rotamers are isoenergetic although they have different structures. High-level electron correlation MP2 and MP4(SDQ) ab initio methods and density functional methods employing a B3LYP and the new M06-2X functional were used to study the structure and relative stability of 16 tautomers/rotamers of diphosphocytosine. The dienol tautomers of diphosphocytosine are shown to be much more stable than the keto-enol and diketo forms. The tautomers/rotamers stability could be ranked as PC3 = PC12 < PC2 = PC11 < PC1 < PC10 < PC8 < PC9 < PC15 < PC16 < PC6 ~ PC7 < PC13 < PC4 ~ PC14 < PC5. This stability order was discussed in the light of stereo and electronic factors. Solvation effect has been modeled in a high dielectric solvent, water using the polarized continuum model (PCM). Consideration of the solvent causes some reordering of the relative stability of diphosphocytosine tautomers: PC3 ~ PC12 ~ PC2 ~ PC11 < PC1 < PC10 < PC8 < PC9 < PC15 ~ PC16 < PC13 < PC6 ~ PC7 ~ PC14 < PC4 ~ PC5. Abdullah G. Al-Sehemi, Tarek M. El-Gogary, Karl Peter Wolschann, and Gottfried Koehler Copyright © 2013 Abdullah G. Al-Sehemi et al. All rights reserved. Sun, 24 Feb 2013 09:47:04 +0000 http://www.hindawi.com/isrn/physchem/2013/616532/ Chlorobenzene was reacted with NO2, in the initially acid-free zeolite NaZSM-5, to yield para-chloronitrobenzene exclusively. The precursors were loaded sequentially into self-supporting pellets of the zeolite, contained within a stainless steel cell, from the gas phase. The reaction proceeds spontaneously at room temperature. It is, however, very temperature dependent and effectively ceases at zero degrees Celsius. The reaction was monitored in situ using FT-IR. The active nitrating agent is formed from the partial electron donation by the NO2 to the Na+ cations present in the zeolite lattice. Under the reaction conditions, chlorobenzene is not readily mobile through the pore system; thus, only the molecules adsorbed near a cation site react to form para-chloronitrobenzene. Scott J. Kirkby Copyright © 2013 Scott J. Kirkby. All rights reserved. Mon, 18 Feb 2013 16:13:43 +0000 http://www.hindawi.com/isrn/physchem/2013/143870/ The theoretical model for an amperometric glucose biosensor is discussed. In this model glucose oxidase enzyme is immobilized in conducting polypyrrole. This model contains a nonlinear term related to enzyme reaction kinetics. He’s homotopy perturbation method is used to find the approximate analytical solutions of coupled non-linear reaction diffusion equations. A closed-form expression of substrate and mediator concentration under non-steady-state conditions is obtained. A comparison of the analytical approximation and numerical simulation is also presented. An agreement between analytical expressions and numerical results is observed. M. Uma Maheswari and L. Rajendran Copyright © 2013 M. Uma Maheswari and L. Rajendran. All rights reserved. Sun, 17 Feb 2013 10:17:33 +0000 http://www.hindawi.com/isrn/physchem/2013/202781/ Mathematical modeling of amperometric biosensor with cyclic reaction is discussed. Analytical expressions pertaining to the concentration of substrate, cosubstrate, reducing agent and medial product and current for hybrid enzyme biosensor are obtained in terms of Thiele module and saturation parameters. In this paper, a powerful analytical method, called homotopy analysis method (HAM) is used to solve the system of nonlinear differential equations. Furthermore, in this work the numerical simulation of the problem is also reported using Scilab/Matlab program. Our analytical results are compared with simulation results. A good agreement between analytical and numerical results is noted. Indira Krishnaperumal and Rajendran Lakshmanan Copyright © 2013 Indira Krishnaperumal and Rajendran Lakshmanan. All rights reserved. Thu, 14 Feb 2013 13:07:46 +0000 http://www.hindawi.com/isrn/physchem/2013/487485/ The structure of carbonic layer in three samples composed of 4H polytype of silicon carbide and the following sequence of layers: carbon/nickel/silicon/nickel/silicon was investigated with Raman spectroscopy. Different thermal treatment of the samples led to differences in the structure of carbonic layer. Raman measurements were performed with visible excitation focused on two interfaces: silicon carbide/carbon and carbon/silicide. The results showed differences in the structure across carbon film although its thickness corresponds to 8/10 graphene layers. Paweł Borowicz, Adrian Kuchuk, Zbigniew Adamus, Michał Borysiewicz, Marek Ekielski, Eliana Kamińska, Anna Piotrowska, and Mariusz Latek Copyright © 2013 Paweł Borowicz et al. All rights reserved. Thu, 31 Jan 2013 11:36:17 +0000 http://www.hindawi.com/isrn/physchem/2013/487240/ The mathematical modeling of nonlinear boundary value problems in catalytically chemical reactor is discussed. In this paper, we obtain the approximate analytical solution and the effectiveness factors for the evolution of single-step transformations under non-isothermal conditions using homotopy perturbation method. We have applied it to many reaction models and obtained very simple analytical expressions for the shape of the corresponding transformation rate peaks. These analytical solutions represent a significant simplification of the system’s description allowing easy curve fitting to experiment. The accuracy achieved with our method is checked against several reaction models and numerical results. A satisfactory agreement is noted. Vembu Ananthaswamy and Lakshmanan Rajendran Copyright © 2013 Vembu Ananthaswamy and Lakshmanan Rajendran. All rights reserved. Sun, 13 Jan 2013 08:56:59 +0000 http://www.hindawi.com/isrn/physchem/2013/753139/ A detailed theoretical study of hydrogen-bond formation in different polyethylene glycol + water complex and dipropylene glycol + water have been performed by Hartree Fock (HF) method, second-order Møller-Plesset perturbation theory (MP2), and density functional theory (DFT) using 6-31++G(d,p) basis set. B3LYP DFT-D, WB97XD, M06, and M06-2X functionals have been used to describe highly dispersive hydrogen-bond formation appropriately. Geometrical parameters, interaction energies, deformation energies, deviation of potential energy curves of hydrogen bonded O–H from that of free O–H, frontier orbitals, and charge transfer have been studied to analyze stability and nature of hydrogen bond formation of various glycol and water complexes. It is found that WB97XD is best among all the applied DFT functionals to describe hydrogen bond interaction, and intermolecular hydrogen bonds have higher covalent character and accordingly higher strength when glycol acts as proton donor for glycol + 1 water complex system. Snehanshu Pal and T. K. Kundu Copyright © 2013 Snehanshu Pal and T. K. Kundu. All rights reserved. Wed, 19 Dec 2012 12:02:33 +0000 http://www.hindawi.com/isrn/physchem/2012/835397/ Surface pressure area isotherms of Langmuir monolayers formed by spreading mixed solutions of varying concentrations of N-octadecyl-N′-phenylthiourea (OPT) and octadecanoic acid or stearic acid (SA) over air-water interface are described. Examination of the hysteresis behavior and an analysis of the limiting area per molecule of the isotherms show that when the spread solution has an excess of OPT, the limiting surface area is consistent with a monolayer composed of equimolar amounts of the two components. This indicates that any excess thiourea, which on its own does not form a stable monolayer, is squeezed out and is not part of the monolayer. On the other hand, when the spreading mixture has an excess of SA over OPT, the isotherm indicates that the entire originally spread material is incorporated into the surface film. In this case, the values of area/molecule indicate that the monolayer is composed of SA : OPT complex with a ratio of 1 : 1 together with the excess SA remaining in the monolayer. Siji Sudheesh, Jamil Ahmad, and Girija S. Singh Copyright © 2012 Siji Sudheesh et al. All rights reserved. Mon, 17 Dec 2012 13:51:46 +0000 http://www.hindawi.com/isrn/physchem/2012/943429/ Ultrasonic velocities and densities of the binary liquid mixtures of anisaldehyde with alcoxyethanols like methoxyethanol (MOE), ethoxyethanol (EOE), and butoxyethanol (BOE) have been measured at temperatures 303.15 K, 308.15 K, 313.15 K, and 318.15 K over the entire composition range of mole fractions. The theoretical values of ultrasonic velocity were evaluated using Nomoto's relation (), impedance relation (), ideal mixing relation (), Jungie's relation (), and Rao’s specific velocity relation (). The molecular interaction parameter () has been evaluated from the values of experimental and theoretical velocities. The variation of this interaction parameter with the composition mixture has been discussed in terms of molecular interactions. Zareena Begum, P. B. Sandhya Sri, and C. Rambabu Copyright © 2012 Zareena Begum et al. All rights reserved. Sun, 09 Dec 2012 09:13:14 +0000 http://www.hindawi.com/isrn/physchem/2012/985853/ The present study aims to investigate the adsorption behavior of Cu(II) and Cd(II) ions from wastewater onto low-cost adsorbents either raw date pits (RDP), cheap agricultural and nontoxic materials, or chemically activated carbon (ADP) prepared by modified date pits using phosphoric acid. A series of experiments were conducted in a batch system to evaluate the effect of system variables. The adsorption process is affected by various parameters such as solution pH, contact time, initial concentrations of metals, and adsorbent dose. The optimum pH required for maximum adsorption was found to be . The experimental data were tested using Langmuir, Freundlich, Dubinin-Radushkevich (D-R) isotherm equations. It was observed that the adsorption capacity of date pits increased after treatment with phosphoric acid. The maximum uptake capacities () were 7.40 and 33.44 mg copper(II) per gram of RDP and ADP, respectively, while 6.02 and 17.24 mg cadmium(II) per gram of RDP and ADP, respectively. The results showed that although the equilibrium data could be described by the three models used, Langmuir model gave slightly better results while Freundlich model gave better results when using raw and activated date pits. Nora M. Hilal, Inas A. Ahmed, and Ragaa E. El-Sayed Copyright © 2012 Nora M. Hilal et al. All rights reserved. Wed, 28 Nov 2012 13:32:20 +0000 http://www.hindawi.com/isrn/physchem/2012/570394/ A detailed quantum chemical calculation based study of hydrogen bond formation in trimethylene glycol- (TMG-) water complex has been performed by Hatree-Fock (HF) method, second-order Møller-Plesset perturbation theory (MP2), density functional theory (DFT), and density functional theory with dispersion function (DFT-D) using 6-31++G(d,p) basis set. B3LYP DFT-D, WB97XD, M06, and M06-2X functionals are used to capture highly dispersive hydrogen bond formation. Geometrical parameters, interaction energy, deviation of potential energy curve of hydrogen-bonded O–H from that of free O–H, natural bond orbital (NBO), atom in molecule (AIM), charge transfer, and red shift are investigated. It is observed that hydrogen bond between TMG and water molecule is stronger in case of TMG acting as proton donor compared to that of water acting as proton donor, and dilute TMG solution would inhibit water cluster formation. Snehanshu Pal and T. K. Kundu Copyright © 2012 Snehanshu Pal and T. K. Kundu. All rights reserved. Mon, 19 Nov 2012 11:17:08 +0000 http://www.hindawi.com/isrn/physchem/2012/724230/ For thermodynamic performance to be optimized, particular attention must be paid to the fluid’s thermal pressure coefficients and thermodynamics properties. A new analytical expression based on the statistical mechanics is derived for thermal pressure coefficients of dense fluids using the intermolecular forces theory to be valid for liquid lithium as well. The results are used to predict the parameters of some binary mixtures at different compositions and temperatures metal-nonmetal lithium fluid which agreement with experimental data. In this paper, we have used newly presented parameters of analytical expressions based on the statistical mechanics and predicted the metal-nonmetal transition for liquid lithium. The repulsion term of the effective pair potential for lithium shows well depth at 1600 K, and the position of well depth maximum is in agreement with X-ray diffraction and small-angle X-ray scattering. Vahid Moeini Copyright © 2012 Vahid Moeini. All rights reserved. Thu, 25 Oct 2012 13:59:36 +0000 http://www.hindawi.com/isrn/physchem/2012/254167/ The interaction of ethanol vapour at 293 K with modified Corning controlled porous glass (CPG-10) samples of various pre-silylation is reported. Ethanol adsorption on CPG-10 was greatly reduced by silylation to extents largely depending on the silylation extent, type of silane used, and on the concentration and accessibility of residual silanols. The obtained adsorption isotherms, BET surface areas, as well as the observed changes at the various stages during the sorption particularly in the capillary condensation region also showed similar dependence. In the capillary condensation region, in the case of the dimethyl dichlorosilane-modified sample, hysteresis type was changed from H3 to H1. On the triethyl chlorosilane-modified sample an unexpected suppression of hysteresis effects occurred with a consequent transformation of type IV to type II adsorption isotherm. Misael Silas Nadiye-Tabbiruka Copyright © 2012 Misael Silas Nadiye-Tabbiruka. All rights reserved. Mon, 15 Oct 2012 08:07:21 +0000 http://www.hindawi.com/isrn/physchem/2012/260171/ Quantitative structure-property relationship (QSPR) study on the acid dissociation constant, pKa of various 22 N-base ligands including pyridines, pyrimidines, purines, and quinolines has been carried out using Codessa Pro methodology and software. In addition, the formation constant, Kc of these ligands with Pt(II) (bpy = 2,2′-bipyridine) ion has also been modelled with the same methodology. Linear regression QSPR models of pKa and Kc were established with descriptors derived from AM1 calculations. Among the obtained QSPR models of pKa presented in the study, statistically the most significant one is a four parameters linear equation with the squared correlation coefficient, values of ca. 0.95 and the squared cross-validated correlation coefficient, values of ca. 0.89, and external the squared correlation coefficient, values of ca. 0.97. Statistically the most significant QSPR model of Kc is also a four parameters linear equation with the squared correlation coefficient, values of ca. 0.75 and the squared cross-validated correlation coefficient, values of ca. 0.55, and external the squared correlation coefficient, values of ca. 0.81. An analysis of descriptors that involved in the pKa models indicate that reactivity index and charge distribution related descriptors play major roles to model acid dissociation constant of ligands of N bases. Selami Palaz, Baki Türkkan, and Erol Eroğlu Copyright © 2012 Selami Palaz et al. All rights reserved. Sun, 14 Oct 2012 15:49:48 +0000 http://www.hindawi.com/isrn/physchem/2012/103817/ Pyrenes substituted with tert-butylethynyl, trimethylsilylethynyl, and trimethylsilylbutadiynyl groups were prepared, and the fluorescence yields (), lifetimes, and triplet-triplet absorption were measured in cyclohexane. Upon introduction of the groups possessing triple bond(s) to the pyrene skeleton, the fluorescence rate () increased. The variation of the terminating groups did not appreciably affect the and values. Increasing the number of the triple bond, the values increased by the magnitude of order whereas the were not varied. The effect of the ethynyl groups on the values was rationalized by the Strickler-Berg equation considering an increase of the 1 transition moment. Triplet-triplet absorption spectra of pyrene derivatives were obtained. The intersystem crossing rates () increased upon increasing the number of triple bonds terminated with the trimethylsilyl group whereas those between ethynylpyrenes were independent of the terminating groups. Heavy atom effect failed to rationalize the enhancement of the values upon adding the triple bond to the pyrene moiety. Minoru Yamaji, Hajime Maeda, Yasuaki Nanai, and Kazuhiko Mizuno Copyright © 2012 Minoru Yamaji et al. All rights reserved. Mon, 17 Sep 2012 10:50:24 +0000 http://www.hindawi.com/isrn/physchem/2012/619251/ Photoactivatable fluorophores switch from a nonemissive to an emissive state upon illumination at an activating wavelength and then emit after irradiation at an exciting wavelength. The interplay of such activation and excitation events can be exploited to switch fluorescence on in a defined region of space at a given interval of time. In turn, the spatiotemporal control of fluorescence translates into the opportunity to implement imaging and spectroscopic schemes that are not possible with conventional fluorophores. Specifically, photoactivatable fluorophores permit the monitoring of dynamic processes in real time as well as the reconstruction of images with subdiffraction resolution. These promising applications can have a significant impact on the characterization of the structures and functions of biomolecular systems. As a result, strategies to implement mechanisms for fluorescence photoactivation with synthetic fluorophores are particularly valuable. In fact, a number of versatile operating principles have already been identified to activate the fluorescence of numerous members of the main families of synthetic dyes. These methods are based on either the irreversible cleavage of covalent bonds or the reversible opening and closing of rings. This paper overviews the fundamental mechanisms that govern the behavior of these photoresponsive systems, illustrates structural designs for fluorescence photoactivation, and provides representative examples of photoactivatable fluorophores in actions. Françisco M. Raymo Copyright © 2012 Françisco M. Raymo. All rights reserved. Tue, 31 Jul 2012 14:11:16 +0000 http://www.hindawi.com/isrn/physchem/2012/504038/ The new Schiff base ligand (FIAS) 2,4-furyliminobenzylacetophenone has been synthesized with 4-aminoacetophenone and furane-2-carboxaldehyde by condensation in ethanol. Metal complexes of the ligand were prepared with chloride salts of copper(II), nickel(II) and cobalt(II) in ethanol. The ligand and its metal complexes have been characterized by microanalysis, magnetic susceptibility, FTIR, 1H and 13C NMR, mass spectrum, and UV-visible spectroscopy techniques. From these findings, it is suggested that metal ion coordinate by imines nitrogen and carboxylic oxygen atoms of FIAS to form octahedral geometry. All the newly compounds were tested antimicrobial activity against bacterial and fungal species. Jagvir Singh and Prashant Singh Copyright © 2012 Jagvir Singh and Prashant Singh. All rights reserved. Tue, 26 Jun 2012 15:14:34 +0000 http://www.hindawi.com/isrn/physchem/2012/959074/ A photoionization spectrometer for velocity map imaging has been developed for measuring the scattering distribution of fragment ions from polyatomic molecules. The spectrometer contains a mass gate and an ion reflector which are able to discriminate ions with a particular mass-to-charge ratio m/z. The basic functions and feasibility of these devices were tested experimentally and theoretically. First, the photoions from Kr and C60 were extracted into a time-of-flight (TOF) mass spectrometer by a transient or continuous electrostatic field. When the pulse application on the mass gate was tuned to the arrival timing of ions with a specific m/z, the peak of the selected ions alone was present on a TOF spectrum. Second, compatibility between velocity map imaging and ion discrimination was investigated by the computer simulations of the ion trajectories of photofragments from C60. A pulsed voltage was applied to the mass gate synchronously with the arrival timing of C+58 ions. The initial three-dimensional velocity distribution of C+58 was projected onto the image plane with an energy resolution better than 10 meV. The C+58 image was free from the contamination of other ions such as C+60 and C+56. Koichiro Mitsuke, Hideki Katayanagi, Bhim P. Kafle, and Md. Serajul I. Prodhan Copyright © 2012 Koichiro Mitsuke et al. All rights reserved. Wed, 09 May 2012 10:20:57 +0000 http://www.hindawi.com/isrn/physchem/2012/243741/ The vibrational spectrum of matrix-isolated indole-3-pyruvic acid has been studied aiming to obtain information about the structures of the stable vapour-phase forms of the molecule. Together with results from theoretical density functional calculations, the spectroscopic data enable to undertake an attribution for most of the observed bands. The FTIR spectrum of crystalline indole-3-pyruvic acid has been compared with that of matrix isolation study. Luigi Bencivenni, Andrea Margonelli, Alessandro Mariani, Andrea Pieretti, and Stella Nunziante Cesaro Copyright © 2012 Luigi Bencivenni et al. All rights reserved. Wed, 18 Apr 2012 09:21:52 +0000 http://www.hindawi.com/isrn/physchem/2012/820653/ The purpose of the present study was to examine and compare the cosolvency using three different cosolvents, namely PEG 400, PG, and glycerin on the aqueous solubility enhancement of a poorly aqueous soluble drug, etoricoxib, since solubilization of nonpolar drugs constitutes one of the important tasks in the formulation design of liquid dosage forms. The aqueous solubility of etoricoxib was 0.0767±0.0018 mg/mL, which was significantly improved by the addition of PEG 400, PG, and glycerin as cosolvents. It was scrutinized that the less-polar solvents were found to increase the aqueous solubility by greater extent, thus accentuating hydrophobic interaction mechanism. Among various solvent-cosolvent blends investigated, water-PEG 400 showed highest solubilization potential. Thus, the study generated an important array of data to compare the effect of these cosolvents on the aqueous solubility of etoricoxib. Amit Kumar Nayak and Prachi Prava Panigrahi Copyright © 2012 Amit Kumar Nayak and Prachi Prava Panigrahi. All rights reserved. Mon, 09 Apr 2012 10:14:38 +0000 http://www.hindawi.com/isrn/physchem/2012/431367/ Potential energy surfaces for three unimolecular elimination reactions: (CH3)3C−OH→(CH3)3=C=CH2+H2O, CH3−CF3→CH2=CF2+HF, and CH3−CH2−CH2C1→CH3−CH=CH2+HC1 were calculated using a variety of quantum chemical methods. It was shown that, in all the three cases, the transition state in the first step of the reaction leads to the production of the complex intermediates based on van der Waals interactions. In addition to the fact that the three complexes appear as intermediates on the potential energy surfaces, which means that they are not free entities, the entropy values of the two elimination products are far above those of the complexes due to their additional Sackur-Tetrode entropy. Moreover, the three vibrational frequencies of the H2O group in the (CH3)3COH complex and the H–Cl and H–F stretch frequencies in CH3CF3 and CH3CH2CH2Cl are quite different (see the various tables). The energy levels of the complexes were found to be below those of the corresponding decomposition products. Rate constants for the elimination processes were calculated from the potential energy surfaces using transition-state theory and were compared to available experimental data. Faina Dubnikova and Assa Lifshitz Copyright © 2012 Faina Dubnikova and Assa Lifshitz. All rights reserved.