http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2013 , Hindawi Publishing Corporation . All rights reserved. Tue, 16 Apr 2013 11:29:03 +0000 http://www.hindawi.com/journals/apc/2013/948189/ Research efforts to improve our understanding of electronic polymers are developing fast because of their promising advantages over silicon in photovoltaic solar cells. A major challenge in the development of polymer photovoltaic devices is the viable fabrication strategies of stable bulk heterojunction architecture that will retain functionality during the expected lifetime of the device. Block copolymer self-assembly strategies have attracted particular attention as a scalable means toward thermodynamically stable microstructures that combine the ideal geometrical characteristics of a bulk heterojunction with the fortuitous combination of properties of the constituent blocks. Two primary routes that have been proposed in the literature involve the coassembly of block copolymers in which one domain is a hole conductor with the electron-conducting filler (such as fullerene derivatives) or the self-assembly of block copolymers in which the respective blocks function as hole and electron conductor. Either way has proven difficult because of the combination of synthetic challenges as well as the missing understanding of the complex governing parameters that control structure formation in semiconducting block copolymer blends. This paper summarizes important findings relating to structure formation of block copolymer and block copolymer/nanoparticle blend assembly that should provide a foundation for the future design of block copolymer-based photovoltaic systems. A. Benmouna, R. Benmouna, M. R. Bockstaller, and I. F. Hakem Copyright © 2013 A. Benmouna et al. All rights reserved. Sun, 31 Mar 2013 16:11:30 +0000 http://www.hindawi.com/journals/apc/2013/905910/ The static linear and nonlinear optical properties of the σ-conjugated polymer α-t-Bu-ω-CN-poly(methylphenyl)silane (PMS) are studied at the Coupled-Perturbed Hartree-Fock (CPHF) level with 6-31+G(d) basis set. The calculated results reveal that the static first hyperpolarizabilities of this system increase with the main chain length and have a good agreement with experiments. The (hyper)polarizabilities per unit cell have been extrapolated to infinite chain limit and a comparison is made to those of polysilane and polyacetylene (PA). Besides, other structural properties depending on the σ-conjugated Si–Si skeleton length are investigated as well. Electron correlation effect is estimated and it turns out that the MP2 static first hyperpolarizability is about times larger than the corresponding CPHF value for the polymer with . Jing Li, Liang Peng, and Feng Long Gu Copyright © 2013 Jing Li et al. All rights reserved. Wed, 20 Mar 2013 09:45:23 +0000 http://www.hindawi.com/journals/apc/2013/497267/ The relationship between the spin of an individual electron and Fermi-Dirac statistics (FDS), which is obeyed by electrons in the aggregate, is elucidated. The relationship depends on the use of spin-dependent quantum trajectories (SDQT) to evaluate Coulomb’s law between any two electrons as an instantaneous interaction in space and time rather than as a quantum-mean interaction in the form of screening and exchange potentials. Hence FDS depends in an ab initio sense on the inference of SDQT from Dirac’s equation, which provides for relativistic Lorentz invariance and a permanent magnetic moment (or spin) in the electron’s equation of motion. Schroedinger’s time-dependent equation can be used to evaluate the SDQT in the nonrelativistic regime of electron velocity. Remarkably FDS is a relativistic property of an ensemble of electron, even though it is of order in the nonrelativistic limit, in agreement with experimental observation. Finally it is shown that covalent versus separated-atoms limits can be characterized by the SDQT. As an example of the use of SDQT in a canonical structure problem, the energies of the 1Σg and 3Σu states of H2 are calculated and compared with the accurate variational energies of Kolos and Wolniewitz. Burke Ritchie and Charles A. Weatherford Copyright © 2013 Burke Ritchie and Charles A. Weatherford. All rights reserved. Mon, 18 Mar 2013 13:31:36 +0000 http://www.hindawi.com/journals/apc/2013/842425/ Investigation of the sorption potential of rice husk, an agricultural waste, as an adsorbent was carried out. The rice husk was modified with orthophosphoric acid and was used for adsorption of lead (II) ions (Pb2+) from aqueous solution. Physicochemical properties of the modified rice husk were determined. Equilibrium sorption data were confirmed with Langmuir, Freundlich and Temkin adsorption isotherms. On the basis of adsorption isotherm graphs, values were determined to be 0.995, 0.916, and 0.797 for Langmuir, Temkin, and Freundlich isotherms, respectively, indicating that the data fitted well into the adsorption isotherms, but Langmuir isotherm is a better model. The maximum monolayer coverage from Langmuir studies,  mg/g, Langmuir isotherm constant,  L/mg, and the separation factor, at 100 mg/L of lead(II) ions indicating that the sorption process, was favourable. The suitability of modified rice husk as an adsorbent for the removal of lead ions from aqueous solution and its potential for pollution control is established. A. O. Dada, J. O. Ojediran, and Abiodun Paul Olalekan Copyright © 2013 A. O. Dada et al. All rights reserved. Mon, 04 Mar 2013 17:00:12 +0000 http://www.hindawi.com/journals/apc/2013/146585/ Polyethylene glycols (PEGs) were found to be efficient media for decarboxylative nitration of α,β-unsaturated aromatic carboxylic acids by ceric ammonium nitrate (CAN) in acetonitrile to give β-nitrostyrene derivatives. Kinetics of the reaction exhibited second order kinetics with a first order dependence on [CAN] and [substrate]. Reactions were too sluggish to be studied in the absence of PEG; therefore detailed kinetics were not taken up. Reaction times were reduced from 24 hrs to few hours. The catalytic activity was found to be in the increasing order PEG-300 > PEG-400 > PEG-600 > PEG-200. Mechanism of PEG-mediated reactions was explained by Menger-Portnoy's scheme as applied in micellar kinetics. K. Ramesh, S. Shylaja, K. C. Rajanna, P. Giridhar Reddy, and P. K. Saiprakash Copyright © 2013 K. Ramesh et al. All rights reserved. Tue, 25 Dec 2012 15:38:16 +0000 http://www.hindawi.com/journals/apc/2012/292908/ Dramatic rate enhancements have been observed in the oxidation of acetone (MMK), ethyl methyl ketone (EMK), and isobutyl methyl ketone (IBMK) by N-bromosuccinimide (NBS) in the presence of a mixture of metal ions [Ru(III) + Ir(III)]. The rate of oxidation in the the [Ru(III) + Ir(III)] system is much faster than either in the Ru(III) or in Ir(III) catalyzed system. The order in [NBS] was found to be zero both in catalyzed as well as uncatalyzed reactions. However, the order in [ketone] changed from unity to a fractional one in metal ion catalyzed systems. On the basis of kinetic features, the most plausible mechanism involving the oxidation of [Ir(III)-ketone] by Ru(III) to give [Ir(V)-ketone] and Ru(I) in the rate limiting step is proposed. Ru(I) thus formed is oxidized by NBS to Ru(III) in a fast step is discussed and individual rate parameters were evaluated. P. Giridhar Reddy, K. Ramesh, S. Shylaja, K. C. Rajanna, and S. Kandlikar Copyright © 2012 P. Giridhar Reddy et al. All rights reserved. Sat, 08 Dec 2012 10:41:14 +0000 http://www.hindawi.com/journals/apc/2012/798492/ Several microstructures are evolved at the interface when sparingly soluble solid surfactants come in contact with water. One class of these microstructures is termed as “myelin figures”; these were observed when phosphatidylcholine came in contact with water. Although the myelins are initially simple rod-like, complex forms like helices, coils and so forth. appear in the later stage. Finally, the myelins fuse together to form a complex mosaic-like structure. When studied by taking a cross-section using cryoscanning electron microscopy, it revealed concentric circular pattern inside the myelin figures. The cross-sections of (dioctyl sodium dodecyl sulfosiccinate) AOT/water system myelin internal structures were lost. When p-toluenesulfonic acid (PTS) 2 wt% was present in the water phase, AOT myelins revealed the internal microstructures. It has annular concentric ring-like structure with a core axon at the centre. Further investigation revealed new microstructures for the first time having multiple axons in the single-myelin strand. M. K. Temgire, C. Manohar, Jayesh Bellare, and S. S. Joshi Copyright © 2012 M. K. Temgire et al. All rights reserved. Tue, 20 Nov 2012 09:03:46 +0000 http://www.hindawi.com/journals/apc/2012/143734/ Reduction of [PtCl6]2− by L-ascorbic acid (H2ASc) in 0.1 M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2− = 0.005–0.007 mol dm−3, 0.05 ≤ [H2ASc]/mol dm−3 ≤ 0.3, 298 K ≤ ≤ 308 K, [H+] = 0.14 mol dm−3,  mol dm−3. The redox reaction follows the rate law: d[Pt(IV)]/dt = [H2ASc][Pt(IV)], where is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction . Activation parameters favor the electron transfer reaction. Sadhana Senapati, S. P. Das, and A. K. Patnaik Copyright © 2012 Sadhana Senapati et al. All rights reserved. Mon, 19 Nov 2012 13:58:07 +0000 http://www.hindawi.com/journals/apc/2012/205380/ Experimental study of the plasma gas phase in low-pressure radiofrequency discharges of oxygen and hexamethyldisiloxane is presented. The plasma phase has been studied by means of optical emission spectroscopy. Mass spectroscopy of the neutral and of the charged species has been performed too, directly sampling the plasma gas phase, by a dedicated spectrometer. We also measured the ion energy distribution. We have studied the influence of the operating conditions on the plasma gas-phase composition which plays a primary role in the formation process of SiO2 films, which are known for their important applicative uses. Ruggero Barni, Stefano Zanini, and Claudia Riccardi Copyright © 2012 Ruggero Barni et al. All rights reserved. Wed, 24 Oct 2012 09:25:49 +0000 http://www.hindawi.com/journals/apc/2012/175146/ The cage compound CL-20 (a.k.a., 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, HNIW, or 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane) is a well-studied high-energy-density material (HEDM). The high positive gas- ) and solid- () phase heat of formation values for CL-20 conformers have often been attributed to the strain energy of this cage compound and, by implication, to the conventional ring strain energy (CRSE) inherent in isowurtzitane which may be viewed as a “parent compound” (although not the synthetic precursor) of CL-20. values and destabilization energies (DSEs), which include the contribution from CRSE, were determined by computation using a relatively new multilevel ab intio model chemistry. Compared to cubane, isowurtzitane does not have an exceptionally high CRSE. It is about the same as that of cyclopropane and cyclobutane. These investigations demonstrate that instead of the CRSE inherent in the isowurtzitane parent compound, the relatively high and DSE values of CL-20 conformers must be due, primarily, to torsional strain (Pitzer strain), transannular strain (Prelog strain), and van der Waals interactions that occur due to the presence of the six >N–NO2 substituents that replace the six methylene (–CH2–) groups in the isowurtzitane parent compound. These conclusions are even more pronounced when 2,4,6,8,10,12-hexaazaisowurtzitane is viewed as the “parent compound.” John A. Bumpus Copyright © 2012 John A. Bumpus. All rights reserved. Thu, 11 Oct 2012 08:25:33 +0000 http://www.hindawi.com/journals/apc/2012/324098/ The ultrasonic velocity and density of binary liquid mixtures of quinoline with o-xylene, m-xylene, and p-xylene have been measured over the entire range of composition at = 303.15, 308.15, 313.15, and 318.15 K. Using these data, various parameters like adiabatic compressibility (β), intermolecular free length (), and acoustic impedance () and some excess parameters like excess adiabatic compressibility (), excess intermolecular free length (), excess acoustic impedance (), and excess ultrasonic velocity () have been calculated for all the three mixtures. The calculated deviations and excess functions have been fitted to Redlich-Kister polynomial equation. The observed deviations have been explained on the basis of the intermolecular interactions present in these mixtures. Sk. Fakruddin, Ch. Srinivasu, B. R. Venkateswara Rao, and K. Narendra Copyright © 2012 Sk. Fakruddin et al. All rights reserved. Thu, 30 Aug 2012 17:42:46 +0000 http://www.hindawi.com/journals/apc/2012/135172/ Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design. Dániel Kozma and Gergely Tóth Copyright © 2012 Dániel Kozma and Gergely Tóth. All rights reserved. Thu, 30 Aug 2012 15:39:52 +0000 http://www.hindawi.com/journals/apc/2012/304686/ This work presents a new quantitative model to predict the heat of explosion of nitroaromatic compounds using the natural bond orbital (NBO) charge and 15N NMR chemical shifts of the nitro groups (15NNitro) as structural parameters. The values of the heat of explosion predicted for 21 nitroaromatic compounds using the model described here were compared with experimental data. The prediction ability of the model was assessed by the leave-one-out cross-validation method. The cross-validation results show that the model is significant and stable and that the predicted accuracy is within 0.146 MJ kg−1, with an overall root mean squared error of prediction (RMSEP) below 0.183 MJ kg−1. Strong correlations were observed between the heat of explosion and the charges (R2 = 0.9533) and 15N NMR chemical shifts (R2 = 0.9531) of the studied compounds. In addition, the dependence of the heat of explosion on the presence of activating or deactivating groups of nitroaromatic explosives was analyzed. All calculations, including optimizations, NBO charges, and 15NNitro NMR chemical shifts analyses, were performed using density functional theory (DFT) and a 6-311+G(2d,p) basis set. Based on these results, this practical quantitative model can be used as a tool in the design and development of highly energetic materials (HEM) based on nitroaromatic compounds. Ricardo Infante-Castillo and Samuel P. Hernández-Rivera Copyright © 2012 Ricardo Infante-Castillo and Samuel P. Hernández-Rivera. All rights reserved. Thu, 23 Aug 2012 07:56:24 +0000 http://www.hindawi.com/journals/apc/2012/829523/ Conformational preference of N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium cation ([DEME]+), which is one of the quaternary ammonium-based ionic liquid cation, in the gas phase has been investigated using a density functional theory (DFT) calculation. Eight candidates for the stable conformers of [DEME]+ exist in the gas phase, and can it energetically classify into two groups. One is a five conformers group, which has the N+⋯O− intramolecular attractive interaction form (the folded form). The other is a three conformers group, which is the noninteraction form (the extended form). The transformation from the folded form to the extended form induces large changes in the dipole moment and partial charges of N and O atoms. Here we show that the difference in the dipole moment and partial charges of N and O atoms associated with the conformational change of [DEME]+ are closely related to the molecular orientation of [DEME]-based ionic liquids in the liquid state. Takahiro Takekiyo, Yusuke Imai, Hiroshi Abe, and Yukihiro Yoshimura Copyright © 2012 Takahiro Takekiyo et al. All rights reserved. Tue, 21 Aug 2012 11:18:50 +0000 http://www.hindawi.com/journals/apc/2012/431962/ The present approach describes the 𝑒+ fate since its injection into a liquid until its annihilation. Several stages of the 𝑒+ evolution are discussed: (1) energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between 𝑒+ and the constituents of its blob, and effect of local heating; (2) positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation; (3) fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-paraconversion by radiolytic products, reaction rate constants, and interpretation of the PAL spectra in water at different temperatures; (4) Ps bubble models. Inner structure of positronium (wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius). Sergey V. Stepanov, Vsevolod M. Byakov, Dmitrii S. Zvezhinskiy, Gilles Duplâtre, Roman R. Nurmukhametov, and Petr S. Stepanov Copyright © 2012 Sergey V. Stepanov et al. All rights reserved. Thu, 09 Aug 2012 11:28:35 +0000 http://www.hindawi.com/journals/apc/2012/970369/ FTIR spectroscopy was used to investigate the effects of extremely low frequency (50 Hz) electromagnetic field and of microwaves at 900 MHz on the secondary structure of a typical protein, the lysozyme, evaluating the bioprotective effectiveness of trehalose. Lysozyme in D2O solution (60 mg/ml) was exposed to 50 Hz frequency electromagnetic field at 180 μT. The FTIR spectra indicated an increase of CH2 group at 1921 and 1853 cm−1 after 3 h of exposure. Such effect was not observed after the addition of trehalose (150 mg/mL) at the same exposure conditions. Lysozyme dissolved in D2O at the concentration of 100 mg/mL was exposed up to 4 h to 900 MHz mobile phone microwaves at 25 mA/m. A significant increase in intensity of the amide I vibration band in the secondary structure of the protein was observed after 4 h exposure to microwaves. This effect was inhibited by the presence of trehalose at the concentration of 150 mg/mL. Fourier self-deconvolution spectral analysis of lysozyme in D2O solution after exposure to microwaves revealed an increase in intensity of the conformational components of amide I mode, particularly of β-sheet and turn that can be attributed to disorder and unfolding processes of the protein. Emanuele Calabrò and Salvatore Magazù Copyright © 2012 Emanuele Calabrò and Salvatore Magazù. All rights reserved. Sun, 15 Jul 2012 14:08:34 +0000 http://www.hindawi.com/journals/apc/2012/962594/ The Stern-Volmer constant is specified for the luminescence quenched by reversible ionization of excited molecules. The exergonic branch of the Rehm-Weller free energy dependence of this constant is known to be a plateau determined by irreversible ionization being under diffusion control. In the endergonic region the ionization is reversible and competes with the irreversible in-cage recombination of ions and their escape from the cage. At strong Coulomb attraction the latter phenomenon is shown to be negligible compared to the former that determines the shape and location of the descending branch of the Rehm-Weller curve. At weaker Coulomb attraction (at higher solvent polarity), this curve turns down at larger endergonicity. The experimental data obtained in solvents of different polarities are put in order and in full accordance with present theory. A. I. Burshtein and A. B. Doktorov Copyright © 2012 A. I. Burshtein and A. B. Doktorov. All rights reserved. Tue, 03 Jul 2012 11:01:48 +0000 http://www.hindawi.com/journals/apc/2012/598243/ The emergence of putative Hammett equation in mid 1930s was a boon to physical-organic chemists to elucidate the reaction mechanisms of several organic reactions. Based on the concept of this equation several hundreds of papers have emerged in chemical literature in the last century on the effect of structure, on reactivity, and very few on thermodynamic stability and kinetic reactivity of intermediates. In this article an attempt is made to explain the effect of hetero atom on Hammett’s reaction constant (ρ) taking the dissociation equilibriums of benzoic acids, dithiobenzoic acids, phenols, and thiophenols. Jagannadham Vandanapu and Sanjeev Rachuru Copyright © 2012 Jagannadham Vandanapu and Sanjeev Rachuru. All rights reserved. Tue, 12 Jun 2012 08:28:00 +0000 http://www.hindawi.com/journals/apc/2012/903272/ This paper describes the ordering degree of anionic, cationic, and zwitterionic surfactants with the increase of their packing density on Ge substrate by using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy. This work shows new insights on the conformational order of sodium dodecyl sulfate (SDS), N-hexadecyl-N-N-dimethyl-3-ammonio-1-propane-sulfonate (HPS), hexadecyl-trimethylammonium bromide (CTAB), and dodecyl trimethylammonium bromide (DTAB). DFT and semiempirical calculations are also performed in order to evaluate the effect of headgroup hydration and counterion. The CH2 asymmetric and symmetric stretching bands for the SDS molecule show a shift of 1.7 and 0.9 cm−1 to higher frequencies as the packing density increases, while it is observed a shift of 2.6 and 2.7 cm−1 for the HPS molecule, respectively. The DTAB molecule shows a shift of 4.5 cm−1 to lower frequencies for both CH2 asymmetric and symmetric stretching bands as the packing density increases, indicating the decrease of gauche conformations and the increase of all-trans conformations over the aliphatic chain. Rommel B. Viana, Albérico B. F. da Silva, and André S. Pimentel Copyright © 2012 Rommel B. Viana et al. All rights reserved. Sun, 06 May 2012 15:40:36 +0000 http://www.hindawi.com/journals/apc/2012/679869/ Laimutis Bytautas, Joel M. Bowman, Xinchuan Huang, and António J. C. Varandas Copyright © 2012 Laimutis Bytautas et al. All rights reserved. Mon, 09 Apr 2012 14:26:13 +0000 http://www.hindawi.com/journals/apc/2012/362608/ The effects of substituents on the N⋯HF interactions in the X-pyridazine⋯(HF)𝑛 (X = N(CH3)2, NHCH3, NH2, C2H5, CH3, OCH3, OH, CN, OF, NO2, F, Br, Cl, and 𝑛=1,2) complexes have been studied at the B3LYP/6-311++G(d,p) level of theory. In all complexes, the binding energies increase for the electron-donating substituents and decrease for the electron-withdrawing substituents. A negative cooperativity is observed for two hydrogen bond interactions. There are meaningful relationships between the Hammett constants and the energy data and the results of population analysis in the binary and ternary complexes. Symmetryadapted perturbation theory (SAPT) analysis was also carried out to unveil the nature of hydrogen bond in the complexes 2 and 3. The electron-donating substituents increase the magnitude of the SAPT interaction energy components and the electron-withdrawing substituents decrease those components. The highest/lowest change is observed for the 𝐸exch/𝐸disp component. The effect of C2H5 (or CH3) on different components is higher than OCH3 in the complex 2 while the trend is reversed in the complex 3. It is demonstrated that the electrostatic interaction plays a main role in the interaction, although induction and dispersion interactions are also important. Ali Ebrahimi, Mostafa Habibi-Khorassani, Farideh Badichi Akher, and Abdolkarim Farrokhzadeh Copyright © 2012 Ali Ebrahimi et al. All rights reserved. Wed, 21 Mar 2012 16:10:18 +0000 http://www.hindawi.com/journals/apc/2012/180604/ Milan M. Jaksic, Wolfgang Schmickleer, and Gianluigi Botton Copyright © 2012 Milan M. Jaksic et al. All rights reserved. Tue, 20 Mar 2012 08:32:24 +0000 http://www.hindawi.com/journals/apc/2012/491604/ Complex electrochemical reactions such as Oxygen Reduction Reaction (ORR) involving multi-electron transfer is an electrocatalytic inner-sphere electron transfer process that exhibit strong dependence on the nature of the electrode surface. This criterion (along with required stability in acidic electrolytes) has largely limited ORR catalysts to the platinum-based surfaces. New evidence in alkaline media, discussed here, throws light on the involvement of surface-independent outer-sphere electron transfer component in the overall electrocatalytic process. This surface non-specificity gives rise to the possibility of using a wide-range of non-noble metal surfaces as electrode materials for ORR in alkaline media. However, this outer-sphere process predominantly leads only to peroxide intermediate as the final product. The importance of promoting the electrocatalytic inner-sphere electron transfer by facilitation of direct adsorption of molecular oxygen on the active site is emphasized by using pyrolyzed metal porphyrins as electrocatalysts. A comparison of ORR reaction mechanisms between acidic and alkaline conditions is elucidated here. The primary advantage of performing ORR in alkaline media is found to be the enhanced activation of the peroxide intermediate on the active site that enables the complete four-electron transfer. ORR reaction schemes involving both outer- and inner-sphere electron transfer mechanisms are proposed. Nagappan Ramaswamy and Sanjeev Mukerjee Copyright © 2012 Nagappan Ramaswamy and Sanjeev Mukerjee. All rights reserved. Wed, 14 Mar 2012 15:27:53 +0000 http://www.hindawi.com/journals/apc/2012/212818/ Theoretical analysis corresponding to the diffusion and kinetics of substrate and product in an amperometric biosensor is developed and reported in this paper. The nonlinear coupled system of diffusion equations was analytically solved by Homotopy perturbation method. Herein, we report the approximate analytical expressions pertaining to substrate concentration, product concentration, and current response for all possible values of diffusion and kinetic parameters. The numerical solution of this problem is also reported using Scilab/Matlab program. Also, we found excellent agreement between the analytical results and numerical results upon comparison. K. Indira and L. Rajendran Copyright © 2012 K. Indira and L. Rajendran. All rights reserved. Wed, 22 Feb 2012 09:22:26 +0000 http://www.hindawi.com/journals/apc/2011/813987/ Transient exciplex formation mechanism of excited-state electron transfer reactions is analyzed in terms of experimental data on thermodynamics and kinetics of exciplex formation and decay. Experimental profiles of free energy, enthalpy, and entropy for transient exciplex formation and decay are considered for several electron transfer reactions in various solvents. Strong electronic coupling in contact pairs of reactants causes substantial decrease of activation energy relative to that for conventional long-range ET mechanism, especially for endergonic reactions, and provides the possibility for medium reorganization concatenated to gradual charge shift in contrast to conventional preliminary medium and reactants reorganization. Experimental criteria for transient exciplex formation (concatenated) mechanism of excited-state electron transfer are considered. Available experimental data show that this mechanism dominates for endergonic ET reactions and provides a natural explanation for a lot of known paradoxes of ET reactions. Michael G. Kuzmin, Irina V. Soboleva, and Elena V. Dolotova Copyright © 2011 Michael G. Kuzmin et al. All rights reserved. Thu, 09 Feb 2012 12:09:00 +0000 http://www.hindawi.com/journals/apc/2011/786759/ TiO2-based nanomaterials play currently a major role in the development of novel photochemical systems and devices. One of the key parameters determining the photoactivity of TiO2-based materials is the position of the band edges. Although its knowledge is an important prerequisite for understanding and optimizing the performance of photochemical systems, it has been often rather neglected in recent research, particularly in the field of heterogeneous photocatalysis. This paper provides a concise account of main methods for the determination of the position of the band edges, particularly those suitable for measurements on nanostructured materials. In the first part, a survey of key photophysical and photochemical concepts necessary for understanding the energetics at the semiconductor/solution interface is provided. This is followed by a detailed discussion of several electrochemical, photoelectrochemical, and spectroelectrochemical methods that can be applied for the determination of band edge positions in compact and nanocrystalline thin films, as well as in nanocrystalline powders. Radim Beranek Copyright © 2011 Radim Beranek. All rights reserved. Wed, 08 Feb 2012 11:08:25 +0000 http://www.hindawi.com/journals/apc/2011/252591/ We describe a multiscale modeling hierarchy for the particular case of Au-island ripening on Au(100). Starting at the microscopic scale, density functional theory was used to investigate a limited number of self-diffusion processes on perfect and imperfect Au(100) surfaces. The obtained structural and energetic information served as basis for optimizing a reactive forcefield (here ReaxFF), which afterwards was used to address the mesoscopic scale. Reactive force field simulations were performed to investigate more diffusion possibilities at a lower computational cost but with similar accuracy. Finally, we reached the macroscale by means of kinetic Monte Carlo (kMC) simulations. The reaction rates for the reaction process database used in the kMC simulations were generated using the reactive force field. Using this strategy, we simulated nucleation, aggregation, and fluctuation processes for monoatomic high islands on Au(100) and modeled their equilibrium shape structures. Finally, by calculating the step line tension at different temperatures, we were able to make a direct comparison with available experimental data. Karin Kleiner, Aleix Comas-Vives, Maryam Naderian, Jonathan E. Mueller, Donato Fantauzzi, Mostafa Mesgar, John A. Keith, Josef Anton, and Timo Jacob Copyright © 2011 Karin Kleiner et al. All rights reserved. Thu, 19 Jan 2012 09:20:58 +0000 http://www.hindawi.com/journals/apc/2011/412165/ The core subject of the present paper represents the interrelated spillover (effusion) phenomena both of the primary oxide and the H-adatoms, their theory and practice, causes, appearances and consequences, and evidences of existence, their specific properties, and their alterpolar equilibria and kinetic behavior, structural, and resulting catalytic, and double layer charging features. The aim is to introduce electron conductive and d-d interactive individual and composite (mixed valence) hypo-d-oxide compounds, of increased altervalent capacity, or their suboxides (Magnéli phases), as the interactive catalytic supports and therefrom provide (i) the strong metal-support interaction (SMSI) catalytic effect and (ii) dynamic spillover interactive transfer of primary oxides (M-OH) and free effusional H-adatoms for further electrode reactions and thereby advance the overall electrocatalytic activity. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. In fact, altervalent hypo-d-oxides impose spontaneous dissociative adsorption of water molecules and then spontaneously pronounced membrane spillover transferring properties instantaneously resulting with corresponding bronze type (Pt/HxWO3) under cathodic and/or its hydrated state (Pt/W(OH)6), responsible for Pt-OH effusion, under anodic polarization, this way establishing instantaneous reversibly revertible alterpolar bronze features (Pt/H0.35WO3⇔ Pt/W(OH)6) and substantially advanced electrocatalytic properties of these composite interactive electrocatalysts. Such nanostructured-type electrocatalysts, even of mixed-valence hypo-d-oxide structures (Pt/H0.35WO3/TiO2/C, Pt/HxNbO3/TiO2/C), have for the first time been synthesized by the sol-gel methods and shown rather high stability, electron conductivity, and nonexchanged initial pure monobronze spillover and catalytic properties. Such a unique electrocatalytic system, as the striking target issue of the present paper, has been shown to be the superior for substantiation of the revertible cell assembly for spontaneous reversible alterpolar interchanges between PEMFC and WE. The main target of the present thorough review study has been to throw some specific insight light on the overall spillover phenomena and their effects in electrocatalysis of oxygen and hydrogen electrode reactions from diverse angles of view and broad contemporary experimental methods and approaches (XPS, FTIR, DRIFT, XRD, potentiodynamic spectra, UHRTEM). Georgios D. Papakonstantinou, Jelena M. Jaksic, Diamantoula Labou, Angeliki Siokou, and Milan M. Jaksic Copyright © 2011 Georgios D. Papakonstantinou et al. All rights reserved. Wed, 18 Jan 2012 14:51:02 +0000 http://www.hindawi.com/journals/apc/2012/720197/ We review ab initio studies based on quantum mechanics on the most important mechanisms of reaction leading to the C–H, Si–H, and Ge–H bond breaking of methane, silane, and germane, respectively, by a metal atom in the lowest states in Cs symmetry: X(2nd excited state, 1st excited state and ground state) + YH4→ H3XYH → H + XYH3 and XH + YH3. with X = Au, Zn, Cd, Hg, Al, and G, and Y = C, Si, and Ge. Important issues considered here are (a) the role that the occupation of the d-, s-, or p-shells of the metal atom plays in the interactions with a methane or silane or germane molecule, (b) the role of either singlet or doublet excited states of metals on the reaction barriers, and (c) the role of transition probabilities for different families of reacting metals with these gases, using the H–X–Y angle as a reaction coordinate. The breaking of the Y–H bond of YH4 is useful in the production of amorphous hydrogenated films, necessary in several fields of industry. Octavio Novaro, María del Alba Pacheco-Blas, and Juan Horacio Pacheco-Sánchez Copyright © 2012 Octavio Novaro et al. All rights reserved. Sun, 15 Jan 2012 13:56:41 +0000 http://www.hindawi.com/journals/apc/2011/275695/ This paper reports the growth of MgO nanofilms on BaMgAl10O17:Eu2+ blue phosphors by using the atomic layer deposition method. MgO films were prepared at 120°C by using Mg(CpEt)2 and H2O as the precursor and reactant gas, respectively. X-ray photoelectron spectroscopy (XPS) analysis showed that the Mg peak of the coated powders was higher than that of the uncoated powders. This confirmed that the surface of the coated phosphor powder comprised MgO nanoscale film. Through TEM and FE-SEM analysis, it was observed that the growth rate was about 0.33 Å/cycle and that the surface morphology of the coated phosphors was smoother and clearer than that of uncoated phosphor. The photoluminescence (PL) intensity for the coated phosphors was 5%–19% higher than that of uncoated phosphor. This means that the reactive surface is uniformly grown with stable magnesium oxide to reduce the dead surface layer without change of bulk properties. Hyug Jong Kim, Hee Gyu Kim, In Gu Kang, and Byung Ho Choi Copyright © 2011 Hyug Jong Kim et al. All rights reserved.