Photoelectrochemical oxidation of methanol on oxide nanosheets

Photoelectrochemical oxidation of alcohol on various nanosheet electrodes such as Nb6O17, Ca2Nb3O10, Ti(0.91)O2, Ti4O9, and MnO2 system host layers were measured to evaluate the photocatalysis of water photolysis with alcohol as a sacrificial agent. The nanosheet electrodes were prepared by the layer-by-layer (LBL) method, using electrostatic principles. The highest photooxidation current density was observed in methanol solution for Nb6O17 and Ca2Nb3O10 nanosheets, while the density was lower for Ti(0.91)O2, Ti4O9, and MnO2 nanosheets in decreasing order. The rank in the photocurrent density was in agreement with that in the photocatalytic activity, which means that the degree of photooxidation of the alcohol determines the activity of the alcohol in the water photolysis process. The photocurrent was independent of the number of nanosheet layers on the electrode, indicating that only the mono-nanosheet layer attached directly on a substrate acts as a photoelectrocatalyst and that the interlayer space is not important. Consequently, higher photooxidation current on the Nb6O17 mono-nanosheet layer means that the charge separation of electron and hole under illumination is very large and that the hole-capturing process by CH3OH is very quick compared with the surface recombination on the Nb6O17 nanosheet. The adsorption of a transition metal cation on the nanosheet acted as the surface recombination center, because the photocurrent decreased after the adsorption. The photocatalytic mechanism has been discussed in detail in terms of various photoelectrochemical behaviors.     

Removability of the logarithmic singularity for the elliptic PDEs with measurable coefficients and its consequences

This paper introduces the notion of log-regularity (or log-irregularity) of the boundary point \(\zeta \) (possibly \(\zeta =\infty \)) of the arbitrary open subset \(\Omega \) of the Greenian deleted neigborhood of \(\zeta \) in \({\mathbb {R}}^2\) concerning second order uniformly elliptic equations with bounded and measurable coefficients, according as whether the log-harmonic measure of \(\zeta \) is null (or positive). A necessary and sufficient condition for the removability of the logarithmic singularity, that is to say for the existence of a unique solution to the Dirichlet problem in \(\Omega \) in a class \(O(\log |\cdot - \zeta |)\) is established in terms of the Wiener test for the log-regularity of \(\zeta \). From a topological point of view, the Wiener test at \(\zeta \) presents the minimal thinness criteria of sets near \(\zeta \) in minimal fine topology. Precisely, the open set \(\Omega \) is a deleted neigborhood of \(\zeta \) in minimal fine topology if and only if \(\zeta \) is log-irregular. From the probabilistic point of view, the Wiener test presents asymptotic law for the log-Brownian motion near \(\zeta \) conditioned on the logarithmic kernel with pole at \(\zeta \).     

Generalized entropic structures and non-generality of Jaynes’ Formalism

The extremization of an appropriate entropic functional may yield to the probability distribution functions maximizing the respective entropic structure. This procedure is known in Statistical Mechanics and Information Theory as Jaynes’ Formalism and has been up to now a standard methodology for deriving the aforementioned distributions. However, the results of this formalism do not always coincide with the ones obtained following different approaches. In this study we analyse these inconsistencies in detail and demonstrate that Jaynes’ formalism leads to correct results only for specific entropy definitions.     

On minimal and Chen immersions in space forms

By using the push-out map we obtain some results on minimal immersions and Chen immersions with non-flat normal bundle in space forms under some conditions. We then build up many examples of minimal and Chen immersions.     

Lichens and mosses for correlation between trace elements and 210Po in the areas near coal-fired power plant at Yatağan, Turkey

The lichensRhizoplaca melanophthalma, Cladonia convoluta, Cladonia pyxidata and the mossesGrimmia pulvinata, Hypnum cupressiforme were analyzed for Pb, Cr, Cd, Co, Ni, Mn, Cu, Zn and Fe using atomic absorption spectrophotometry over a wide area around a coal-fired power plant located in Yataan. The results were compared with the ²¹⁰Po concentrations previously measured in the same samples. Correlations between ²¹⁰Po and trace elements for different moss and lichen species of the same localization and for different localizations for the same species were also studied. In general trace element concentrations do not show significant differences from site to site for all species except Mn in Hypnum cupressiforme and ²¹⁰Po in Grimmia pulvinata. To discuss the ²¹⁰Pb level and sources in indicator plants analyzed, also radium contents of surface soil at each sampling station was measured and compared with the average values for similar soil types in the literature.     

Swelling of interpenetrating networklike particles in a soft polymer matrix

Fast transient fluorescence technique was used to monitor swelling of hard latex particles in a soft polymer matrix. Various film samples were prepared from pyrene (P) and/or naphthalene (N)-labeled poly(methyl methacrylate) (PMMA) particles in a low-molecular-weight poly(isobutylene) (PIB) matrix. These PMMA particles contain interpenetrating PIB channels. Film samples were annealed at elevated temperatures to promote particle swelling. Fluorescence lifetimes, tau, were measured for each film sample. It was observed that tau values decrease as the PIB content in the matrix is increased. The decrease in tau was explained by the increase in quenching of excited P and N molecules by low-molecular-weight PIB penetrating into the PIB channels in the PMMA particles. A drastic decrease in tau above a certain temperature was attributed to the effect of particle size on the swelling of the latex particles in the PIB matrix. It was observed that small particles (P-labeled) swell at much lower annealing temperatures than large (N-labeled) particles.     

Visible light photoelectrochemical activity of K4Nb6O17 intercalated with photoactive complexes by electrostatic self-assembly deposition

Electrostatic self-assembly deposition (ESD) results in the intercalation of Ru(bpy)₃²⁺ or methylene blue (MB) into the niobate layered oxide right after the cations come into contact with [Nb₆O₁₇]⁴⁻ nanosheets. Monolayers can be obtained by the exfoliation of proton exchanged K₄Nb₆O₁₇ (KNbO) in an aqueous tetrabutylammonium (TBA) solution as revealed by the atomic force microscopy micrographs. UV-vis spectra show that intercalated films are able to absorb in the visible light range. Heat-treatment of Ru(bpy)₃²⁺ resulted in the red-shift in the absorption spectra, which was assigned to the enhancement in the interaction between the complex molecules and [Nb₆O₁₇]⁴⁻ host layer. Intercalated niobate layered oxides are able to produce photocurrent as a result of the electron transfer from the excited guest molecule to the host layer under visible light illumination. Ru(bpy)₃²⁺ intercalated niobate layered oxide shows photocatalytic activity under visible light illumination to produce H₂ from water-methanol solution.     

Viscous behavior of linear and three‐branch alkanes: Linking the equilibrium and transport theories

A new model for zero‐shear viscosity, η, is proposed. The model combines the Simha–Somcynsky (SS) statistical thermodynamic theory of liquids with the Eyring Significant Structure (ESS) transport theory. Using the new model, a successful linearization of the experimental viscosity vs. hole fraction data was obtained. A comparison between the new model and Utracki's relation, ln η = a₀ + a₁/(h + a₂) was also made. The former was found to be more successful for both linear and nonlinear structures, provided that an appropriate choice of the degrees of freedom of normal and activated states was made. The proportionality constant of the activation energy and transmission coefficient were also calculated for each species. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 879–887, 1999     

Microwave‐Assisted Synthesis of Novel 2,4‐Dihydro‐5‐[4‐(trifluoromethyl)phenyl]‐3H‐1,2,4‐triazol‐3‐ones and Potentiometric Determination of Their pKa in Nonaqueous Solvents

The novel 4‐amino‐ or 4‐aryl‐substituted 2,4‐dihydro‐5‐[(4‐trifluoromethyl)phenyl]‐3H‐1,2,4‐triazol‐3‐ones 3a – 3g were synthesized by reaction of N‐(ethoxycarbonyl)‐4‐(trifluoromethyl)benzenehydrazonic acid ethyl ester ( 2 ) and primary amines or hydrazine by microwave irradiation. Compounds 3a – 3g were potentiometrically titrated with tetrabutylammonium hydroxide (Bu₄NOH) in four nonaqueous solvents, i.e., ⁱPrOH, ^tBuOH, MeCN, and N,N‐dimethylformamide (DMF). Also half‐neutralization potential values and the corresponding pK_a values were determined in all cases.     

Atom transfer graft copolymerization of 2‐ethyl hexylacrylate from labile chlorines of poly(vinyl chloride) in an aqueous suspension

Copper‐mediated atom transfer radical polymerization (ATRP) is presented as a versatile tool for the graft copolymerization of 2‐ethyl hexylacrylate with poly(vinyl chloride) (PVC) in an aqueous suspension. The appreciable solubility of PVC in 2‐ethyl hexylacrylate (30%) at temperatures around 130 °C makes grafting of the monomer possible from labile chlorines of PVC in aqueous suspensions without the use of additional solvent. The first‐order kinetics (rate constant k = 4.2 × 10^?6 s^?1) of the mass percentage increase reveals a typical ATRP fashion of the graft copolymerization at low conversions. The use of a completely organosoluble copper(I) complex of hexylated triethylene tetramine, in combination with α‐methylcellulose as a stabilizer, makes the graft copolymerization possible in a dispersed organic phase. Nearly spherical, green particles can be obtained with moderate stirring rates (1000 rpm) in high graft yields. Although the kinetics of the reaction deviates from the first order at high conversions, reasonable graft yields (146%) can be attained within a reaction period of 24 h. In this study, the reaction conditions of the grafting have been studied, and graft products have been confirmed by common techniques such as ¹H NMR, gel permeation chromatography, and differential scanning calorimetry. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1900–1907, 2006