bluuebunny/crossref_metadata_2025_split huggingface dataset:
In situ Infrared Spectroscopy at Electrodes: On the Adsorption of CO and CO2 on Copper, Platinum and Gold
Authors: Westerhoff Bernard , Holze Rudolf 
Published: July 2012

AbstractIn situ Infrared reflection absorption spectroscopy RAIRS of adsorbed CO and CO2 on copper, platinum and gold electrodes has been used to study the interaction between adsorbate and electrode and to identify products of reactions following the adsorption. COad on electrochemically roughened copper shows a Surface Enhanced Raman spectrum significantly different from the one recorded with RAIRS, this is attributed to the presence of different adsorption sites probed with these spectroscopies. Reduction of CO2 on platinum results in a CO‐adsorbate with a vibrational behavior different from that of COad.
Probe Beam Deflection for the Analysis of Ion Fluxes at the Solid/Liquid Interface
Authors: Kötz R. , Barbero C. , Haas O. 
Published: July 2012

AbstractThe probe beam deflection (PBD) technique is based on the deflection of a laser beam, aligned parallel to the electrode surface, caused by the concentration profile evolving in front of the electrode during an electrochemical reaction. Monolayer and sub‐monolayer sensitivity has been achieved by means of PBD for (i) the proton flux during oxide formation/reduction on a polycrystalline gold electrode and (ii) for the under potential deposition (UPD) of copper on platinum. The potential of the PBD technique for the analysis of electrochemical reactions is demonstrated for the intrinsic redox reaction occurring on activated glassy carbon (GC) electrodes as a consequence of the generation of surface functional groups. PBD clearly reveals that protons are exchanged in acidic electrolyte on activated GC. Finally, the O2 reduction on Au in alkaline electrolytes has been monitored by the probe beam deflection technique.
Optical In‐situ Methods of High Local Resolution for the Investigation of Corrosion Processes
Authors: Michaelis A. , Schultze J. W. 
Published: July 2012

AbstractDifferent optical in‐situ methods which can be combined with standard electrochemistry are discussed. The related methods of micro‐ellipsometry (resolution ca. 40 μm) and micro‐reflection‐spectroscopy (resolution ca. 10 μm) have been added to a well proved laser scanning apparatus (resolution ca. 2 μm), which allows not only probing of sample surfaces but also, by using high laser power, modifying of the layers under investigation. — With these non destructive methods not only new and complement properties are obtained but also local electrode processes in the μm2 scale can be investigated, whereas standard electrochemistry is limited to the mm2 range. — As an example for the application of these methods, the investigation of grain depending passive layer formation on electropolished titanium surfaces is chosen. Herewith predictions about the local corrosion behaviour of this material can be deduced.
Undoped and Doped Oligothiophenes: an In‐situ XPS‐, UPS‐, and HREELS‐Study
Authors: Oeter D. , Ziegler Ch. , Gopel W. , Naarmann H. 
Published: July 2012

AbstractA new method for doping organic semiconductors is presented. The most common dopant for the widely used α‐sexithiophene (α6T), FeCl3, was co‐sublimed with the oligothiophene under UHV‐conditions. The solid‐state doping effects were studied for systematically varied dopant concentrations in‐situ with XPS. UPS, and HREELS. Up to a doping level of one effective charge per α6T the results can be interpreted as polaron formation. At higher dopant concentrations polaron bands are most probably formed.
In‐Situ Time Resolved Impedance Spectroscopy of Processes in the Solid/Liquid Interface: Electropolymerization of Bithiophene
Authors: Popkirov G. S. , Schindler R. N. 
Published: July 2012

AbstractExperimental EIS results are presented which were obtained during polymerization of bithiophene on a Pt electrode under potentiostatic conditions. A FFT impedance spectrometer which uses a sum of selected sine waves as a perturbation was employed in this study. A numerical approach was applied to obtain correct impedance data from these measurements. The investigation confirmed that electropolymerization is accompanied by the build‐up of a very large capacitance in the electrode double layer.
Examination of the Time Dependence of Concentration of Defects and Surface States during Intrinsic Redox Processes in Oxide Films
Authors: König U. , Blum O. , Christ R. , Reeh I. 
Published: July 2012

AbstractIntrinsic redox reactions of oxides are closely related to the electronic properties of the examined systems. Information about the electronic structure can be achieved by examining the potential dependence of the electrode capacity at various polarisation times and potentials. — Redox processes within passive layers on Ni (d < 10 nm) and within LaNiO3 (d > 1 μm) are shown as example of intrinsic reactions. Oxidation as well as reduction starts with the charging of surface states and defects during 100 μs. The redox process of the Ni—O‐matrix needs 10 ms to start. During oxidation, formation of Ni3+ and O2‐evolution takes place. Surface states, formed by Ni3+, covers nearly the whole surface. They will be compensated during O2‐evolution. During reduction, the amount of surface states decreases down to 30% of the surface and the defect number decreases as well. The redox process within LaNiO3 is governed by the reaction of Ni‐ions. It depends strongly on the mobility of vacancies. — The doping of oxides by protons is demonstrated for passive layers on Ti. During polarisation near Ufb (reduction), protons penetrate into the layer and the donor number increases. Polarisation at anodic potentials (oxidation) forces the protons out of the layer. During the redox process, no change of the oxide takes place and surface states can be neglected.
In‐situ Investigation of Electrochemical Alloy Formation, Electroless Metal Deposition, and Selective Alloy Oxidation
Authors: Pittermann Udo , Weil Konrad G. 
Published: July 2012

AbstractExamples will be presented for applications of the following in‐situ techniques: determination of mass changes with a quartz microbalance, determination of double layer properties with a fast impedance spectroscopy, and determination of surface microstructures from impedance analysis of vibrating quartz crystals. These examples are: Formation of copper/gold alloys from underpotential layers of copper on gold, electroless copper deposition with formaldehyde, and selective oxidation of copper/gold alloys.
Ion Movements during Redox Switching of Polypyrrole — Experiment and Simulation
Authors: Heinze JüRgen , Bilger Ralf 
Published: July 2012

AbstractOxidation of pyrrole yields a charged polymer film with incorporated anions. During the following reduction electroneutrality can be maintained by expulsion of these anions or by incorporation of cations. The contribution of both processes to the overall charge transport is found to depend strongly on the formation potential during polymerization. The redox process of polypyrrole formed at +1.0 V vs. Ag/AgCl is accompanied by a change in mass, which can be interpreted by a simultaneous transport of anions and cations. A lower formation potential leads to a separation of the charge transport in an either anion or cation dominated region. These differences are related to a cathodically shifted first reduction which occurs if a low formation potential was used. The charge transfer at the electrode and at the polymer‐solution interface is illustrated by a physical model. It consists of an (E)n—C—(E)m mechanism for the redox behavior of the polymer and a first‐order reaction for incorporation and expulsion of ions. Computed voltammograms and mass curves are presented for different situations and compared to experimental conditions.
Rate Constants for the Reactions of CH2 (X̄3B1) with Selected Alkenes at Temperatures Between 296 K≤T≤728 K
Authors: Kraus H. , Oehlers C , Temps F. , Gg. Wagner H. , Wolf M. 
Published: July 2012

AbstractThe kinetics of the reactions of CH2 (X̄3B1) with selected alkenes R = ethylene (1), tetramethylethylene (2), cycloheptatriene (3), and 1,3‐butadiene (4) were studied at temperatures between 296 K≤T≤728 K. Rate constants were measured for reactions (2–4) using the discharge flow technique with Far‐Infrared Laser Magnetic Resonance (FIR–LMR) detection of 3CH2. The experimental data can be described by the rate expressions (±2σ)magnified image These data and results for reaction (1) obtained earlier were analyzed to separate the contributions to the CH2 (X̄) depletion by reactive channels versus collisional excitation to the ã1A1 state of CH2 followed by reactions of CH2 (ã). The rate expressions (±2σ) for the reactive pathways of CH2 (X̄) were found to be magnified image.
Rayleigh‐Brillouin Scattering of Molten ZnCl2
Authors: Zhu Hongmin , Sato Yuzuru , Yamamura Tsutomu , Sugimoto Katsuhisa , Sato Yoshiyuki 
Published: July 2012

AbstractThe Rayleigh‐Brillouin scattering experiment has been carried out for molten ZnCl2. The complete profiles of Rayleigh‐Brillouin spectra were obtained at scattering angles of 90° and 140°, and at temperatures ranging from 550 to 1000 K by the use of the carefully purified samples. The remarkable change in the shape of the spectrum with temperature variation has been observed and has been concluded to be due to a structural relaxation in the melt. The spectra have been analyzed by the viscoelastic theory on the assumption of a single relaxation. The sound velocities at the limiting low and high frequencies and the relaxation time have been determined.
Static Relative Permittivity of Carbon Dioxide and Nitrous Oxide up to 30 MPa
Authors: Moriyoshi T. , Kita T. , Uosaki Y. 
Published: July 2012

AbstractThe static relative permittivity εrof carbon dioxide and nitrous oxide has been measured in a temperature range from 273.15 to 353.15 K at pressures up to 30 MPa. The measurements were performed by means of a transformer ratio‐arm bridge with a three‐terminal capacitance cell installed in a pressure vessel at frequencies between 10 to 50 kHz. The newly‐designed capacitance cell and pressure apparatus are described. Experimental εr‐values obtained for the two fluids were estimated to be accurate to within ±0.02%. The critical relative permittivity εr,C, evaluated from the εr‐values of coexisting saturated vapor and saturated liquid, was 1.267±0.001 for carbon dioxide and 1.288±0.003 for nitrous oxide. The density dependence of the εr‐values can be expressed by a quadratic function of density, independent of temperature. The εr‐data for each fluid were combined with available densities from the literature to calculate the molar polarizationPmgiven by the Clausius‐Mossotti (CM) equation. Some consideration is given for the coefficients of the dielectric virial equation, i.e., the expansion of the CM equation in powers of density.
1H NMR Study of Molecular Motions and Phase Transitions in Methyl Ammonium Hexabromo Selenate [(CH3NH3)2SeBr6]
Authors: Murthy B. V. S. , Ramesh K. P. , Ramakrishna J. 
Published: July 2012

AbstractThe temperature dependence of 1H spin‐lattice relaxation time, T1, and that of the second moment, M2, are analysed in the temperature range 390 K to 77 K. A plot of T1 vs inverse temperature shows three phase transitions at 250 K, 167 K and 111 K. At 167 K, T1 displays a large jump while it shows changes in slope at 250 K and 111 K. In the high temperature phase (> 167 K), the correlated motion of CH3 and NH3 groups is found to cause the relaxation while their uncorrelated motion takes over in the low temperature phases (< 167 K). The unusual T1 behaviour in phase II (250 K‐167 K) is ascribed to the small angle torsion of the cation. A constant M2 value of ∼ 9.7 G2, throughout the range of temperature studied, indicates the presence of reorientation of CH3 and NH3 groups.
Thermodynamics of Hydrogen Dissolved in Palladium‐rich PdErAg(Au,Cu) Ternary Solid Solution Alloys
Authors: El‐Sanabary Fatma , Ramaprabhu Sundara , Weiss Alarich 
Published: July 2012

AbstractUsing a volumetric method, pressure‐composition hydrogen absorption isotherms have been determined for the ternary face centered cubic solid solution alloys (Pd1‐xMx)1‐yEry (M = Ag, Au, Cu; xAg = xAu = 0.079; xCu = 0.08; yEr = 0.00‐0.08) within 10 ≤ PH2/mbar ≤ 1000 and 473 ≤ T/K ≤ 873. The lattice constants a0 of the ternary alloys increase with increasing yEr and the increase in a0 with a given erbium and noble metal content is in the order ao[(Pd1‐xAux)1‐yEry] > ao[(Pd1‐xAgx)1‐yEry] > a0[(Pd1‐xCux)1‐yEry], as in the erbium free binary Pd1‐xMx (M = Au, Ag, Cu) solid solution alloys. The hydrogen solubility r increases with increasing yEr in the (Pd1‐xMx)1‐yEry ternary solid solution alloys; the increase in r with a given erbium and noble metal content is in the order r[(Pd1‐xAgx)1‐yEry] > r[(Pd1‐xAux)1‐yEry] > r[(Pd1‐xCux)1‐yEry], a trend noted in the erbium free binary alloys Pd1‐xMx (M = Ag, Au, Cu). The partial molar enthalpy of hydrogen solution at infinite dilution (ΔH0H) becomes more exothermic with yEr and the increase of exothermicity of hydrogen absorption at given yEr and xM is in the order (ΔH0H[(Pd1‐xAgx)1‐yEry] > (ΔH0H[Pd1‐xAux)1‐yEry] > (ΔH0H[Pd1‐xCux)1‐yEry]. The partial molar excess entropy of hydrogen solution at infinite dilution (ΔSE,0H) and the chemical potential of dissolved hydrogen at infinite dilution (Δ0H), both, decrease with yEr. The hydrogen solubility and the exothermicity of hydrogen absorption in Pd0.903Cu0.078Er0.019 alloy are higher than those in pure palladium, even though a0 of Pd0.903Cu0.078Er0.019 alloy is less that of pure palladium, due to the larger metal‐hydrogen attractive interaction in Pd0.903Cu0.078Er0.019 alloy than in pure Pd. As in Pd1‐yREy‐H (RE = Er, Y, Dy, Gd, and Sm) and Pd1‐xMx‐H systems, a correlation between ΔH0H and ΔSE,0H exists in (Pd1‐xMx)1‐yErx‐H systems.
Links Between Bulk and Surface Activity in Micellar Solutions
Authors: Mesa Camillo La , Ranieri Giuseppe A. 
Published: July 2012

AbstractThe surface tension of aqueous surfactant systems and its dependence on the concentration of surfactant in micellar form, Xm ≅ X‐CMC, have been investigated. A modification of the adsorption equation, based on the introduction of activity coefficients, allows to get information on micelle aggregation numbers, 〈N〉, from the slope of surface tension versus ln Xm. The resulting equation, tested on data relative to non ionic surfactants, gives aggregation values in fair good agreement with those inferred from other methods. The limits of the model are discussed in some detail.
Highly Monodisperse Quantum Sized CdS Particles by Size Selective Precipitation
Authors: Chemseddine A. , Weller H. 
Published: July 2012

AbstractNanometer sized cadmium sulfide particles were prepared in N,N‐dimethylformamide, using thiourea as the sulfurizing agent and thioglycerine as stabilizer. For particles with diameters of less than 40 Å the size dependent solubility was utilized to separate the particles according to their size. The absorption spectra of the size separated samples exhibit well pronounced excitonic absorption bands indicating a very narrow size distribution.
Prediction of the Thermodynamic Properties of Hydrogen‐Oxygen Mixtures from 80 to 373 K and to 100 MPa
Authors: Deiters Ulrich K. , Neichel Monika , Franck Ernst U. 
Published: July 2012

AbstractThe equations of state of Deiters and of Christoforakos and Franck, together with appropriate mixing rules, have been used to predict fluid phase equilibria, the critical curve, molar volumes and excess enthalpies of the binary hydrogen‐oxygen system between 80 and 373 K and to pressures of 100 MPa. The applicability of the equations of state has been tested with experimental data which exist for the hydrogen‐nitrogen system and, to some extent, for the systems neon‐nitrogen and neon‐oxygen. Binary interaction parameters for the hydrogen‐oxygen system have been derived from these systems. Results from both equations of state have been compared. Numerical values for the thermodynamic properties of the hydrogen‐oxygen system are given. The calculated critical line is of the interrupted type; the upper branch begins at the critical point of oxygen (154.6 K) and tends to approximately 83–99 K at 100 MPa, depending on the calculation method. Hydrogen appears to be considerably less miscible with oxygen than with nitrogen at high pressures. Predicted pressures for oxygen‐hydrogen solid‐gas equilibria at 49.8 K agree well with experimental data to 12 MPa.
Kinetic and Primary Product Studies of the Reaction of O (3P) with Styrene in the Gas Phase
Authors: Buchta Chr. , Frerichs H. , Stucken D.‐V. , Tappe M. , Wagner H. G. G. 
Published: July 2012

AbstractThe rates of the reaction of styrene with atomic oxygen have been measured in a discharge flow system with mass spectrometric detection. The measurements were carried out under oxygen atom excess in the temperature range 298 K < T < 873 K. The main reaction channel at room temperature is O atom addition to the vinyl side chain, yielding as main product (identified by mass spectrometric product analysis) styrene oxide. Towards higher temperatures O atom addition to the aromatic ring as a second reaction channel becomes more important. Using Hammett plots the following Arrhenius expressions for the addition to the aromatic ring (kar) and to the alkene double bond (kdb) of the side chain can be derived: magnified image First experiments with indene give similar results, showing a somewhat higher reactivity for this molecule compared to styrene.
Nitrogen Quadrupole Coupling Constants of Nitrobenzene and o‐Nitrophenol
Authors: Heineking N. , Dreizler H. 
Published: July 2012

AbstractThe microwave spectra of nitrobenzene, C6H5NO2, and o‐nitrophenol, C6H4 (OH)NO2, have been observed with high resolution using a waveguide microwave Fourier transform spectrometer. Nuclear quadrupole hyperfine structures have been resolved and analysed to obtain the following nitrogen quadrupole coupling constants: χaa = ‐1.1589 (24) MHz, χbb = 0.3195 (36) MHz, χcc = 0.8394 (36) MHz for nitrobenzene; χaa = ‐1.234 (4) MHz, χbb = 0.348 (3) MHz, χcc = 0.886 (3) MHz for o‐nitrophenol. For nitrobenzene, the variation of the coupling constants with torsional state has also been studied.
Solution and Solid State Properties of 1,4‐Diketo‐3,6‐bis‐(4'‐pyridyl)‐pyrrolo‐[3,4‐c]‐pyrrole on Protonation and Deprotonation
Authors: Mizuguchi Jin 
Published: July 2012

AbstractSolution and solid state properties of 1,4‐diketo‐3,6‐bis‐(4'‐pyridyl)‐pyrrolo‐[3,4‐c]‐pyrrole (DPPP: red pigment) have been investigated with respect to protonation and deprotonation. DPPP undergoes both protonation and deprotonation, because it behaves not only as a base due to electron lone pairs of the nitrogen in the pyridyl ring but also as an acid due to the NH group in the heterocyclic chromophore. Protonation at the pyridyl nitrogen and deprotonation at the NH group induce large bathochromic shifts in solution. These are interpreted in terms of Pariser‐Parr‐Pople calculations, using the variable β, γ‐approximation. Protonation in the solid state due to acid vapor brings about significant changes in photoelectrical properties, such as a reduction in electrical resistivity from about 1010 to 105 Ωcm and strong photoconduction enhancement. The protonated solid state has been characterized systematically through spectroscopy, crystallography and thermo‐analysis with particular attention to its potential applications, e.g., to proton sensors and optical information storage systems.
Temperature Dependence of the Permittivity of o‐Nitroanisole‐Benzene and o‐Nitroanisole‐Carbon Tetrachloride Mixtures in the Vicinity of its Melting Point
Authors: Szurkowski B. , Hilczer T. , Saliwińska‐Bartkowiak M. 
Published: July 2012

AbstractAn investigation of the permittivity of o‐nitroanisole mixtures with benzene and carbon tetrachloride was performed in the vicinity of the liquid‐solid state phase transition. In the concentration range considered, the phase diagrams (T, x2)p of these mixtures were proved to be similar in character to those of the ideal eutectic systems, where molecular interactions are a simple function of the mixture composition.
In situ FTIR Study on the Adsorption of Phosphate Species on Well Ordered Platinum (111) Single Crystal Surfaces
Authors: Nart F. C. , Iwasita T. , Weber M. 
Published: July 2012

AbstractThe adsorption of ions on single crystal electrodes is followed via in situ Fourier transform infrared spectroscopy. The results for the adsorption of phosphate species on Pt(111) indicate a strong influence of the substrate structure on the adsorption geometry. A change in the nature of the adsorbed species is observed as the potential is shifted in the anodic direction.
The Mechanism of the Anodic Oxidation of Silicon in Acidic Fluoride Solutions Revisited
Authors: Gerischer H. , Allongue P. , Costa Kieling V. 
Published: July 2012

AbstractThe present experience of the electrochemical dissolution of silicon and previous assumptions upon the mechanism are briefly reviewed. A new model is developed which explains how the coverage of the surface by hydrogen can be maintained in spite of the continuous anodic dissolution.
Characterization of Vanadia/Silica Mixed Gel Catalysts by 51V and 29Si CP/MAS Solid State NMR Spectroscopy
Authors: Walther K. L. , Kümmerlen J. , Wokaun A. , Baiker A. 
Published: July 2012

AbstractThe structure of V2O5/SiO2 mixed oxides prepared by sol‐gel techniques is investigated by solid state NMR experiments. For low V2O5 contents ( < 10 mol%), 51V wideline spectra reveal a predominance of tetrahedrally coordinated vanadia, as found in oligomeric vanadate species. With higher vanadia concentrations (15–25 mol%), an increasing fraction of vanadium centers in an octahedral environment is observed. This transition indicates an increasing degree of cross‐linking of the vanadia, to form two‐ and three‐dimensional aggregates. The influence of the vanadia component on the compactness of the network is reflected in the 29Si MAS spectra, where the fraction of completely cross‐linked Q4 sites is observed to increase with the vanadia contents. The 1H → 29Si cross polarization dynamics is characterized by a bi‐exponential time dependence. Evidence for the existence of Si—O—V bridges at vanadia contents of 1 wt.% is derived from an analysis of the relevant cross polarization time constants.
p,T‐Dependence of Self‐diffusion in Liquid Ethanol and the Propanols
Authors: Shaker‐Gaafar N. , Karger N. , Wappmann S. , Lüdemann H.‐D. 
Published: July 2012

AbstractThe p,T‐dependence of the self diffusion coefficients D for ethanol‐OD, 1‐ and 2‐propanol‐OH and ‐OD have been studied in a wide temperature range at pressures up to 200 MPa. The experiments were performed in strengthened high pressure glass cells by the pulsed field gradient NMR‐technique. The isobaric temperature dependence of D is given by the VTF‐equation. The isotherms can be fitted to the rough hard sphere model with an A‐parameter that decreases strongly with falling temperature.