摘要:

AbstractVarious organic free radicals as well as Ni+ions produce hydrogen in the presence of some 10−4M of colloidal gold. The gold catalyst was prepared via the reduction of HAuCl4either thermally by citrate or by y‐irradiation. The organic radicals were radiolytically produced. The mechanism of H2formation includes electron transfer from the organic radicals to the gold particles, storage of a large number of electrons per gold particle, conversion of the electrons into adsorbed H‐atoms and desorption of the latter to form H2. — The rates of some of these steps were measured using the method of pulse radiolysis. 1‐Hydroxy‐1‐methyl ethyl radicals, (CH3)2COH, react with colloidal gold particles almost diffusion controlled provided that the gold particles are not charged with excess electrons. Charged gold particles react at a substantially lower rate. The stored electrons live seconds or even minutes depending on their number per gold particle. In the stationary state, up to 0.38 Coulomb of electrons could be stored per liter of a 2.9 · 10−4molar gold solution, each gold particle carrying about 39 electrons. A comparison is also made between the catalytic activities of colloidal gold and silver. Due to the relative fast conversion of electrons into adsorbed H‐atoms, colloidal gold has less capacity for the storage of electrons than colloidal silver. — The dependence of the hydrogen yield on the pH of the solution, the concentration of gold, the size of the gold particles, the concentration of the polyvinyl alcohol stabilizer, and the intensity of radiation was also investigated. At high intensities, some of the radicals are destroyed in a gold catalyse

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850302

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe decomposition of the spray propellants CFCl3and CF2Cl2on the surface of variously treated zinc oxides has been studied by X‐ray photoelectron spectroscopy. Whereas decomposition on “untreated” surfaces could only be induced photolytically ( λ<400 nm) “activated” surfaces caused both spontaneous dark and additionally, photocatalytic decomposition. Indications are that the mechanism involves interaction between physisorbed substrate molecules and surface electrons of the catalyst. Decomposition causes chlorination of the zinc oxide resulting in a surface approaching hypochlorite‐perchlorate

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850303

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractPowdered TiO2samples were reduced by hydrogen plasma treatment at room temperature. The ESR spectra reveal the formation of Ti3+ions with similar concentrations as obtained in samples which were reduced conventionally, i.e. at elevated temperature either in vacuo or with hydrogen gas. The effect of O2adsorption on plasma and conventionally treated TiO2samples is compared and discussed.

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850304

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractMonomolecular layers of pheophytin were investigated by absorption spectroscopy, by thermodynamic, and by light‐ and electron microscopical measurements. — It is shown, that a pressure increase induces reorientations of the porphyrin rings. At pressures above a critical valuepkpheophytin aggregates in an arrangement with coplanar stacking of the porphyrin rings. Size and shape of the aggregates are determined microscopically. The diameters amount to 2 μm, the thickness to 500 Å. — The results prove the stability of the monolayers for pressures belowpk= 15 dyn/cm and the existence of instable phases at higher pr

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850305

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractWe have compared the D.C. conductivity and the low‐concentration optical absorption coefficients of the two‐component Hg/Xe metal rare‐gas mixtures (MRGSM) and the one‐component expanded Mercury, the properties of both materials being expressed on a common density scale. For the density range corresponding to the strong scattering regime the transport properties of both materials are surprisingly similar. At high Xe concentration the polarization effects of the Xe atoms are of considerable importance, resulting in marked deviations between the transport properties of those two types of ma

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850306

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe micelle formation in aqueous solutions of p‐(6′‐Dodecyl)‐benzenesulfonate (LBS) with the counterions Na+, H2N(CH3)2+, H2N(CH2CH3)3+and H2N(CH2CH2CH3)2+was investigated with the aid of relaxation measurements. The existence of small and probably spherical micelles in a concentration range above a first critical micelle concentration could be shown. At higher concentrations the association leads to larger aggregates or mesophases. In the system H2N(CH2CH2CH3)2‐LBS the second cmc approaches to the value of the first cmc. — The small micelles have a narrow distribution variance σ. The reaction volumes are positive but much smaller than the values which were found on surfactant systems with a single alkyl chain. With the exception of the system H2N(CH2CH2CH3)2‐LBS negative reaction volumes are found in the oligomer region. The values for the relative distribution variance σ2/nwere obtained from the concentration dependence of the short relaxation time and from the analysis of the amplitudes of the slow process. The results from both methods are in a

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850307

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractComponent self‐diffusion coefficients in solutions: n‐hexane‐cyclohexane, n‐hexane‐benzene, benzene‐nitrobenzene, and n‐hexane‐nitrobenzene have been determined as a temperature function over the entire composition range. The activation energies of component self‐diffusion have been calculated. The excess self‐diffusion coefficients as a useful way to determine a solution structure

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850308

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe paper reports new, accurate measurements of the thermal conductivity of mixtures of helium and methane in the pressure range 1–13 MPa at 27.5 °C. The measurements have been carried out in a transient hot‐wire instrument and have an estimated uncertainty of ± 0.2%. — The experimental data as a function of density have been extrapolated to yield reliable values of the zero‐density thermal conductivity of the mixtures. It is found that these experimental data cannot be satisfactorily represented by the existing first‐order kinetic theory formulae using independently determined collision numbers for rotational energy relaxation, unless empirical adjustments are made to certain collision integral ratios occurring in the equations. A recently proposed scheme for the prediction of the density dependence of the thermal conductivity of the mixtures is found to correlate the observed density dependence sat

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850309

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractThe paper presents the derivation of equations for the determination of semiquinone formation and dimerization constants from the half peak width and the peak distance of a double peak by means of thin layer and adsorbat voltammetry. As an experimental example flavin adenine dinucleotide adsorbed on a roughened glassy carbon electrode was chosen, for which a semiquinone formation constant of 2.6 (0.77 in solution) was found at pH 7.

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850310

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY

摘要:

AbstractA mechanism is described whereby the influence of an external magnetic field on the sublevels of a triplet exciplex, subject to heavy‐atom‐induced sublevel‐selective deactivation, modulates the radical dissociation yield of the exciplex. A sublevel selection rule for the heavy atom effect on T1— S0intersystem crossing in the triplex exciplex is derived. The magnetic field influence is treated on the basis of an approximate solution of a stochastic Liouville equation, leading to a simple analytic expression for the magnetic field effect on the radical yield. The result is applied to explain a previously observed magnetic field effect. The mechanism described may induce magnetic field effects on any triplet reaction competing with sublevel‐selective dea

ISSN:0005-9021    

DOI:10.1002/bbpc.19810850311

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1981

数据来源: WILEY