摘要:

AbstractA gas aggregation technique is used to produce NaxSby, clusters. After passing a flow‐tube reactor, the clusters are ionized with unfocused high fluence KrF‐excimer laser radiation and then mass analyzed in a time‐of‐flight mass spectrometer. Dramatic changes are observed in the cluster ion distribution upon adding high purity chlorine gas into the flow tube. As a result of reactions with Cl2, all NaxSby, clusters disappear while pure antimony cluster ions arise. The distribution patterns of the produced Sbx+clusters are the same as those observed in experiments with pure a

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001102

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

年代:1996

数据来源: WILEY

摘要:

AbstractSolid ZnSe is evaporated from a Knudsen cell in vacuum. The effective molecular weight of the ZnSe vapor is directly determined by weighing the cell with and without effusion taking place. The rate of effusion is adjusted by a moveable furnace. An effective molecular weight of 135 ± 5 g/mol is found for temperatures between 1190 and 1310 K. The weight indicates the complete dissociation of the sublimed ZnSe into Zn and Se2vapor. In that temperature range, the total equilibrium vapor pressure of solid ZnSe is estimated from the recoil force according to\documentclass{article}\pagestyle{empty}\begin{document}$ \log _{10} (P/{\rm kPa}) = - (12896 \pm 96){\rm K}/T + (9.19 \pm 0.08). $\end{document

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001103

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

年代:1996

数据来源: WILEY

摘要:

AbstractIn order to expand the range of high‐quality nanosized semiconductor materials that can be obtained as quantum dots through a wet chemical route a series of oxidize‐stable CdTe nanoclusters with narrow size distributions and extremely small particle sizes ranging from 1.3 to 2.4 nm has been prepared in aqueous solution using 2‐mercaptoethanol and 1‐thioglycerol as stabilizers. It has been investigated by means of UV‐vis absorption and photoluminescence spectroscopy, X‐ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive x‐ray a

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001104

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe adsorption of uracil, 6‐methyluracil, 5‐methyluracil (thymine) and 5,6‐dimethyluracil from aqueous solutions on Au(111) and Ag(111) has been investigated by cyclic voltammetry, capacity measurements and current transients, to elucidate the role of the electrode surface and of the intermolecular forces in the formation of ordered adlayers. From the calculated free adsorption enthalpies stability sequences for the condensed physisorbed phase were established. Our data show that the properties of the physisorbed adlayer are strongly influenced by the intermolecular forces, whereas in the chemisorbed state the influence of the substrate becomes dominant. For the chemisorbed molecules on Au(111) electrosorption valencies were estimated, which indicate an appreciable charge tra

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001105

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

年代:1996

数据来源: WILEY

摘要:

AbstractFiltration experiments with phenolsulfonic acid‐formaldehyde cation exchange membranes are carried out with aqueous solutions containing two electrolytes with a common anion: HCl/NaCl, HCl/CaCl2and NaCl/SrCl2. The concentration difference of each electrolyte between the high pressure phase and the filtrate in the stationary state has the same sign as the reflection coefficients of the electrolytes in the mixtures determined in independent experiments. This confirms theoretical predictions. Corresponding experiments with Nafion membranes show the influence of unstirred layers on the sign of the concentration difference in filtration experiment

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001106

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

年代:1996

数据来源: WILEY

摘要:

AbstractA newin‐situellipsometric procedure has been used for determination of the optical properties and thickness of polyaniline films as a function of. the redox state in sulphuric and p‐toluenesulfonic acids. The results could be interpreted successfully only when the optical properties of the electrolyte/polymer was considered variable with the redox state. Most probably for the first time, the study shows, that the apparent refractive index of electrolyte varies with the redox state in a similar manner to the optical properties and thickness of the polymer film. In this case, for all calculations a one layer model was sufficient. The origin of such observation is attributed to the change in electrolyte composition at the polymer surface and heterogeneity of the film when oxidi

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001107

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

年代:1996

数据来源: WILEY

摘要:

AbstractThe electrochemical behavior of spirobenzopyran derivatives with substituted groups of OCH3, Br and NO2in the benzopyran ring and the indoline ring has been studied by cyclic voltammetry and spectro‐electrochemistry in a dimethylformamide (DMF) solvent at a platinum electrode. The six spirobenzopyran derivatives studied can be divided into two groups according to the presence or the absence of a nitro group substituted in the benzopyran ring. In the potential range of −1.8 V ∼ +1.0 V (vs. Ag QRE), neither redox reactivity nor reversible color changes were observed for those derivatives without a substituted nitro group, while the nitro‐substituted spirobenzopyrans exhibited appreciable redox behavior and the electrochromism corresponding to the redox reaction of the nitro group.In addition, an irreversible oxidation wave observed at about + 1.3 V (vs. Ag QRE) for all the derivatives studied (except SP‐18) was assigned to the oxidation of the nitrogen atom in indoline moiety. These oxidation wave potentials of the nitrogen atom are linear with the Hammett values Σσ*of the substituted group, and thus suggest that a significant electron‐induced interaction existed between the benzopyran and the indoline ring in the spirobenzop

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001108

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

年代:1996

数据来源: WILEY

摘要:

AbstractQuantum yields of illuminated single crystalline n‐pyrite (FeS2)/electrolyte junctions were measured at λ = 632.8 nm and found to be significantly higher in the presence of negatively charged redox species, such as I−and [Fe(CN)6]4−in contrast to species like Fe2+. Higher photocurrents and photovoltages at (100) n‐pyrite rotating disc electrodes in comparison with (111) electrodes fabricated from the same single crystal are obtained. Further, (100) n‐pyrite electrode surfaces were treated with pyrazine and 4,4'‐bipyridine. A significant decrease of dark current and a shift of the equilibrium potential in 0.5 M FeSO4is ascribed to chemical complex formation between the electron donating ligands and the Lewis acidic Fe(II) centres of the (100) n‐pyrite surface. In the case of pyrazine treatment an enhancement of photocurrent and photovoltage could be observed. The observed phenomena are discussed in terms of coordinated chemical surface complex formation and charge trans

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001109

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

年代:1996

数据来源: WILEY

摘要:

AbstractRate constantskRof the ene reaction of singlet oxygen (1Δg) with tetramethylethylene (TME) have been determined in six solvents with different polarity at elevated pressures up to 1200 bar using time‐resolved phosphorescence technique. Experimental activation volumes, ΔV ≠exp, resulted in the range between −20.7 cm3· mol−1(in benzonitrile) and −35.1 cm3· mol−1(in n‐hexane). These results were analysed taking into account contact complex formation as the initial step. The reaction volume ΔVcof the formation of the contact complex was evaluated using the statistical model developed by Yoshimura and Nakahara. The data obtained confirm the assumption of a polar intermediate resembling a perepoxide. The intrinsic activation volume ΔV ≠PEwas found to be −14.5 cm3· mol−1and the dipole moment of the transition state was

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001110

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

年代:1996

数据来源: WILEY

摘要:

AbstractAn optical method for the determination of interdiffusion coefficients in mixtures of nematic liquid crystals is described. In this method a liquid crystal mixture with a concentration gradient is placed between the plates of a Fabry‐Perot etalon. Illumination with parallel monochromatic light gives an interference pattern from which the index of refraction and the concentration can be determined as a function of the position. This method of measurement does not require the addition of dyes, chiral substances or radioactive substances.The set‐up was tested with the isotropic system n‐hexane/n‐dodecane for which the diffusion coefficients are known. The diffusion coefficients in the system 4‐n‐butylbenzoic acid‐4'‐n‐hexylphenyl ester/4,4'‐di‐n‐hexylazoxybenzene were determined as a function of temperature. The system 4'‐n‐butyloxybenzylidene‐4‐n‐butylaniline/ethylhydroquinone‐di‐4‐n‐hexylbenzoate was studied at a temperature for which the first component is in t

ISSN:0005-9021    

DOI:10.1002/bbpc.19961001111

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

年代:1996

数据来源: WILEY