ISSN:0005-9021    

DOI:10.1002/bbpc.19830871202

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

年代:1983

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871203

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

年代:1983

数据来源: WILEY

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871205

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

年代:1983

数据来源: WILEY

摘要:

AbstractGold electrodes were emersed from the electrolyte during potential control and subsequently transferred into a UHV chamber for their surfaces to be analysed by ESCA as a function of emersion potential and electrolyte composition. The ESCA measurements confirm the view that electrodes can be removed from the electrochemical cell with the electrochemical double layer unchanged and the bulk electrolyte otherwise absent. The potential power of ex‐situ studies, such as ESCA, on emersed electrodes is demonstrated by determining surface excesses and adsorption isotherms for a number of weakly and strongly adsorbing ions, as well as for metal deposits. Observations of chemical shifts for double‐layer constituents are reported and briefly discus

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871206

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe ratio of copper‐to‐selenium in cuprous selenide has been determined as function of the copper activity in the selenide at 435°C with the help of coulometric titrations. At 435°C the homogeneity range of cuprous selenide extends from a Cu/Se ratio of 1.998 to a value lower than 1.860. Analysis of the experimental data shows that the change of the chemical potential of copper by a change of the composition is only given by a change of concentration of the defect electrons or of the quasifree electrons. From these studies, the energy gap in coprous selenide is at least 0.

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871207

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe present article presents data on the formation and characterization of water in oil (W/O) microemulsion systems composed of ionic surfactants‐water‐benzene‐n‐alcohols (C4– C8). The influence of the alcohol chain length and surfactant concentration, on the formation of microemulsion systems, has been investigated. When the amount of benzene or water was increased, the microemulsion system's appearance changed from clear to bluish to turbid. The transitions were identified on the basis of both visual appearance and specific resistance measurements. A dramatic change in the specific resistance was observed for the transitions. This was rationalized by assuming a change in the water structure from spherical to cylindrical to lamellae type. The criticalnwater/noilratio (Vc), for stable microemulsion system was calculated with the help of viscosity mea

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871208

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

年代:1983

数据来源: WILEY

摘要:

AbstractSmall angle neutron scattering experiments (SANS) on solutions of cetylpyridiniumsalicylate (CPS) in D2O over a large concentration range show a characteristic scattering maximum due to mutual interactions between the rodlike micelles. From the scattering rates structure factorsS(Q), pair correlation functionsg(r) and corresponding mean potentialsW(r) are derived. Furthermore it is shown, that the lengthLof the scatterers decreases in a concentration range from 20 mM to 160 mM CPS. To study the influence of interaction on the rods, increasing amount of salt (NaCl and NaSal) was added to a 5 mM solution of CPS. As one would expect, the scattering maximum decreases, while the length of the micelles increases. It is shown, that the rods remain rather stiff when small amounts of salt are added. In the case of 32 mM NaCl it was also possible to fit the data with a persistence length model showing that the rods may become flexible when large amounts of salt are added. A persistence length of 8000 – 12000 Å was evaluated for these conditio

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871209

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

年代:1983

数据来源: WILEY

摘要:

AbstractAddition of synthetic bilayer membrane formed by a new type of amphipathic viologen containing two hexadecyl groups to aqueous solution of zwitterionic propylviologen sulfonate (PS2– V2+) remarkably increased the yield of viologen photoreduction as sensitized by tris(2,2'‐bipyridine)‐ruthenium complex, Ru(bpy) 32+, in the presence of triethanolamine. Zwitterionic viologen was confirmed to shuttle as an efficient electron mediator between bulk aqueous solution and the interface of the bilayer membrane with a viologen head group. The quantum yield of viologen cation radicals was close to the net cage‐escape yield of photogenerated Ru(bpy) 33+‐ PS2‐V+ion pair. The electrostatic field of positively charged interface of bilayer membrane was concluded to attract PS2‐Vc which transports electron to viologen head groups of bilayer membranes. Remarkable (500‐fold) suppression of the reverse electron transfer reaction was attained by the addition of viologen bilayer membrane. It was attributed to Coulombic repulsion between Ru(bpy) 33+and positively charged interface of bilayer membranes. Relevance of the present system to chemical conversion of sola

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871210

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

年代:1983

数据来源: WILEY

摘要:

AbstractAzobenzene‐containing, single‐chain ammonium amphiphiles in which the alkyl chain length in the tail and spacer portions was systematically varied were prepared, and their aggregation behavior in water was studied by electron microscopy, differential scanning calorimetry and absorption spectroscopy. These amphiphiles exist as molecular dispersions, hydrated microcrystals, micelles, or bilayers. The formation of stable bilayers was deduced on the basis of three criteria which include the spectral agreement between aqueous dispersions and the corresponding cast films. Stable bilayers were obtainable when the sum of tail and spacer is not smaller than C14to C16, and the tail is at least C8. Double‐chain ammonium amphiphiles which possess an octadecyl chain in addition to the azobenzene‐containing chain were prepared and shown to form stable bilayers. The absorption spectrum reflected the aggregate structure. In particular, the bilayer spectra were classified into four types: type A (λmaxca. 300 nm) for the parallel chromophore orientation (H aggregate), type B (330 – 340 nm) for the dimeric chromophore, type C (ca. 355 nm) for the isolated chromophore, and type D (360–390 nm) for the head‐to‐tail chromophore orientation (J‐like aggregate). Liquid‐crystalline bilayers gave type B spectra, while crystalline bilayers gave either of types A, B, and D, depending on the alkyl chain length. Finally, various examples of spectral control were discussed in relation to

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871211

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe dual fluorescence in polar solvents of 9,9′‐bianthryl (BA) and of the electronically perturbed BA‐derivatives 10‐chloro‐BA (BACl), BA‐10‐carboxaldehyde (BAA) and N‐(9‐anthryl)‐carbazole (C9A) as well as of N‐(4‐cyanophenyl)‐carbazole (CBN) is analysed and interpreted in terms of a simplified microstructural solvent interaction model. Dipole moments μTrelative to μT(CBN) of the fluorescent charge transfer state have been derived from the solvatochromic band shifts in nitrile and alcohol homologous solvent series and are similar for BA, BACl and C9A. This implies that the charge transfer in the excited state occurs to a maximum degree even in the symmetric molecule BA. – QCFF/PI‐potential energy curves have been calculated and are used to discuss these findings. BAA fluoresces in alcohols only, μT‐compared to the other compounds studied being somewhat smaller probably because of specific H‐bond interactions with the solvent. – Using relative fluorescence quantum yields and energetic considerations the dependence of the excited states equilibrium on both solvent polarit

ISSN:0005-9021    

DOI:10.1002/bbpc.19830871212

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

年代:1983

数据来源: WILEY