Interlayer Electron Transfer Research Articles

External electric field effect on interlayer vectorial electron transfer from photoexcited oxacarbocyanine to viologen in Langmuir-Blodgett films

Photoinduced interlayer electron transfer from the excited state of oxacarbocyanine (OCC) to viologen (VIO) is depressed or enhanced by an external electric field, depending on the direction of applied electric fields, in a donor-acceptor system composed of mixed monolayers of OCC and mixed monolayers of VIO separated by a spacer layer of fatty acid. As a result, field-induced increase and decrease of the quantum yield of OCC fluorescence are observed in the molecular assemblies of LB films.

Effect of an external electric field on photoinduced interlayer electron transfer in Langmuir–Blodgett films as revealed by the effect of the field on fluorescence: a D–A system of thiacyanine and viologen

Electron donor and acceptor layers separated by a spacer layer were prepared with thiacyanine and viologen using the Langmuir–Blodgett technique, and the effect of an external electric field on the fluorescence of thiacyanine was examined. Interlayer electron transfer from the photoexcited molecules of thiacyanine to viologen was affected by the external electric field. The magnitude and direction of the field-induced change in the electron transfer rate were evaluated on the basis of measurements of the field-induced change in the fluorescence intensity combined with fluorescence decay measurements. © 1997 Elsevier Science S.A.

Direct observation of optical magnons in YBa2Cu3O6.2.

We have used high-energy inelastic neutron scattering to detect optical magnons directly in antiferromagnetic Y${\mathrm{Ba}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6.2}$. The optical magnon gap is 67\ifmmode\pm\else\textpm\fi{}5 meV. This implies an intrabilayer superexchange constant perpendicular to the Cu${\mathrm{O}}_{2}$ layers of ${J}_{\ensuremath{\perp}}=0.08{J}_{\ensuremath{\parallel}}$ where ${J}_{\ensuremath{\parallel}}$ is the in-plane nearest-neighbor superexchange constant.

Langmuir-Blodgett film formation of disteroidal-TCNQ

Disteroidal tetracyano- p-quinodimethane (TCNQ) with two ester groups ( 1) (2,2′-[2,5-bis(5α-cholestan-3-yl-oxycarbonylethyl)-2,5- cyclohexadiene-1,4-diyliden]bis-propanedinitrile) was newly synthesized in order both to improve the monolayer stability on a water surface and to decline its TCNQ plane for interlayer electron transfer compared with the monosteroidal-TCNQ ( 3) (5β-cholan-24-yl-TCNQ) reported previously (K. Naito, A. Miura and M. Azuma, Langmuir, 7 (1991) 627). Compound 1 yielded a stable and condensed monomolecular film on a pure water surface with a large occupied area, with a low surface viscosity and with a high collapse pressure, resulting in a good Y-type deposition property. Monosteroidal-TCNQ-propionic acid ( 2) (2,2′-carboxyethyl-5-(5α-cholestan-3-yl-oxycarbonylethyl)-2,5- cyclohexadine-1,4-diyliden]bis-propanedinitrile) was also obtained. Compound 2 yielded a stable monomolecular film. However, its surface viscosity was high, resulting in a poorer deposition property. The molecular orientation of 1 in a Langmuir-Blodgett film was determined by X-ray diffraction and polarized UV-visible and Fourier transform IR spectroscopy.

Core-electron spectra and electronic structure of CeNbS3.

Core-electron-spectroscopy studies have been made for CeNbS 3 , which is one of the misfit-layer compounds. The Ce 3d and 4d x-ray photoemission (XPS) spectra are quite similar to those in CeSe. Ce exists mainly as a trivalent ion and the 4f electrons hybridize with other conduction and valence electrons. The S 2p XPS spectrum exhibits only a broad peak which consists of plural spin-orbit-split structures at different chemical environments. We find some evidence which indicates interlayer interaction and electron transfer from the Ce 5d band to the Nb d z 2 band. The Nb n 2,3 inner-shell-electron energy-loss spectrum exhibits a small peak just above the threshold, indicating that the d z 2 band is still incompletely filled after charge transfer

Interlayer electron transfer in porphyrin Langmuir-Blodgett multilayer-modified gold electrodes

Interlayer electron transfer in electroactive Langmuir-Blodgett multilayer-modified electrodes was studied. A model for the theoretical treatment of cyclic voltammetry (CV) was proposed by developing the models for ultra-thin film modified electrodes by Laviron and by Daifuku et al. Cyclic voltammetry was carried out with hematoporphyrin(IX) bis (tridecanoyl ether) Ru(II) (pyridine) 2 complex [RuHP(Py) 2] modified gold electrodes. The amount of charge flowing during the sweep is proportional to the number of monolayers. Then CV with a three-monolayer modified electrode was carried out at sweep rates from 0.05 to 102.4 V s −1. Good agreement was obtained between the experimental and the simulated cyclic voltammograms, and the electron diffusion coefficient for the interlayer electron transfer was determined to be 0.8–1.6 × 10 −11 cm 2 s −1.

Mean Field Theory of RVB and Superconductivity

The mean field theory for the coupled fermion (spinon)-boson (holon) system is developed by taking account self-consistently of coherent motions of both spinon and holon and singlet pair of spinon (RVB). The relative phase of RVB order parameters in x - and , y -directions, whose magnitudes are fixed to be the same, is treated as arbitrary. The phase, which minimizes the free energy, is found to be π for wide range of parameters. The bose condensation of holons is also examined in the case of weak interlayer electron transfer integrals. The specific heat, magnetic susceptibility and nuclear relaxation rate are calculated. It is found that their anomalies at the superconducting transition temperature depend markedly on the concentration of holons. The T -linear term in specific heat at low temperatures is shown to be vanishing, which is consistent with the recent experiments in Bi-Sr-Ca-Cu-O by Sera et al . and Kumagai et al .

Mean field theory of superconductivity in strong correlations

The implications of the mean field approximation are explored for the coupled fermion(spinon)-boson(holon) system representing the strong correlations in the two-dimensional Hubbard model. There exists a sharp crossover as a function of the density of holons depending on which of the RVB correlation and the coherent motion of holon is stabilized first. Here the RVB order parameters in the x and y directions are assumed to have same amplitude but with arbitrary phases. The bose condensation of holons is also examined by taking into account of weak interlayer electron transfer integral. It is found that anomalies of physical quantities at the superconducting transition are markedly different in each side of this crossover, which should be checked experimentally.