Spin injection in a coupled system of a diluted magnetic semiconductor Zn0.80Mn0.20Se and self-assembled quantum dots of CdSe

Spin injection processes from a Zn_0.80Mn_0.20Se diluted magnetic semiconductor (DMS) to adjacent self-assembled CdSe quantum dots (QDs) were investigated by cw and time-resolved magneto-optical spectroscopy in combination with tunable laser excitation. Direct experimental evidence for the spin injection was provided from the generation of the spin polarization in the QDs, which was opposite to their expected intrinsic polarization, by resonantly generating the spins in the DMS. The observed limited spin polarization generated by the spin injection, together with the sensitivity of the spin injection efficiency on structure design, indicates severe spin loss during the process and calls for further investigations to optimize spin injection efficiency in quantum structures.     

Preparation of single-crystalline platinum nanowires with small diameters under mild conditions

We report a convenient method to synthesize single-crystalline platinum nanowires with high aspect ratio of ca. 2.0 nm diameter by sophisticated and precise control of Pt(0) nuclei and their growth.     

Particle size determination by radioisotope x-ray absorptiometry with sedimentation method]

The possibility of radioisotope X-ray absorptiometry to determine the particle size of powder in conjunction with sedimentation was investigated. The experimental accuracy was primarily determined by Cow and X-ray intensity. where Co'=weight concentration of the particle in the suspension w'=(micron/rho)l/(mu/rho)s-rhol/rhos rho; density micron/rho; mass absorption coefficient, suffix l and s indicate dispersion and particle, respectively. The radiosiotopes, Fe-55, Pu-238 and Cd-109 have high w-values over the wide range of the atomic number. However, a source of high micron value such as Fe-55 is not suitable because the optimal X-ray transmission length, Lopt is decided by the expression, micronlLopt approximately 2/(1+C'ow') by using Cd-109 AgKX-ray source, the weight size distribution of particles from the heavy elements such as PbO2 to light elements such as Al2O3 or flyash was determined.     

Simultaneous light emission from a mixture of dendrimer encapsulated chromophores: a model for single-layer multichromophoric organic light-emitting diodes

The site isolation of two dyes capable of electronic interaction via Forster energy transfer has been studied with the two dyes coumarin 343 and pentathiophene encapsulated by dendrons containing both solubilizing and electroactive moieties. Photoluminescence studies of mixtures of the dendritic dyes show that at high dendron generation, significant site isolation is achieved with relative emission characteristics influenced by both the degree of site isolation and the emission quantum yield of the dyes. Electroluminescence studies carried out in organic light emitting diode devices confirm that color tuning may be achieved by mixing the two encapsulated dyes in a single layer. However, selective carrier trapping by one of the core component dyes can dramatically influence the effectiveness of other components in the device.     

Electron spin resonance of phosphorescent triplet molecules observation of the proton hyperfine structure of Δm = ±2 transitions in stretched poly (vinyl alcohol) films

By applying a microwave magnetic field parallel to an external magnetic field, ESR of naphthalene, quinoxaline, quinoline and isoquinoline in their phosphorescent triplet states has been studied at 77 K. The proton hyperfine structures in the Δm = ± 2 transitions were distinctly resolved, especially when the stretched film was used as a host, compared with observations in ethanol glasses. The assignment of these ESR signals was carried out with the aid of the stretched-film method.     

X-ray crystal structure of a thiabenzene derivative

The first success of an X-ray analysis of a thiabenzene derivative, 1-benzoyl-2-methyl-2-thianaphthalene is described.     

Stereochemistry of cholesterol hydroxylation at C-22 during pregnenolone biosynthesis

Cholesterol and 20-hydroxycholesterol labelled at C-22 stereospecifically by deuterium were incubated with the enzyme of bovine adrenocortical mitochondria. The results indicated that hydroxylation occurs with retention of the configuration of C-22 to give exclusively the 22R stereoisomers of 22-hydroxy- and/or 20,22-dihydroxycholesterol.