Yasumasa Tomita

Photostability enhancement of anionic natural dye by intercalation into hydrotalcite.

The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.

Effect of Heat Treatment on Charge-Discharge Property of Fluoride Cathode Materials for Li Ion Secondary Batteries

ron fluoride (III) anhydrate fine particle was prepared by drying in vacuum from FeF3·3H2O, a mechanical milling process and a calcination at 473 773 K. Particle size of FeF3·3H2O was ca. 3 5 μm and that of FeF3 anhydrate was 100 500 nm after drying and milling. FeF3 sample only after drying and milling was hygroscopic and became FeF3·3H2O under atmosphere. FeF3 became stable under atmosphere after oxidation at 673 K for more than 20 minutes. It was found that Fe2O3 was produced by calcination and covered the surface of FeF3 particles. In Charge-discharge measurements, the discharge capacity of these FeF3 samples was 150 - 200 mAh/g at a discharge rate of 0.1 C. The oxidation could improve the discharge properties of FeF3 cathode.

Structure and Dynamics of Li3InBr6 and NaInBr4 by Means of Nuclear Magnetic Resonance

Abstract Li3InBr6 and NaInBr4 have been synthesized and characterized by means of DTA, 81Br NQR, 6Li, 7Li, 23Na, and 115In NMR, and AC conductivity. These measurements revealed the presence of phase transitions and cationic diffusion in both compounds. From the spin-lattice relaxation times of 81Br NQR and the peak widths of 7Li and 23Na NMR spectra, it is deduced that the conduction is due to cationic diffusion. The activity energy for the Li+ diffusion was found to be 24 kJ/mol for Li3InBr6 .

Doping of Bonds into ZnO Films and the Changes of their Electric Properties

ZnO films codoped with Mg and N atoms have been prepared by sputtering of a target of a mixture of ZnO and Mg3N2 powders. The c-axis lengths of ZnO films increase with the concentration of Mg3N2 in the target. After annealing in an atmosphere of 99% N2 and 1% O2, the ZnO film prepared by sputtering of 20 at.% Mg3N2 target at 70 W in an N2 atmosphere becomes a p-type semiconductor with the resistivity of 400 Ωcm although the ZnO films prepared at 20 and 120 W in an N2 atmosphere become insulators. INTRODUCTION Zinc Oxide (ZnO) has attracted a great deal of attention from ultraviolet laser diodes. The p-n junction is necessary for the fabrication of such laser diodes. An n-type ZnO has been obtained by doping Group III elements. Although the preparation of p-type ZnO has been attempted by doping of N atoms, no one succeeded in the growth of p-type ZnO. In recent, several groups reported that hole-conductivity was found in ZnO containing excess Zn-N bonds or Ga-N bonds [1,2], but there were serious problems on reproducibility. In addition to the low solubility of N atoms, there is a possibility that the energy levels of N-related acceptors are not shallow [3]. According to the codoping theory [4], the N-related levels could be lowered by the incorporation of Be-N or Mg-N bonds into ZnO. In previous papers [5,6], we reported that hole conductivity was achieved in ZnO films containing Be and N atoms. Although Be-N bonds in ZnO are expected to act as effective acceptors, it is not preferable to use such toxic Be compounds. In the present work, we attempt to prepare p-type ZnO films by doping Mg-N bonds. ZnO films codoped with N and Mg atoms are prepared by sputtering of a target of a mixture of ZnO and Mg3N2 powders. The characterization of sputtered films is carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopic (XPS) measurements. The effects of codoping of Mg and N atoms on both the electric resistivity and carrier types are discussed. EXPERIMENTAL ZnO films containing Mg and N atoms were prepared by a radio frequency (RF) magnetron sputtering technique. A target was a mixture of ZnO (99.999%) and Mg3N2 powders. The concentration of Mg3N2 in the target was changed from 0 to 40 at.%. ZnO films containing Mg Key Engineering Materials Online: 2004-08-15 ISSN: 1662-9795, Vol. 269, pp 79-82 doi:10.4028/www.scientific.net/KEM.269.79

Diffusion mechanism of copper (I) ion in CuAlBr4 studied by nuclear magnetic resonance

Abstract The diffusion mechanism for Cu+ was studied by means of NMR, powder X-ray diffraction and AC conductivity measurements. The satellite spectra of the 63Cu- and 27Al-NMR varied anomalously with temperature. The quadrupole coupling constant of the 63Cu nucleus and the asymmetric parameter of the 27Al nucleus changed remarkably with decreasing temperature and the quadrupole coupling constant of the 27Al nucleus did not change so much. From calculation of the electric-field-gradient tensors, it was confirmed that these temperature dependencies are produced by both Cu+ diffusion and variation of the lattice constants. The diffusion path of Cu+ in CuAlBr4 was confirmed by NMR experiments: Cu+ jumps between normal sites via an interstitial site. The ionic conductivity was evaluated by assuming that the diffusion mechanism and its value were consistent with the observed AC conductivity.

Doping of Nitrides into Zinc Oxide Films

ZnO films containing Be and N atoms have been prepared by simultane ous sputtering of ZnO and Be in a N2 atmosphere. The c-axis length of ZnO film is shortened with an increase of dc power of the Be sputtering, indicating the incorporation of Be atoms in Z nO. The hole conductivity is found in ZnO film containing both 18% Be and 1.2% N atoms.

Fabrication of p–i–n devices consisting of ZnO quantum dots embedded in Ga2ZnO4 film

ZnO films have been prepared at substrate temperatures of 125 to 200 ?C by chemical vapor deposition with a precursor of Zn4O(CH3COO)6. As the substrate temperature decreases, the grain size of ZnO crystals decreases. From transmission electron microscopic observations, the film grown at 125 ?C is found to be constructed from ZnO quantum dots with a diameter of ca. 5 nm. Ultraviolet emissions are seen at 367, 375, 380, and 384 nm in photoluminescence spectra of the ZnO films grown at 125, 150, 175, and 200 ?C, respectively. The blue shift of the ultraviolet emissions is ascribed to the quantum confinement effect. After the deposition of a Ga2ZnO4 film with a thickness of 20 nm on the ZnO QD film grown at 125 ?C, a visible emission disappears and the ultraviolet emission intensity significantly increases. Such an increase is due to the partial embedding of ZnO QDs in Ga2ZnO4 films. The insertion of the ZnO QD films in the p?i?n devices constructed from In1.8Zn0.2O3/InGaZnO4/Ga2ZnO4/Ni0.7Zn0.3O/Ni does not improve their rectification properties, and electroluminescence is not observed in these devices at forward voltages of 10 V or more.

Preparation and Characterization of Mesoporous Silica and Lithium-Ion-Conductive Halocomplex Salt Composite

Composites of mesoporous SiO2 and LiAlCl4 were synthesized, and the change in ionic conductivity due to the formation of the composites was investigated. The electrical conductivity of the composite with the SiO2 : LiAlCl4 of 2 : 3 was the highest with a value of 2 x 10-6 S/cm at room temperature. A higher order of conductivity was observed for the composite compared to the non-composite LiAlCl4. In addition, it was found that the conductivity of the composites depends on the pore size of the mesoporous SiO2.

Preparation of N-Doped ZnO Films by MOCVD

Crystalline ZnO films were grown on Y-stabilized ZrO2 substrates heated at 300 - 600 °C in NH3 atmosphere. It is clarified from Fourier transform infrared measurements that N-doped ZnO films grown at 350 and 400 °C contain N-C and Zn-H bonds. In the devices of n-type ZnO/N-doped ZnO/Au, a good rectification characteristic is attained for an N-doped ZnO film deposited at 300°C, whereas a linear current vs. voltage characteristic is seen for a film deposited at 500 °C.

Photoluminescence Spectra of ZnO Films Doped with Li and Cl Atoms

ZnO films doped with Li and Cl atoms have been prepared by organometallic chemical vapor deposition method. In photoluminescence spectra of the doped ZnO films, strong emission appears at 376 nm which is slightly longer than that of free-excitons. As excitation intensity increases, a peak wavelength of the emission is shifted toward a shorter value. The emission near band-gap edge is assigned to radiative recombination via Li-Cl pairs.