排序方式: 共有19条查询结果,搜索用时 15 毫秒
1.
Nogami Masayuki Nagakura Takehito Hayakawa Tomokatsu Kasuga Toshihiro 《Journal of Sol-Gel Science and Technology》2000,19(1-3):253-256
Persistent spectral hole burning was studied in Eu3+ ions-doped Al2O3-SiO2 glass prepared by a sol-gel method. The gel synthesized by the hydrolysis of Si- and Al-alkoxides and EuCl3·6H2O was heated in air and hydrogen gas atmospheres. For the glass heated in air to contain OH bonds, the hole was formed by the photoinduced rearrangement of the OH bonds surrounding the Eu3+ ions, and was thermally refilled and erased above 200 K. On the other hand, the glass heated in hydrogen gas showed the hole spectrum above 200 K. It was found that the hole depth was independent of the temperature and was 7% of the total intensity at room temperature. The proposed mechanism was the electron transfer between the Eu3+ ions and the defect centers formed in glass matrix. 相似文献
2.
Hiromi Matsushita Ritsuko Nagao Masayuki Nogami Toshihiro Kasuga Tomokatsu Hayakawa 《Journal of Sol-Gel Science and Technology》2000,19(1-3):559-562
High proton-conducting P2O5-SiO2 glass was applied to the electrolyte of the hydrogen concentration cell for hydrogen gas sensing. 5P2O5·95SiO2 glass was prepared using the sol-gel method and its electrical conductivity and electromotive force were measured at 50°C as a function of both the ambient humidity and hydrogen gas concentration. The electrical conductivities increased with increasing humidity and reached 10–2 S/cm at 90% relative humidity. The electromotive force of the hydrogen concentration cell, where the glass was used as a membrane, showed good Nernstian response to hydrogen pressure in the high relative humidity region. 相似文献
3.
Virginie Gueu Hongpeng You Tomokatsu Hayakawa Masayuki Nogami 《Journal of Sol-Gel Science and Technology》2007,41(3):231-236
Fluorescence and spectral hole burning properties of Eu3+ ions were studied in nanocrystals-precipitated SnO2-SiO2 glasses. The glasses were prepared to contain various amount of Eu2O3 using the sol-gel method, in which SnO2 nanocrystals were precipitated by heating in air. In the glasses containing Eu2O3 less than 1%, the Eu3+ ions were preferentially doped in the SnO2 nanocrystals and their fluorescence intensities were enhanced by the energy transfer due to the recombination of electrons
and holes excited in SnO2 crystals. The SnO2 nanocrystals-precipitated glasses exhibited the persistent spectral holes with the depth of ∼25% of the total fluorescence
intensities of the Eu3+ ions. With the increasing Eu2O3 concentration, the amount of SnO2 nanocrystals decreased and the Sn4+ ions formed the random glass structure together with the silica network. This structure change induced the fluorescence intensities
and the hole depth to decrease. 相似文献
4.
Tomohiro Sago Tomokatsu Tokami Hideyuki Itagaki Nobuhide Ishihara Christina Canter Jean-Michel Guenet 《Macromolecular Symposia》2011,303(1):48-55
Summary: Gelation of syndiotactic poly(p-tert-butylstyrene) (sPTBS), a syndiotactic polystyrene (sPS) derivative having a larger side-chain group, was first examined with several solvents. The temperature-concentration phase diagram of sPTBS/trans-decalin gel clearly exhibited that sPTBS formed a polymer-solvent molecular compound with a ratio of 2.7 trans-decalin per one monomer unit. Our polarized fluorescence technique demonstrated that there appeared to exist more spacious free volume among sPTBS chains than sPS in a gel state. A cause determining the morphology of sPTBS with organic solvents was discussed in the present paper. 相似文献
5.
Masahiro Aoyama Tomokatsu Hayakawa Sawao Honda Yuji Iwamoto 《Journal of luminescence》2012,132(10):2603-2607
In this research, zeolite-derived aluminosilicate phosphors were synthesized through the ion exchange route. Red light-emitting property of Eu3+-doped aluminosilicate phosphors were discussed from a view point of the Eu content, heat-treatment condition and the oxidation state of Eu ions. The crystalline phase of the host aluminosilicates could be successfully controlled as designed based on the published NaAlO2–SiO2 binary phase diagram. Orange-red emission peaks derived from the 5D0→7Fj (j=0, 1, 2, 3, 4) transition of Eu3+ were observed around 590–700 nm, and 4f65d→4f7 transition of Eu2+ was observed at around 400–500 nm. The relative intensity I(5D0→7F2) of the dominant emission peak at 612 nm increased consistently with the Eu content. The results of the XANES spectroscopy analysis revealed that Eu2+ ion in the 1400 °C as heat-treated host aluminosilicate were successfully converted to Eu3+ by the additional annealing at 1100 °C. The Eu contents and heat-treatment conditions were determined to exhibit the best performance as a red phosphor, which were 10 wt% and 1500 °C, respectively 相似文献
6.
Masayuki Nogami Tomokatsu Hayakawa 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1001-1004
Persistent spectral hole burning was investigated for the Eu3+ ions-doped glasses prepared by a sol-gel method. For the glasses containing OH bonds, persistent spectral hole is burned by the laser-induced rearrangement of the OH bonds surrounding the Eu3+ ions, which is thermally unstable to erase up to 200 K. On the other hand, the Eu3+-doped Al2O3-SiO2 glasses which are heated under H2 gas or irradiated with X-ray exhibit room temperature PSHB. The depth of the burnt hole increases as the Al2O3 content increases. The hole-formation could be explained by a model of the excitation of the Eu3+ ions and subsequent electron transfer with the excited [Eu3+]– or oxygen-defect centers in the Al—O bonds. The burnt holes are more stable compared with those burned by the rearrangement of the OH bonds. 相似文献
7.
Yohei Ishikawa Tomokatsu Hayakawa Koji Inoue Masayuki Nogami 《Journal of Sol-Gel Science and Technology》2013,65(3):324-328
Transparent, luminescent films of Pr3+-doped (Ca0.6Sr0.4)TiO3 (CSTO) have been prepared for cathodo-excitation of pure red luminescence by a sol–gel method from a stabilized sol with Ca2+, Sr2+, Pr3+ ions and titanium-isopropoxide in acetic acid. The structure and surface morphology of the obtained films are characterized by X-ray diffraction and Atomic Force Microscopy, respectively. The photoluminescence and cathodoluminescence (CL) properties of the films are evaluated. The films exhibit a strong single line of 1D2 → 3H4 red photoluminescence of Pr3+ ions doped, which increases almost linearly with the number of the dip-coated layers. It is also found that strong single red photoemission is observed and the CL intensity increases with increasing acceleration voltage. The results demonstrate that it is potential for application in field-emission display devices. 相似文献
8.
Tomokatsu Hayakawa S. Tamil Selvan Masayuki Nogami 《Journal of Sol-Gel Science and Technology》2000,19(1-3):779-783
We have investigated the energetic correlation between rare-earth ions and semiconductor nanocrystals, using europium ion (Eu3+) doped silica (SiO2) gel with adsorbed cadmium sulfide (CdS) particles. Samples were prepared by a sol-gel technique, in which several methods for the precipitation of CdS colloids were attempted. The fluorescence intensities were compared for different gels, with and without CdS particles. The intrinsic emission lines due to 5D0 7FJ(J = 0–4) transitions of Eu3+ were observed, which were enhanced for 24 h-immersed gel (dried at 50°C). From the results on the decay dynamics of fluorescence, we proposed the model that surface-trapped electrons on CdS particles nonradiatively excited 4f electrons in Eu3+ ions due to an energy transfer process. 相似文献
9.
Junko Masuda Hiroshi Kawamoto Warren Strober Eiji Takayama Akifumi Mizutani Hiroshi Murakami Tomokatsu Ikawa Atsushi Kitani Narumi Maeno Tsukasa Shigehiro Ayano Satoh Akimasa Seno Vaidyanath Arun Tomonari Kasai Ivan J. Fuss Yoshimoto Katsura Masaharu Seno 《Applied biochemistry and biotechnology》2016,180(8):1559-1573
10.