Akio Makishima

Photochemical hole‐burning study of 1,4‐dihydroxyanthraquinone doped in amorphous silica prepared by alcoholate method

Preparation of amorphous silica doped with organic dye molecules, 1,4‐dihydroxyanthraquinone, and the observation of the amorphous structure of this system by photochemical hole burning using the dye molecules as a spectral probe are reported. The various kinds of organic molecule‐doped inorganic glassy materials are obtained with the alcoholate method. The appearance of the photochemical hole in this system shows the molecular dispersion of the dye molecules in the matrix without cracking or decomposition. The burning yield, 1.2×10−4, is the same as that observed in organic glasses. The intrinsic holewidth, 0.9 cm−1 at zero burning time limit, the burning‐time dependence and the annealing effects on the hole profile were observed and compared with those in the alcoholic organic glass. It is suggested that the nearest‐neighbor structures around quinizarin molecules consist of some hydroxyl groups. The matrix cages seem to be fairly tight and rigid in comparison with those of the alcoholic glass. The possi...

Properties and cytotoxicity of water soluble Na2O–CaO–P2O5 glasses

Various compositions of Na2OCaO-P2O5 glasses are prepared to estimate glass formation, dissolution properties and cytotoxicity. In the wide composition range of 40 mol% of P2O5 or more, clear glass samples were obtained. The estimated glass forming region was consistent with other ternary phosphate glass systems. The glass transition temperatures and crystallization temperatures decreased with increasing P2O5 content and increased with CaO content. Dissolution properties in distilled water and simulated body fluid (SBF) were measured. In distilled water, CaO free glasses showed extremely fast dissolution. The dissolution rate decreased with increasing CaO content and decreasing P2O5 content. This composition effect results from cross-link formation between the non-bridging oxygens of two different chains by Ca2+ ions which improves the phosphate network strength. In SBF, the dissolution rate followed a similar trend, but glass dissolution was suppressed. This suppression occurred due to the existence of soluble species of glass such as Na+, Ca2+ and HPO(2-)4. The cytotoxicity decreased with increasing CaO content and with decreasing PO2.5 content. This was the result of a change in pH and ion concentration in the medium.

Upconversion mechanism in Er3+-doped fluorozirconate glasses under 800 nm excitation

The upconversion emission intensities of Er3+ ion around 550 and 660 nm in fluorozirconate glasses were measured under 800 nm excitation. Though energy transfer processes played an important role in upconversion mechanism at high concentration of ErF3, those have not been treated quantitatively. The energy transfer rates were calculated from the optical parameters assuming some distribution of Er3+ ions. We calculated the upconversion intensities around 550 and 660 nm by using rate equations. It was found that the dependence of upconversion emission intensities on the ErF3 concentration could be reproducible and the principal upconversion mechanism could be evaluated.

Calculation and simulation of spectroscopic properties for rare earth ions in chloro-fluorozirconate glasses

Abstract Europium doped fluorozirconate and chloro-fluorozirconate glasses with Zr–Ba–La–Al–F–Cl system were prepared by conventional melting method and their emission spectra were studied. Simulation of emission spectra of these glasses by point charge models of crystal field were performed. We found that the variation of electronic state of rare earth (RE) ions should be taken into account for the simulation of optical spectra in chloro-fluorozirconate mixed anion glasses. We applied electronic state calculations for estimating the electronic state of europium ions in glass structural models that were derived from molecular dynamics simulations. By applying the parameters derived from DV-Xα calculation, point charge model of the crystal field and Judd–Ofelt theory, the simulation of spectra agreed with observed spectra of the europium ions in chloro-fluorozirconate glasses in terms of spectral width and intensity.

Preparation and properties of TiO2CeO2 coatings by the sol-gel process

The preparation and properties of TiO2CeO2 coatings by the sol-gel dip-coating process, using cerium chloride and various titanium alkoxides, and the effect of catalysts were studied. Gelation time of the coating solution became longer with an increase in the molecular weight of titanium alkoxide. The transmittance, thickness, chromaticity and acidic durability of the coating films were measured as a function of aging time of the coating solution. The most transparent and acidic durable coating film was obtained by using a solution just before gelation. In the case of using a solution with a catalyst, the thickness became thinner with increasing pH of the coating solution.

Preparation of CeO2-TiO2 coatings by the sol-gel process

Abstract Yellow coatings have been prepared from titanium tetraisopropoxide and cerium chloride by the sol-gel dip-coating process, and the transmittance, chromaticity, thickness and acidic durability of the coating films produced on glass or aluminum were studied. The effects of the pH of the solution on the preparation of the transparent and homogeneous coating films were studied by adding the alkali or acid, and as a result transparent and homogeneous yellow coating films were prepared by dipping the substrate in a solution containing acetic acidic solution. The acidic durability of the aluminum foil was improved by dip-coating the brilliant yellow CeO 2 -TiO 2 coating three times.

Fluorescence properties of fluorozirconate glasses containing Eu3+ ions

Abstract Fluorozirconate glasses containing Eu 3+ ions and chloride ions were prepared and the lifetimes of the 5 D 0 state and the phonon side bands in these glasses were measured. It was found that the addition of chloride ions had a great effect to increase the radiative transition rate. The phonon side bands of the 7 F 0 - 5 D 0 transitions were clearly observed for several glasses. These spectra were compared with the FT-IR spectra and the electron-phonon coupling strengths of total vibrational modes were calculated from the phonon side band spectra.

Preparation and properties of sol-gel thin films with porphins

Amorphous silica films doped with porphine derivatives were prepared by the sol-gel method with a dip-coating technique. The films doped with tetrakis(1-methylpyridinium-4-yl)-porphine p-toluenesulfonate (TMPyP) or tetraphenylporphine tetrasulfonic acid (TPPS) were heat treated at various temperatures, and the changes in the optical spectra were observed as a function of temperature. It was found that the porphins in the films could be heat treated up to ~200°C. A photochemical hole was formed in the lowest transition of the Q band of TMPyP in the silica film at ~20 K.

Simulation of the optical properties of Er:ZBLAN glass

Abstract Absorption and emission spectra of Er3+-doped ZBLAN glass at room temperature were estimated from structural models prepared by using molecular dynamics (MD) simulation based on crystal field theory and point-charge approximation. The calculated absorption and emission spectra substantially agreed with the observed ones. Furthermore, it was found that the emission spectra at low temperatures could be also reproduced to some extent. The relation between the splitting of the energy level and the crystal field parameters calculated from the Er3+ ion in each structural model was examined. According to this relation, the energy levels could be classified into several groups. The splitting of the group represented by the 4 I 9/2 level was dominated by the short-range structure around the Er3+ ions. The transition process for the measurement of the well-defined fluorescence line narrowing (FLN) spectrum was estimated from the characteristics of the splitting of the energy levels.

r-GRIN glass rods prepared by a sol-gel method

Preparation of radial gradient refractive index (r-GRIN) glass rods has been undertaken by a sol-gel process using metal alkoxides. Two binary systems, Si(OCH3)4Ge(OC2H5)4 and Si(OCH3)4−Ti(O−n-C4H9)4 have been investigated. It has been shown that immersion of rod-shaped wet gels in neutral or acidic water gives rise to leaching of the dopants (germanium and titanium components). Since this leaching is controlled predominantly by diffusion, the dopants remaining in the gels are expected to form concentration gradients. Optical measurements of the glass rods obtained after drying and sintering of the leached gels have shown that the concentration gradients are retained in the glass rods and they give r-GRIN profiles.