Tadaharu Ueda

Bio: Tadaharu Ueda is an academic researcher from Kōchi University. The author has contributed to research in topics: Aqueous solution & Acetonitrile. The author has an hindex of 22, co-authored 99 publications receiving 1445 citations. Previous affiliations of Tadaharu Ueda include Kobe University.

Raman studies on the identification of isopolymolybdates in aqueous solution

Abstract: Molybdenum(VI) solutions were investigated in detail by Raman spectroscopy with a view to establishing the speciation of the predominant polynuclear species (isopolymolybdates) formed in aqueous solution. The most intense Raman frequencies due to asymmetric stretching vibration of Mo=O were very sensitive to even small changes of the structure of the isopolymolybdates. As the pH was lowered, the major Raman line showed no gradual shift but exhibited a discrete change. Evidence was obtained for the existence of Mo7O246− (pH 4—6), Mo3O102− (pH 3.5—5), α-Mo8O264− (pH 2—5), β-Mo8O264− (pH 1.5—4), and Mo36O1128− (pH 0.5—1.5). On the other hand, neither of Mo6O192− and γ-Mo8O264− existed in any appreciable amount in aqueous solution.

Bluish-White Luminescence in Rare-Earth-Free Vanadate Garnet Phosphors: Structural Characterization of LiCa3MV3O12 (M = Zn and Mg).

Abstract: Extensive attention has been focused toward studies on inexpensive and rare-earth-free garnet-structure vanadate phosphors, which do not have a low optical absorption due to the luminescence color being easily controlled by its high composition flexibility. However, bluish emission phosphors with a high quantum efficiency have not been found until now. In this study, we successfully discovered bluish-white emitting, garnet structure-based LiCa3MV3O12 (M = Zn and Mg) phosphors with a high quantum efficiency, and the detailed crystal structure was refined by the Rietveld analysis technique. These phosphors exhibit a broad-band emission spectra peak at 481 nm under near UV-light excitation at 341 nm, indicating no clear difference in the emission and excitation spectra. A very compact tetrahedral [VO4] unit is observed in the LiCa3MV3O12 (M = Zn and Mg) phosphors, which is not seen in other conventional garnet compounds, and generates a bluish-white emission. In addition, these phosphors exhibit high quantum...

Effects of Salts, Acids, and Phenols on the Hydrogen-Bonding Structure of Water−Ethanol Mixtures

Abstract: The effects of salts, acids, and phenols on the hydrogen-bonding structure of water in 20% (v/v) EtOH−H2O solution were investigated on the basis of 1H NMR chemical shifts of the OH of water and et...

Hybrid Organic−Inorganic Polyoxometalate Compounds: From Structural Diversity to Applications

Abstract: Polyoxometalates (POMs) are discrete anionic metaloxygen clusters which can be regarded as soluble oxide fragments. They exhibit a great diversity of sizes, nuclearities, and shapes. They are built from the connection of {MOx} polyhedra, M being a d-block element in high oxidation state, usually VIV,V, MoVI, or WVI.1 While these species have been known for almost two centuries, they still attract much interest partly based on their large domains of applications. They play a great role in various areas ranging from catalysis,2 medicine,3 electrochemistry,4 photochromism,5 to magnetism.6 This palette of applications is intrinsically due to the combination of their added value properties (redox properties, large sizes, high negative charges, nucleophilicity...). Parallel to this domain, the organic-inorganic hybrids area has followed a similar expansion during the last 10 years. The concept of organic-inorganic hybrid materials * To whom correspondence should be addressed. E-mail: dolbecq@ chimie.uvsq.fr. Chem. Rev. 2010, 110, 6009–6048 6009

A highly selective fluorescent chemosensor for Pb2

Abstract: A new fluorescent sensor based on rhodamine B for Pb2+ was synthesized. The new fluorescent sensor showed an extreme selectivity for Pb2+ over other metal ions examined in acetonitrile. Upon the addition of Pb2+, an overall emission change of 100-fold was observed, and the selectivity was calculated to be 200 times that of Zn2+. The signal transduction occurs via of reversible CHEF (chelation-enhanced fluorescence) with this inherent quenching metal ion.

Raman spectroscopy of molybdenum oxides

Abstract: A special sample was prepared by controlled oxidation of MoO2, which contained MoO2, Mo4O11 and MoO3, in order to extend the knowledge about the resonance Raman effect in reduced molybdenum oxides from those close to MoO3 to those close to MoO2. This knowledge is of paramount importance because technical partial oxidation catalysts often contain intermediate Mo oxides of the Magneli type, e.g. Mo4O11, or Mo5O14. The Raman spectra of orthorhombic Mo4O11 and MoO2 have been identified in a Raman microspectroscopic image of 100 single spectra recorded of a mixture of MoO3, MoO2 and Mo4O11. A resonance Raman effect was proven to be responsible for the detection of the molybdenum oxide phases Mo4O11 and MoO2 in dilution with BN when excited at a laser wavelength of 632.8 nm by comparison with Raman microspectroscopic images of the identical sample when excited at 532 nm. The resonance Raman detection of reduced molybdenum oxide phases is discussed in the above mentioned context of their active role in catalytic partial oxidation reactions.

Database of Absorption and Fluorescence Spectra of >300 Common Compounds for use in PhotochemCAD.

Abstract: The design of new molecules for photochemical studies typically requires knowledge of spectral features of pertinent chromophores beginning with the absorption spectrum (λabs ) and accompanying molar absorption coefficient (e, m-1 cm-1 ) and often extending to the fluorescence spectrum (λem ) and fluorescence quantum yield (Φf ), where the fluorescence properties may be of direct relevance or useful as proxies to gain insight into the nature of the first excited singlet state. PhotochemCAD databases, developed over a period of 30 years, are described here. The previous databases for 150 compounds have been expanded to encompass 339 compounds for which absorption spectra (including e values), fluorescence spectra (including Φf values) and references to the primary literature have been included where available (552 spectra altogether). The compounds exhibit spectra in the ultraviolet, visible and/or near-infrared spectral regions. The compound classes and number of members include acridines (21), aromatic hydrocarbons (41), arylmethane dyes (11), azo dyes (18), biomolecules (18), chlorins/bacteriochlorins (16), coumarins (14), cyanine dyes (19), dipyrrins (7), heterocycles (26), miscellaneous dyes (13), oligophenylenes (13), oligopyrroles (6), perylenes (5), phthalocyanines (11), polycyclic aromatic hydrocarbons (16), polyenes/polyynes (10), porphyrins (34), quinones (24) and xanthenes (15). A database of 31 solar spectra also is included.