Kumiko Iwai

Characterization of iron oxide in Fe2O3/SiO2 catalyst

Abstract Silica-supported iron oxide catalyst was prepared by hydrolysis of a mixed solution of ethyl silicate and iron(III) nitrate dissolved in ethylene glycol. A gel obtained by the hydrolysis was dried and calcined at various temperatures. The iron oxide particles thus prepared were maghemite (γ-Fe2O3), deduced by EXAFS (extended X-ray absorption fine structure) measurements and the sample color. The maghemite particles were classified into two groups: one is small but detectable by transmission electron microscopy (TEM) and the other is too small to be detected by TEM. The former was well controlled to a consistent size, which depended on the calcination temperature, and exhibited ferrimagnetic properties. The latter showed superparamagnetic properties and was estimated to be smaller than 10 A in particle size by magnetic and Mossbauer measurements at low temperature. For comparison, the catalyst was also prepared by a conventional impregnation method using silica powder and an aqueous solution of iron(III) nitrate. Iron oxide thus prepared was hematite (α-Fe2O3) and the particle sizes were broadly distributed.

Low molecular weight polysaccharide complexes for nuclear magnetic resonance imaging

There is disclosed an imaging agent for diagnosis comprising a compound composed of a polynuclear type compound of the formula I or II: ##STR1## wherein each X is a hydrogen atom or a bifunctional ligand, at least one of them are bifunctional ligand and m or n is an integer of 1 to 6, and at least one metal ion being coordinated with at least one bifunctional ligand moiety, said metal ion being selected from the group consisting of metal ions having the atomic number of 21-29, 31, 32, 37-39, 42-44, 49 and 56-83.

Nuclear magnetic resonance imaging agent comprising a di-aldehyde complex

There is disclosed a nuclear magnetic resonance imaging agent comprising a complex compound composed of (a) a dialdehyde-saccharide having a molecular weight of from 500 to 10,000, at least one of the constituent monosaccharides of which is oxidation-cleaved, (b) at least one complexing agent which is chemically coupled to an aldehyde group of the dialdehyde-saccharide and (c) a paramagnetic metal ion which is chemically coupled to the complexing agent.

Studies of molecular motions in the three phases of 1,1′,2,2′-tetrachloroferrocene by Mössbauer and1H-NMR spectroscopy

The molecular motions in the three phases of 1,1′,2,2′-tetrachloroferrocene below m.p. were studied by using57Fe-Mossbauer and1H FT-NMR spectroscopy. In the plastic phase at the low temperature, a rotational mode around the pseudo C5 molecular axis was found to be activated with activation energy of 15 kJ/mol and in the higher temperature phase the rotational mode of the pseudo C5 axis itself was found to be activated with activation energy of 23 kJ/mol in addition to the rotational mode around the pseudo C5 axis. On the57Fe-Mossbauer spectra, a steep decrease of the areal intensity was observed above the first transition temperature. The areal intensity in the lower plastic phase was estimated to be less than a few percent relative to that at 298 K. The results were discussed in terms of different possibilities for the movement of the molecules.

Mössbauer spectroscopic studies of iron carbonyls adsorbed on γ-Al2O3 and SiO2

Characterization of Fe3/CO/12 cluster adsorbed on γ-Al2O3 and SiO2 was undertaken by means of57Fe-Mössbauer spectroscopy. In the case of Fe3/CO/12 adsorbed on γ-Al2O3, iron atoms were found to be similar to metallic iron. Fe3/CO/12 adsorbed on SiO2 retains its original molecular structure and chemical nature.