Masaharu Okazaki

Characterization of MCM-41 mesoporous molecular sieves containing copper and zinc and their catalytic performance in the selective oxidation of alcohols to aldehydes

MCM-41 mesoporous molecular sieves containing copper and zinc with different metal contents were synthesized at room temperature (RT) by the method of direct insertion of metal ions as precursors in the initial stage of synthesis. The physicochemical properties of the materials were thoroughly investigated employing X-ray powder diffraction, high-resolution transmission electron microscopy. UV-Visible diffuse reflectance spectroscopy, electron paramagnetic resonance spectroscopy, temperature programmed reduction and N adsorption-desorption methods, The results indicated that MCM-41 materials with long range hexagonal ordering could be successfully synthesized at RT in the presence of copper and zinc salts with the (Cu + Zn) contents of around 2-3 wt.%. A further increase in the metal content deteriorated the ordering of the materials. Removal of the template upon calcination resulted in the formation of CuO-like species with a distorted octahedral coordination. The Cu2+ ions in the MCM-41 materials were reduced completely to metallic copper in the temperature range 230-260 degreesC. On the other hand, the presence of zinc together with copper impeded the Cu2+ reducibility. The catalytic partial oxidation of methanol and ethanol over CuMCM-41 and CuZnMCM-41 materials yielded corresponding aldehydes as predominant products. The activity for alcohol conversion increased with increasing copper content, and this indicated that the Cu2+ ions in the CuMCM-41 and CuZnMCM-41 materials were located on the readily accessible interior surfaces of the mesopores

Effect of high magnetic fields on the reverse electron transfer process in an α-cyclodextrin inclusion complex of phenothiazine-viologen chain-linked compound

The effect of high magnetic fields (< 14 T) on the lifetime of a triplet biradical generated by a photoinduced intramolecular electron transfer reaction of the title compound has been studied in water at room temperature by using pulse-magnet laser flash photolysis apparatus. On increasing the magnetic field from zero to ca. 1 T, the lifetime of the biradical increases steeply, and then decreases gradually in higher magnetic fields. The lifetime at ca. 13 T is about 30% of that at 1 T. This drastic reversal of the effect is qualitatively interpreted by a spin-lattice relaxation (SLR) mechanism. The SLR induced by the anisotropic Zeeman interaction is responsible for the decrease in lifetime in the higher magnetic fields. The mechanism is discussed in detail based on model calculations.

A laser flash photolysis study of the effect of intense magnetic fields on the photoreaction of benzophenone in SDS micellar solution

Abstract The magnetic field dependence of the lifetime of the benzophenone ketyl-SDS-derived radical pair in SDS micellar solution is divided into three regions. In a low magnetic field (

Effects of solution chemistry on the hydrothermal synthesis of kaolinite

The hydrothermal synthesis of kaolinite was examined in the Al2O3-SiO2-H2O system to study inhibitory effects of additional ions on the formation of kaolinite. Syntheses were carried out with amorphous starting materials and salt solutions of various concentrations in Teflon pressure vessels at 220°C for 5 days. The reaction products were characterized by XRD, IR, DTA-TG, NMR and TEM. In all of the runs using solutions with cation concentrations less than 0.001 M, no significant effect on the formation of kaolinite was observed. The inhibitory effect of the univalent cations Li+, Na+ or K+ was less than that of divalent cations such as Mg2+ or Ca2+. The addition of trivalent Fe3+ or excess Al3+ ions interfered with the formation of kaolinite significantly. Sulfate and acetate solutions interfered with the formation of kaolinite more than chlorides and nitrates. No crystalline product was obtained using a 1.0 M basic solution of carbonate or hydroxide. The addition of the lithium ion to the system affected the crystallization of kaolinite only slightly. The use of 0.1 M LiCl and LiNO3 solutions for the syntheses improved crystallization of kaolinite along the [001] direction.

Paramagnetic attraction of erythrocyte flow due to an inhomogeneous magnetic field

Abstract The effect of an external inhomogeneous magnetic field on the flow of erythrocytes containing paramagnetic hemoglobin was studied systematically, with three experimental setups. (1) The attraction of a narrow stream of erythrocyte suspension towards stronger magnetic field, in a wide laminar flow, was found to be proportional to the magnetic susceptibility of erythrocytes χ, the product of the field strength and its spatial gradient B × d B /d z , and the reciprocal of flow velocity 1/ v , and also to the hematocrit h of the suspension. (2) A model flow of erythrocyte suspension in the vessel showed a small change in the radial distribution of erythrocytes arising from a magnetic field, which is proportional to χ, B × d d B /d z (up to 20 T 2 /m), 1/ v , and h ( B × d B /d z and h . (3) Acceleration of the sedimentation rate was detected for paramagnetic erythrocytes in an inhomogeneous magnetic field, but not with diamagnetic erythrocytes. In short, the paramagnetic attraction takes place with venous blood, and depends on the product of the field strength and its spatial gradient, the degree of deoxygenation, the flow velocity, and the hematocrit.

Excimer formation of pyrene as a probe to investigate the recombination of geminate pairs: ODESR and fluorescence study of dilute pyrene in squalane

Abstract It is shown that the monomer fluorescence and the excimer fluorescence from a dilute pyrene solution in squalane at room temperature are mainly from “delayed” geminate pairs (Py−, S+) and (Py−, Py+), respectively, from the ODESR spectra observed at the monomer and the excimer fluorescence. The recombination time of the former pair is found to be much shorter than that of the latter from analysis of these ODESR amplitudes. This indicates that the hole (S+) hops between the solvent molecules towards the solute anion.

Optically detected electron paramagnetic resonance and fluorescence study on geminate ion recombination in low-density polyethylene doped with pyrene

The optically detected electron paramagnetic resonance (ODEPR) spectrum of pyrene-doped low-density polyethylene has been studied. This is the first ODEPR spectrum observed on an ordinary polymer, and its intensity was comparable to that of spectra recorded in viscous solutions. The dependence of the ODEPR and fluorescence spectra on the concentration of pyrene as well as temperature led us to deduce the geminate recombination process in this inhomogeneous material. We found that: (1) charge recombination occurs mainly through electron hopping between the solute pyrenes. (2) Hole hopping between the pyrenes following hole transfer from the polymer matrix to the solute on the ODEPR timescale is allowed only at high temperatures and high solute concentrations.

Electron spin resonance study on the structure and dynamics of propane cation radical: The intrinsic form with a CS symmetry

Propane cation radicals with CS symmetry were found by electron spin resonance in C3F8 and C2F6 at 4 K. They have one C–C bond elongated considerably, and the unpaired electron is in the 10a’ orbital of CS symmetry, which is derived from the 4b1 orbital of C2V symmetry by the deformation. The highest spin density appears in the elongated C–C bond, and the in‐plane methyl proton at the other end has the largest hyperfine coupling (hfc) of about 9 mT. The degree of deformation from the C2V form is dependent on the matrices. From the general consideration on the structure of propane cation, it is deduced that the cation in SF6, which has been considered to have C2V symmetry, also has CS symmetry with a smaller distortion, and that distortion to CS symmetry is an intrinsic nature of the propane cation.

The solution flow through the nanochannel of MCM-41: a spin-probe study

A spin-probe electron spin resonance (ESR) study was made on the alcoholic solution flowing through a quartz column packed with MCM-41 to clarify the dynamics of the liquid molecules in the nanochannel. The ESR spectra of a few hydrophobic spin probes showed that they undergo rotational diffusion preferentially along the longest molecular axis, indicating that the nanochannel is effectively narrowed further for these radicals by the influence of the solvent. Since almost identical ESR spectra were observed for the static samples, which were prepared in vacuo by introducing the solutions into the quartz tube with the MCM-41 powder and sealing off, the solution in the above-mentioned experiment should really flow through the nanochannel of MCM-41. Although a laminar flow is expected from the classical theory, the calculated flow rate is almost zero. In addition, the duration for the spin-probe molecules to flow through the column was basically not dependent on their affinity to the silica surface. To explain all these phenomena, we propose a model that the liquid molecules flow collectively by slipping on the surface of the nanochannel.

Boycott effect with vertical cylinder for paramagnetic red blood cells under the inhomogeneous magnetic field

Abstract The sedimentation rate of paramagnetic erythrocytes in a vertical cylinder increased with the application of an inhomogeneous magnetic field in the horizontal direction. This phenomenon is similar to the so-called Boycott effect, which produces increased sedimentation in an inclined cylinder or channel. The detailed mechanism of this effect has not been obtained. Since the direction of force acting on the particles in a suspension can be changed continuously by changing the magnetic field strength, our method may be used to control the sedimentation rate of small paramagnetic particles in a liquid.