Formation of fractal porous silica by hydrolysis of TEOS in a bicontinuous microemulsion

Mesoporous silica particles have been prepared by hydrolysis of TEOS (Si(OC₂H₅)₄) in bicontinuous microemulsions containing polyoxyethylene (POE) dodecylether, isooctane and water. TEOS was dissolved in a continuous water phase and hydrolyzed by the dispersed water at around the phase inversion temperature (60°C). Undulating solid materials with layered mesostructures were produced from middle-phase microemulsions in the three phase region (o/w=0.2–0.7). On the other hand, the solids obtained from the lower aqueous phase in the three phase region were found to have a heterogeneous disordered structure. Measurements of the fractal dimensions were performed in the macropore region using a box-counting method for the outline of the SEM texture. We found that the macropore size distribution in the particles prepared from the middle-phase microemulsion follows the fractal rule with a dimension of 1.7. From the results of nitrogen adsorption/desorption curves on the silica, a steep increase in the adsorption amounts was observed at a relative pressure below 0.2, and adsorption/desorption hysteresis was also observed at a relative pressure between 0.3 and 0.5. These studies suggest that the silica synthesized in the bicontinuous microemulsion mesostructure has a very broad size range from micro to macropores with a fractal distribution.     

Scintigraphy in the small animals using a human gamma camera--evaluation of bone scintigraphy in the rat mandible and maxilla

In order to obtain clear scintigrams of small animals, some improvements were brought on a pinhole collimator. Then, using a human gamma camera with this collimator improved, bone scintigraphy was attempted in the rat mandible and maxilla, experimentally to examine the desirable conditions of scintigraphy. The most desirable bone scan images were obtained under the conditions that the pinhole was 1.5 mm in diameter, the distance between the collimator and the object was 0 cm, and the exposure was 400.     

Application of the single comparator method to instrumental photon activation analysis

Journal of Radioanalytical and Nuclear Chemistry - Instrumental photon activation analysis (IPAA) is nondestructive and multi-elemental analysis method like instrumental neutron activation...     

Complex formation of light and heavy lanthanides with DGA and DOODA,and its application to mutual separation in DGA–DOODA extraction system

We studied the stepwise formation constants (β) of water-soluble diglycolamide (DGA) and dioxaoctanediamide (DOODA) for the mutual separation of Ln in a solvent extraction system. TODGA (N,N,N?,N?-tetraoctyl-diglycolamide) and DOODA(C8) (N,N,N?,N?-tetraoctyl-dioxaoctanediamide) exhibit opposite behaviors in extracting both light and heavy Ln through Ln-patterns. Metal complexes of two- and three-folding with water-soluble DOODA and DGA, respectively, were found, and each β value was calculated using distribution ratios. Taking β, their distribution ratio, D, and separation factor, SF, values into consideration, the suitable separation conditions (aqueous phase: 30 mM DOODA(C2) in 1 M HNO₃; organic phase: 0.1 M TODGA in n-dodecane) of multistage extraction (10?×?10 extraction using aqueous and organic phases, including one sample solution) were determined. In this study, La, Pr, and Nd were mainly present in the aqueous phase, whereas Sm–Dy existed in the organic phase. Although these two groups can be easily separated into two phases, the resolution, Rs, values provide for little mutual separation between La–Nd and Sm–Dy under the present conditions.

     

Insoluble monolayers of irisresorcinol at the air/water interface

Monolayer properties of irisresorcinol [5-(cis-10-heptadecenyl) resorcinol] were measured at the air/water interface. TheA-T isobars of the monolayers at 10 and 15 mN/m gave two-dimensional thermal expansivities of 1.4 × 10^–4/K and 1.3 × 10^–4/K at a temperature span from 7–40 C, respectively. The- A isotherms of the material showed only a little dependence on temperature from 5–35 C and onpH except at highpH, where monolayers expanded by ionization of resorcinol headgroups. Some types of saccharose in the subphase exhibited a characteristic interaction with irisresorcinol in monolayers, and there is a possibility that this material will be used for molecular recognition of some saccharoses.     

Analysis of charge transfer distance between Ru(bpy)32+ complexes incorporated into a nafion film as studied by spectrocyclic voltammogram

An ITO electrode was coated by a Nafion film incorporating Ru(bpy)₃²⁺ complex as redox centers either by mixture casting method, adsorption method, or swelling method and the electrochemical reactivity of the modified electrode was determined by the in-situ spectrocyclic voltammogram (SCV) in a sodium perchlorate aqueous solution at pH 1.2. A modified Poisson statistics equation was used to estimate the charge transfer distance (Ro) between the Ru(bpy)₃²⁺ complexes. The estimated charge transfer distances for the electrodes prepared by swelling method (Ro = 1.63 nm for the electrode modified in M/W 1:10, and 1.69 nm in M/W 1:2) and adsorption method (Ro = 1.61 nm) were longer than that for mixture casting method (Ro = 1.5 nm). Based on the different procedure of Ru(bpy)₃²⁺ complex incorporation in the Nafion film, the reasons that affect the apparent charge transfer distance were discussed.     

Synthesis of polymers in aqueous solutions: Polyaddition of bis(oxazolines) with dithiol in aqueous solutions

Polyaddition of bis(4-mercaptophenyl) sulfide ( BMPS ) with m-phenylenebis(2-oxazoline) ( MPBO ) proceeded very smoothly in the mixtures of aprotic ploar solvents such as N-methyl-2-pyrrolidone ( NMP ) with water to produce the corresponding poly(amide–sulfide) with high molecular weights at 90°C under nitrogen. The reaction of BMPS with MPBO , p-phenylenebis(2-oxazoline), and 1,4-butylenebis(2-oxazoline) was also examined in water under the same conditions, and it was found that the reaction proceeds successfully to give the corresponding poly(amide–sulfide)s with high molecular weights. These results mean that water along as well as the mixed solvents of aprotic polar solvents such as NMP with water can be uses as suitable reaction media for the polyaddition of bis(oxazolines) with dithiol to synthesize poly(amide—sulfide)s with high molecular weights. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2711–2717, 1997     

ESR Study of a Nitroxide Radical in Sol-Gel Glasses

A spin probe TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxy) was dissolved in a tetraethyl orthosilicate sol-gel reaction system and measured by electron spin resonance spectroscopy at 295 K. The nitrogen hyperfine coupling constant was from 1.64–1.66 mT in the sol-gel solutions. The values were sensitive to the ethanol-to-water ratio of the solutions. The hyperfine coupling constant in the xerogels was 1.70 mT, which was almost the same as that in water, indicating that the probe molecules were trapped in silica pores with water adsorbed on the silica surfaces. The motion of TEMPOL in the xerogels was considerably slower than in the sol-gel solutions. The local viscosity estimated was from 70–90 cP. The ESR spectra of TEMPOL were altered during the sol-gel process, indicating that adsorbed water on the silicas surfaces has an important role for trapping organic molecules in sol-gel glasses.