Tomokazu Yoshimura

Preparation of noble metal nanoparticles in supercritical carbon dioxide

Abstract Silver, palladium, and silver–palladium nanoparticles have been prepared by reduction of silver acetylacetonate and palladium acetate with dimethylamine–borane in the presence of a fluorinated surfactant (FOMBLIN HC/P2-1000) in supercritical carbon dioxide. The sizes of silver and palladium nanoparticles increases with increasing concentrations of both the soluble precursors and FOMBLIN. The size of silver nanoparticles obtained is 3–12 nm, while that of palladium nanoparticles is 3–6 nm. For preparation of silver–palladium nanoparticles, the particle size is ranged between 4 and 5 nm and dependent on the feed molar ratio of palladium acetate. It is found that silver–palladium nanoparticles consist of a core-shell structure with enriched palladium in the surface.

Effect of dilution on aqueous dispersion of drug particles

Aqueous suspensions of 5-(3-ethoxy-4-pentyloxyphenyl)-2,4- thiazolidinedione (CT112) have been prepared by neutralization of alkaline solutions of CT112 in the presence of surfactant/polymer with HCl. Sodium dodecyl sulfate (SDS) and celluloses have been used. The effect of dilution of water on the aqueous CT112 dispersion has been studied by measuring the amount adsorbed of surfactant and polymer, ζ-potential, particle size, and sedimentation behavior. The dispersion stability of aqueous CT112 suspension in the presence of polymer or SDS by dilution of water depends on the initial concentration of polymer or SDS. On the other hand, the dispersion stability of aqueous CT112 suspension in the presence of both polymer and SDS is stable even by dilution of water. The mechanism for the effect of dilution of water has been discussed.

Physicochemical properties of aqueous mixed solutions of sugar-persubstituted poly(amidoamine)dendrimers and bovine serum albumin

Abstract The interactions of bovine serum albumin (BSA) with sugar-persubstituted poly(amidoamine)dendrimers (SB, generation 3 and 5) have been studied using several techniques including interfacial rheometer. The sample solutions are prepared by mixing SB5 or SB3 to BSA under a fixed concentration of BSA. In BSA–SB5 system, mixed solutions become turbid due to the formation of aggregates between BSA and SB5 by adding a small amount of SB5, but a further addition of SB5 renders the aggregates redispersed. These results are reflected in the changes of surface tension, interfacial rheology, and circular dichroism (CD) spectra for BSA–SB5 system. On the other hand, BSA–SB3 system does not show significant physicochemical properties due to a weak interaction between BSA and SB3.

Interactions of fluorocarbon-modified poly(acrylic acid) with a cationic fluorocarbon surfactant

Abstract The physicochemical properties of mixed systems of fluorocarbon-modified poly(acrylic acid) (FA) with a cationic fluorocarbon surfactant, bis(2-hydroxyethyl)(2-hydroxy-3-perfluoro-octylpropyl)methylammonium chloride (DEFUMAC), have been investigated by surface tension, fluorescence, solubility, and 19F NMR spin–lattice relaxation measurements. The result obtained from the surface tension measurement indicates that surface DEFUMAC–FA complexes are formed by strong electrostatic attraction at pH 10, while they are formed by hydrogen bond at pH 4. However, hydrophobic interaction is hardly observed at both pHs. In the bulk properties estimated from fluorescence and solubility measurements, DEFUMAC–FA complexes exhibit large solubility capacity for fluorocarbon compounds when the content of fluorocarbon in FA increases. Moreover, the result obtained from the spin–lattice relaxation time measurement suggests that the mobility of hydrophobic end group of DEFUMAC for DEFUMAC–FA complex at pH 10 is more restricted than that at pH 4.