Kunio Esumi

Structure-performance relationships in surfactants

Theoretical studies of surfactants: theory of micelle formation - quantitative approach to predicting micellar properties from surfactant molecular structure, R. Nagarajan Modelling association and adsorption of surfactants, Luuk K. Koopal. Physicochemical properties of surfactants at air-liquid interface and in solutions: adsorption of vesicle-forming surfactants at the air-water interface Makoto Aratono, Masumi Villeneuve, and Norihiro Ikeda physicochemical properties of bile salts, Minoru Ueno and Hiroyuki Asano characterization and functionalization of biosurfactants, Yutaka Ishigami physicochemical properties of ring-structured surfactants, Yoshifumi Koide and Kunio Esumi dimeric (Gemini) surfactants, Raoul Zana fluorinated surfactants having two hydrophobic chains, Norio Yoshino surface-active properties of telomer-type surfactants having several hydrocarbon chains, Tomokazu Yoshimura and Kunio Esumi viscoelastic surfactant solutions, Heinz Hoffmann microstructures of nonionic surfactant-water systems - from dilute micellar solution to liquid crystal phase, Tadashi Kato association behaviour of amphiphilic dendritic polymers, Toyoko Imae polymer/surfactant systems, Raoul Zana highly concentrated cubic phase-based emulsions Md. Hemayet Uddin, Hironobu Kunieda, and Conxita Solans. Surfactant behaviours at solid-liquid interface: adsolubilization and related phenomena, Claude Treiner adsorption of polymer and surfactant from their binary mixtures on an oxide surface, Kunio Esumi dispersion of particles by surfactants, Kunio Esumi arrangement of adsorbed surfactants on solid surfaces by AFM observation, Masatoshi Fujii.

Resonant light scattering from metal nanoparticles: Practical analysis beyond Rayleigh approximation

We propose a simple analytical formula that can quantitatively predict resonant light scattering from metal nanoparticles of arbitrary shape, whose sizes are too large for Rayleigh approximation to be applicable. The formula has been derived as an empirical extension of Mie’s rigorous calculation for light scattering from spheres. It can very well reproduce the experimental characteristics of light scattering from Au nanorods.

Antioxidant-potentiality of gold–chitosan nanocomposites

Abstract Gold nanoparticles were prepared in the presence of chitosan via reduction of HAuCl 4 with sodium borohydride. The average particle size of gold nanoparticles was significantly affected with the concentration of chitosan added and was ranged between 6 and 16 nm. The gold–chitosan nanocomposites are formed by adsorbing chitosan molecules on the gold nanoparticles. The catalytic activity of gold–chitosan nanocomposites upon elimination of hydroxyl radicals formed in an H 2 O 2 /FeSO 4 system was examined using a spin-trapping method. The catalytic activity increased with the concentration of chitosan added and showed a maximum and then decreased with a further concentration of chitosan added, although a strict correlation between the average diameter of gold and the catalytic activity was not found. In addition, the activity of gold–chitosan was 80 times higher than that of ascorbic acid, which is well known as an antioxidant.

Aggregation behavior of mixed fluorocarbon and hydrocarbon surfactants in aqueous solutions

The aggregation behavior of lithium perfluorooctanesulfonate (LiFOS), of mixtures of LiFOS with lithium dodecyl sulfate (LiDS) and with octa- and hexaoxyethylene glycol dodecyl ether (C12E8 and C12E6), and of C12E6LiDS in aqueous solutions has been investigated by means of pyrene fluorescence probing. For the pure LiFOS, the micelle aggregation number N as obtained from the analysis of the fluorescence decay of micelle-solubilized pyrene in the presence of a micelle-solubilized quencher was found to increase considerably with the surfactant concentration. In these micelles, pyrene is located very close to, or at, the micelle surface. The measurements of the pyrene fluorescence lifetime τ0 and of the ratio I1I3 of the intensities of the first and third bands of the pyrene monomer fluorescence spectrum appear to indicate that only one type of mixed micelle exists in the mixed systems LiDSLiFOS, C12E6LiFOS, and C12E8LiFOS. The micelle aggregation numbers for these three systems have been determined as has that for the C12E6LiDS system. They decrease as the mole fraction of LiFOS in the first three systems is increased. The evidence for probe intermicellar migration in the C12E6-containing mixed systems has been obtained. This migration is inhibited by the incorporation of LiFOS or LiDS in C12E6 micelles.

Dendrimers for Nanoparticle Synthesis and Dispersion Stabilization

Since dendrimers consisting of regularly branched structure are controlled by chemical structure, molecular weight, and its distribution as well as molecular size and molecular shape, they are unique macromolecules with many functional properties.

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.

Preparation of gold nanoparticles in formamide and N,N-dimethylformamide in the presence of poly(amidoamine) dendrimers with surface methyl ester groups

Abstract Gold nanoparticles were prepared by reduction of HAuCl4 with NaBH4 in the presence of poly(amidoamine)dendrimers with surface methyl ester groups in formamide or N,N-dimethylformamide. Although solutions of HAuCl4 in formamide, in the presence of the dendrimers, were reduced to some extent before reduction, the addition of NaBH4 provided gold nanoparticles whose size decreased with an increase of the dendrimer generation as well as with the concentration of the dendrimers. On the other hand, gold nanoparticles prepared in N,N-dimethylformamide in the presence of the dendrimer were highly monodispersed. In addition, we discussed how the dendrimers acted as templates for the preparation of gold nanoparticles.

Preparation of organopalladium sols by thermal decomposition of palladium acetate

Abstract The preparation of organopalladium sols by thermal decomposition of palladium acetate dissolved in various organic solvents has been carried out. In particular, in methylisobutylketone very stable organopalladium sols are obtained. Their average particle diameters increase from 7 to 260 nm with increase in the concentration of palladium acetate, where uniform spherical particles are obtained in a certain concentration range of palladium acetate. The stability of palladium particles obtained is also discussed.

Physicochemical properties of the α,ω-type surfactant in aqueous solution

The physicochemical properties of the α,ω-type surfactant (disodium dodecyl disulfate) in aqueous solution have been investigated by means of surface tension, conductivity, solubilization of various solubilizates, static light scattering, and 13 C NMR chemical shifts. The surface tension and conductivity measurements indicate the existence of two discontinuities which are referred to as the first CMC and the second CMC. The α,ω-type surfactant molecules change their conformation at an air-water interface and form a “wicket-like” conformation at the second CMC. By the static light scattering being measured the micellar aggregation number above the second CMC is determined to be 90 ± 5 (25°C). This value agrees fairly well with that obtained by 13 C NMR chemical shift data. The above results support the notion that between the first CMC and the second CMC the α,ω-type surfactant forms premicellar (several numbers of aggregates) and, above the second CMC, forms ordinary micelles which are very loosely aggregated.

Adsorption of sodium dodecyl sulfate on hydrotalcite and adsolubilization of 2-naphthol

Abstract Adsorption behavior of sodium dodecyl sulfate (SDS) on hydrotalcite was investigated by measuring the amount of SDS adsorbed, ζ potential and pyrene fluorescence spectra of suspensions. The amount of SDS adsorbed increased sharply and then reached a plateau with SDS concentration, accompanying the change of ζ potential from positive to negative. The X-ray diffraction and fluorescence measurements show that the interlayer separation of hydrotalcite increases, while the microenvironment of SDS adsorbed layer becomes hydrophobic with SDS concentration. The amount of 2-naphthol adsolubilized increased considerably at low SDS concentration and then decreased gradually with SDS concentration. In addition, the amount of 2-naphthol adsolubilized increased proportionally with increasing feed concentration of 2-naphthol.