Kensuke Naka

Adsorption of Inorganic and Organic Arsenic Compounds by Aluminium‐loaded Coral Limestone

Coral limestones were treated with an aqueous solution of aluminium sulfate and thereby aluminium-loaded coral limestones (Al-CL) were prepared. By use of Al-CL as an adsorbent, the adsorption of inorganic arsenic compounds (arsenate [As(V)] and arsenite [As(III)] and of organic arsenic compounds (methylarsonic acid, dimethylarsinic acid, and arsenobetaine) was examined. The adsorption ability of Al-CL is superior to that of iron(III)-loaded coral limestone (Fe-CL) for As(V), As(III), methylarsonic acid and dimethylarsinic acid. The adsorption of As(V) and As(III) is almost independent of the initial pH over a wide range (2 or 3 to 11). The addition of other anions, such as chloride, nitrate, sulfate and acetate, in the solution does not affect the adsorption of As(V) and As(III), whereas the addition of phosphate greatly interferes with the adsorption. Arsenic adsorption is effectively applied to a column-type operation and the adsorption capability for As(V) is 150 μg/g coral limestone.

Iron(III) Hydroxide-Loaded Coral Limestone as an Adsorbent for Arsenic(III) and Arsenic(V)

Abstract Trace levels of As(III) and As(V) in aqueous media were effectively adsorbed onto a coral limestone loaded by Fe(OH)3. The adsorption of As(III) was almost comparable to that of As(V). The adsorption of As(III) and As(V) was almost independent of the pH of the aqueous phase (pH range: 3–10) because of a self-buffering effect of the coral. The addition of such anions as chloride, nitrate, sulfate, and acetate in the aqueous phase did not significantly affect the adsorption of As(III), whereas the addition of phosphate brought about a great decrease in the adsorption. The arsenic adsorption was effectively applied to the column method. Unloaded coral itself was effective as an adsorbent for As(V) when Fe(III) coexisted in the aqueous solutions.

Preparation of a novel core-shell nanostructured gold colloid-silk fibroin bioconjugate by the protein in situ redox technique at room temperature.

A novel core-shell gold colloid-silk fibroin (SF) bioconjugate was prepared by the protein in situ redox technique at room temperature, in which the tyrosine (Tyr) residue of the SF, having strong electron donating properties, in situ reduced Au(III) ions to Au colloids showing a stable and highly monodispersed nature.

Functional polymers based on electron-donating TTF and derivatives

This review highlights the recent progress of electron-donating polymers containing thio-cyclic units (tetrathiafulvalene, dithiafulvene, thioketene dimers). These polymers with TTF derivatives in the main chain and side chain have been studied with the aim of improving processability of their charge transfer complexes and increasing the dimensionality of their conducting paths in the solid state. This review also highlights a novel synthetic methodology of the electroactive polymers, i.e., cycloaddition polymerization of bisthioketene to produce poly(dithiafulvene) and oxidative polymerization of bisdithiafulvenyl monomers and thioketene dimers. In the application of poly(dithiafulvene)s to the polymer–metal hybrid systems, they act as not only the reducing agent but also the stabilizer for the formed metal nanoparticles.

Supramolecular sensor based on SnO2 electrode modified withoctadecylsilyl monolayer having molecular binding sites

Abstract Octadecylsilyl (ODS) monolayer covalently bound onto SnO2 was found to aquire molecular binding sites via extracting out co-implanted inert guest(n-hexadecane). Intense electrochemical response of ODS/SnO 2 was found toward vit-K 1 , K 2 and E adsorbed to the molecular binding sites.

A Bod Sensor Using Klebsiella Oxytoca AS1

Abstract A BOD sensor using Klebsiella oxytoca AS 1 was investigated with special emphasis on the effect of cell properties, such as the number, and growth phase, of immobilized cells, on the sensor response. The sensor response was almost independent of the cell number in the case of low BOD solutions, whereas the response increased with increasing cell number when high BOD solutions were used. The growth phase of the cells immobilized in the membrane affected the sensor response, especially when the membrane had been stored at 30 °C for long time. Cells immobilized at the beginning of the stationary growth phase were the most effective in terms of both the sensitivity and preservability. 1 he response of K. oxytoca sensor to various substrates, including sugars and amino acids, was similar to that of a Trichosporon cutaneum sensor. The K. oxytoca sensor showed a higher resistance to some toxic substances, such as phenol, compared to T. cutaneum sensor.

Modulation of morphology and conductivity of mixed-valence tetrathiafulvalene nanofibers by coexisting organic acid anions.

We describe here the facile preparation of conductive casting films consisting of mixed-valence tetrathiafulvalene (TTF) nanofibers. Self-assembled nanofibers of mixed-valence TTF with organic acid anions were grown during film deposition, and the conductivities of the resulting films were significantly altered by the type of the anion. In particular, the casting films containing heptafluorobutyrate, propanesulfonate, and undecanesulfonate work as semiconductors (10(-2) S/cm). It was revealed that anion species played a crucial role in the formation of the nanofibers and the morphology of the film was varied.

Effect of dendrimers on the crystallization of calcium carbonate in aqueous solution.

Construction of organic-inorganic hybrid materials with controlled mineralization analogous to those produced by nature is now a current interest for both organic and inorganic chemists to understand the mechanism of natural biomineralization processes as well as to seek industrial and technological applications. Model systems, in which low-molecular-weight, linear polymeric organic materials have been used to study the effect of molecular properties such as charge and functionality on inorganic crystallization, are providing insights into the possible mechanisms operating in biology. Due to unique and well-defined secondary structures of the dendrimers, the starburst dendrimers should be a good candidate for studying inorganic crystallization. This review provides a general survey of recent research on crystal nucleation and growth of calcium carbonate by a carboxylic acid derivative of hyperbranched polyphenylene polymer, poly(amidoamine) (PAMAM) dendrimers with carboxylate groups at the external surface, and poly(propyleneimine) dendrimers modified with long aliphatic chains.

The effect of an anionic starburst dendrimer on the crystallization of CaCO3 in aqueous solution

Crystallization of CaCO3 in the presence of poly(amidoamine) (PAMAM) dendrimer containing carboxylate groups at the external surface resulted in the formation of spherical vaterite crystals whereas rhombohedral calcite crystals were formed in the absence of additive.

Preparation of hydrophobic CaCO3 composite particles by mineralization with sodium trisilanolate in a methanol solution

Hydrophobic CaCO3 composite particles were prepared via crystallization of CaCO3with a sodium trisilanolate [(c-C5H9)7Si7O9(ONa)3] in methanol. The molar ratio of calcium ion to the sodium trisilanolate was varied from 0.1 to 0.5. FT-IR and TGA analysis of the obtained product indicated that the trisilanol was bound to the crystalline CaCO3. By changing the concentration of the trisilanol, composite particles with different shapes and polymorphism were obtained. Low concentration of the trisilanol gave stable vaterite crystals, the polymorph of which did not change when the composite was kept in water for more than 1 week. The contact angle of the modified vaterite was 62±4°. Dispersability of the composites in a polystyrene matrix was significantly improved compared with a bare CaCO3. We have succeeded in surface modification of particles with the hydrophobic trisilanolate.