Our study on soft chemical process using the metal oxide and metal hydroxide nanosheets obtained by exfoliation their layered compounds were reviewed. Ni(OH)₂⁄MnO₂ sandwich layered nanostructure can be prepared by layer by–layer stacking of exfoliated manganese oxide nanosheets and nickel hydroxide layers. Manganese oxide nanotubes can be obtained by curling the manganese oxide nanosheets using the cationic surfactants as the template. The layered titanate oriented thin film can be prepared by restacking the titanate nanosheets on a polycrystalline substrate, and transformed to the oriented BaTiO₃ and TiO₂ thin films by the topotactic structural transformation reactions, respectively. The titanate nanosheets can be transformed anatase–type TiO₂ nanocrystals under hydrothermal conditions. The TiO₂ nanocrystals are formed by a topotactic structural transformation reaction. The TiO₂ nanocrystals prepared by this method expose specific crystal plane on their surfaces, and show high photocatalytic activity and high dye adsorption capacity for high performance dye–sensitized solar cell. A series of layered basic metal salt (LBMS) compounds were prepared by hydrothermal reactions of transition metal hydroxides and organic acids. We succeeded in the exfoliation of these LBMS compounds in alcohol solvents, and obtained the transition metal hydroxide nanosheets for the first time.

View full abstract

In ion–pair extraction system using a neutral complexation reagent and a counter anion, use of higher selective reagent is one of the most important factors to realize their mutual separation. In this study, we paid attention to Schiff base ligands synthesized from amines and carbonyl compounds, and systematically investigated the effects of ligand structure on extraction selectivity and extactability. From the obtained results, it was suggested that the ion recognition ability was able to be controlled by changing the ligand structure. Futhermore, complexing agents with very high selectivity to Cu²⁺ and Ni²⁺ were able to be synthesized. Studies on adsorption behavior of metal ions using mesoporous silicate MCM-41 were performed. It was found that metal ions such as Cd²⁺ and Pb²⁺ were adsorbed on MCM-41 as neutral acetylacetonato complexes by using acetylacetone as a chelating agent. Futhermore, by using the adsorption ability of organic molecules to MCM-41, adsorption behavior of metal ions with thenoyltrifluoroacetone supported on MCM-41 was investigated. As a result, it was found that Cu²⁺ and Zn²⁺ were adsorbed and MCM-41 was able to use as a support of high performance chelating agents.

View full abstract

Zr(IV) surface–immobilized resins for removal of fluoride ion were prepared by surface template polymerization using polystyrene as a porogen. At polymerization, polystyrene was added in order to increase mesopores (2–50 nm) and macropore (>50 nm) with large macropores (around 300 nm) formed with internal aqueous phase of W⁄O emulsion. The pore structure of Zr(IV) surface–immobilized resins was evaluated by measuring specific surface area, pore volume, and pore size distribution with volumetric adsorption measurement instrument and mercury porosimeter. The adsorption isotherms were well fitted by Langmuir equation. The removal of fluoride was also carried out with column method. Zr(IV) surface–immobilized resins, using 10 g⁄L polystyrene in toluene at polymerization, possessed higher volume of not only mesopores and macropores but also large macropores. Furethermore, by adding the polystyrene with smaller molecular size, the pore volume of mesopores, macropores and large macropores was significantly increased, and the fluoride ion adsorption capacity and the column utilization also increased.

View full abstract

Adsorption behavior of Pd(II) chloride complexes using pyridine series ionic liquid (BPHFP) was investigated to establish a clean Pd(II) recovered process by use of ionic liquids as an adsorvent. Adsorption amount of Pd(II) to BPHFP reached a maximum under a low HCl concentration. This is a similar result using a traditional ion–exchange resin, however, no Langmuir adsorption behavior was confirmed in the case of Pd(II) concentration of 1–50 mmol⁄dm³. PdCl₂ exists as a soluble monomeric PdCl₄²⁻ species in higher HCl concentration solution. On the other hand, an insoluble polymeric Pd species is generated in the solution of low HCl concentration. These results indicaled that Pd(II) adsorption using BPHFP was controlled by chemisorption, and the direct coordination of Pd(II) onto pyridine was possibly occurred. Moreover, inorganic support–BPHFP composite material (ILISP) was also developed. The ILISP showed an availability as a Pd(II) adsorbent.

View full abstract

The principle and applications of multiple–angle incidence resolution spectrometry (MAIRS) coupled with infrared spectroscopy are described for analysis of molecular architecture in a polymer thin film. Material characters of polymer are often difficult to discuss from a view point of the chemical structure of the monomer unit, since the characters are largely influenced not only by the monomeric structure, but by inter– or intra–molecular interactions. To understand the relationship between the material character and the fundamental unit, therefore, anisotropic molecular interactions should appropriately be revealed. To do that, infrared spectroscopy is powerful, and a newly innovated technique of MAIRS is particularly useful. In this review, the physical concept of this technique is briefly introduced, followed by an application study using MAIRS for revealing anisotropic molecular structure and interactions in a dipcoated thin film of linear polyethyleneimine deposited on a germanium substrate.

View full abstract