Low-Temperature Synthesis of Single-Phase Barium Strontium Titanate Thin Film with a nm-Seeding Technique and Its Dielectric Properties

Dielectric barium strontium titanate (Ba_0.5Sr_0.5TiO₃, BST) thin films containing crystalline seeds of BST nanoparticles were prepared on indium titanium oxide (ITO) glass electrodes with a complex alkoxide precursor method. BST precursor solution that dispersed the BST particles was spin-coated on the electrode and annealed at various temperatures. Thickness of the film was about 300 nm, and BST particle concentration in the film was varied from 0 to 17 mol%. An unseeded BST film was crystallized into a perovskite structure by annealing at 600C, while the seeding with the 17 mol%-BST particles promoted crystalline growth of BST perovskite and lowered crystallization temperature of the films to 525C. Measurement of dielectric properties at 1 kHz showed that the 4.9 mol% BST-seeded film annealed at 600C had a relative dielectric constant of 303, which was higher than that of the unseeded BST film.     

Effect of α-Hydroxyketones as Chelate Ligands on Dip-Coating of Zirconia Thin Films

The stabilization effects of -hydroxyketones such as acetoin, acetol, and their imine derivatives of monoethanolamine (MEA) on the 2-propanol solution of metal alkoxides (Al, Ti, Zr, Nb and Ta) were investigated. The hydroxyketones, especially acetoin which has a moderate boiling point around 150°C, were found to have a stabilization effect on the alkoxides of Ti^IV, Nb^V and Ta^V already in their molar ratios of 2, while the Zr^IV alkoxide was stabilized at the molar ratio of 4. By sol-gel processing using this acetoin-stabilized solution, crystallized ZrO₂ thin films could be prepared at temperatures as low as 400°C, which was lower than that from a diethanolamine (DEA)-stabilized precursor (450°C). The films prepared in this study showed a high transparency (more than 90%, UV-VIS spectroscopy), suggesting that the use of chelate ligands with low boiling points is a good way to lower the crystallization temperature of sol-gel-derived ZrO₂ thin films. The Zr complexes of the imines made by the reaction between the hydroxyketones and MEA were stable and photosensitive (<500 nm), making it possible to pattern ZrO₂ films by photo-irradiation of their gel films.     

Interactions of quaternary ammonium salt-type gemini surfactants with sodium poly(styrene sulfonate)

The interactions of cationic gemini surfactants, 1,2-bis(alkyldimethylammonio)ethane dibromide (m-2-m: m is hydrocarbon chain length, m = 10 and 12), and an anionic polymer, sodium poly(styrene sulfonate) (PSS), have been characterized by several techniques such as tensiometry, fluorescence spectroscopy, and dynamic light scattering. The surface tension of gemini surfactant/PSS mixed systems decreases with surfactant concentration, reaching break points, which are taken as critical aggregation concentrations (cac). The surface tension at the cac of mixtures is higher than that of single surfactants, and it is found that at concentrations above the cac, the surfactant molecules are associated with the polymer in the bulk. The 12-2-12/PSS mixed system shows higher surface activity than both 10-2-10/PSS and the monomeric surfactant of dodecyltrimethylammonium bromide/PSS systems. Fluorescence measurements of these mixed systems suggest the formation of a complex with a highly hydrophobic environment in the bulk of the solution. Additionally, dynamic light scattering measurements show that the hydrodynamic diameter of the 12-2-12/PSS mixed system is smaller than that of PSS only at low concentration, indicating interactions between surfactant and polymer. These result from the electrostatic attraction between ammonium and sulfate headgroups as well as the hydrophobic interaction between their hydrocarbon chains.     

Solid‐Solution Alloy Nanoparticles of the Immiscible Iridium–Copper System with a Wide Composition Range for Enhanced Electrocatalytic Applications

For the first time, we synthesize solid‐solution alloy nanoparticles of Ir and Cu with a size of ca. 2 nm, despite Ir and Cu being immiscible in the bulk up to their melting over the whole composition range. We performed a systematic characterization on the nature of the Ir_xCu_1?x solid‐solution alloys using powder X‐ray diffraction, scanning transmission electron microscopy coupled with energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy. The results showed that the Ir_xCu_1?x alloys had a face‐centered‐cubic structure; charge transfer from Cu to Ir occurred in the alloy nanoparticles, as the core‐level Ir 4f peaks shifted to lower energy region with the increase in Cu content. Furthermore, we observed that the alloying of Ir with Cu enhanced both the electrocatalytic oxygen evolution and oxygen reduction reactions. The enhanced activities could be attributed to the electronic interaction between Ir and Cu arising from the alloying effect at atomic‐level.     

Ground- and excited-state dynamic control of an anion receptor by hydrostatic pressure

Stimulus-responsive supramolecular architectures have become an attractive alternative to conventional ones for many applications in sensing, drug-delivery and switchable memory systems. Herein, we used an anion receptor (H: host) as a hydrostatic-pressure-manipulatable fluorescence foldamer and halide anions as chiral (binaphthylammonium) and achiral (tetrabutylammonium) ion pairs (SS or RR·X and TBA·X; X = Cl, Br), and then investigated their (chir)optical properties and molecular recognition behavior under hydrostatic pressures. The conformational changes and optical properties of H in various organic solvents were revealed by UV/vis absorption and fluorescence spectra and fluorescence lifetimes upon hydrostatic pressurization. The anion-recognition abilities of H upon interactions with SS or RR·X and TBA·X at different pressure ranges were determined by hydrostatic-pressure spectroscopy to quantitatively afford the binding constant (K_anion) and apparent reaction volume changes . The results obtained indicate that hydrostatic pressure as well as solvation plays significant roles in the dynamic control of the present supramolecular system in the ground and excited states. This work will provide a new guideline for further developing hydrostatic-pressure-responsive foldamers and supramolecular materials.

Hydrostatic pressure can control interactions of chiral countercations with helical receptors containing anions, causing remarkable chiroptical changes.     

Preparation of optically active peralkyldiphosphines and their use, as the rhodium(I) complex, in the asymmetric catalytic hydrogenation of ketones

Two types of the optically active peralkyldiphosphine, 2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(dialkylphosphino)butane (Rdiop 3) and N-(N′-substituted carbamoyl-4-dicyclohexylphosphino-2-dicyclohexylphosphinomethylpyrrolidine (R-Cycapp 8), have been prepared by various synthetic methods. Rhodium(I) complexes of 3 and 8 showed high catalytic activity for hydrogenation of various kinds of prochiral ketones, which were reduced smoothly to the corresponding optically active hydroxy compounds, under hydrogen at atmospheric pressure and ambient temperature. The neutral rhodium(I) complexes (diphosphine-Rh^N) hydrogenated -ketoamides and -ketopantolactone in fairly high optical yields (66–77%ee). In the hydrogenation of N-(-ketoacyl)--amino esters, the Cydiop-Rh^N catalyst showed a marked contrast to the diop-Rh^N system; in the hydrogenation of the methyl ester of N-(phenylglyoxyl)-(S)--phenylalanine, 72%de was attained with little double asymmetric induction by the chiral center in the substrate.     

Determination of the chemical forms of iodine with IC-ICP-MS and its application to environmental samples

An online analytical system using ion chromatography (IC) followed by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the separate determination of I⁻ and IO₃⁻ in aqueous solutions with a detection limit 0.1–1 μg 1/1. The total iodine concentration was also directly determined by ICP-MS. Iodine in several environmental samples (i.e., rain, river water, brine, and soil solution) was successfully determined with information on its chemical form. The release of I⁻ into soil solution with decreasing Eh was observed in an incubation experiment with flooded soil. An iodine form other than I⁻ and IO₃⁻ was observed in several environmental samples.     

Physicochemical properties of quaternary ammonium bromide-type trimeric surfactants

Trimeric surfactants of quaternary ammonium bromide (m-2-m-2-m, where m is the hydrocarbon chain length of 8, 10, or 12) with three hydrocarbon chains and three hydrophilic groups connected by two ethylene spacer chains were synthesized by the reaction of N,N,N',N",N"-pentamethyldiethylenetriamine and the corresponding alkyl bromide. Their physicochemical properties were characterized by surface tension, static and dynamic light-scattering, and fluorescence spectrum of pyrene techniques. The critical micelle concentrations (cmc's) of m-2-m-2-m shifted to lower concentrations with increasing hydrocarbon chain length, and their values were smaller by about one to three orders of magnitude than those of the corresponding dimeric (m-2-m) and monomeric surfactants (C(m)TAB) with the same hydrocarbon chain length. Of these surfactants, 10-2-10-2-10 showed the greatest efficiency in lowering the surface tension and provided the smallest occupied area per molecule, indicating that it adsorbs more compactly at the air/water interface. In addition, from the static and dynamic light-scattering measurements, the aggregation numbers of the trimeric surfactants at the cmc were very small, and two hydrodynamic diameters above the cmc were observed.     

Efficient anodic pyridination of poly(3-hexylthiophene) toward post-functionalization of conjugated polymers

Nucleophilic substitution reaction of poly(3-hexylthiophene) (P3HT) with pyridine derivatives as nucleophile was demonstrated in anodic oxidation process. The key reaction involves efficient nucleophilic attack of the pyridine derivatives toward thiophene rings in partly oxidized polymer, i.e., doped state, in the similar manner in which anodic pyridination of electrochemically generated pi-radical cation of a series of oligothiophene takes place in quantitative yield (Y. Li, K. Kamata, T. Kawai, J. Abe and T. Iyoda, J. Chem. Soc., Perkin Trans. 1, 2002, 1135-1140). When 1-methyl-4-(4'-pyridyl)pyridinium hexafluorophosphate (MPP+PF6-) was used as a functional nucleophile, the anodic pyridination reaction gave viologen-tailored poly(3-hexylthiophene) (P3HT), which was confirmed by electrochemical and spectroelectrochemical methods. The introduced ratio of viologen units was about 60% with respect to the polaron, i.e., one-electron oxidized state localized over five thiophene units.