Crystallization of Confined Water Pools with Radii Greater Than 1 nm in AOT Reverse Micelles

Freezing of water pools inside aerosol sodium bis­(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles has been investigated. Previous freezing experiments suffer from collision and fusion of AOT micelles and resultant loss of water from the water pool by shedding out during the cooling process. These phenomena have restricted the formation of ice to only when the radius of the water pool (<i>R</i>_w) is below 1 nm, and only amorphous ice has been observed. To overcome the size limitation, a combination of rapid cooling and a custom-made cell allowing thin sample loading is applied for instantaneous and homogeneous freezing. The freezing process is monitored with attenuated total reflection infrared spectroscopy (ATR-IR) measurements. A cooling rate of ca. −100 K/min and a sample thickness of ca. 50 μm overcomes the limitations mentioned above and allows the crystallization of water pools with larger radii (<i>R</i>_w > 1 nm). The corresponding ATR-IR spectra of the frozen water pools with <i>R</i>_w < 2.0 nm show similar features to the spectrum of metastable cubic ice (I_c). Further increase of the radius of the water pool (<i>R</i>_w > 2.0 nm), unfortunately, drastically decreased the integrated area of the ν­(OH) band observed just after freezing, indicating the breakup of the micellar structure and shedding out of the water pool. In addition, it was revealed that I_c ice can also be formed in flexible organic self-assembled AOT reverse micelles for at least <i>R</i>_w ≤ ca. 2 nm, as well as in inorganic and solid materials with a pore radius of ca. 2 nm. The dependence of the phase transition temperature on the curvature of the reverse micelles is discussed from the viewpoint of the Gibbs–Thomson effect

Efficient Catalytic Epoxidation in Water by Axial N‑Ligand-Free Mn-Porphyrins within a Micellar Capsule

Epoxidation of styrenes is efficiently catalyzed by micelle-like molecular capsules providing Mn-porphyrins in water at room temperature. In contrast to usual Mn-porphyrin catalysts, the encapsulated Mn-porphyrin catalysts show higher reactivities (up to 1350 TON for 1 h) even without the addition of imidazole ligands. Spectroscopic studies and competitive-binding experiments demonstrate that the efficient catalytic cycle stems from the enforced proximity of the catalyst and substrates as well as the smooth replacement of the products by substrates in the hydrophobic cavity of the capsule

High-Speed Morphology Control of Boehmite Nanoparticles by Supercritical Hydrothermal Treatment with Carboxylic Acids

This study demonstrates that the morphology of boehmite (AlOOH) nanoparticles can be controlled over a short timespan by supercritical hydrothermal treatment in the presence of alkyl carboxylic acids including hexanoic, octanoic, decanoic, tetradecanoic, and octadecanoic acids. Boehmite nanoparticles were treated with carboxylic acid in supercritical water at 400 °C and at a water density of 0.35 g/cm³ in a batch-type reactor. When the carboxylic acid was not added, the particles were shaped as rhombic plates. However, the addition of carboxylic acid changed the crystal morphology to hexagonal plates. The aspect ratio (i.e., [length along the <i>a</i>-axis]/[length along the <i>c</i>-axis]) of the rhombic plates increased with a treatment time of 2–30 min, which is a much shorter timespan than that used for conventional hydrothermal crystallization. The aspect ratio of the hexagonal plates increased with increasing concentration of alkyl carboxylic acids. These results clearly indicate that carboxylic acids enhance the dissolution and recrystallization of boehmite. The aspect ratio increased with decreasing length of the alkyl chain of alkyl-carboxylic acid added to the system. Thermogravimetric analysis (TGA) showed that carboxylic acids modified the surface of the boehmite particles. The coverage of the alkyl carboxylic acid on the surface of the nanoparticles was evaluated from the weight loss curve obtained from TGA, and the surface area was evaluated from transmission electron microscopy, which showed that the aspect ratio of the particles increased with increasing the coverage. The results suggest that the carboxylic acid suppresses crystal growth along the shorter axis through surface-capping, thus enhancing dissolution and crystal growth along the <i>a</i>-axis

Electrical Conductivities, Viscosities, and Densities of <i>N</i>-Methoxymethyl- and <i>N</i>-Butyl-<i>N</i>-methylpyrrolidinium Ionic Liquids with the Bis(fluorosulfonyl)amide Anion

This paper reports the densities, viscosities, and electrical conductivities of the two pyrrolidinium ionic liquids, <i>N</i>-methoxymethyl-<i>N</i>-methylpyrrolidinium bis­(fluorosulfonyl)­amide ([Pyr_1,1O1]­[FSA]) and <i>N</i>-butyl-<i>N</i>-methylpyrrolidinium bis­(fluorosulfonyl)­amide ([Pyr_1,4]­[FSA]), over the temperature range <i>T</i> = (273.15 to 363.15) K at atmospheric pressure. The densities were fitted to polynominals, and the viscosities and electrical conductivities were analyzed with the Vogel–Fulcher–Tammann and Litovitz equations. The densities and electrical conductivities of [Pyr_1,1O1]­[FSA] are higher than those of [Pyr_1,4]­[FSA], while the viscosities of the former salt are smaller than those of the latter. The Walden plots (double logarithm graph of molar conductivity vs fluidity (reciprocal viscosity)) give the straight lines with the slopes being 0.91 to 0.94. The present results for [Pyr_1,1O1]­[FSA] and [Pyr_1,4]­[FSA] are compared with those for the bis­(trifluoromethanesulfonyl)­amide ([NTf₂]⁻) analogues, [Pyr_1,1O1]­[NTf₂] and [Pyr_1,4]­[NTf₂]

Attack rate during the influenza A(H3N2) outbreak period.

<p>Attack rate for (A) children aged <20 years and (B) adults aged ≥20 years.</p

Epidemic curves for each affiliation.

<p>Epidemic curves of household transmission index cases, household transmission secondary cases, and non-household transmission ILI cases in (A) school A, (B) school B, (C) preschool C, (D) preschool D, (E) preschool E, (F) preschool F, (G) children at home, and (H) adults. The letters attributed to the household transmission secondary cases are the affiliations of their index cases; A, school A; B, school B; C, preschool C; D, preschool D; E, preschool E; F, preschool F; G, children at home; H, adults.</p

Secondary attack rates and relative risk of ILI by age and gender of household contacts.

<p>Abbreviations: ILI, influenza-like illness; SAR, secondary attack rate; CI, confidence interval; NA, not applicable.</p

Secondary attack rates and relative risk of ILI by household size.

<p>Abbreviations: ILI, influenza-like illness; SAR, secondary attack rate; CI confidence interval.</p

Secondary attack rates and relative risk of ILI by age group of index cases.

<p>Abbreviations: ILI, influenza-like illness; SAR, secondary attack rate; CI, confidence interval; NA, not applicable.</p

Relationship between index cases and secondary cases with household transmission.

<p>Relationship of household transmission (A) among children and (B) among children and adults. Red circles represent index cases, blue triangles represent secondary cases, and arrows show the direction of transmission. The letters represent affiliations; A: school A; B: school B; C: preschool C; D: preschool D; E: preschool E; F: preschool F; G: children at home; H: adults.</p