Crystal-face dependence and photoetching-induced increases of dye-sensitized photocurrents at single-crystal rutile TiO2 surfaces

Dye-sensitized photocurrents at (100)-, (001)-, and (110)-cut TiO(2) rutile surfaces were increased by photoetching of TiO(2), but the increasing ratio strongly depended on the cut crystal faces and the illumination intensity for the photoetching. For the (110)-cut surface, the photocurrent increase was moderately large and in proportion to the increase in the surface area of TiO(2) induced by the photoetching, irrespective of the illumination intensity for the photoetching. On the other hand, the photocurrent increases for the (001)- and (100)-cut surfaces, especially that for the (001)-cut surface, were prominent and largely exceeded the increases in the surface area. The results were explained by taking into account the following factors: (1) The (001)- and (100)-cut surfaces were thermodynamically unstable in contrast to the (110)-cut surface and had thicker inactive surface layers (or higher densities of surface defects), produced by surface reconstruction during heat treatment of TiO(2) at 550 degrees C in a hydrogen atmosphere for getting n-type semiconductivity. (2) Photoetching not only increased the surface area through formation of nanoholes and grooves at the surface but also effectively removed the thin inactive surface layers (or surface defects).     

In-situ FTIR studies on self-assembled monolayers of surfactant molecules adsorbed on H-terminated Si(111) surfaces in aqueous solutions

The adsorption of a surfactant, sodium di-2-ethylhexyl sulfosuccinate (SDES), [C4H9CH(C2H5)CH2OCO][C4H9CH(C2H5)CH2OCOCH2]CHSO3- Na+, in an aqueous solution on an atomically flat H-terminated Si(111) [abbreviated as H-Si(111)] surface with a hydrophobic property was investigated by in-situ FTIR measurements. Immersion of the H-Si(111) surface in a solution of 1.0 x 10(-2) M SDES for more than 2 h led to formation of a self-assembled monolayer (SAM) with the alkyl chains having a tendency to be assembled perpendicular to the Si surface. The in-situ FTIR observation revealed that the adsorption was nearly complete about 60 min after the start of the immersion, and after that the adsorbed molecules changed their arrangement into an ordered mode. The Si-H peak in the FTIR spectrum remained unchanged with time in aqueous surfactant solution, in contrast to the case of immersion in pure water, indicating that the adsorbed surfactant protects the H-Si(111) surface from oxidation. No structural change in the SAM was observed when a negative potential of -700 mV vs Ag/AgCl was applied to the Si, whereas the adsorbed molecules changed their arrangement, accompanied by their substantial desorption and oxidation of the Si surface, when a positive potential of +700 mV was applied.     

Macromolecular Recognition of Cyclodextrin: Inversion of Selectivity of β‐Cyclodextrin toward Adamantyl Groups Induced by Macromolecular Chains

Interaction of β‐cyclodextrin (β‐CD) with alternating copolymers (pAdMA and pAdPhMA) of sodium maleate with adamantyl (Ad) and with adamantylphenyl (AdPh) vinyl ether has been investigated by several NMR techniques. Comparing the apparent association constants (K) for the polymers with the K for the model compounds, which are determined by the analysis of ¹H NMR and isothermal titration calorimetry data, respectively, the selectivities of β‐CD toward Ad and AdPh moieties are contrasting for the model and polymer systems. This phenomenon is described by circular dichroism and 2D NMR as follows; the most stable inclusion complex for the β‐CD/AdPh model system is extremely destabilized for the corresponding polymer system because of competition with hydrophobic interaction between neighboring AdPh moieties.

     

Stryphnosides A-F, six new triterpene glycosides from the pericarps of Stryphnodendron fissuratum

Six new triterpene glycosides stryphnosides A-F (1-6) were isolated from the pericarps of Stryphnodendron fissuratum (Leguminosae). The structures of 1-6 were determined on the basis of extensive spectroscopic analysis, including two-dimensional (2D) NMR data, and the results of hydrolytic cleavage. The sugar moieties of 3-6 are very unique in structure having not only novel sugar sequences but also the terminal α-l-arabinopyranosyl unit with a ¹C₄ conformation. Stryphnosides C (3)-F (6) are the first representative of naturally occurring glycosides with the ¹C₄ terminal α-l-arabinopyranosyl group.     

Boundary from Bulk Integrability in Three Dimensions: 3D Reflection Maps from Tetrahedron Maps

We derive the macroscopic laws that govern the evolution of the density of particles in the exclusion process on the Sierpinski gasket in the presence of a variable speed boundary. We obtain, at the hydrodynamics level, the heat equation evolving on the Sierpinski gasket with either Dirichlet or Neumann boundary conditions, depending on whether the reservoirs are fast or slow. For a particular strength of the boundary dynamics we obtain linear Robin boundary conditions. As for the fluctuations, we prove that, when starting from the stationary measure, namely the product Bernoulli measure in the equilibrium setting, they are governed by Ornstein-Uhlenbeck processes with the respective boundary conditions.

     

Synthesis and toxicity assay of ceramic nanophosphors for bioimaging with near-infrared excitation

Yttrium hydroxyl carbonate (Y(OH)CO₃) precursors were synthesized by the homogeneous co-precipitation method in the presence of polyacrylic acid (PAAc). Resultant precursor particle size is about 15–20 nm with narrow size distribution whereas the particle size is smaller than those acquired by the conventional homogeneous precipitation method. Effective decrease of Y(OH)CO₃ particle size was found to be higher for the presence of weak polyanionic ionomer such as PAAc than the presence of strong polyanionic ionomer such as sodium polystyrene sulfonate (PSS). It was observed that the morphology and size of the precursors are almost unchanged after the calcination process. Er³⁺ doped Y₂O₃ nanoparticles were synthesized by PAAc assisted homogeneous co-precipitation method showed bright green (550 nm) and red (660 nm) upconversion (UC) as well as near-infrared (NIR) fluorescence (1550 nm) under 980-nm excitation. UC and NIR fluorescence bioimaging and in-vitro cytotoxicity assay of Er³⁺ doped Y₂O₃ nanoparticles were successfully attempted with commercially available macrophages and B-cell hybridomas. Cellular uptake of nanoparticles is evidenced from bright field, UC and NIR fluorescence images of macrophages.     

Wide control of proton conductivity in porous coordination polymers

The proton conductivities of the porous coordination polymers M(OH)(bdc-R) [H(2)bdc = 1,4-benzenedicarboxylic acid; M = Al, Fe; R = H, NH(2), OH, (COOH)(2)] were investigated under humid conditions. Good correlations among pK(a), proton conductivity, and activation energy were observed. Fe(OH)(bdc-(COOH)(2)), having carboxy group and the lowest pK(a), showed the highest proton conductivity and the lowest activation energy in this system. This is the first example in which proton conductivity has been widely controlled by substitution of ligand functional groups in an isostructural series.     

Baseline noise and measurement uncertainty in liquid chromatography.

The stochastic properties of baseline noise in HPLC systems with a UV photo-diode array, photo-multiplier and gamma-ray detector were examined by dividing the noise into auto-correlated random process (Markov process) and an independent process (white noise). The present work focused on the effect of the stochastic noise properties on a theoretical estimation of the standard deviation (SD) of area measurements in instrumental analyses. An estimation theory, called FUMI theory (Function of Mutual Information), was taken as an example. A computer simulation of noise was also used. It was shown that the reliability (confidence intervals) of theoretical SD estimates mainly depends on the following factors: the ratio of the white noise and Markov process occurring in the baselines; the number of data points used for the estimation; the width of a target peak for which the SD is estimated.     

Polymorphism of ZnTe at elevated pressure

Simultaneous measurements of the electrical resistance and X-ray diffraction under pressure have revealed that ZnTe exhibits two subsequent structural transitions at approximately 85 and 130 kbar, accompanied by a conspicuous rise and drop in the resistance, respectively.     

Total synthesis of myxol and deoxymyxol stereoisomers and their application to determining the absolute configurations of the natural products

The total synthesis of myxol stereoisomers 1a,b and deoxymyxol (plectaniaxanthin) stereoisomers 2a,b was accomplished by Wittig reaction of (S)- and (R)-C₁₀-phosphonium salts 8a,b bearing a silyl-protected 1,2-dihydroxy-ψ end group with C₃₀-apocarotenals 6 and 7. The phosphonium salts 8a,b were derived from aldehydes 11a,b possessing a cyclopentylidene ketal moiety, prepared via Sharpless asymmetric epoxidation of allylic alcohol 12 followed by regioselective cleavage of the oxirane ring. We established an analytical HPLC method using a chiral column to separate stereoisomers 1a,b and 2a,b and thus determined the absolute configurations of the natural products. The HPLC analyses established that both myxol and deoxymyxol isolated from bacteria have the 2′S-configuration.