Synthesis of nanosized TiO2 particles in reverse micelle systems and their photocatalytic activity for degradation of toluene in gas phase

Nanosized pure TiO₂ particles with high crystallinity and large surface area were prepared by hydrolysis of tetrabutyl titanate in water/Triton X-100/isooctane reverse micelle solutions as reaction media followed by hydrothermal treatment to improve crystallinity. The prepared TiO₂ nanoparticles were characterized by XRD, BET, TGA, FT-IR and TEM. The size of ultrafine particles was controlled by changing the water content of the reverse micelle solution. The TiO₂ particles showed monodispersity, large surface area and high degrees of crystallinity and thermostability. The photocatalytic activity of the TiO₂ particles was evaluated by decomposition of toluene in the gas phase. The activity of the TiO₂ nanoparticles was higher than that of commercially available anatase fine particles, such as ST-01, which is one of the most active photocatalysts for degradation of organic compounds in the gas phase.     

Reverse fluorous solid-phase extraction: a new technique for rapid separation of fluorous compounds

Fluorous-tagged compounds can rapidly be separated from organic (non-tagged) compounds by the new separation technique of reverse fluorous solid-phase extraction (r-fspe). In a reversal of the roles of solid and liquid phases in standard fluorous spe, a mixture is charged to a polar solid phase (standard silica gel) and then eluted with a fluorous solvent or solvent mixture. The organic components of the mixture are retained, while the fluorous components pass. [structure: see text]     

Effect of Pt loading on the photocatalytic reactivity of titanium oxide thin films prepared by ion engineering techniques

Platinum-loaded titanium oxide thin-film photocatalysts were prepared by using an ionized cluster beam (ICB) deposition method and a RF magnetron sputtering (RF-MS) deposition method as dry processes. From the results of the photocatalytic oxidation of acetaldehyde with O₂ under UV light irradiation, small amounts of Pt loading (less than 10 nm film thickness) were found to dramatically enhance the photocatalytic reactivity. However, when TiO₂ thin films were loaded with relatively larger amounts of Pt (more than 30 nm as the film thickness), the photocatalytic reactivity became lower than for the pure TiO₂ thin films. Moreover, investigations of the ratio of Pt loaded onto the surface of the thin film catalysts by XPS measurements revealed that the small amounts of Pt loaded exist as very small clusters working to efficiently enhance the charge separation, whereas, large amounts of Pt covers the entire surface of the TiO₂ thin films, resulting in a decrease of the photocatalytic reactivity.     

Structure of sclerosporin,a sporogenic substance of sclerotiniafructicola

Sclerosporin, the major sporogenic substance of $\text{S. fructicola}$, and its related metabolite, sclerosporal, were shown to have the plain structures, $\text{1}$, and $\text{2}$, respectively. by using a micro-amount of the samples, and co-occurring sclerosporene probably to have the structure $\text{3}$.     

Synthesis of vinyl polymers with pendant phenoxazinyl group

Vinyl monomers bearing phenoxazine units, were synthesized: 2-vinyl-phenoxazine starting with phenoxazine in a five-step synthesis; 3-acrylamido- or 3-methacrylamido-phenoxazines with or without 10-PhCH₂ or 10-Me-substituent starting with o-benzylideneaminophenol or o-anisidine via 3-aminophenoxazines; and 3-(p-styrenesulfonamido)phenoxazines with or without 10-PhCH₂- or 10-Me-substituent, also via 3-aminophenoxazines. Polymerizations of these noval monomers proceeded smoothly, except those having no 10-substituent. Changes of the visible absorption spectrum of iodine in THF with addition of the polymers and oligomers thus prepared were considerable, with the appearance of new absorption peaks for polymers with 10-Me-substituent.     

A rapid label-free electrochemical detection and kinetic study of Alzheimer's amyloid beta aggregation

We present the first electrochemical detection, characterization, and kinetic study of the aggregation of Alzheimer's disease (AD) amyloid beta peptides (Abeta-40, Abeta-42) using three different voltammetric techniques at a glassy carbon electrode (GCE). This method is based on detecting changes in the oxidation signal of tyrosine (Tyr) residue. As the peptides aggregate, there are structure conformational changes, which affect the degree of exposure of Tyr to the molecular surface of the peptides. The results show significant differences in the aggregation process between the two peptides, and these correlate highly with established techniques. The method is rapid and label-free, and the principle can be universally applied to other protein aggregation studies related to diseases, such as Huntington's, Parkinson's, and Creutzfeldt Jacob (CJD). This method could also be explored in screening for the effectiveness of AD therapies.     

Application of the recursion method to the study of the end effects on the bond length alternation in polyacetylene

We describe how the local equilibrium electronic structure in a large system can be determined by using the recursion method of Haydock. By applying this method to the polyacetylene molecule, the energies of each atomic site and the forces acting on each bond are estimated and the equilibrium structure near the end of polyacetylene is determined. It is found out that the degree of localization of π electrons and the bond length alternation become stronger near the end of the polyacetylene molecule.     

Surface structures, photovoltages, and stability of n-Si(111) electrodes surface modified with metal nanodots and various organic groups

The surface structures, photovoltages, and stability of n-Si(111) electrodes surface-modified with Pt nanodots and organic groups were studied in an I-/I3- redox electrolyte, using alkyls of varied chain length and those having a double bond and ester at the terminal as the organic groups. The n-Si was first modified with the organic groups, and then Pt was electrodeposited on it. Linear sweep voltammetry revealed that, for the modification with alkyls, the overvoltage for the Pt deposition became significantly larger with increasing alkyl chain length, though this does not necessarily hold for the modification with alkyls having a double bond and ester. Scanning electron microscopic inspection showed that the Pt particle density decreased and the particle size increased, with increasing alkyl chain length. The photovoltaic characteristics and stability for the n-Si electrodes modified with the organic groups were much improved by the Pt nanodot coating, though they became somewhat inferior with increasing alkyl chain length. On the basis of these results, it is concluded that surface alkylation at high coverage together with coating with small Pt nanodots gives efficient and stable n-Si electrodes.     

Gas transport properties in thermally cured aromatic polyimide membranes

Aromatic polyimide derived from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 3,3′-diaminodiphenylsulfone (m-DDS) has been synthesized to facilitate the study of relationships between the polymer structure and the gas transport properties (permeability and selectivity). The gas permeability and selectivity of CO₂, O₂, N₂, and CH₄ for the 6FDA-m-DDS membranes cured at 150, 200, and 250°C have been determined at 35°C and at pressures up to 760 cmHg. The packing density and the fluorescence intensity of the 6FDA-m-DDS polyimide increased sharply with the increasing curing temperature. We propose that this behavior is associated with an increase in intermolecular and/or intramolecular interactions by a charge transfer complex formed in 6FDA-m-DDS containing an alternating sequence of electron donor and electron aceptor molecules. The effect of the microstructure of the thermally cured 6FDA-m-DDS membranes on their gas transport properties is discussed.     

Diffusion current at microdisk electrodes—application to accurate measurement of diffusion coefficients

Stationary electrodes (platinum and glassy carbon) were used for accurate measurement of diffusion coefficients. The theoretical diffusion current-time profile was calculated by digital simulation, by means of which the diffusion coefficient and the product of the charge number of electrode reaction n and the reactant concentration c^o were determined simultaneously from a single chronoamperogram. The feasibility of the method was demonstrated by measuring the diffusion coefficients of Tl(I) ions. When the nc^o value agreed with the corresponding known value, the diffusion coefficients were in good agreement with the standard values determined by the thin-walled hanging mercury drop electrode method. The diffusion coefficient of hexacyanoferrate(III) ions in 1 mol dm^?3 KCl at, 25°C was also determined.