TiO2–SiO2 in PEG: A Highly Efficient Green Catalytic System for One‐Pot Synthesis of Benzo[a]xanthen‐11‐ones

Polyethylene glycol was found to be an inexpensive non‐toxic and effective medium for the one‐pot synthesis of benzo[a]xanthen‐11‐ones in the presence of TiO₂–SiO₂ as the catalyst in good to excellent yield. The salient features of this protocol are the simplicity of the procedure, the ready accessibility of the catalyst, its cost effectiveness, and reusable catalyst in relatively short reaction times.     

α,β-Unsaturated acyl cyanide synthesis via triethylamine catalyzed redox cyanation

Stereoselective redox cyanation of alkynyl aldehydes was explored, furnishing (E)-α,β-unsaturated acyl cyanides. This reaction was catalyzed by mild TEA base, as a dual role of Lewis base and Brönsted base. TMSCN treated with TEA was an effective reagent for generating umpolung intermediates from alkynyl aldehydes, and this nucleophilic intermediate can be protonated by equimolar amount of EtOH, promoting the efficient conversion into α,β-unsaturated acyl cyanides. The synthesized acyl cyanides were successfully applied as the synthetic precursors in the iron-catalyzed arylation reactions.     

Composition dependence of the photocatalytic activities of BiOCl(1-x)Br(x) solid solutions under visible light

We prepared BiOCl(1-x)Br(x) (x=0-1) solid solutions and characterized their structures, morphologies, and photocatalytic properties by X-ray diffraction, diffuse reflectance spectroscopy, scanning electron microscopy, Raman spectroscopy, photocurrent and photocatalytic activity measurements and also by density functional theory calculations for BiOCl, BiOBr, BiOCl(0.5)Br(0.5). Under visible-light irradiation BiOCl(1-x)Br(x) exhibits a stronger photocatalytic activity than do BiOCl and BiOBr, with the activity reaching the maximum at x=0.5 and decreasing gradually as x is increased toward 1 or decreased toward 0. This trend is closely mimicked by the photogenerated current of BiOCl(1-x)Br(x) , indicating that the enhanced photocatalytic activity of BiOCl(1-x)Br(x) with respect to those of BiOCl and BiOBr originates from the trapping of photogenerated carriers. Our electronic structure calculations for BiOCl(0.5)Br(0.5) with the anion (O(2-), Cl(-), Br(-)) and cation (Bi(3+)) vacancies suggest that the trapping of photogenerated carriers is caused most likely by Bi(3+) cation vacancies, which generate hole states above the conduction band maximum.     

Three-dimensionally crossing manifold micro-mixer for fast mixing in a short channel length

In this study, we report a neo-conceptive three-dimensionally (3D) crossing manifold micromixer (CMM) embedded in microchannel. Fabricated by sequential processes of photolithography and two photon absorption stereolithography, this leads to a microfluidic system with a built-in micromixer in a site controlled manner. The effectiveness of CMM is investigated numerically and experimentally. Through the numerical simulation, it is estimated that a high mixing ratio of 90% can be obtained even in a channel length shorter than five times the channel width. This compares well with the conventional passive type of micromixers that have a gradual increase in mixing efficiency with the length of the channel. Furthermore, the mixing performance of the realized CMM built-in microchannel is observed by confocal microscopy.     

Prediction error sampling procedure based on dominant Schur decomposition. Application to state estimation in high dimensional oceanic model

Iterative procedure is described to generate patterns of dominant Schur vectors of the system dynamics. Their roles in estimating the filter gain is study. These patterns are produced by several integrations of the model from a set of perturbations. This approach is motivated by a number of interesting results on stability of the filter whose gain is approximated in a subspace of dominant Schur vectors. A simple method for the filter design is presented which is aimed at overcoming the most serious drawback of advanced filtering algorithms for high dimensional systems related to very high computational cost in evaluation of the filter gain.The resulting filter will be compared with the existing ones, showing its relevance from a practical point of view. In order to demonstrate its efficiency, the new filter is tested on various experiments. These experiments include the much studied problem of estimating the solution of the Lorenz system as well as that of assimilating sea surface height observations in a high dimensional oceanic model. It is shown that significant increases in efficiency can be obtained by using this filter and that the proposed filter is very promising for solving realistic assimilation problems in meteorology and oceanography.     

Ba4KFe3O9: a novel ferrite containing discrete 6-membered rings of corner-sharing FeO4 tetrahedra

Single crystals of a new iron-containing oxide, Ba(4)KFe(3)O(9), were grown from a hydroxide melt, and the crystal structure was determined by single-crystal X-ray diffraction. This ferrite represents the first complex oxide containing isolated 6-membered rings of corner-sharing FeO(4) tetrahedra. M?ssbauer measurements are indicative of two tetrahedral high-spin Fe(3+) coordination environments. The observed magnetic moment (~3.9 μ(B)) at 400 K is significantly lower than the calculated spin-only (~5.2 μ(B)) value, indicating the presence of strong antiferromagnetic interactions in the oxide. Our density functional theory calculations confirm the strong antiferromagnetic coupling between adjacent Fe(3+) sites within each 6-membered ring and estimate the nearest-neighbor spin-exchange integral as ~200 K; next-nearest-neighbor interactions are shown to be negligible. The lower than expected effective magnetic moment for Ba(4)KFe(3)O(9) calculated from χT data is explained as resulting from the occupation of lower-lying magnetic states in which more spins are paired. X-band (9.5 GHz) electron paramagnetic resonance (EPR) spectra of a powder sample consist of a single line at g ~ 2.01 that is characteristic of Fe(3+) ions in a tetrahedral environment, thus confirming the M?ssbauer results. Further analysis of the EPR line shape reveals the presence of two types of Fe(6) magnetic species with an intensity ratio of ~1:9. Both species have Lorentzian line shapes and indistinguishable g factors but differ in their peak-to-peak line widths (δB(pp)). The line-width ratio δB(pp)(major)/δB(pp)(minor) ~ 3.6 correlates well with the ratio of the Weiss constants, θ(minor)/θ(major) ~ 4.     

The synthesis and spectral properties of a stimuli-responsive D-π-A charge transfer dye

A new donor-π-acceptor (D-π-A) type isophorone dye was synthesized by the condensation reaction between 2-(3,5,5-trimethylcyclohex-2-enylidene)-malononitrile and indole-3-carboxaldehyde. The chemical structure of the dye was characterized by 1H NMR, EA and MS. A novel, chromogenic, fluorescent dye based on indol as donor unit and isophorone as acceptor unit displayed marked UV-visible absorption changes and highly selective fluorescence quenching in the presence of fluoride ion. The dye also exhibited sizeable colour changes when used as a pH-induced molecular switch and as a detector for volatile organic compounds. The absorption and fluorescent intensity of the dye can be reversibly selected by protonation/deprotonation of the amine moiety via control of intramolecular charge transfer (ICT), leading to a molecular switch with "on" and "off" states.     

SnSe2 nanoplate-graphene composites as anode materials for lithium ion batteries

Through a solution approach, SnSe(2) nanoplate-graphene composites were prepared and applied as anode materials in lithium ion batteries, showing promising storage performance superior to SnSe(2) nanoplates or graphene alone.