Spectrofluorometric determination of thallium(III) with pyrogallol red and 3,4,5,6-tetrachlorofluorescein

Summary A spectrofluorophotometric determination of thallium(III) is proposed. It is based on the enhancement of the fluorescence reaction of 3,4,5,6-tetrachlorofluorescein (TCF) with Pyrogallol Red (PR) by thallium(III) in the presence of Swanol (AM 301, lauryldimethyl aminoacetic acid betain) as an amphoteric surfactant. The method was found to be suitable for the determination of thallium(III) down to 4.0 g in 10.0 ml by measuring the difference in the relative fluorescence intensities of a TCF/PR/thallium(III) solution and a TCF/PR solution. The recovery test in artificial urine was satisfactory (96±2%).     

(10R̃, 11R̃)-(+)-squalene-10, 11-epoxide: Isolation from Laurencia okamurai and the asymmetric synthesis

From a red alga $\text{Laurencia okamurai}$ (10$\text{R}\text{?}$, 11$\text{R}\text{?}$)-(+)-squalene-10, 11-epoxide $\text{1}\text{?}$ was isolated and its asymmetric synthesis has been achieved starting from $\text{trans, trans}$-farnesol.     

Single structure widely distributed in a GeTe-Sb2Te3 pseudobinary system: a rock salt structure is retained by intrinsically containing an enormous number of vacancies within its crystal

GeTe(1-x)-Sb2Te3(x) sputtered amorphous film was crystallized into a simple NaCl-type structure through instantaneous laser irradiation over a wide composition range from x = 0 to at least 2/3. When the ratio of Sb2Te3 increases, a vacancy is generated at every Na site for two Sb atoms. The fraction of vacancies, v(x), changes according to x/(1 + 2x), and the cubic root unit cell volume varies with a strong correlation to v(x). Through these created vacancies, valence electrons provided by adjacent Ge/Sb and Te atoms remain constant regardless of the composition, ensuring that these electrons occupy predominantly the bonding molecular orbitals. This results in crystal chemical stability, with the closed shell p-p bondings in the valence electrons arranging the crystal's atomic configuration into an NaCl-type structure.     

First observation of In(x)Ga(1-x)As quantum dots in GaP by spherical-aberration-corrected HRTEM in comparison with ADF-STEM and conventional HRTEM.

In(x)Ga(1-x)As quantum dots in GaP(100) crystals prepared by the OMVPE technique are observed along the [011] direction with a newly developed 200-kV spherical aberration(Cs)-corrected HRTEM, a 200-kV annular dark-field (ADF)-STEM, and a 200-kV conventional HRTEM equipped with a thermal field-emission gun. The dots are 6-10 nm in size and strongly strained due to the misfit of about 9% with the GaP substrate and GaP cap layer. All of the cross-sectional high-resolution electron micrographs show dumbbell images of Ga and P atomic columns separated by 0.136 nm in well-oriented and perfect GaP areas, but the interpretable images are limited to those taken with the Cs-corrected HRTEM and ADF-STEM with Fourier filtering of the images. The Cs-corrected HRTEM and ADF-STEM are comparable from the viewpoint of interpretable resolution. A detailed comparison between the Cs-corrected HRTEM images and the simulated ones with electron incidence tilted by 1 degree to 5 degrees from the [011] zone axis gives information on local lattice bending in the dots from the images around 0.1 nm resolution. This becomes one of the useful techniques newly available from electron microscopy with sub-angstrom resolution.     

Partially nanowire-structured TiO2 electrode for dye-sensitized solar cells

Partially nanowire-structured TiO₂ was prepared by a hydrothermal processing followed by calcination in air. The hydrogen titanate powder as-synthesized was calcined at 300 °C for 4 h to obtain the partially nanowire-structured TiO₂. A dye-sensitized solar cell (DSC) with a film thickness of 5.6 μm, fabricated using the partially nanowire-structured TiO₂ showed better performance than using a fully nanowire-structured TiO₂ or a conventional equi-axed TiO₂ nanopowder. The short-circuit current density (J_SC), the open-circuit voltage (V_OC), the fill factor (FF) and the overall efficiency (η) are 11.9 mA/cm², 0.754 V, 0.673 and 6.01 %, respectively. The effects of one-dimensional nanostructure and electron expressway concept are discussed.     

Phase diagrams of surfactant/water/synthetic perfume ternary systems

The phase diagrams of hexadecyl polyoxyethylene ether (C₁₆POE₁₀)/water/synthetic perfume, and sodium dodecyl sulfate (SDS)/water/synthetic perfume ternary systems were prepared. The synthetic perfumes used are, d-limonene, -hexylcinnamaldehyde, -ionone, benzyl acetate, linalool, and eugenol. In a series of C₁₆POE₁₀/water/synthetic perfume ternary systems, as the hydrophilicity of synthetic perfume increases, the regions of normal and inverse micellar solution phases were found to be extended, while that of the lamellar liquid crystal phase was reduced. Moreover, every region of normal micellar solutions, inverse micellar solutions, and lamellar liquid crystal phases in SDS/water/synthetic perfume ternary systems was found to be smaller than those in C₁₆POE₁₀/water/synthetic perfume systems.     

Studies of polymers from cyclic dienes. IV. Determination of the structure of polycyclopentadiene

3,4- and 3,5-Dimethylcyclopentenes were prepared as model compounds of the structural unit in polycyclopentadiene. These two isomers give characteristic NMR spectra. The assignment based on the 60 Mc./sec. spectrum was further confirmed by decoupling experiments on the 100 Mc./sec. spectrum of 3,5-dimethylcyclopentene. By comparing the NMR spectra of these compounds with that of polycyclopentadiene methods were developed for estimating the polymer structure from the relative peak area of the methine–methylene and olefinic protons. Polycyclopentadiene obtained with Friedel-Crafts catalysts at lower temperatures was shown to be composed mostly of the 1,4 and 1,2 structures. Polycyclopentadiene obtained with several Ziegler-type catalysts possessed comparable amounts of both structures, contrary to the earlier proposals.     

First Principles Calculations Toward Understanding SERS of 2,2′-Bipyridyl Adsorbed on Au,Ag, and Au–Ag Nanoalloy

First principles electrodyanmics and quantum chemical simulations are performed to gain insights into the underlying mechanisms of the surface enhanced Raman spectra of 22BPY adsorbed on pure Au and Ag as well as on Au–Ag alloy nanodiscs. Experimental SERS spectra from Au and Ag nanodiscs show similar peaks, whereas those from Au–Ag alloy reveal new spectral features. The physical enhancement factors due to surface nano-texture were considered by numerical FDTD simulations of light intensity distribution for the nano-textured Au, Ag, and Au–Ag alloy and compared with experimental results. For the chemical insights of the enhancement, the DFT calculations with the dispersion interaction were performed using Au₂₀, Ag₂₀, and Au₁₀Ag₁₀ clusters of a pyramidal structure for SERS modeling. Binding of 22BPY to the clusters was simulated by considering possible arrangements of vertex and planar physical as well as chemical adsorption models. The DFT results indicate that 22BPY prefers a coplanar adsorption on a (111) face with trans-conformation having close energy difference to cis-conformation. Binding to pure Au cluster is stronger than to pure Ag or Au–Ag alloy clusters and adsorption onto the alloy surface can deform the surface. The computed Raman spectra are compared with experimental data and assignments for pure Au and Ag models are well matching, indicating the need of dispersion interaction to reproduce strong Raman signal at around 800 cm^–1. This work provides insight into 3D character of SERS on nanorough surfaces due to different binding energies and bond length of nanoalloys. © 2018 Wiley Periodicals, Inc.     

Palladium-catalyzed diastereoselective synthesis of homoaldol equivalent products

A palladium-catalyzed reaction of easily accessible 3-(pinacolatoboryl)allyl acetates and aldehydes provides facile access to synthetically useful homoaldol equivalent products with high diastereoselectivity. The reaction presumably proceeds via allylation of aldehydes with α-acetoxy allylboronates that produced in situ by reductive elimination from allylic gem-palladium/boryl intermediates.     

Convenient preparation of dichloromethyl alkyl ethers

Dichloromethyl alkyl ethers have been synthesized from alkyl formates (C1–C4) and oxalyl chloride in the presence of catalytic amount of N-methylformanilide. N,N-Dimethylformamide is not suitable for the reaction. The method has the advantages of simple experimental procedure, which is applicable to large scale synthesis, without use of harmful reagents.