Chemistry of Hybrid Organic-Inorganic. Access to Silica Materials through Chemical Selectivity

Hybrid organic-inorganic materials containing labile organic fragments with various structural features have been prepared. The mild cleavage of Si–C bonds allowed removal of the organic moities. It led to silica which pore structure varied according to the nature of the organic component eliminated.     

Les conducteurs ioniques NaxYxZr1−xS2

Results about new ionic conductors Na_xY_xZr_1?xS₂ are presented. The electronic conductivity normally induced by sodium intercalation layered chalcogenides has been suppressed by performing at the same time a substitution of zirconium by yttrium in the slabs of the host structure. Electrical measurements using the complex impedance technique lead to the activation energy of the ionic conduction. This energy was found to present a marked minimum around x = 0.50. A NMR study showed quadrupole coupling to prevail in relaxation process. Electrical field gradient is maximum for x = 0.50. The activation energy of the local motion remains practically constant throughout the composition range. The above results are compared to others obtained from compounds having the same structure.     

La polyveoline,nouvel indolosesquiterpene isole du polyalthiasuaveolens,annonacees

The structure and absolute configuration of polyveoline, new indolosesquiterpene from Polyalthiasuaveolena, Annonaceae, were determined by X-ray crystal lographic study.     

Guattescine et guattescidine,nouveaux alcaloïdes aporphiniques de Guatteria scandens,annonacees

Two new aporphinic alkaloids, guattescine, $\text{1}$, and guattescidine, $\text{2}$, were isolated from $\text{Guatteria scandens}$. Their structure are caracterized by a quaternary methyle at C-6a.     

A faster pseudo-primality test

We propose a pseudo-primality test using cyclic extensions of ?/n?. For every positive integer k?logn, this test achieves the security of k Miller-Rabin tests at the cost of k ^1/2+o(1) Miller-Rabin tests.     

Voltammetric Detection of Copper Ions on a Gold Electrode Modified with a N-methyl-2-naphthyl-cyclam film

A voltammetric sensor based on a methyl-naphthyl cyclam (1,4,8,11-tetraazacyclotetradecane) film deposited through dip coating on gold electrodes allowed the sensitive detection of copper (II). The obtained film was characterized in terms of the composition and morphology using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy. In the presence of divalent metallic ions (copper and nickel) and trivalent metallic ions (iron), at pH 7 and 7.7, the current density of the ionic oxidation peak maximum was determined using square wave voltammetry. The relative variation of this current density varies linearly with the base-ten logarithm of the ion concentration. From this calibration curve, a detection limit of 7?×?10^?12?M was obtained for copper (II) at pH 7. At this pH value, the sensitivity of detection of copper (II) was 2.5 times higher than for nickel (II) and 5.8 times higher than for iron (III). The methyl-naphthyl cyclam film-modified gold sensor was validated for the detection of copper in spiked urine samples.     

Structure et proprietes de conduction du compose K0,1Li0,9SbO3

Single-crystals of K_0,1Li_0,9SbO₃ are obtained by ion exchange method from crystals of KSbO₃, $\text{1}\text{6}$ KF and crystallize in the cubic system, space group Pn3, a = 9,681 (3) Å, Z = 4. Using 398 independent reflections, the structure has been refined by full-matrix least squares, to factor R = 0,043.In this space group, the alkaline ions are in an ordered state.The ionic conductivity of cubic KSbO₃ phases is very high and the motion of cations is three-dimensional along <111> tunnels. The authors discusse the influence of ordered (Pn3) and disordered (Im3) states on the conductivity of these compounds.