Anion complexation. A ditriphenylphosphonium calix[4]arene derivative as a novel receptor for anions

A novel anionic receptor 2 consisting of a calix[4]arene bearing two alkytriphenylphosphonium has been prepared by two different procedures. The complexation occurred at the phosphonium sites probably due to electrostatic and/or π-anion forces.     

Double-T metamaterial for parallel and normal transverse electric incident waves

Electric and magnetic hybridized plasmonic modes are obtained by stacking two T-shaped resonators. We show that head-to-toe configuration leads to inverse the hybridization. The frequency shift between the resonances is finely controlled by adjusting the gap between the two resonators. A negative refractive index close to -1 is numerically and experimentally demonstrated at 4.3 GHz for TE waves. This left-handed behavior is similar for parallel and normal TE incident wave vectors. The proposed double-T unit cell is well adapted for developing terahertz and IR metamaterials.     

Sodium hydrogen telluride as a useful nucleophilic reagent for the cleavage of epoxides and of quaternary ammonium salts

Sodium hydrogen telluride opens many epoxides cleanly by an SN₂ process to give telluro-alcohols, which by reduction with nickel boride afford alcohols. An intermediate telluro-alcohol was converted to olefin in high yield by treatment with $\text{p}$-toluene-sulphonyl chloride in pyridine. Quaternary ammonium salt are also cleaved efficiently by sodium hydrogen telluride.     

Selective reduction of the N-O bond in n-oxides and in nitrones by sodium hydrogen telluride

Sodium hydrogen telluride reduces $\text{tert}$.-amine $\text{N}$-oxides to the corresponding amines in very high yield, but does not reduce sulphoxides. This reagent also reduces nitrones to $\text{sec}$.-amines at pH6 and to imines at alkaline pH (10–11).     

Existence Result for a Superlinear Fractional Navier Boundary Value Problems

In this paper, we study the following fractional Navier boundary value problem

$$\begin{aligned} \left\{ \begin{array}{lllc} D^{\beta }(D^{\alpha }u)(x)=u(x)g(u(x)),\quad x\in (0,1), \\ \displaystyle \lim _{x\longrightarrow 0}x^{1-\beta }D^{\alpha }u(x)=-a,\quad \,\,u(1)=b, \end{array} \right. \end{aligned}$$

where \(\alpha ,\beta \in (0,1]\) such that \(\alpha +\beta >1\), \(D^{\beta }\) and \(D^{\alpha }\) stand for the standard Riemann–Liouville fractional derivatives and a, b are nonnegative constants such that \(a+b>0\). The function g is a nonnegative continuous function in \([0,\infty )\) that is required to satisfy some suitable integrability condition. Using estimates on the Green’s function and a perturbation argument, we prove the existence of a unique positive continuous solution, which behaves like the unique solution of the homogeneous problem.

     

Combined static electromagnetic radiation and plant extract contribute to the biosynthesis of instable nanosilver responsible for the growth of microstructures

The instant biosynthesis of silver nanoparticles under static electromagnetic induction, its antibacterial activity and its post exposure monitoring were reported here. A mix of silver nitrate solution and Ruta chalepensis leaf extract was irradiated by a static electromagnetic field (SMF) of 200 mT. The characteristics and stability of the biosynthesized silver nanoparticles (Ag NPs) were determined. Compared to the non-irradiated exposure, the morphology and state of the obtained material change once the exposition to SMF is turned off. Shifting from 453 to 473 nm, the percentage of the needles shaped silver nanoparticles increased and continue to win and dominate the biomixture toward the spherical silver nanoparticles. TEM microscopy showed a wide range of silver materials designed in different nanoscale morphology and beyond where they undergo major changes affecting mainly the size, shape and form (dispersity) of nanosilver.     

A spirobiscalix[4]azacrown: synthesis and complexing properties

The synthesis and complexation properties of a novel type of calix[4]azacrown, in which two cone calix[4]arenes are linked via a spiro C-atom incorporated into polyaminoalkylene chains are presented.     

A dipyrenyl calixazacrown chemosensor for Mg

A new fluorogenic calix[4]tetraaza-crown-6 (4) bearing two pyrene amide groups has been prepared. It was shown to be selective for Mg²⁺. When Mg²⁺ is bound to 4, the pyrene monomer emission increased while the excimer emission declined in a ratiometric manner. It is shown by ¹H NMR that this ratiometric change is due to the conformational changes of the pyrenes during the chelation of Mg²⁺ by the amide functions to form a 1:1 complex.     

Polaronic and charge ordering effects in Pr 0.5 Sr 0.5 Mn 1− x Fe x O 3

In this work we report the results of X-ray diffraction and Mössbauer spectroscopy for the systems Pr_0.5Sr_0.5Mn_1???x Fe _x O₃ (with x?=?0.05, 0.10, 0.15, 0.20, 0.25, 0.30). XRD patterns indicated that all samples were single phase with slightly distorted orthorhombic symmetry. Room temperature Mössbauer spectra are all quadrupole split, indicating paramagnetic relaxation of the Fe moment for all values of Fe concentrations. The spectra are fitted with two doublet components associated with Fe^3?+? ions in octahedral sites with different distortions. Mössbauer spectra recorded at liquid nitrogen temperature for this system also indicate paramagnetic relaxation of the Fe moments down to liquid nitrogen temperature (LNT). In these spectra a third quadrupole component with quadrupole splitting close to zero develops. This component is associated with the delocalization of the charge carriers and the consequent disappearance of lattice distortions produced by the polaronic effect at room temperature. The component with the high quadrupole splitting (0.81 to 1.07 mm/s) results from Jahn–Teller distortion as a consequence of charge ordering transition at low temperature.