FexNi100−x nanometric films deposited by laser ablation on SiO2/Si substrates

Fe_xNi_100−x nanometric films were deposited on SiO₂/Si substrates at room temperature using the pulsed laser deposition technique. The targets were Fe-Ni amorphous magnetic foils with composition Fe₅₀Ni₅₀, Fe₃₅Ni₆₅ and Fe₂₂Ni₇₈. Morphological and structural properties of the deposited films were investigated using scanning electron microscopy, Rutherford backscattering spectrometry, grazing incidence X-ray diffraction, and X-ray reflectivity. Electrical and magnetic characteristics of the films were investigated by using the four-point probe and the magneto-optic Kerr effect techniques, respectively. The film properties are strictly dependent on the Fe-Ni compositional ratio.     

First example of the formation of bipolar spiro σ-complexes from 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide

The reactions of 3,5,7-trimethyltropolone and 2-(N-benzylamino)tropone with 6-bromo-5,7-dinitrobenzo[e]-1,2,3,4-tetrazine 1,3-di-N-oxide afforded novel bipolar spiro -complexes. The kinetic and activation parameters of the R,S-enantiotopomerization of a chiral spiro -complex of 2-(N-benzylamino)tropone were determined using dynamic ¹H NMR spectroscopy.     

Axial dispersion in coiled tubular reactors

A theoretical and experimental treatment of axial dispersion in coiled tubes is presented. The dispersion, δ, is related to the theoretical plate height divided by four times the radius of the tube (H/4r). This parameter, when plotted against the product of the Reynolds number and the Schmidt number (ReSc), accurately predicts maxima in dispersion curves. Variations in the boundary layer thickness and the velocity profile cause the dispersion to pass through a maximum at a constant value of log (De²Sc^1·14) equal to 6.13 for unretained solutes (De is the Dean number). A new measure of dispersion is proposed; the reduced dispersion, ? = 256/(Re^0.667Sc), is derived from the experimental behavior of dispersion at values of log (De²Sc^1·14) smaller than 6.13. The logarithm of ? is found to be approximately zero for 2.2 < log (De²Sc^1·14) < 6.1 and to decrease linearly with log (De²Sc^1·14) at higher values. Experiments with four solutes that have a wide range of molecular diffusivities are reported. Results agree with theory.     

Crystal chemistry and thermodynamic properties of anisotropic Ce2Ni7H4.7 hydride

A new intermetallic deuteride Ce₂Ni₇D_4.7 with an anomalous volume expansion has been studied. Its structure was solved on the basis of in situ neutron diffraction data. Expansion proceeds along the c-axis and within the CeNi₂ slabs only. All D atoms are located inside these slabs and on the border between CeNi₂ and CeNi₅. Ordering of D atoms in the bulk of CeNi₂ is accompanied by substantial deformation of these slabs thus lowering the hexagonal symmetry to orthorhombic [space group Pmcn (No. 62); a=4.9251(3) Å, b=8.4933(4) Å, c=29.773(1) Å]. Inside the CeNi₂ layer the hydrogen sublattice is completely ordered; all D-D distances exceed 2.0 Å. Local coordination of Ni by D inside the CeNi₂ blocks is of “open”, saddle-like type. Hydrogen ordering is mainly determined by Ce-H and H-H interactions. The pressure-composition-temperature measurements yielded the following thermodynamic parameters of the formation of the hydride: ΔH=−22.4 kJ/mol_H, ΔS=−59.9 J/(K mol_H).     

Voltammetric Determination of Allura Red AC onto Carbone-paste Electrode Modified by Silica with Embedded Cetylpyridinium Chloride

In current study the carbon-paste electrode modified by silica with embedded cetylpyridinium chloride for determination of Allura Red AC have been developed. The optimal conditions were determined to be for the square-wave voltammetric quantification: pH=2, E_ads=300 mV, t_ads=300 s, amplitude – 40 mV, frequency – 25 Hz and potential scan rate is 250 mV sec⁻¹. The calibration plot has linearity in the concentration ranges 0.04–0.2 μM and 0.2–1.00 μM. The LOD and LOQ are equal to 0.005 μM and 0.015 μM respectively. The crafted sensor has been applied successfully to model solutions and in jelly candies analysis with RSD no more than 10 %.     

Voltammetric and spectroscopic studies of water/formamide ratios in the production of the cerium (III) hexacyanoferrate (II) nanoparticles

The present study describes the simple and fast preparation of Cerium (III) hexacyanoferrate (II) (CeHCF) solid nanoparticles at three different water/formamide (%) ratios used as solvent (v/v) (100:0, 80:20, 0:100). CeHCF nanoparticles (Nps) were characterized by fourier transform infrared pectroscopy (FTIR), x-ray diffraction (XRD), scanning electron microscopy (SEM), zeta potential and cyclic voltammetry (CV). Electrodes modified with CeHCF presented a well-defined redox pair with formal potential (E^o′) of approximately 0.29 V (vs. Ag/AgCl(sat) attributed to the Fe^{2 +}/Fe³⁺ redox pair in the presence of cerium (III)). The Nps in the three systems investigates, presents a random size distribution to different surface, where most were distributed between 20 and 160 nm. Considering the three investigated systems, only CeHCF-1 (100:0) was sensitive to L-dopamine, presenting a linear signal region as a function of L-dopamine concentrations, with a limit of detection (LD) of 0.125 mmol L⁻¹, limit of quantification (LQ) of 0.419 mmol L⁻¹ and amperometric sensitivity (S) of 148.16 μA mmol L⁻¹.     

Intramolecular π-complexes based on nitroaryl derivatives of furotroponimine: structure and stereodynamics

Neutral aromatic electrophiles, such as trinitrobenzene and dinitrobenzofuroxane, covalently bound to the furotroponimine moiety form intramolecular through-space charge-transfer π-complexes both in solution and in the crystalline state. The kinetic and activation parameters of stereodynamic processes were determined by dynamic NMR spectroscopy. These parameters provide quantitative estimates of the kinetic stability of the p-complexes. The electronic and geometric characteristics of the π-complexes were calculated by the B3LYP/6-31G** method.