Synthesis and characterization of polypyrrole–magnetite–vitamin B12 hybrid composite electrodes

In this study vitamin B12 covered magnetite nanoparticles have been incorporated into a conducting polypyrrole. This polymer was electrochemically synthesized in the presence of the B12-coated magnetite. The adsorption of B12 was demonstrated by the decrease in absorbance of the vitamin in the supernatant liquid after B12 has been in contact with magnetite sol overnight. The composition of the layers was studied by the electrochemical quartz crystal microbalance technique during the polymerization. The slope of the mass change–charge curves indicate the incorporation of 27 m/m% magnetite and 15 m/m% B12. The redox transformation of the film in monomer- and nanoparticle-free solutions was also investigated by this method and the difference in the virtual molar masses of the moving species was evidenced. The morphology and the composition of the layers were characterized by scanning electron microscopy combined with energy dispersive X-ray microanalysis measurements, which latter proved the successful incorporation of the magnetic and bio-active components. The electrochemical behavior of the films unambiguously showed the complex redox activity of the composites and the current surplus were quantified by the redox capacity of the layers. These data show the doubling of the redox capacity in case of the hybrid material compared to the neat polymer. The successful enrichment of B12 can be exploited in the recently evidenced redox mediation process performed by a PPy/B12 film.     

Square product of three integers in short intervals

In this paper we list all the integer triplets taken from an interval of length whose products are perfect squares.

     

Study of active carbons by X-ray methods

The X-ray scattering properties of carbon black and charcoals, activated chemically and by steam have been studied in a transmission arrangement. The radial distribution functions calculated from the experimental data indicate that the majority of carbon atoms in chemically activated samples have sp³ configurations, characteristic of strained ring systems. Activation by steam produces a small amount of crystalline graphite. Most of the carbon atoms in carbon black are in an sp²-hybrid state, apparently because of the presence of contaminating atoms in appreciable amount, although no crystalline graphite can be detected.     

On the mechanism of propylene epoxidation catalyzed by molybdenum naphthenate

The mechanism of the catalytic epoxidation of propylene with -phenylethyl hydroperoxide has been investigated. The epoxidation step is a molecular interaction between propylene and a complex formed from hydroperoxide and catalyst, while part of side products is formed in free radical reactions. This mechanism is valid for the kinetics of both epoxidation and catalytic decomposition of hydroperoxide.

---

. — . . .

     

Unraveling the surface reactions during liquid-phase oxidation of benzyl alcohol on Pd/Al2O3: an in situ ATR-IR study

The palladium-catalyzed liquid-phase reaction of benzyl alcohol to benzaldehyde was investigated in the presence and absence of oxygen by attenuated total reflection infrared (ATR-IR) spectroscopy. The 5 wt % Pd/Al2O3 catalyst was fixed in a flow-through ATR-IR cell serving as a continuous-flow reactor. The reaction conditions (cyclohexane solvent, 323 K, 1 bar) were set in the range commonly applied in the heterogeneous catalytic aerobic oxidation of alcohols. The in situ ATR-IR study of the solid-liquid interface revealed a complex reaction network, including dehydrogenation of benzyl alcohol to benzaldehyde, decarbonylation of benzaldehyde, oxidation of hydrogen and CO on Pd, and formation of benzoic acid catalyzed by both Pd and Al2O3. Continuous formation of CO and its oxidative removal by air resulted in significant steady-state CO coverage of Pd during oxidation of benzyl alcohol. Unexpectedly, benzoic acid formed already in the early stage of the reaction and adsorbed strongly (irreversibly) on the basic sites of Al2O3 and thus remained undetectable in the effluent. This observation questions the reliability of product distributions conventionally determined from the liquid phase. The occurrence of the hydrogenolysis of the C-O bond of benzyl alcohol and formation of toluene indicates that Pd was present in a reduced state (Pd0) even in the presence of oxygen, in agreement with the dehydrogenation mechanism of alcohol oxidation.     

Partial structure correlations in amorphous Ni83La17

Short range order in amorphous Ni₈₃La₁₇ was examined by neutron and X-ray diffraction. The two experimental total pair correlation functions (TPCF) were used as input data for model calculations. Computer modelling was based on a new method using the molecular dynamic (MD) technique and the Born–Green–Bogoljubov (BGB) equation (without superposition approximation). All three PPCF, atomic first neighbour angle distributions, Voronoy polyhedra (VP) distributions and other structure properties were derived.     

Partial correlations in Ni60Nb40 metallic glass

Combined X-ray and neutron diffraction experiments were performed on the Ni₆₀Nb₄₀ metallic glass samples prepared by rapid quenching from the melt with natural Ni^nat and isotope ⁵⁸Ni, respectively. The partial structure factors were separated for the three kinds of atomic pairs: NiNi, NiNb and NbNb. The partial distribution functions were calculated by means of Fourier transformation and the following atomic distances were obtained: $\text{r}{}_{\mathrm{<mtext>NiNi</mtext>}}\text{=2.52}\text{A}\text{?}\text{, r}{}_{\mathrm{<mtext>NiNb</mtext>}}\text{=2.72}\text{A}\text{?}$ and $\text{r}{}_{\mathrm{<mtext>NbNb</mtext>}}\text{=2.70}\text{A}\text{?}$. The values n_NiNi=7.3, n_NiNb=4.5, n_NbNi=6.8 and n_NbNb=5.4 were obtained for the number of nearest neighbours.     

Possibilities for the simultaneous preconcentration and flame atomic absorption spectrometric determination of Cr(III) and Cr(VI) using a C18 column and sorption loop

The sorption loop as a preconcentration unit used so far in the low-pressure flow injection (FI) system was combined with the hydraulic high-pressure nebulizer (HHPN) and a high-pressure liquid chromatographic (HPLC) column. Thus, the sorption preconcentration of Cr(VI) can be coupled to a powerful sample introduction method or preconcentration techniques of Cr(III). The subsequent determination of the Cr(VI) content of the samples was carried out by flame atomic absorption (FAAS).     

Determination of antioxidant capacities of vegetable oils by ferric-ion spectrophotometric methods

Two ferric-ion-based total antioxidant capacity methods: 1,10-phenanthroline (Phen) and ferric reducing antioxidant power (FRAP) were used for determination of antioxidant capacities (AC) of the acetonic and methanolic extracts of vegetable oils. The obtained mean Phen and FRAP values for acetonic extracts of olive oils, rapeseed, rice and four sunflower oils (39.3–336.5 and 39.5–339.6 μmol Fe/100 g) were higher than for methanolic extracts (22.8–307.3 and 23.5–300.1 μmol Fe/100 g). However, antioxidant capacities of methanolic extracts of corn oil, blended oils and two sunflower oils with garden green flowers (56.5–312.9 and 53.9–306.5 μmol Fe/100 g for Phen and FRAP methods, respectively) were higher than for acetonic extracts of these oils (54.2–249.2 and 52.9–244.7 μmol Fe/100 g for Phen and FRAP methods, respectively). There is a linear and significant correlation between these two analytical methods (r = 0.9989 and 0.9986 for acetonic and methanolic extracts). Also, total phenolic compounds (TPC) in the studied oils correlated with their antioxidant capacities determined by Phen and FRAP methods (r = 0.9012, 0.7818 and 0.8947, 0.7830 for acetonic and methanolic extracts, respectively). The comparable precision (R.S.D. = 0.8–4.6%, 0.9–4.9% and 0.7–4.0%, 0.6–4.0% for acetonic and methanolic extracts, respectively) and sensitivity ( = 1.27 × 10⁴, 1.11 × 10⁴ and 2.62 × 10⁴ dm³ mol⁻¹ cm⁻¹) for the proposed Phen and the modified FRAP methods, demonstrate the benefit of the Phen method in the routine analysis of antioxidant capacities of vegetable oils.