Platinum–polytyramine composite material with improved performances for methanol oxidation

Polytyramine (PTy) is shown to be a possible alternative to other conducting polymers as a support material for fuel cell electrocatalysts such as platinum. In this work, a Pt–PTy composite was prepared via potentiodynamic deposition of polytyramine on graphite substrate, followed by the electrochemical deposition of Pt nanoparticles. The material obtained by this straightforward method exhibited, for platinum loadings as low as ca. 0.12 mg cm⁻², a specific electrochemically active surface area of the electrocatalyst of ca. 54 m² g⁻¹, together with a good electrocatalytic activity for methanol oxidation in acidic media, thus ensuring better efficiency of Pt utilization. The system Pt–PTy appears to be worthy of development for methanol fuel cell applications also because the results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to fouling during CH₃OH oxidation.     

Determination of free cyanide and zinc cyanide complex by capillary electrophoresis

A capillary electrophoretic (CE) protocol was developed for the separation and quantification of free cyanide and zinc cyanide complex, two key species in gold cyanidation of zinc-bearing sulfidic ores. Several common carrier electrolytes were implemented in an indirect UV detection method. The effect of electric field strength, injection volume, concentration of electro-osmotic flow (EOF) modifier and UV-absorbing agent in background electrolyte (BGE) was examined while peak height, peak area and noise were considered for optimization. The best results were obtained using a BGE that contained 35 mM sodium chromate, 12 mM free cyanide and 0.45 mM hexamethonium bromide at pH 10.5. Free cyanide concentration was compared to that measured with the conventional silver nitrate titration method in solutions containing free cyanides and weak cyano-complexes. The developed CE protocol proved very robust in capturing the concentration of free cyanides (4% error) unlike the titration method which exhibited substantial sensitivity to the interfering weak cyano-complexes (38% error).     

Minerals from Macedonia. XXVI. Characterization and spectra–structure correlations for grossular and uvarovite. Raman study supported by IR spectroscopy

The characterization and spectra–structure correlations of grossular and uvarovite garnets by Raman and infrared (IR) spectroscopy were carried out. Attention was focused on the explanation of the spectral differences between both minerals from structural and compositional points of view because they are isomorphous and share the general chemical formula [Ca₃Y₂(SiO₄)₃; Y = Al (grossular) and Cr (uvarovite)]. It was established that the prominent spectral differences are mainly due to the presence of various Y³⁺ cations and the possibility for their interchange. It was found that the substitution of Al³⁺ with Cr³⁺ promotes blue shifting of the high‐energy Raman bands (SiO₄ stretchings) and red shifting of the corresponding IR bands. This peculiar observation is explained by the introduction of two different effects that promote band shifting in opposite directions—the effect of different cation crystal field stabilization energies versus the effect of different cation masses and radii. Copyright © 2010 John Wiley & Sons, Ltd.     

An ergodic theorem in the qualitative behavior of (non)linear semiflows

Take σ$\sigma$ to be a continuous semiflow on the locally compact metric space Θ$\Theta$, and let _{{A(θ)}θ∈Θ}${\left\{A\left(\theta \right)\right\}}_{\theta \in \Theta }$ be a family of (possibly unbounded) densely defined closed operators on the Banach space X$X$.     

An enhanced colorimetric chemosensor for the detection of various nitro-explosives

A simple and rapid colorimetric chemosensor for the detection of several nitro-explosives is presented. The method is based on the oxidation of colorless ABTS to its intense blue–green colored radical cation ABTS⁺ by nitrogen dioxide, which can be generated from nitro-explosives by one of the following two methods: (i) digestion of very small amounts of explosives with alkali hydroxide, yielding nitrite anions, which in acidic medium generate nitrogen dioxide, or (ii) by thermal decomposition of nitro-explosives, which generates directly nitrogen dioxide. In these processes nitrogen dioxide acts as a catalytic intermediate, thus enhancing the detection.     

Azorubine: physical,thermal and bioactive properties of the widely employed food,pharmaceutical and cosmetic red azo dye material

Journal of Thermal Analysis and Calorimetry - Azorubine (E122), an azoic dye with the chemical formula C20H12N2Na2O7S2, has a wide range of applications in the food and cosmetic industries....     

The stability problem and special solutions for the 5-components Maxwell–Bloch equations

For the 5-components Maxwell–Bloch system the stability problem for the isolated equilibria is completely solved. Using the geometry of the symplectic leaves, a detailed construction of the homoclinic orbits is given. Studying the problem of invariant sets for the system, we discover a rich family of periodic solutions in explicit form.     

Synthesis and microbiological evaluation of several benzocaine derivatives

Starting from benzocaine, a well-known anaesthetic, ten derivatives were synthesized and characterized by UV–vis, IR, NMR, and elemental analysis. Most of the compounds contain residues with recognized biological activity, like nicotinic acid (vitamin B3 or PP), biotin (vitamin B7 or H), lipoic acid (thioctic acid), adamantine, as well as other residues of crown-ether type, benzofurazane, naphtylurea, di- and tri-nitrobenzene, and a nitroxide radical. The biological evaluation of the obtained compounds included hydrophobicity (lipophobicity) assay, total antioxidant and microbiological activity tests.