Enhancement of electrocatalytic properties of carbonized polyaniline nanoparticles upon a hydrothermal treatment in alkaline medium

The electrocatalytic activity of carbonized polyaniline nanostructures (Carb-nanoPANI) towards oxygen reduction reaction (ORR), estimated in 0.1 mol dm⁻³ KOH solution, was significantly improved upon a hydrothermal treatment in 1 mol dm⁻³ KOH solution. Namely, the onset of ORR was shifted by ∼70 mV to more positive potentials, and the number of electrons consumed per O₂ molecule was enhanced in comparison to the original material. The number of electrons involved in ORR depended on loading, and with a loading of 0.5 mg cm⁻², for the potentials lower than −0.5 V vs SCE, the number of electrons approached 4. For this material, high stability of electrochemical behavior and resistance to the poisoning by ethanol was evidenced by potentiodynamic cycling.     

Oxidation,Redox Disproportionation and Chain Termination Reactions Catalysed by the Pd‐561 Giant Cluster

Redox disproportionation of benzyl alcohol to benzaldehyde and toluene catalysed by the Pd₅₆₁phen₆₀(OAc)₁₈₀ (phen=1,10‐phenanthroline) giant cluster 1 under anaerobic conditions was found, whereas in an O₂ atmosphere cluster 1 catalyses the oxidation of benzyl alcohol to benzaldehyde and inhibits further oxidation of the latter. A study of the AIBN‐initiated and non‐initiated oxidation of benzyl alcohol, sec‐butyl alcohol and styrene in the presence of cluster 1 revealed that cluster 1 performs three functions in the oxidation reactions: 1) catalysis of polar oxidation of the substrates with O₂, 2) termination of the chains of radical oxidation, and 3) catalysis of redox disproportionation.     

Raman Spectroscopy of Nanocrystalline Ceria and Zirconia Thin Films

The results of Raman-scattering studies of nanocrystalline CeO₂ and ZrO₂:16% Y (YSZ) thin films are presented. The relationship between the lattice disorder and the form of the Raman spectra is discussed and correlated with the microstructure. It is shown that the Raman line shape results from phonon confinement and spatial correlation effects and yields information about the material nonstoichiometry level.     

Defect and Mixed Conductivity in Nanocrystalline Doped Cerium Oxide

The results obtained from a study on the microstructure and the electrical properties of Gd-doped CeO₂ thin films were reported. Dense, nanocrystalline films on sapphire substrates are prepared using a polymeric precursor spin coating technique. The electrical conductivity was studied as a function of temperature and oxygen activity and correlated with the grain size. For nanocrystalline Gd-doped CeO₂ thin films, the ionic conductivity increased with decreasing activation energy as the grain size decreased. A conductivity model was developed to analyze P _O2 behavior of the electrical conductivity. Using the conductivity model, the hopping energy of electron conduction and the enthalpy of oxygen vacancy formation were determined for different microstructures.     

Selective Synthesis of Glyceryl Tris[9,10-(threo)-dihydroxyoctadecanoate]

Elaborating novel triacylglyceride (TAG) based polyester hyperbranched unimolecular encapsulating agents represents an original and promising approach to the selective delivery of hydrophobic biologically active compounds. However, selective modification of double bonds in unsaturated TAG to obtain corresponding pure polyhydroxy derivatives with high yields is still a big challenge. Two novel approaches to synthesize the glyceryl tris[9,10-(threo)-dihydroxyoctadecanoate] were proposed and tested: (1) via the bromination and nucleophilic substitution of secondary halide functions by oxyacetyl groups followed by the hydrolysis of acetyls, and (2) direct transformation of the double bonds by the reaction with peroxoformic acid in an excess of formic acid, and the removal of formyl protective groups. Glycerol trioleate and natural olive oil were used as starting materials. The first synthetic route allowed for successful preparation of the corresponding polyhalide and polyoxyacetyl products; however, a more effective final deacetylation procedure is required. The second proposed approach showed a very good reproducibility in obtaining hydroxy-oxyformyl derivatives. The optimal conditions of the reaction involve the use of diethyl ether as a cosolvent and stirring at room temperature for 30 min. To remove the formyl groups, three original procedures using organic solvent medium at room temperature were proposed: in the presence of cesium carbonate in chloroform–methanol mixture, and two methods using hydrochloric acid in chloroform–methanol mixture or in acetone. All three methods were efficient to carry out the deformylation; nevertheless, TAG esters remained stable only with 15–17 % hydrochloric acid in acetone. Simple isolation procedures and high overall yields (95.6 and 94.9 % for both triolein and olive oil, respectively) allow considering the second approach as a promising method to obtain threo-polyhydroxy derivatives from unsaturated TAG.     

Diaminofuroxan: Synthetic Approaches and Computer‐Aided Study of Thermodynamic Stability

Different approaches to synthesize diaminofuroxan are presented herein. Mathematical and quantum chemical methods were used to study the possible reasons for failures in the syntheses of diaminofuroxan. Additionally, structural isomers of this compound were generated. With the help of the results of quantum chemical calculations at levels of DFT B3LYP 6‐31G(d) and MP2 6‐31G(d), screening of the most stable isomeric forms in the gaseous phase and in water was performed. It was shown that diaminofuroxan is not the thermodynamically most stable isomer among its structural analogues.     

Polytetrafluorethylene-based high-k composites with low dielectric loss filled with priderite (K1.46Ti7.2Fe0.8O16)

Composite materials with a high permittivity (high-k) and low dielectric loss represent an important research direction for the rapid development of modern electronic. This article is about high-k composite with low dielectric loss (dielectric constant is approximately 11, and dielectric loss is only 0.02 at 1 MHz and about 50 wt % of filler) based on a polytetrafluorethylene (PTFE) compounded with priderite (K_1.46Ti_7.2Fe_0.8O₁₆). The dielectric permittivity about ε' ≈ 10³ and the dielectric loss of tgδ ≈ 2 have been found for filler content about 50 wt % (30 vol %) and, respectively, ε' ≈ 11 and tgδ ≈ 0.02 for 1 MHz. To produce filler, amorphous potassium polytitanate was synthesized by molten salt method, modified in aqueous solution of iron sulfate, crystallized at 700 °C and further treated in the aqueous dispersion of PTFE. The obtained product was pressured, dried and investigated by X-ray diffraction and scanning electron microscopy. Dielectric properties of the composite with different ceramic filler content (1–90 wt %) were studied using impedance spectroscopy in the frequency range of 10⁻² to 10⁶ Hz. The influence of frequency on electric conductivity, permittivity, and dielectric losses was analyzed taking into account the experimental data on porosity, apparent density obtained for the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48762.     

“Arbequina” Olive Oil Composition Is Affected by the Application of Regulated Deficit Irrigation during Pit Hardening Stage

Three new regulated deficit irrigation (RDI) treatments were applied to “Arbequina” olive orchards during pit hardening. Oil quality was determined by measuring analytical parameters for olive oil grading, antioxidant activity, total phenol content, fatty acid profile, volatile compounds profile, and sensory analysis. Oils from RDI were classified as “extra virgin olive oil” and their quality was improved due to their higher antioxidant potential (ABTS⁺ [increased ~75%] and DPPH^˙ [increased ~25%] assays) and phenols (increased ~53%) than control. Concentration of total volatile compounds decreased (~27%) but RDI olive oils showed a more balanced profile (alcohols, aldehydes, and esters). Monounsaturated fatty acid content increased (~5%) and atherogenic and thrombogenic indexes decreased (~8.5%) in RDI olive oil. Regarding sensory analysis, RDI provided more balanced oils with higher fruit aroma than control. Other benefits of RDI olive oil, when compared with oil from full irrigated orchards are reduced use of water and improved functional and sensory quality.     

Surfactant-Assisted Dispersion of MWCNTs in Epoxy Resin Used in CFRP Strengthening Systems

The epoxy resin used as the bonding agent in carbon fiber-reinforced polymer (CFRP) strengthening systems was modified by the infusion of multiwalled carbon nanotubes (MWCNTs). Two types of surfactants, Triton X-100 and C₁₂E₈, were used to disperse the nanotubes in the epoxy resin employing ultrasonic mixing. Dynamic mechanical analysis and tensile tests were conducted to study the effect of the surfactant-assisted dispersion of nanotubes on the thermal and mechanical properties of epoxy composites. The morphology of the epoxy composites was interpreted using scanning electron microscopy (SEM). Moreover, the effect of surfactant treatment on the structure of nanotubes was investigated by Fourier transform infrared (FT-IR). Based on the experimental results, the tensile strength and the storage modulus of the epoxy resin were increased by 32% and 26%, respectively, by the addition of MWCNTs. This was attributed to the homogeneous dispersion of nanotubes in the epoxy resin according to the SEM images. Another reason for the enhancement in the tensile properties was the reinforced nanotube/epoxy interaction as a result of the surfactant anchoring effect which was proved by FT-IR. A moderate improvement in the glass transition temperature (T _g) was recorded for the composite fabricated using Triton X-100, which was due to the restricted molecular motions in the epoxy matrix. To characterize the temperature-dependent tensile behavior of the modified epoxy composites, tensile tests were conducted at elevated temperatures. It was revealed that the MWCNT modification using surfactant substantially improves the tensile performance of the epoxy adhesive at temperatures above the T _g of the neat epoxy.