XPS, XRD and SEM characterization of a thin ceria layer deposited onto graphite electrode for application in lithium-ion batteries

Thin ceria layer deposited by electro-precipitation onto graphite was synthesised and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electro-precipitated ceria has a cubic structure with nanocrystallites of about 6 nm. The SEM analyses shows that the ceria layer reflects the morphology of the graphite electrode, exhibits small cracks usually found on the electro-precipitated films but covers almost completely the surface of the graphite. The ceria layer is composed of 75% Ce(IV) and 25% Ce(III) oxides as indicated by the XPS analyses. Cyclic voltammetry and galvanostatic charge-discharge tests in ethylene carbonate/dimethyl carbonate (1/1) (wt/wt) in the presence of 1 M LiPF₆ show that reversible lithium insertion and deinsertion occurs in the graphite/ceria electrode and that the ceria layer on the graphite electrode prevents from the loss of capacity during the first four cycles. The reduction of the electrolyte occurs at about 0.7 V vs Li/Li⁺ on both electrodes but XPS and SEM analyses show that the SEI layer is thin and not as homogenous on the graphite as on the graphite/ceria electrode. The composition of the SEI layer on the graphite/ceria electrode, mainly composed of Li₂CO₃, ROCO₂Li, R-CH₂OLi and LiF, is different than those obtained on the graphite.     

Hydrophilic Quaternary Ammonium Ionenes—Is There an Influence of Backbone Flexibility and Topology on Antibacterial Properties?

The antimicrobial properties of polycations are strongly affected by the structural features such as the backbone flexibility and topology (isomerism) through the polymer ability to attain proper conformation in interaction with the cell membrane. In this paper, a synthesis and biocidal properties evaluation of ionenes characterized by different backbone topology (isomerism) and flexibility are presented. The findings reveal influence of variation in topology on activity against different microorganisms, and general positive effect of improved flexibility. Furthermore, one of the obtained ionenes displays degradable properties in near physiological environment (phosphate‐buffered saline pH 7.4, 37 °C). The degradation proceeds via Hofmann elimination reaction and the products are not of acidic character. For the first time a new class of degradable ionenes with a high antimicrobial potential is presented.     

Facile Synthetic Route to Selectively Protected Spermidine Homologues

Several selectively protected spermidine homologues were synthesized via cyanoethylation reaction of monoprotected diamines, subsequent protection of their secondary amino group, hydrolysis of nitrile to primary amide function, and final Hofmann degradation of amides to amines with the aid of iodosobenzene diacetate (PIDA). The protected spermidine homologues may be directly used in the synthesis of polyamine amides or may be further functionalized.     

Application of Alkali Metal Hydroxides for the Preparation of gem‐Chlorophenylcyclopropanes

gem‐Chlorophenylcyclopropanes 3 are conveniently prepared by reaction of benzal chloride (1) with alkenes 2, carried out either in the presence of solid potassium hydroxide and 18‐crown‐6 as a catalyst or cesium hydroxide monohydrate, without solvent.     

Simultaneous Densitometric Determination of Rifampicin and Isoniazid by High-Performance Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - High-performance thin-layer chromatography (HPTLC) on silica gel 60 F254 TLC plates, with ethyl acetate-methanol-acetone-acetic...     

Oxidative stability of lubricants measured by PDSC CEC L-85-T-99 test procedure

Summary The CEC L-85-T-99 pressure differential calorimetry (PDSC) test was developed in Europe for ACEA E5 specification for heavy duty diesel oils. This test differentiate between base oils, additives, indicates synergies between antioxidants and correlates with other oxidation tests. Occasionally, the PDSC test can have difficulties to provide a true value for the OIT, which can vary between samplings. This work gives evidence of such case and concludes that variability in results is caused by variability in the oil rather than in the test itself. It appeared possible that certain oils might not be fully homogenous and this could produce a problem for representative PDSC sampling.     

Mixing time of a non-Newtonian liquid in an unbaffled agitated vessel with an eccentric propeller

Experimental study of mixing time of non-Newtonian shear-thinning fluids within the transitional regime (3 × 10² < Re < 3 × 10³) of liquid flow is presented. The purpose of this study was to analyze the effect of eccentricity and pumping mode of the impeller as well as of position of the tracer dosage point into the agitated liquid on mixing time. The measurements were conducted in an unbaffled agitated vessel with inner diameter D = 0.7 m equipped with an up-or down-pumping propeller located centrically (e/R = 0) or eccentrically (e/R ≠ 0) in the vessel. Experiments were carried out by means of computer-aided unsteady-state thermal method for three positions of the tracer dosage point. The experimental data show that eccentric position of the propeller in an unbaffled vessel causes a decrease of the mixing time compared to that obtained in a vessel with a centrically located propeller. Mixing time depends also on the pumping mode of the propeller as well as on the position of the tracer dosage point. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

ZnFe2O4 as a new catalyst in theC-methylation of phenol

This paper reports the investigation ofC-alkylation of phenol with methanol over zinc ferrite as a catalyst. The reactions were carried out in gas phase at atmospheric pressure in dependence of increasing temperature. The total selectivity towardsortho-cresol and 2,6-xylenol over 300°C surpassed 90%. ZnFe₂O₄ was obtained by oxidative precipitation method from solution of iron (II) sulphate and zinc sulphate at 60°C. Based on the results, the best equation describing the oxidation reaction rate was found. The obtained products have been investigated using X-ray fluorescence spectrometry and X-ray diffraction analysis.     

Application and properties of butyl acrylate/pentaerythrite triacrylate copolymers and cellulose-based Granocel as carriers for trypsin immobilization

The main point was the search for a proper carrier and the kind of carrier activation for trypsin (EC 3.4.21.4) immobilization. The acrylic and cellulose-based carriers were specially prepared in that they possessed the most often used anchor groups: -OH, -NH(2), DEAE and/or -COOH. The immobilization procedures were selected to apply mainly to protein amine groups and appropriate anchor groups on the carrier. As activity tests low (N-benzoyl-dl-arginine-p-nitroanilide, BAPNA) and high (casein) molecular weight substrates were used. It was found, as a rule, that trypsin bound to -COOH groups with the help of carbodiimide was less active and that the amount of bound protein and measured activity (BAPNA) are considerably higher when protein is immobilized via divinyl sulfone. Both rules were observed irrespective of the nature of the polymer matrix. Both types of carriers were found suitable for trypsin immobilization and they were far better than the corresponding Eupergit C-bound enzyme preparations. Taking into account storage stability and activity for both substrates, the divinylsulfone linkage formed between unmodified Granocel and trypsin was the most effective method for the enzyme immobilization. For this preparation, BAPNA and casein conversion, thermal stability at 60 degrees C and estimated kinetic parameters were compared with those obtained for the native enzyme. It was shown that mass transport limitations could be effectively eliminated by suitable conditions and immobilized trypsin was considerably more stable. The values k(cat)/K(m) indicated that the immobilized enzyme was even better as amidase activity was regarded and its potential for protein hydrolysis was only less than twice.