Renáta Oriňáková

The influence of iron powder microstructure on its electrolytical coating with nickel

Reactivity of the metallic powder material is an important property in the process of its electrolytical coating. The effect of iron powder activation was investigated prior to its electrolytic nickel-plating. The main attention was focused on the verification of the existence of correlation between the microstructure of differently pre-treated powder samples, reflected in X-ray diffraction characteristics full width at half maximum and efficiency of its electrochemical coating by nickel. In this article are presented the following methods of activation: without pre-treatment, mechanical activation and thermal one, and their combination. The highest efficiency of powder particles coating was obtained for mechanically activated iron powder. The thermal activation lowers the electroplating efficiency and minimum nickel-coating was found in experiments with nonactivated powder and for samples activated mechanically and thermally.

4-Aminothiophenol Strong SERS Signal Enhancement at Electrodeposited Silver Surface

Strong surface enhancement Raman spectroscopy signal of 4-aminothiophenol on silver substrate prepared by controlled electrodeposition is documented in this article. Enhancement factor was found to be affected not only by nanoparticle size, shape, orientation and spatial distribution, but also by interaction of Ag nanoparticles with thiol group of testing analyte. Self-assembled monolayers formation was contributed to this unique signal enhancement. The enhancement factor was established of 1.81×1014.

New approaches to coupling TLC with TOF-SIMS

A new hyphenated technique that enables coupling of thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry (TOF-SIMS) has been used for identification of gibberellic acid, as model analyte. TOF-SIMS has outstanding capabilities for molecular surface analysis, trace metal determination on surfaces, and surface imaging. When TLC and TOF-SIMS are coupled on-line, the chromatographic thin layer must be modified to avoid TOF-SIMS background signal activity from the chromatographic material or solvents used. Two different types of TLC plate were used for coupling with TOF-SIMS. The first was an aluminum backed plate modified to form a universal porous TLC–TOF-SIMS coupling interface. The second was a commercially available plate with a monolithic silica layer. Low TOF-SIMS background signal intensity, surface homogeneity, and integral analyte transfer characterize this novel TLC–TOF-SIMS interface. TOF-SIMS images of the TLC surfaces with separated gibberellic acid were used for identification purposes. SIMS enables analyte detection with high mass resolution at a level of concentration not achieved by other methods. The system described can easily be coupled with dynamic microcolumn high-performance liquid chromatography (μHPLC).

Effect of PPy/PEG conducting polymer film on electrochemical performance of LiFePO4 cathode material for Li-ion batteries

Rechargeable lithium-ion batteries (LIBs) have been the most commonly used batteries in the portable electronics market for many years. Polypyrrole (PPy) was now investigated as a conducting addition agent to enhance the cathode and anode materials performance in LIBs. Actual development in the synthesis and modification of the most promising cathode materials, LiFePO4, is described in this mini-review. The main aim of this mini-review is to highlight the effect of PPy based conducting polymer films on the electrochemical efficiency of LiFePO4 based cathode materials for LIBs summarizing our own research. Influence of the polyethylene glycol (PEG) additive in the PPy coating layer was evaluated. The improved electrochemical performance can be attributed to the enhanced electronic conductivity, higher solubility of ions originating from the electrolyte, higher movability of dissolved Li+ ions, and improved structural flexibility resulting from the incorporation of the PPy or PPy/PEG conducting polymer layer. The stabilizing effect of PEG in PPy was reflected in lowered cross-linking and reduced structural defects and, in consequence, in higher specific capacity of PPy/PEG-LiFePO4 cathodes compared to that of PPy-LiFePO4 cathodes and bare LiFePO4 cathodes.

Nanomaterial-based electrochemical sensors for detection of glucose and insulin

Electrochemical sensors for the detection of specific biomolecules have attracted a lot of interest over the recent years due to their high sensitivity, selectivity, simple preparation and quick response. This article summarizes the recent progress related to the application of nanomaterials in electrochemical detection of glucose and insulin. We give an overview of electrode concepts based on nanomaterials for electrochemical non-enzymatic glucose detection and non-immune insulin detection and review the electrochemical performances and limitations of these sensors. The mechanisms of the electrocatalytic oxidation of glucose on different nanomaterial-based metallic electrodes are compared. Attention is also focused on schemes of insulin detection on selected nanoparticle-modified carbon electrodes. Finally, the review outlines perspectives of future developments in electrochemical detection of both biomolecules.

New interfaces for coupling TLC with TOF SIMS

Two interfaces have been tested for coupling thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry (TOF SIMS). The first interface was formed by vacuum deposition of silver on to the chromatographic layer and on to a track formed by scraping the layer from the glass plate. The unmodified aluminum backing of a TLC plate (again formed by scraping adsorbent from the plate) was used as the second interface. TOF SIMS analysis of separated spot extracts on silver targets was performed for comparison of results. From TOF SIMS spectra it was found that although unmodified aluminum-backed plates result in a low background intensity the interface is not highly suitable because the analyte mass does not move suitably on to the interface. Transfer to the interface is irregular—the analyte spot becomes spread and does not occupy the same chromatographic position (RF) on the interface as on the chromatographic layer. The positions of analytes tested on the silver-coated interface were regular, and three specific single ion intensities from the mass spectrum were obtained.

Thin-layer chromatography of mixed-ligand zinc complexes coupled with atomic absorption spectrometric analysis of zinc

Off-line coupling of two analytical methods: thin-layer chromatography (TLC) and atomic absorption spectrometry (AAS) was investigated for preliminary stability studies of zinc carboxylato complexes bound to nicotinic acid and their chromatographic separation on a Silufol layer. Zinc content, determined by an AAS method in fractions scrapped off the layers after zinc carboxylato complex (ZC) chromatographic analyses responds to ZC dissociation during chromatographic process. It was found that solute chromatographic stability is influenced substantially by the concentration of organic modifier in the eluent. To reveal relations between zinc distribution, corresponding solute retention and complex stability was the main aim of the presented paper.

A study of cytocompatibility and degradation of iron-based biodegradable materials.

Biodegradable metallic implants are of significant importance in the replacement of bones or the repair of bone defects. Iron-phosphate-coated carbonyl iron powder (Fe/P) was prepared by the phosphating method. Moreover, Fe/P–Mn alloy was produced by sintering the Fe/P powder mixed with manganese powder. Bare carbonyl iron samples and the Fe/P and Fe/P–Mn sintered samples were evaluated for their microstructure, cytotoxicity, and hemocompatibility. The microstructure of the sintered samples was examined using an optical microscope and scanning electron microscopic analysis. Corrosion behavior was evaluated by potentiodynamic polarization in Hank’s solution. The in vitro biocompatibilities were investigated by cytotoxicity and hemolysis tests. The results obtained demonstrate that the addition of Mn resulted in higher surface inhomogeneity, porosity and roughness as well as in increased cytotoxicity. The phosphate coating has a moderately negative effect on the cytotoxicity. The corrosion rates determined from Tafel diagrams were ordered in the following sequence: Fe/P–Mn, Fe, Fe/P from high to low. The hemocompatibility of experimental samples was ordered in the following sequence: Fe/P, Fe/P–Mn, Fe from high to low. All samples were found to be hemocompatible.

Static Corrosion Test of Porous Iron Material with Polymer Coating

Abstract At present biodegradable implants received increased attention due to their use in various fields of medicine. This work is dedicated to testing of biodegradable materials which could be used as bone implants. The samples were prepared from the carbonyl iron powder by replication method and surface polymer film was produced through sol-gel process. Corrosion testing was carried out under static conditions during 12 weeks in Hank’s solution. The quantity of corrosion products increased with prolonging time of static test as it can be concluded from the results of EDX analysis. The degradation of open cell materials with polyethylene glycol coating layer was faster compared to uncoated Fe sample. Also the mass losses were higher for samples with PEG coating. The polymer coating brought about the desired increase in degradation rate of porous iron material.

Preparation and Compaction Behaviour of Poly(methyl methacrylate) Coated Iron Microparticles

The p oly(methyl methacrylate) (PMMA) coatings onto surface of iron particles were electrochemically prepared and the efiect on both surface structure and internal structure of the resulted material after compaction was carried out. The electrochemical polymerization treatment was performed in a ∞uidized bed electrolyzer using sulphuric acid solution containing potassium persulphate and methyl methacrylate (MMA). The surface topography and the microstructure of the samples were observed by scanning electron microscopy (SEM) and optical microscopy (OM). It was found that the PMMA layer coated onto iron particles results in improvement of their compressibility compared with uncoated powders, and classical lubricants are not necessary for compacting particles coated.