Electrochemistry of Acetaminophen

The contribution is focused on electrochemical oxidation of acetaminophen mainly in non-aqueous media. The influence of various organic solvents as well as the pH effect is described herein. The redox properties of acetaminophen were studied by means of cyclic voltammetry, and rotating-disk voltammetry. We found that the protonation/deprotonation of acetaminophen acts as a ratedetermining step, where the stability of phenoxy radical intermediate plays an important role

New Characterisation Approaches for Carbon Ionic Liquid Electrodes (CILES)

Within this study, some new approaches to characterize the carbon paste mixtures and the respective carbon ionic liquid electrodes (CILEs) are presented and their properties discussed. Particular attention has been paid to the changes of the resistivity, relative to the dependence on composition of the CILE. Three types of carbon ionic liquid pastes were examined, and for the interpretation of experimental data, the results were compared with those of "classic" carbon paste electrode (CPE) based on graphite powder. Some problems connected with homogeneity and stability of carbon pastes are also discussed

Carbon nanotubes - material for carbon paste electrodes, possibilities of preparation and characterization

In this article, some new approaches to characterize the carbon paste mixtures and the respective carbon nanotube paste electrodes (CNTPEs) are presented, discussed. Particular attention has been paid to the changes of the ohmic resistance, relative to the dependence on composition of the CNTPE, the materials used, the time. Four types of carbon nanotube pastes were examined, and for the interpretation of experimental data. Some problems connected with homogeneity and stability of carbon pastes, their storage, or eventual aging effects are also discussed

Some New Approaches to the Characterization of the Carbon Paste Electrodes

Uhlíkové pastové elektrody mají dvě hlavní výhody: jejich povrch lze snadno reprodukovatelně obnovovat a dále, je možné je modifikovat v objemu za účelem získání specifických senzorů. Příprava těchto elektrod však závisí jednak na použitých materiálech, tedy na uhlíkovém prášku i na olejovém médiu, jednak na jejich vzájemném poměru. To umožňuje velikou variabilitu vlastností, současně ale otázka charakterizace těchto elektrod je velmi významná. Bylo zjištěno, že graf závislosti odporu elektrody na jejím složení je ve tvaru dvou protínajících se přímek. K vysvětlení této závislosti byl navržen, testován a diskutován model vycházející z představy těsně uspořádaných koulí (známé z krystalografie). Další způsob charakterizace těchto elektrod je založen na interpretaci cyklických voltamogramů nějakého dobře reverzibilního systému. Obě tyto metody jsou kompatibilní, navíc umožňují vysvětlení dalších jevů spojených s morfologií a se stárnutím těchto elektrod

Electrochemical Study of Triazaborine Chromophores

This contribution describes a basic electrochemical behaviour of a series of newly synthesized chromophores based on triazaborine core. The main attention has been paid to the investigation of the first oxidation and first reduction process of such compounds using cyclic voltammetry, rotating disk voltammetry and polarography. The oxidation is mostly a two-electron irreversible process, whereas the first reduction is in most cases revesible, involving one-electron. For better understanding of the relationship between the structure and redox properties, the Linear Free Energy relationship (LFER) approach using sigma (para) constants of Hammett type was applied, the oxidation and reduction centers were localized, the difference between E(ox) and E(red) was correlated with the HOMO-LUMO gap and the anomalous cases were elucidated

Electrochemical Study of Oxazaborine Chromophores

This contribution describes a basic electrochemical study of a series of newly synthesized chromophores based on the oxazaborine core. The attention was focused on determination of the first oxidation and the first reduction potentials, their difference and the relationship to the calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies. The oxidation is mostly a two-electron irreversible process, the first reduction is also irrevesible, but involving one-electron. For better understanding of the relationship between the structure and redox properties, the approach using sigma (para) constants of Hammett type was applied, the difference between E(ox) and E(red) was correlated with the HOMO-LUMO gap

Photophysical and Electrochemiluminescence of Coumarin-Based Oxazaborines

We describe the synthesis, electrochemistry, photophysics, computational analysis and electrochemiluminescence (ECL) of a new series of oxazaborine molecules. Our strategy is based on the modification of the coumarin-oxazaborine moiety to be directly joined through a carbon-carbon bond, forming donor-acceptor (D-A) chromophores. These new structures substantially change the electron distribution as well as photophysical and electrochemical behaviors with a strong effect on the final quantum yield. For all compounds, we observed a very high PL quantum yield (70\u201375 %) and relatively accessible first oxidation and first reduction. All of these characteristics allow us to study the ECL of these molecules, obtaining a very high ECL efficiency that is four times higher than the standard dyes, opening the application of oxazaborine as bright ECL luminophores

Micro/nano-structured titanium surfaces modified by NaOH–CaCl2-heat-water treatment: Biomimetic calcium phosphate deposition and hMSCs behavior

The unexplored effect of chemical treatment of laser micro/nanostructured titanium surfaces deserves attention due to broadening our knowledge of surface enhancement of biomimetic synthesis of hydroxyapatite and osseointegration of titanium implants. In this study, NaOH-CaCl2-heat-water treatment of titanium is revisited and used to modify porous laser micro/nanostructured oxidic and flat titanium surfaces which are characterized by XRD, electron microscopy, zeta potential and FTIR and Raman spectroscopy. These surfaces are also assessed for their ability to induce biomimetic Ca phosphate deposition from a simulated body fluid (SBF) and to grow human Mesenchymal stem cells (hMSCs). The treatment of titanium surfaces is shown to involve unreported formation of crystalline CaCO3 and the related interpretation of physicochemical changes of the treated titanium surface in soaked SBF raises doubts about the specific role of an intermediary CaTiO3 in the biomimetic formation of apatite on titanium substrates. We show that the biomimetic formation of Ca phosphate in Tas SBF solution occurs both on the surface and in the bulk solution, it is enhanced on the structured surfaces and is affected by a Ca-O(Ti) layer originating on the pristine and chemical treated flat and micro/nanostructured topographies with different delays. These findings are confronted with the pilot results of in vitro analyses showing that the cell growth, shape and osteogenic differentiation of hMSCs are impeded on the surfaces modified by the NaOH-CaCl2-heat-water treatment

Korozní chování povrchu silicidu titanu v přítomnosti peroxidu vodíku: Tvorba sub-μm kuliček na bázi TiOx, nanokompozitních fází TiOx / SiOx a mezoporézní sítě TiOx / SiOx

Dosud neprozkoumaná koroze povrchu silicidu titanu (Ti5Si3) okyseleným peroxidem vodíku je zajímavá díky svému potenciálnímu využití při zlepšování osseointegrace titanových implantátů potažených silicidy titanu. Detailní charakterizace produktů koroze pomocí FTIR, Ramanovy a XP spektroskopie, elektronové mikroskopie, XRD, BET a techniky rozptylu světla umožňují rozpoznání hydratovaných nanokompozitních fází TiOx / SiOx (x≤2) složených ze segregovaných amorfních fází SiOx a sítě na bázi TiOx obsahující vazby Ti-O-Si a -O-O. ¨ Vzhled TiOx síťoví závisí na rozsahu peroxidace. Méně postupující peroxidace poskytuje submikronové kuličky na bázi Tild, které po žíhání vyvíjejí anatasová nahozena, která odolávají do teploty 800 °C. Výraznější peroxidace produkuje větší mesoporézní tělíska na bázi TiOx, která se desintegrují po působení ultrazvuku na entity o velikosti mikrometrů. Navrhovaný mechanismus povrchové koroze vyplývá z komplementárního použití analytických technik. Jednokroková produkce bioaktivních (hydratovaných TiOx a SiOx) druhů je vhodná pro další výzkum osseointegrace mírně zkorodovaných titanových implantátů potažených Ti5Si3.silicid titanu, peroxid vodíku, mikrofáze SiOx, nanofáze TiOx a SiOx, mezoporézní a mikroporézní částice na bázi TiOxSo far unexplored corrosion of titanium silicide (Ti5Si3) surface with acidified hydrogen peroxide is of interest due to its potential use in improving osseointegration of titanium implants coated by titanium silicides. Detailed examination of corrosion products by FTIR, Raman and XP spectroscopy, electron microscopy, XRD, BET and light scattering techniques allows recognition of hydrated nanocomposite TiOx/SiOx (x≤2) phases composed of segregated amorphous SiOx species and TiOx–based networks containing Ti-O-Si and -O-O- bonds. The appearance of the TiOx networks depends on the extent of peroxidation. A less progressed peroxidation yields sub- μm-sized TiOx-based spheres which upon annealing develop anatase nanograins withstanding 800° C. A more progressed peroxidation produces larger mesoporous TiOx-based bodies which disintegrate upon sonication into micrometer-sized entities. The proposed mechanism of surface corrosion is based on the complementary use of analytical techniques. The one-step production of bioactive (hydrated TiOx and SiOx) species deserves to be explored in osseointegration studies of slightly corroded Ti5Si3-coated titanium implants