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EN
Recently, transition metal oxides, which exhibit favorable catalytic abilities, have also been investigated as a material for the detection of hydrazine (N2H4). It has been reported that mixed metal oxides usually offer a higher electrochemical activity than binary oxides. In this work, a TiO2-Fe2O3 coupled system is presented as an enhanced material with major applications in electrochemical detectors. The electrochemical behavior of glassy carbon electrodes modified with TiO2-Fe2O3 in the absence and presence of hydrazine was evaluated via cyclic voltammetry (CV). Experimental results also suggest that the formation of the TiO2-Fe2O3 coupled system enhances electrochemical catalytic performance in N2H4 detection. The modificationTiO2+2 mol% Fe2O3 provides good analytical performance of detection (0.13 mM) and quantification limits (0.39 mM). The presented coupled system provides the premise for a suitable material for a stable and sensitive N2H4 sensor.
EN
New monomer, 4,4’-[(2,3-dihydrothieno[3,4-b][1,4]diorin-5-yl)vinyl]-1,1’-biphenyl (BPE), was synthesized, characterized and polymerized electrochemically via a potentiostatic method. The corresponding polymer poly(4,4’-[(2,3-dihydrothieno[3,4-b][1,4] diorin-5-yl)vinyl]-1,1’-biphenyl) (PBPE) obtained as a thin-layer film, was characterized by cyclic voltammetry, X-ray photoelectron spectroscopy, infrared spectroscopy and UV-Vis spectroscopy. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the obtained polymer were determined from cyclic voltammograms as –4.89 eV and –3.81 eV, respectively. Its optical and electrochemical band gaps were calculated, and found to be 1.08 eV and 1.49 eV, respectively. PBPE can be used as a donor material in bilayer organic photovoltaic solar cells having PCBM as acceptor material.
EN
Nanoparticles of Li2MnO3 were fabricated by sol-gel method using precursors of lithium acetate and manganese acetate, and citric acid as chelating agent in the stoichiometric ratio. TGA/DTA measurements of the sample in the regions of 30 °C to 176 °C, 176 °C to 422 °C and 422 °C to 462 °C were taken to identify the decomposition temperature and weight loss. The XRD analysis of the sample indicates that the synthesized material is monoclinic crystalline in nature and the calculated lattice parameters are 4.928 Å (a), 8.533 Å (b), and 9.604 Å (c). The surface morphology, particle size and elemental analysis of the samples were observed using SEM and EDAX techniques and the results confirmed the agglomeration of nanoparticles and, as expected, Li2MnO3 composition. Half cells of Li2MnO3 were assembled and tested at C/10 rate and the maximum capacity of 27 mAh/g was obtained. Charging and discharging processes that occurred at 3 V and 4 V were clearly observed from the cyclic voltammetric experiments. Stability of the electrodes was confirmed by the perfect reversibility of the anodic and cathodic peak positions observed in the cyclic voltammogram of the sample. The Li2MnO3 nanoparticles exhibit excellent properties and they are suitable for cathode materials in lithium ion batteries.
EN
An useful electrochemical sensing approach was developed for norepinephrine (NE) detection based on semiconducting polymer (9-nonyl-2,7-di(selenophen-2-yl)- 9H-carbazole) and laccase modified platinum electrode (Pt). The miniature Pt biosensor was designed and constructed via the immobilization of laccase in an electroactive layer of the electrode coated with thin polymeric film. This sensing arrangement utilized the catalytic oxidation of NE to norepinephrine quinone. The detection process was based on the oxidation of catecholamine in the presence of enzyme – laccase. With the optimized conditions, the analytical performance demonstrated selectivity in a wide linear range (0.1–200x10-6 M) with a detection limit of 240 nM and a quantification limit of 365 nM. Moreover, the method was successfully applied for selective NE determination in the presence of interfering substances.
EN
In this study, molten salt electrorefining was used to recover indium metal from In-Sn crude metal sourced from indium tin oxide (ITO) scrap. The electrolyte used was a mixture of eutectic LiF-KF salt and InF3 initiator, melted and operated at 700°C. Voltammetric analysis was performed to optimize InF3 content in the electrolyte, and cyclic voltammetry (CV) was used to de-termine the redox potentials of In metal and the electrolyte. The optimum initiator concentration was 7 wt% of InF3 , at which the diffusion coefficients were saturated. The reduction potential was controlled by applying constant current densities of 5, 10, and 15 mA/cm2 using chronopotentiometry (CP) techniques. In metal from the In-Sn crude melt was deposited on the cathode surface and was collected in an alumina crucible.
EN
Cobalt(II), nickel(II), copper(II) and oxidovanadium(IV) cations are coordination centers in many polycarboxylate complexes [1‒16]. A number of coordination compounds of transition metal ions with such ligands as polycarboxylate anions and heterocyclic organic ligands, e.g. 1,10-phenanthroline (phen) or 2,2’-bipyridine (bipy) have been examined for their biological properties [3‒16]. Their selected structures and physicochemical properties have been described in the first chapter. The polycarboxylate coordination compounds of cobalt(II), nickel(II), copper(II) and oxidovanadium(IV) have interesting antioxidant, antibacterial and antifungal activities. The antioxidant properties of polycarboxylate complexes of Co(II), Ni(II), Cu(II) and VO(IV) with 4-picoline, 1,10-phenanhroline and 2,2’-bipyridine have been investigated towards the superoxide anion radical using the nitro blue tetrazolium chloride (NBT) test and the cyclic voltammetry (CV). Their antibacterial and antifungal activities have been tested against bacteria and fungus strains that are antagonistic to the human. The determined biological properties of the oxydiacetate Co(II), Ni(II), VO(IV) complexes with bipy/phen, the thiodiacetate VO(IV) and the iminodiacetate Cu(II) complexes have been compared with these of L-ascorbic acid, which is chemical compounds commonly used as the reference antioxidant substance. Consequently, the comparison of antioxidant properties of selected cobalt( II), nickel(II), copper(II) and oxidovanadium(IV) polycarboxylate compounds is described in this work (Section 3, Tab. 1‒4). The kinetics of substitution reactions of selected copper(II) polycarboxylate complex compounds were monitored using the stopped-flow method in various reaction conditions (concentration of complex, temperature, solvent) (Rys. 5‒6) [5, 6]. The obtained results of the kinetic studies of the substitution reactions of [Cu(tda)]n with 2,2’-bipyridine in aqueous surfactants solvents: sodium dodecyl sulfate (SDSaq) and hexadecyl trimethyl- ammonium bromide (CTABaq) at 298.15 K (25 °C) are presented.
EN
Functionalization of carbon nanotubes is a very important step in their practical use in many fields. Modifications of the chemistry of carbon nanotubes lead to significant changes in the physicochemical (e.g. hydrophilic-hydrophobic properties, acid-base properties), electrochemical and catalytic behavior. Surface oxygen functional groups change the electronic structure of the carbon nanotubes, resulting in the localization of the charge density, which is important in the charge-transfer reactions. In addition, oxygen-functionalized carbon nanotubes can be used as an intermediate to create different connections with metals or their complexes and grafting functionalization by biomolecules or polymers. The unmodified carbon nanotubes (MWCNTs) were subjected to electrochemical processes (oxidation and reduction). After the introduction of oxygen to the cell atmosphere, anodization was carried out by applying a potential of +2.0 V vs. Ag/AgCl (3 M KCl) for 1000 s in 1 M electrolyte solutions of potassium chloride. After electrochemical measurements, the electrodes were reduced in the same electrolyte solution at potential of −2.0 V vs. Ag/AgCl (3 M KCl) for 1000 s. Furthermore, electrochemical behavior of the obtained carbon materials was investigated by cyclic voltammetry using a three-electrode electrochemical cell in an aqueous electrolyte, where the working electrode was a carbon nanotubes sedimentation layer. The shape of the cyclic voltammograms (CVs) of unmodified carbon nanotubes are indicative of capacitive effects, no faradic currents were recorded for the systems tested. The absence of distinctly formed peaks or waves suggests the absence of the functional groups on the surface of the unmodified carbon nanotubes. Oxidative modification of carbon nanotubes causes an increase in the surface concentration of electrochemically inactive functional groups, probably carboxyl moieties (only capacitive and pseudo-capacitive effect). Reductive modification of MWCNTs does not remove the surface oxygen functional groups, however, changes their form, which can be seen on the registered CVs. Oxidation/reduction of hydroxide/ ketone species present on the surface of the reduced MWCNT surface explain the observed, more or less completely formed, overlapping anodic/cathodic peaks. After these modifications, significant changes in the electrochemical behavior was observed. The shape of the current hysteresis recorded (magnitude, peaks or waves) strongly depends on the kind of the degree of surface oxidation/reduction. Modification increases the surface concentration of oxygen-containing groups, some of which are electrochemically active in both the capacitive and faradic sense.
PL
Poddano modyfikacji elektrochemicznej (utlenianiu/redukcji) wielościenne nanorurki węglowe. Brak elektrochemicznie aktywnych grup funkcyjnych lub/i aktywności elektrochemicznej powierzchni niemodyfikowanych wielościennych nanorurek węglowych potwierdza kształt zarejestrowanych cyklowoltamperogramów, na których nie zaobserwowano jakichkolwiek prądów faradajowskich, mogących pochodzić od procesów związanych z przeniesieniem elektronu, obserwuje się jedynie procesy pojemnościowe ładowania/ rozładowania powierzchni. Elektrochemiczne utlenianie MWCNT generuje karboksylowe grupy funkcyjne nieaktywne w procesach przeniesienia elektronu, a te z kolei generują efekty pojemnościowe i pseudopojemnościowe faradajowskie. Natomiast redukcja wcześniej utlenionych MWCNT nie usuwa grup funkcyjnych, jednakże zmienia się ich forma, gdyż powstają grupy funkcyjne aktywne elektrochemicznie, uczestniczące w procesach przeniesienia elektronu (np. karbonyle, hydroksyle).
EN
Seven novel ferrocene derivatives containing (methylamino)benzonitrile and N-methylnitroaniline groups (3a-3f and 4) have been synthesized by conventional methods and characterized by FT-IR, NMR and cyclic voltammetry. The electrochemical behavior of these compounds (3a-3f) has been studied by cyclic voltammetry measurements at a platinum electrode in acetonitrile/0.1 M TBAP. The ferrocenyl group in all compounds showed similar reversible one-electron redox process, suggesting that the ferrocene moieties are equivalent and that there are no interactions among them. The formal potential, , is shifted to the more positive potential, indicating that the (methylamino)benzonitrile and N-methylnitroaniline introduced to ferrocene moiety exercise an electron-withdrawing effect.
EN
The different voltammetry techniques were applied to understand the process of selenium deposition from sulfate solution on gold polycrystalline electrode. By applying the cycling voltammetry with different scan limits as well as the chronoamper-ometry combined with the cathodic and anodic linear stripping voltammetry, the different stages of the deposition of selenium were revealed. It was found that the process of reduction of selenous acid on gold surface exhibits a multistage character. The cyclic voltammetry results showed four cathodic peaks which are related to the surface limited phenomena and which coincide with the bulk deposition process. The fifth cathodic peak is related to the reduction of bulk deposited Se0 to Se-2 ions. Furthermore, the connection of anodic peaks with cathodic ones confirmed the surface limited process of selenium deposition, bulk deposition and reduction to Se-2. Additionally, the cathodic linear stripping voltammetry confirms the process of H2SeO3 adsorption on gold surface. The experiments confirmed that classical voltammetry technique proved to be a very powerful tool for analyzing the electrochemical processes related with interfacial phenomena and electrodeposition.
PL
Zastosowano różne techniki woltamperometryczne w celu pełnego zrozumienia procesu osadzania selenu metodą elektrochemiczną na elektrodzie złotej. Wykorzystano w tym celu cykliczną woltamperometrię, a także chronoamperometrię połączona z katodową i anodową woltamperometrią inwersyjną. Wykazano, że proces osadzania selenu jest bardzo złożony i zachodzi w kilku etapach. Wyróżniono etap podpotencjałowego osadzania selenu, następnie zachodzi redukcja zaadsorbowanych cząsteczek kwasu selenowego(IV), po którym następuje nadpotencjałowe osadzanie selenu. W zakresie wysokich nadpotencjałów dochodzi do redukcji Se0 do jonów Se-2. Powyższe eksperymenty potwierdziły wysoką przdatność technik woltamperometrycznych jako metody badawczej w celu analizy mechanizmu osadzania powłok metodą elektrochemiczną.
10
Content available Electrowinning Of Tellurium From Acidic Solutions
EN
The process of electrochemical deposition of tellurium was studied. Preliminary researches embrace the voltammetry and microgravimetric measurements. According to the results the electrolysis of tellurium was conducted under potentiostatic conditions. There was no deposition of tellurium above potential −0.1 vs. Ag/AgCl electrode in 25°C. The process of deposition is observed in the range of potentials −0.1 to −0.3 V vs. Ag/AgCl. The presence of tellurium was confirmed by XRF and XRD. The obtained deposits were homogenous and compact. Below potential −0.3 V vs. Ag/AgCl the Faradaic efficiency of the tellurium deposition decreased due to reduction of Te to H2Te and hydrogen evolution.
PL
Przeprowadzono badania obejmujące możliwość otrzymywania telluru z roztworów kwaśnych metodą elektrochemiczną. Badania wstępne obejmowały analizę mechanizmu osadzania telluru z wykorzystaniem cyklicznej woltamperometrii oraz elektrochemicznej mikrowagi kwarcowej. Na podstawie otrzymanych wyników przeprowadzono proces elektrolizy w warunkach potencjostatycznych. W temperaturze 25°C powyżej potencjału −0.1 V względem elektrody chlorosrebrowej nie zachodzi proces osadzania telluru. W zakresie potencjałów od −0.1 do −0.3 V względem elektrody chlorosrebrowej następuje jego osadzanie na katodzie. Obecność tellury była potwierdzona metodami XRD i XRF. Osady otrzymane w omawianym zakresie parametrów charakteryzowały się zwartą i jednorodną budową. Poniżej potencjału −0.3 V względem elektrody chlorosrebrowej wydajność oraz szybkość procesu osadzania telluru ulegają obniżeniu w wyniku występowania reakcji konkurencyjnych: redukcji Te do H2Te oraz wydzielania wodoru.
EN
Electrochemistry of lead telluride stationary electrode was studied in nitric acid solutions of pH 1.5-3.0. E-pH diagram for Pb-Te-H2O system was calculated. Results of cyclic voltammetry of Pb, Te and PbTe were discussed in correlation with thermodynamic predictions. Anodic dissolution of PbTe electrode at potential approx. -100÷50 mV (SCE) resulted in tellurium formation, while above 300 mV TeO2 was mainly produced. The latter could dissolve to HTeO+2 under acidic electrolyte, but it was inhibited by increased pH of the bath.
PL
Przeprowadzono elektrochemiczne badania zachowania się tellurku ołowiu w roztworach kwasu azotowego(V) o pH 1,5-3,0. Obliczono diagram równowagi E-pH dla układu Pb-Te-H2O. Przedyskutowano wyniki pomiarów woltamperometrii cyklicznej Pb, Te i PbTe w odniesieniu do przewidywań termodynamicznych. Produktem utleniania tellurku ołowiu przy potencjałach ok. -100÷50 mV (NEK) jest tellur, natomiast powyżej 300 mV tworzy się przede wszystkim 2, który ulega wtórnemu rozpuszczaniu w roztworze kwaśnym z utworzeniem HTeO+2. Proces jest hamowany przez wzrost pH elektrolitu.
EN
Electrochemistry of tellurium stationary electrode was studied in acidic nitrate solutions with pH 1.5–3.0. Cyclic voltammetry indicated that two products were formed at potentials above 300 mV (SCE): soluble HTeO2+ (500 mV) and sparingly soluble H2TeO3 (650 mV), but the former seemed to be an intermediate product for TeO2 precipitation on the electrode surface. Formation of the solid products as porous layers was almost undisturbed and no electrode passivation was observed. H2TeO3 and TeO2 dissolved to HTeO2+ under acidic electrolyte, but this process was hindered by pH increase. Cathodic polarization of tellurium electrode below –800 mV was accompanied by the evolution of H2Te, which was then oxidized at the potentials approx. –700 mV. H2Te generated in the electrochemical reaction decomposed to elemental tellurium as black powdery precipitates in the bulk of the solution and a bright film drifting on the electrolyte surface.
PL
Przeprowadzono badania elektrochemiczne telluru w kwaśnych roztworach azotanowych o pH 1.5–3.0. Pomiary metodą woltammetrii cyklicznej wykazały obecność dwóch produktów tworzących się przy potencjałach powyżej 300 mV (NEK): rozpuszczalny HTeO2+ (500 mV) i trudno rozpuszczalny H2TeO3 (650 mV), przy czym pierwszy z nich stanowi produkt pośredni tworzenia się TeO2. Formowanie się produktów stałych w postaci porowatych warstw nie prowadziłodo pasywacji elektrody. H2TeO3 i TeO2 ulegały rozpuszczaniu pod wpływem roztworu z utworzeniem HTeO2+, lecz proces ten ulegał zahamowaniu przez wzrost pH. Katodowa polaryzacja elektrody tellurowej poniżej –800 mV prowadziła do tworzenia się H2Te, który ulegał utlenianiu przy potencjałach ok. –700 mV. H2 Te generowany w reakcji elektrodowej ulegał rozpadowi do telluru elementarnego występującego w dwóch postaciach (jako czarny osad i srebrzysty film).
13
Content available remote CVD diamond layers for electrochemistry
EN
Diamond electrodes of different morphologies and qualities were manufactured by hot filament chemical deposition (HF CVD) techniques by changing the parameters of diamond growth process. The estimation of diamond quality and identification of different carbon phases was performed by Raman spectroscopy measurements. The effect of diamond quality and amorphous carbon phase content on the electrochemical response of an obtained diamond electrode in 0.5 M H2SO4 as supporting electrolyte was investigated by cyclic voltammetry with [Fe(CN)6]4−/3− as a redox probe. The kinetic parameters such as catalytic reaction rate constant k0 and electron transfer coefficient α were determined. The obtained results show that the analytical performance of undoped diamond electrodes can be implemented just by the change of diamond layers quality.
PL
W artykule przedstawiono wyniki badań czujnika elektrokatalitycznym w atmosferze zawierającej chlor. Prezentowane badania dotyczą czujnika wykonanego w technologii ceramicznej na bazie NASICONu posiadającego dwie okrągłe, platynowe elektrody. Wykonano pomiary w różnych temperaturach w celu wyznaczenia optymalnej temperatury działania czujnika.
EN
In this paper performance of an electrocatalytic sensor in presence of chlorine is investigated. Presented studies concern sensor prepared in ceramic technology based on NASICON as a solid electrolyte with two round shaped platinum electrodes. Measurements in different temperatures have been performed in order to determine optimal sensor working temperature.
EN
The mechanism of selenium electrodeposition from sulfuric acid solution on different substrates was studied with the electrochemical techniques. The cyclic voltammetry was combined with the quartz crystal microbalance technique to analyze selenium deposition process. The electrochemical reduction of selenous acid on gold, silver and copper electrodes was investigated. It was found that reduction of selenous acid is a very complex process and it strongly depends from the applied substrate. The voltammetric measurements indicate the range of potentials in which the process of reduction of selenous acids on the applied substrate is possible. Additionally, the microgravimetric data confirm the deposition of selenium and they reveal the mechanism of the deposition process.
PL
Przedstawione w niniejszej pracy wyniki badań opisują mechanizm elektrochemicznego osadzania selenu z roztworów siarczanowych na różnych podłożach. W celu dokładnej analizy zachodzących procesów elektrodowych w badaniach zastosowano technikę cyklicznej woltamperometrii połączoną z elektrochemiczną mikrowagą kwarcową. W pracy porównano procesy redukcji kwasu selenowego(IV) na elektrodach złotej, srebrnej i miedzianej. Dzięki zastosowanym technikom badawczym jednoznacznie określono zakres osadzania się selenu na wybranych podłożach oraz wskazano możliwy mechanizm przebiegających reakcji elektrodowych.
EN
Electrocatalytic gas sensors belong to the family of electrochemical solid state sensors. Their responses are acquired in the form of I-V plots as a result of application of cyclic voltammetry technique. In order to obtain information about the type of measured gas the multivariate data analysis and pattern classification techniques can be employed. However, there is a lack of information in literature about application of such techniques in case of standalone chemical sensors which are able to recognize more than one volatile compound. In this article we present the results of application of these techniques to the determination from a single electrocatalytic gas sensor of single concentrations of nitrogen dioxide, ammonia, sulfur dioxide and hydrogen sulfide. Two types of classifiers were evaluated, i.e. linear Partial Least Squares Discriminant Analysis (PLS-DA) and nonlinear Support Vector Machine (SVM). The efficiency of using PLS-DA and SVM methods are shown on both the raw voltammetric sensor responses and pre-processed responses using normalization and auto-scaling.
EN
We carried out a detailed study of the kinetics of oxidation of N'-ferrocenylmethyl-N'-phenylbenzohydrazide (FcX) to ferrocenium ion (FcX+) in aqueous and organic mediums. This study using cyclic (CV) and rotating disk electrode (RDE) voltammetry showed that the FcX/FcX+ redox couple is reversible. The N'-ferrocenylmethyl-N'-phenylbenzohydrazide and ferrocenium ion diffusion coefficients (D) were calculated from these results. In addition, the electron transfer rate constant and the exchange current density for the oxidation of ferrocene were determined. A comparison of the kinetic data obtained from the two electrochemical techniques appears to show that the data from the RDE experiments are more reliable because they are collected under strict mass transport control.
EN
This work is a contribution to the calculation of electrochemical parameters from the polarization curves of ferrocene. The parameters are: The anodic (Epa) and the cathodic (Epc) peak potentials, as well as the corresponding anodic (ipa) and cathodic (ipc) peak currents, were obtained at different scan rates (0.05, 0.10, 0.30, 0.50 V.s-1). The half-wave potentials (E1/2) of the couple in the investigated solvents have been evaluated. The diffusion coefficients (D) have been calculated using the Randles-Sevcik equation.
19
Content available remote Zastosowanie warstw diamentowych w woltamperometrii cyklicznej
PL
Zbadano możliwości zastosowania warstw diamentowych otrzymywanych z fazy gazowej do zastosowań elektrochemicznych. Warstwy diamentowe o różnych właściwościach fizycznych otrzymywano przy użyciu reaktora HF CVD (hot-filament chemical vapor deposition) sterując odpowiednio parametrami syntezy. Otrzymane warstwy charakteryzowane były m.in. za pomocą spektroskopii Ramana, skanningowej mikroskopii elektronowej (SEM) oraz dyfrakcji promieni X (XRD). W zależności od warunków syntezy warstwy różniły się morfologią, wielkością krystalitów oraz zawartością fazy węgla amorficznego. Właściwości te miały istotny wpływ na właściwości elektrochemiczne elektrod diamentowych, które badano za pomocą woltamperometrii cyklicznej (CV).
EN
Polycryst. diamond layers (1,5–10 µA thick) were deposited on a W wire by hot-filament decompn. of MeOH vapours in H₂ at 1000 K and 50 mbar and studied for morphology by SEM, Raman spectroscopy and voltammetry. The diamond layers showed a high quality.
20
Content available remote Immobilizacja kwasów aryloboronowych na powierzchni elektrod złotych
PL
W niniejszym artykule zostały przedstawione wyniki badań nad immobilizacją molekuł pochodnej kwasu aryloboronowego na powierzchni klasycznej dyskowej elektrody złotej w postaci samoorganizującej się monowarstwy (SAM). Proces osadzania monowarstw oraz ich oddziaływanie z fruktozą oceniano z wykorzystaniem technik woltamperometrii cyklicznej oraz woltamperometrii fali prostokątnej prowadzonych w roztworze jonów Fe[CN]6 3-/4-. Ponadto zbadano możliwość oznaczania fruktozy za pomocą elektrod modyfikowanych kwasem aryloboronowym.
EN
In this paper we presented results of our research on immobilization of arylboronic acid on the surface of classic gold disk electrode in the form of self-assembled monolayer (SAM). The self-assembly process and interaction of created SAM with fructose has been examined by using cyclic voltammetry and square wave voltammetry measurements conducted in solution of Fe[CN]6 3-/4- ions.
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