Zbigniew Stojek - Academia.edu (original) (raw)

Uploads

Papers by Zbigniew Stojek

Research paper thumbnail of Unusual example of induced codeposition of tungsten. Galvanic formation of Cu–W alloy

Electrochemistry Communications, 2015

The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick lay... more The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick layers of a new, advanced Cu-W alloy with W content of above 10 at.% (26 wt.%) have been obtained by electrodeposition. The alloy was deposited on silver substrate from citrate plating baths under conditions of constant current and high tungstate-copper ion concentration ratio. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the alloys. The obtained results provide evidence for the first successful codeposition of significant amount of tungsten with a metal other than the one belonging to the triad iron group.

Research paper thumbnail of The adsorption of the HgEDTA complex at mercury electrodes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1985

Research paper thumbnail of The Electrical Double Layer and Its Structure

Electroanalytical Methods, 2009

Research paper thumbnail of The finite element method for solutions of electroanalytical problems

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1984

Research paper thumbnail of The Electrical Double Layer and Its Structure

Electroanalytical Methods, 2005

Research paper thumbnail of Self-Enhancement of Voltammetric Waves of Weak Acids in the Absence of Supporting Electrolyte

Research paper thumbnail of Electrodeposition of Silver On Ultra Thin Polypyrrole Films. Approach to Unusual Nucleation of Metal

Research paper thumbnail of An Improved Bath Composition for Electroplating of the Amorphous Cobalt-Tungsten Alloys

Polish Journal of Chemistry, 1994

Research paper thumbnail of Theory of cyclic voltammetry at the mercury film electrodeReversible case with substrate present initially in aqueous solution

J Electroanal Chem, 1984

The theory of cyclic voltammetry has been extended to include the case of a reversible process pr... more The theory of cyclic voltammetry has been extended to include the case of a reversible process proceeding at the mercury film electrode The results of the solution of the diffusion equations were presented in the form of a simple equation coupled with a set of current function values. Such a presentation allows the entire cychc curve to be drawn, when the difference between the switching potential and the peak potential is constant Additionally, simple theoretical relationships were given for the ratio t~/t~, for the differences E~ -Ep and E~/2 -E~, and for the width of the anodlc peak at half height. Experimental results obtained for the Pb(II)-Pb(Hg) couple at the silver-based and glassy carbon-based mercury film electrodes agreed excellently with the theory On the other hand the results obtained at the platinum-based mercury film electrode deviated markedly from the theoretical predict-Ions

Research paper thumbnail of Voltammetric Investigation of Host�Guest Systems in the Absence of a Supporting Electrolyte

J Incl Phenom Macrocycl Chem, 1999

In the classic voltammetric approach to host-guest systems the investigations are carried out in ... more In the classic voltammetric approach to host-guest systems the investigations are carried out in excess of a supporting electrolyte, i.e., an inactive ionic salt. This approach ensures high electric conductivity of solution and ion migration is avoided. However, the presence of supporting electrolyte may introduce competitive equilibria and change activity coefficients, influencing the equilibrium constants using ultramicroelectrodes. Host-guest systems can be studied without addition of supporting electrolyte. Under such conditions, the interpretation of experimental results requires a theoretical description that accounts for migrational transport. Such a description is presented in this paper which also shows that migrational effects are so small that they can be neglected for some systems.

Research paper thumbnail of Anodic stripping voltammetry at a micro-disc mercury film electrodeTheory of the reversible case

J Electroanal Chem, 1985

For p = (ar2/Do) 1/2 < 0.12 and H = al2/DR < 0.14, simple theoretical equations are proposed to c... more For p = (ar2/Do) 1/2 < 0.12 and H = al2/DR < 0.14, simple theoretical equations are proposed to characterize the reversible anodic stripping voltammetric peaks of amalgams obtained with a micro-disc mercury film electrode. The calculated, normalized peaks were higher, thinner and shifted towards more negative potentials compared with the peaks described for the regular size mercury film electrodes. The ADI method was used in calculations.

Research paper thumbnail of Voltammetric investigation of the complexation equilibria in the presence of a low level of supporting electrolyte Part 1: Steady-state current-potential curves for inert complexes

Analytica Chimica Acta, Jan 10, 1997

The use of microelectrodes for voltammetric investigations of the complexation equilibria at very... more The use of microelectrodes for voltammetric investigations of the complexation equilibria at very low concentrations of supporting electrolyte allows the risk of competitive complexation or contamination to be avoided, makes the activities of the species involved closer to their concentrations (which facilitates comparisons with the spectroscopic results) and finally. allows the concentrations of the species to be varied over a broader range. This paper presents the calculations of the steadystate currents for a wide range of complexes that are inert on the experimental time scale, and reports the influence of the concentration of the electroinactive ionic species on the limiting currents. Also, for a number of cases the variation of halfwave potential with the ligand concentration, resulting from changes in the ohmic drop, is given. It is assumed that only one species (the complex or the uncomplexed form) is electroactive; if this is the complex, it may or may not change the number of ligands. The theoretical results were obtained either employing the Myland-Oldham theory extended in this paper or by digital simulation. The results of calculations show that the magnitude of the changes in the steady-state limiting current on complexation depends on the type of complexation equilibrium, the type of the change in the reactant charge number in the electrode process, and the complex formation constant. In a number of situations migrational effects are negligibly small and no special treatment is necessary, despite the lack of supporting electrolyte. In other cases, where migration is significant, the relations between the measured steady-state limiting current and the complex formation constant :? are given in the form of fitted equations that can be used to obtain p from appropriate experimental data.

Research paper thumbnail of Steady-state voltammetry of strong and weak acids with and without supporting electrolyte

Anal Chem, 1992

Voltammetric reduction of perchloric, phosphork, acetk, and ascorbic acid was investigated under ... more Voltammetric reduction of perchloric, phosphork, acetk, and ascorbic acid was investigated under steady-state comlitknr at platinum-and goiddlrk microelectrodes. The ckp.nd.nco of the wave height of proton in perchloric acid on the concentratlon of supporting electrolyte (lithium perchlorate) was compared with the theory for current8 1lmIt.d by migration and dMurlon. The wave height depend8 linearly on hydrog.n ion concentration wlthout and with wpportlng electrolyte up to 0.04 and 0.08 M, respectively. A b , a w t k and ascorbk acids exhibit linear caiibratlon plots with current proportional to concentration of undissociated acid up to 0.1 M. Thk k as would be predlcted for reduction of proton wbwquonl to fad dkrociation of the acid. The fairly wdl-ddhd lknnlng current for dihydrogen phosphate indlcates that weak adds with pK, In excess of 7 are accomible to voltammotrlc investigation.

Research paper thumbnail of Preparation and Characterization of Microcomposite Based On Environmentally Sensitive Microgel and Conducting Polymer

Research paper thumbnail of Assembling Paramagnetic Ceruloplasmin at Electrode Surfaces Covered with Ferromagnetic Nanoparticles. Scanning Electrochemical Microscopy in Presence of Magnetic Field

Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2015

Adsorption of ceruloplasmin (Cp) at a gold electrode modified with ferromagnetic iron nanoparticl... more Adsorption of ceruloplasmin (Cp) at a gold electrode modified with ferromagnetic iron nanoparticles encapsulated in carbon (Fe@C Nps) leads to a successful immobilization of the enzyme in its electroactive form. The proper placement of Cp at the electrode surface on top of the nanocapsules containing an iron core enabled a pre-orientation of the enzyme hence allowing direct electron transfer (DET) between the electrode and the enzyme. Laser ablation coupled with an inductively coupled plasma mass spectrometry (LA-ICP-MS) indicated that Cp was predominantly located at the paramagnetic nanoparticles. Scanning electrochemical microscopy measurements in the sample-generation/tip-collection mode proved that Cp was ferrooxidative inactive if immobilized on the bare gold surface and reached the highest activity if adsorbed on Fe@C Nps in the presence of a magnetic field.

Research paper thumbnail of Migration and Diffusion Coupled with a Fast Preceding Reaction. Voltammetry at a Microelectrode

Analytical Chemistry, 1999

A mathematical model implemented by simulation is presented for voltammetry of a reversible coupl... more A mathematical model implemented by simulation is presented for voltammetry of a reversible couple that involves a fast preceding chemical reaction and mixed diffusional and migrational transport. The hydrogen couple, H(+)/H(2), fulfills the above criteria. For strong acids there is no preceding reaction, whereas for weak acids the preceding reaction is HA = H(+) + A(-). The computed voltammograms are compared with experimental voltammograms for the reduction of strong and weak acids at Pt microelectrodes with excess of and without supporting electrolyte. The key assumption in the calculations is that the flux of hydrogen ion is independent of the anion. This assumption is supported by the experimental fact that the wave heights in the absence of supporting electrolyte of several strong acids of equal concentration and with anions of various size are identical.

Research paper thumbnail of A comparison of simulated and experimental abrasive stripping voltammetric curves of ionic crystals: Reversible case

Journal of Electroanalytical Chemistry, 1993

Research paper thumbnail of Switch of Guanine and Adenine Current Caused By Temperature Change in DNA/NIPA and PAM-Based Hydrogels

Research paper thumbnail of Unusual example of induced codeposition of tungsten. Galvanic formation of Cu–W alloy

Electrochemistry Communications, 2015

The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick lay... more The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick layers of a new, advanced Cu-W alloy with W content of above 10 at.% (26 wt.%) have been obtained by electrodeposition. The alloy was deposited on silver substrate from citrate plating baths under conditions of constant current and high tungstate-copper ion concentration ratio. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the alloys. The obtained results provide evidence for the first successful codeposition of significant amount of tungsten with a metal other than the one belonging to the triad iron group.

Research paper thumbnail of Medico-Parliamentary

Research paper thumbnail of Unusual example of induced codeposition of tungsten. Galvanic formation of Cu–W alloy

Electrochemistry Communications, 2015

The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick lay... more The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick layers of a new, advanced Cu-W alloy with W content of above 10 at.% (26 wt.%) have been obtained by electrodeposition. The alloy was deposited on silver substrate from citrate plating baths under conditions of constant current and high tungstate-copper ion concentration ratio. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the alloys. The obtained results provide evidence for the first successful codeposition of significant amount of tungsten with a metal other than the one belonging to the triad iron group.

Research paper thumbnail of The adsorption of the HgEDTA complex at mercury electrodes

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1985

Research paper thumbnail of The Electrical Double Layer and Its Structure

Electroanalytical Methods, 2009

Research paper thumbnail of The finite element method for solutions of electroanalytical problems

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1984

Research paper thumbnail of The Electrical Double Layer and Its Structure

Electroanalytical Methods, 2005

Research paper thumbnail of Self-Enhancement of Voltammetric Waves of Weak Acids in the Absence of Supporting Electrolyte

Research paper thumbnail of Electrodeposition of Silver On Ultra Thin Polypyrrole Films. Approach to Unusual Nucleation of Metal

Research paper thumbnail of An Improved Bath Composition for Electroplating of the Amorphous Cobalt-Tungsten Alloys

Polish Journal of Chemistry, 1994

Research paper thumbnail of Theory of cyclic voltammetry at the mercury film electrodeReversible case with substrate present initially in aqueous solution

J Electroanal Chem, 1984

The theory of cyclic voltammetry has been extended to include the case of a reversible process pr... more The theory of cyclic voltammetry has been extended to include the case of a reversible process proceeding at the mercury film electrode The results of the solution of the diffusion equations were presented in the form of a simple equation coupled with a set of current function values. Such a presentation allows the entire cychc curve to be drawn, when the difference between the switching potential and the peak potential is constant Additionally, simple theoretical relationships were given for the ratio t~/t~, for the differences E~ -Ep and E~/2 -E~, and for the width of the anodlc peak at half height. Experimental results obtained for the Pb(II)-Pb(Hg) couple at the silver-based and glassy carbon-based mercury film electrodes agreed excellently with the theory On the other hand the results obtained at the platinum-based mercury film electrode deviated markedly from the theoretical predict-Ions

Research paper thumbnail of Voltammetric Investigation of Host�Guest Systems in the Absence of a Supporting Electrolyte

J Incl Phenom Macrocycl Chem, 1999

In the classic voltammetric approach to host-guest systems the investigations are carried out in ... more In the classic voltammetric approach to host-guest systems the investigations are carried out in excess of a supporting electrolyte, i.e., an inactive ionic salt. This approach ensures high electric conductivity of solution and ion migration is avoided. However, the presence of supporting electrolyte may introduce competitive equilibria and change activity coefficients, influencing the equilibrium constants using ultramicroelectrodes. Host-guest systems can be studied without addition of supporting electrolyte. Under such conditions, the interpretation of experimental results requires a theoretical description that accounts for migrational transport. Such a description is presented in this paper which also shows that migrational effects are so small that they can be neglected for some systems.

Research paper thumbnail of Anodic stripping voltammetry at a micro-disc mercury film electrodeTheory of the reversible case

J Electroanal Chem, 1985

For p = (ar2/Do) 1/2 < 0.12 and H = al2/DR < 0.14, simple theoretical equations are proposed to c... more For p = (ar2/Do) 1/2 < 0.12 and H = al2/DR < 0.14, simple theoretical equations are proposed to characterize the reversible anodic stripping voltammetric peaks of amalgams obtained with a micro-disc mercury film electrode. The calculated, normalized peaks were higher, thinner and shifted towards more negative potentials compared with the peaks described for the regular size mercury film electrodes. The ADI method was used in calculations.

Research paper thumbnail of Voltammetric investigation of the complexation equilibria in the presence of a low level of supporting electrolyte Part 1: Steady-state current-potential curves for inert complexes

Analytica Chimica Acta, Jan 10, 1997

The use of microelectrodes for voltammetric investigations of the complexation equilibria at very... more The use of microelectrodes for voltammetric investigations of the complexation equilibria at very low concentrations of supporting electrolyte allows the risk of competitive complexation or contamination to be avoided, makes the activities of the species involved closer to their concentrations (which facilitates comparisons with the spectroscopic results) and finally. allows the concentrations of the species to be varied over a broader range. This paper presents the calculations of the steadystate currents for a wide range of complexes that are inert on the experimental time scale, and reports the influence of the concentration of the electroinactive ionic species on the limiting currents. Also, for a number of cases the variation of halfwave potential with the ligand concentration, resulting from changes in the ohmic drop, is given. It is assumed that only one species (the complex or the uncomplexed form) is electroactive; if this is the complex, it may or may not change the number of ligands. The theoretical results were obtained either employing the Myland-Oldham theory extended in this paper or by digital simulation. The results of calculations show that the magnitude of the changes in the steady-state limiting current on complexation depends on the type of complexation equilibrium, the type of the change in the reactant charge number in the electrode process, and the complex formation constant. In a number of situations migrational effects are negligibly small and no special treatment is necessary, despite the lack of supporting electrolyte. In other cases, where migration is significant, the relations between the measured steady-state limiting current and the complex formation constant :? are given in the form of fitted equations that can be used to obtain p from appropriate experimental data.

Research paper thumbnail of Steady-state voltammetry of strong and weak acids with and without supporting electrolyte

Anal Chem, 1992

Voltammetric reduction of perchloric, phosphork, acetk, and ascorbic acid was investigated under ... more Voltammetric reduction of perchloric, phosphork, acetk, and ascorbic acid was investigated under steady-state comlitknr at platinum-and goiddlrk microelectrodes. The ckp.nd.nco of the wave height of proton in perchloric acid on the concentratlon of supporting electrolyte (lithium perchlorate) was compared with the theory for current8 1lmIt.d by migration and dMurlon. The wave height depend8 linearly on hydrog.n ion concentration wlthout and with wpportlng electrolyte up to 0.04 and 0.08 M, respectively. A b , a w t k and ascorbk acids exhibit linear caiibratlon plots with current proportional to concentration of undissociated acid up to 0.1 M. Thk k as would be predlcted for reduction of proton wbwquonl to fad dkrociation of the acid. The fairly wdl-ddhd lknnlng current for dihydrogen phosphate indlcates that weak adds with pK, In excess of 7 are accomible to voltammotrlc investigation.

Research paper thumbnail of Preparation and Characterization of Microcomposite Based On Environmentally Sensitive Microgel and Conducting Polymer

Research paper thumbnail of Assembling Paramagnetic Ceruloplasmin at Electrode Surfaces Covered with Ferromagnetic Nanoparticles. Scanning Electrochemical Microscopy in Presence of Magnetic Field

Langmuir : the ACS journal of surfaces and colloids, Jan 3, 2015

Adsorption of ceruloplasmin (Cp) at a gold electrode modified with ferromagnetic iron nanoparticl... more Adsorption of ceruloplasmin (Cp) at a gold electrode modified with ferromagnetic iron nanoparticles encapsulated in carbon (Fe@C Nps) leads to a successful immobilization of the enzyme in its electroactive form. The proper placement of Cp at the electrode surface on top of the nanocapsules containing an iron core enabled a pre-orientation of the enzyme hence allowing direct electron transfer (DET) between the electrode and the enzyme. Laser ablation coupled with an inductively coupled plasma mass spectrometry (LA-ICP-MS) indicated that Cp was predominantly located at the paramagnetic nanoparticles. Scanning electrochemical microscopy measurements in the sample-generation/tip-collection mode proved that Cp was ferrooxidative inactive if immobilized on the bare gold surface and reached the highest activity if adsorbed on Fe@C Nps in the presence of a magnetic field.

Research paper thumbnail of Migration and Diffusion Coupled with a Fast Preceding Reaction. Voltammetry at a Microelectrode

Analytical Chemistry, 1999

A mathematical model implemented by simulation is presented for voltammetry of a reversible coupl... more A mathematical model implemented by simulation is presented for voltammetry of a reversible couple that involves a fast preceding chemical reaction and mixed diffusional and migrational transport. The hydrogen couple, H(+)/H(2), fulfills the above criteria. For strong acids there is no preceding reaction, whereas for weak acids the preceding reaction is HA = H(+) + A(-). The computed voltammograms are compared with experimental voltammograms for the reduction of strong and weak acids at Pt microelectrodes with excess of and without supporting electrolyte. The key assumption in the calculations is that the flux of hydrogen ion is independent of the anion. This assumption is supported by the experimental fact that the wave heights in the absence of supporting electrolyte of several strong acids of equal concentration and with anions of various size are identical.

Research paper thumbnail of A comparison of simulated and experimental abrasive stripping voltammetric curves of ionic crystals: Reversible case

Journal of Electroanalytical Chemistry, 1993

Research paper thumbnail of Switch of Guanine and Adenine Current Caused By Temperature Change in DNA/NIPA and PAM-Based Hydrogels

Research paper thumbnail of Unusual example of induced codeposition of tungsten. Galvanic formation of Cu–W alloy

Electrochemistry Communications, 2015

The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick lay... more The codeposition of tungsten with copper was studied. Thin, compact and hard micrometer-thick layers of a new, advanced Cu-W alloy with W content of above 10 at.% (26 wt.%) have been obtained by electrodeposition. The alloy was deposited on silver substrate from citrate plating baths under conditions of constant current and high tungstate-copper ion concentration ratio. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to characterize the alloys. The obtained results provide evidence for the first successful codeposition of significant amount of tungsten with a metal other than the one belonging to the triad iron group.

Research paper thumbnail of Medico-Parliamentary