Teresa Łuczak

Electrocatalytic oxidation of mono- and polyhydric alcohols on gold and platinum

A survey of representative studies on the oxidation of mono- and polyhydric alcohols on gold and platinum electrodes is given, with a special attention to the reaction mechanisms and the effect of the molecular structure of these compounds on their electrocatalytic reactivity.

A comparative study of the adsorption and electrooxidation of isomer butanediols on a gold electrode

Abstract The adsorption of three isomer butanediols on a polycrystalline gold electrode from a 0.02 M NaClO 4 electrolyte solution has been studied with tensammetry. The free enthalpy of adsorption for 2,3-butanediol is higher than the enthalpy of 1,3- and 1,4-butanediol; this is rationalized in terms of a molecular structure dependent surface-adsorbate interaction. The electrooxidation of 2,3-butanediol at the gold electrode in a solution of pH 13 is much faster than the oxidation of the two other isomers; this is explained with the stronger adsorption of this isomer and the resonance effect, especially of the vicinal OH-group, which results in an easier C-H-bond rupture and increased stability of the radical reaction intermediate.

Molecular structure effects in the adsorption of terminal and vicinal aliphatic diols on a gold electrode

Abstract The adsorption of a series of terminal and vicinal aliphatic diols at a polycrystalline gold electrode from a solution of 0.02 M NaClO 4 has been studied. Significant trends and differences in the electrosorption behavior clearly related to the molecular structure of the alcohols were found.

The adsorption of benzylamine on a polycrystalline gold electrode: A combined spectroelectrochemical study

Abstract The adsorption of benzylamine on a polycrystalline gold electrode from aqueous solutions of KClO 4 and HClO 4 has been studied using differential capacitance measurements (tensammetry) and in situ surface enhanced Raman scattering (SERS). Differences in adsorption parameters of benzylamine adsorbed from neutral solutions at θ θ > 0.7 can be explained on the basis of the reorientation of adsorbate molecules. Values of the free enthalpy of adsorption ΔG ad 0 = −40.0 kJ · mol −1 and the interaction coefficient a = −1 at θ ΔG ad 0 = −24.3 kJ · mol −1 with a = 0.55 at θ > 0.7 were obtained. SERS results indicate an edge-on adsorption of benzylamine from KClO 4 solution, with a small contribution from molecules adsorbed flat on the gold surface. For benzylamine adsorbed on gold from acidic solution an end-on orientation of molecules with an interaction via the amino group is concluded.

On adsorption of monohydric alcohols and diols at sp and sd metal electrodes

Abstract A survey of studies on adsorption behaviour of monohydric alcohols and diols at the sp and sd metal electrode/aqueous solution interface is given. Particular attention is paid to the effect of the molecular structure of the surfactants (carbon chain length, number and arrangement of functional groups as well as multiple carbon–carbon bonds) on their interfacial arrangement and interactions.

The kinetic isotope effect in the oxidation of aliphatic alcohols on a gold electrode

Abstract The electro-oxidation of a series of selectively deuterated alcohols (2-propanol, 1,2-butanediol, 1,4-butanediol and 2,3-butanediol) at a polycrystalline gold electrode in alkaline solutions was studied with cyclic voltammetry. Results were evaluated with respect to the mechanism of the electro-oxidation and the conceivable mode of adsorptive interaction between the alcohol and the surface. Differences in electrochemical reactivity are explained in terms of the molecular structure of the transition state and the participation of adsorbed OH-species.

Studies of lithium and sodium complexation by silicon podand solvents

Abstract The complex formation of lithium and sodium ions with silicon podand solvents: phenyl-tris(1,4-dioxapentyl) silane (PhSi23) and ethyl-tris(1,4-dioxapentyl) silane (EtSi23) has been studied by FTIR, 1 H-, 13 C-, 7 Li- and 23 Na NMR. The far FTIR spectra show that the Li + cations fluctuate very fast whereas Na + cations are still localised between the oxygen atoms of the oxaalkyl chains. The 7 Li NMR spectra prove that one Li + cation can be coordinated not only by one but also two silicon podand molecules. The concentration dependence of the molar conductivity of LiClO 4 in the podand solvents indicates charge transfer between ion clusters.

Ethyne oxidation and hydrogenation on porous Pt electrode in acidic solution

Abstract Electrocatalytic ethyne oxidation and reduction on Pt was studied by on-line mass spectrometry (DEMS). It was shown that the initial step in both processes involves a rapid reactant adsorption on the metal surface. The adsorbate consists of molecular ethyne, partially dehydrogenated hydrocarbon residues C 2 H x and C 2 -oxygen-containing species in a ratio dependent on the electrode potential. The maximum electrode coverage is achieved in the potential range 0.2–0.4 V, whereas the major part of the adsorbate is ethyne itself. Ethane was identified as the main volatile product of the cathodic hydrogenation of the surface species. A trace amount of 1-butene was formed in a slow side reaction. Evolution of a mixture of ethane and ethene was observed in the presence of bulk reactant. Measurements at various sweep rates revealed that electrooxidation of the preadsorbed ethyne to CO 2 at E >0.8 V is much faster than its electroreduction in the hydrogen potential region. The optimal conditions for monitoring and/or utilization of ethyne in an electrochemical cell working in a programmed step potential mode are specified.

Highly selective voltammetric sensing of paracetamol on nanogold modified electrode in the presence of interfering compounds

A gold bare template modified with gold nanoparticles deposited on top self-assembled layers (SAMs) results in a high catalytic effect for paracetamol electrooxidation both when paracetamol is alone in solution at pH 7 and in a ternary mixture containing the biogenic interfering compounds ascorbic acid and uric acid. For this novel sensor a linear relationship is found between the current response of paracetamol at the potential of peak maximum (jp) and the concentration of this compound in solution (cACAP) over the range of 0.0001 mM to 2 mM with the detection limit of 0.018 μM. Moreover, the peak to peak separations of the voltammetric responses obtained on the modified electrode confirm that the newly prepared modified gold electrode appears to be a good candidate for the selective detection and analytical determination of paracetamol, ascorbic acid and uric acid in ternary mixtures.

Electrochemical deposition of the new manganese(II) Schiff-base complex on a gold template and its application for dopamine sensing in the presence of interfering biogenic compounds.

Facile and efficient template synthesis of new manganese(II) complex [Mn2(H2L)2](ClO4)2 (1) and its crystal structure are reported. Self-assembly leads to the formation of dinuclear, phenoxo-bridged closed species via exploitation of both binding subunits of the in situ formed new Schiff-base ligand. Gold electrode modified with self-assembled monolayers (SAMs) composed of synthesized complex 1 was applied as a voltammetric sensor for quantitative determination of dopamine (DA) in the presence of ascorbic (AA) and uric acids (UA). The linear relationship between the current response of dopamine at the potential of peak maximum and the concentration was found over a wide analyte concentration range (R(2)≥0.993, 1×10(-10)-8.5×10(-4)M) with a very good sensitivity (4.11Acm(-2)M(-1) at dE/dt=0.1Vs(-1)), high detection limit (6.8×10(-9)M) and excellent reproducibility. It has been proven that current peaks of dopamine, ascorbic and uric acids were clearly separated from each other, thus enabling selective detection of these compounds coexisting in a mixture.