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1

Adenine adsorption in different pH acetate buffer

Gugała-Fekner Dorota

Physicochemical Problems of Mineral Processing

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2022

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Vol. 58, iss. 2

art. no. 144446

EN

The research results facilitate the description of adenine adsorption on the mercury electrode with reference to the pH of the supporting electrolyte which was the acetate buffer with pH of 3, 4, 5 and 6. The thermodynamic analysis indicates that the curves of the differential capacity of the studied systems with adenine do not overlap with the curves for the supporting electrolyte – the acetate buffer. This indicates the occurrence of adsorption of the studied compound on the mercury electrode within the whole range of applied concentrations in the case of every tested pH value of the acetate buffer. Adsorption energy and interaction constants were determined using the Frumkin isotherm and the viral isotherm. It was demonstrated that a adenine molecule is adsorbed on the mercury electrode in a buffer with pH 4, 5 and 6 through the negative pole, whereas in a buffer with pH 3 through the positive pole. Physical adsorption was observed in the studied systems. This is indicated by the occurrence of a typical maximum on the curve of the relation the relative surface excess amounts and the potential of the electrode; crossed curves of the following relation surface charge of the electrode from its potential (surface charge of the electrode from its potential σ = f(E)) at one point and, thus, the possibility of determining electrical parameters characterizing maximum adsorption as well as the absence of linearity of the function free energy of adsorption as a function of electrode potential ∆G0 = f(E).

2

Adsorptionof Urea on the Gold Electrode and Air/Solution Interface

Jurkiewicz-Herbich M.

Polish Journal of Chemistry

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2005

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Vol. 79 / nr 9

1513-1524

EN

The adsorption of urea on gold from aqueous 1MLiClO4 has been determined from measurements of cyclic voltammetry and electrochemical impedance spectroscopy. The film pressure and the Gibbs excess are determined as functions of urea concentrations and potential. The standard free energy of adsorption is a quadratic function of charge with maximum adsorption occurring at a charge of +6 mi C cm-2. These data are interpreted in terms of the partially oriented urea dipoles (with the CO group directed towards the metal) and the contribution of water dipoles.

3

New Methods to Study Thin Organic Films at Electrode Surfaces

Zawisza I., Cai X., Zamlynny V., Burgess I., Majewski J., Szymański G., Lipkowski J.

Polish Journal of Chemistry

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2004

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Vol. 78 / nr 9

1165-1181

EN

Chronocoulometry, scanning tunneling microscopy (STM), neutron reflectometry (NR) and in situ polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) have been employed to study the properties of a monolayer of n-octadecanol at a Au(111) electrode surface. Chronocoulometry has been used to determine the charge density at the electrode surface covered by the film of n-octadecanol. The surface pressure of this film was calculated from the charge density data. The film pressure data were used to describe the film properties at the gold solution interface. It has been found that at film pressures larger than 12 mNm-1 the monolayer is in a compressed state and at lower film pressures in a decompressed state. STM imaging, NR and PM-IRRAS have been employed to determine the nature of the two states.We have demonstrated that the properties of a monolayer of n-octadecanol at the metal-solution interface display many similarities to the properties of an equivalent film at the air-solution interface.

4

Surface-Enhanced Raman Spectroscopy and Electrochemical studies of 4-Phenylpyridine Adsorption at the Silver/Solution Interface

Bukowska J., Calvo M., Jurkiewicz-Herbich M., Jackowska K.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 8

1151-1162

EN

The adsorption of 4-phenylpyridine (4-PhPy) on silver was examined using conventional electrochemical techniques: cyclic voltammetry, impedance measurements and surface enhanced Raman spectroscopy (SERS) in a wide range of electrode potentials. Electrochemical results indicate a weaker adsorption of 4-PhPy molecules on Ag than on Au electrode, but considerably stronger than adsorption of pyridine. For saturated solutions the Raman results point out the reorientation of the 4-PhPy molecules from more flat configuration at potentials more positive than -0.7 V vs SCE, to more perpendicular one at more negative potentials. This reorientation may be connected with the formation of stable surface complexes at potentials more positive than -0.7 V and of molecular stacks at more negative electrode potentials.

5

Adsorption of L-histidine from aqueous solutions on the mercury electrode and air/solution interface

Słojkowska R., Jurkiewicz-Herbich M.

Polish Journal of Chemistry

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1999

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vol. 73 nr 3

527-539

EN

The differential capacitance characteristics of (Hg/0.1 mol dm-3KF and Hg/0.1 mol dm-3 LiClO4 interfaces were studied in the presence of L-histidine (His). The strongest adsorption of His on yhe mercury electrode was observed in solutions at pHł8. Probably, it results from the strong interactions between mercury and His molecules possessing in these solutions one or two deprotonated nitrogen atoms in the imidazole ring. Quantitative analysis of the data was possible for the alkaline solutions only. The anomalies observed in the course of C-E curves in the neutral or acidic solutions are discussed. Adsorption of His on a free surface is very weak. Practically it results from the salting-out effect, because, in the case of the solutions without the electrolyte, the His molecules do not adsorb at this interface.

6

Adsorption of tyrosine on Ag(110) and Ag(111) surfaces

Miłkowska M., Jurkiewicz-Herbich M.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 6

1096-1105

EN

The adsorption of tyrosine at Ag(110) and Ag(111) single crystal electrodes has been studied in aqueous solutions of 0.1 M LiClO4. The standard Gibbs energies of adsorption Delta G(0)-ads, at the potential of maximum adsorption and the interaction parameters, A, using Frumkin's isotherm were calculated. The orientation of the adsorbed tyrosine molecules is different on Ag(111) and Ag(110) electrodes. At Ag(111) the molecules adsorb flat with the benzene ring parallel to the electrode, whereas at Ag(110) electrode the orientation is propably vertical with OH group tawards the metal. The origin of that differences is propably the different atomic structure of both electrodes.