Adsorption of Cytosine on a Mercury Electrode

2006 ◽  
Vol 71 (10) ◽  
pp. 1393-1406 ◽  
Author(s):  
Dorota Sieńko ◽  
Jolanta Nieszporek ◽  
Krzysztof Nieszporek ◽  
Dorota Gugała ◽  
Jadwiga Saba
Keyword(s):  
Charge Density ◽  
Standard Gibbs Energy ◽  
Mercury Electrode ◽  
Repulsive Interaction ◽  
Surface Excess ◽  
Adsorption Parameters ◽  
Frumkin Isotherm ◽  
Constant Charge Density ◽  
Constant Charge ◽  
Zero Frequency

The electrosorption behavior of cytosine at the mercury electrode/acetic buffer of pH 4 and 5 interfaces was determined from the double-layer differential capacity measurements extrapolated to zero frequency. Solutions of cytosine were prepared to cover the range from 1 × 10-4 to 6 × 10-3 mol dm-3. Adsorption of cytosine was described by the adsorption isotherms constants derived from the surface pressure data as a function of electrode charge density and bulk concentration. The obtained values of the relative surface excesses Γ′ were higher in the acetic buffer of pH 4 than of pH 5. Maximum of cytosine adsorption in the mentioned buffers was at -581 and -551 mV, respectively. The values of the standard Gibbs energy ∆G° obtained from the Frumkin isotherm were higher in the buffer of pH 4 than of pH 5. The values of the interaction parameter A indicated weaker repulsive interaction between adsorbed molecules of cytosine in the former buffer. The adsorption parameters obtained from the virial isotherm confirmed corresponding parameters obtained from the Frumkin isotherm. The dependences of ΦM-2 on the relative surface excess at a constant charge density were analyzed in order to calculate the electrostatic parameters of the inner layer.

Studies of a Mixed Adsorption Layer of Butan-1-ol and o-Toluidine on Mercury Electrode

2002 ◽  
Vol 67 (11) ◽  
pp. 1579-1588 ◽  
Author(s):  
Dorota Sieńko ◽  
Dorota Gugała ◽  
Jolanta Nieszporek ◽  
Joanna Jankowska ◽  
Jadwiga Saba
Keyword(s):  
Thermodynamic Analysis ◽  
Adsorption Layer ◽  
Supporting Electrolyte ◽  
Mercury Electrode ◽  
Interaction Constant ◽  
Repulsive Interaction ◽  
Surface Excess ◽  
Adsorption Parameters ◽  
Frumkin Isotherm ◽  
Adsorption Layers

The results of thermodynamic analysis of o-toluidine adsorption on a mercury electrode in the presence of various butan-1-ol amounts complete our previous studies on properties of mixed adsorption layers of toluidine isomers-butan-1-ol. The values of the relative surface excess Γ'°T obtained for o-toluidine show that adsorption of this compound decreases with increasing of butan-1-ol concentration. Analysis of adsorption parameters derived from the Frumkin isotherm indicates that in the presence of 0.33 M BuOH in 1 M NaClO4 with adjusted pH 3 as supporting electrolyte, ∆G0 values for o-toluidine are the highest and, at the same time, the strongest repulsive interaction occurs. In the presence of 0.11 M butan-1-ol, smaller values of ∆G0 for o-toluidine correspond to weaker repulsive interaction. Therefore the change of the Γ'°T value for o-toluidine as a function of butan-1-ol concentration is the result of mutual changes of ∆G0 and interaction constant A between adsorbate molecules.

scholarly journals The Kerr-Schild double copy in Lifshitz spacetime

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Gökhan Alkaç ◽  
Mehmet Kemal Gümüş ◽  
Mustafa Tek
Keyword(s):  
General Relativity ◽  
Gauge Theory ◽  
Charge Density ◽  
Localized Source ◽  
Curvature Term ◽  
Constant Charge Density ◽  
Arbitrary Dimensions ◽  
Double Copy ◽  
Theory Solution ◽  
Constant Charge

Abstract The Kerr-Schild double copy is a map between exact solutions of general relativity and Maxwell’s theory, where the nonlinear nature of general relativity is circumvented by considering solutions in the Kerr-Schild form. In this paper, we give a general formulation, where no simplifying assumption about the background metric is made, and show that the gauge theory source is affected by a curvature term that characterizes the deviation of the background spacetime from a constant curvature spacetime. We demonstrate this effect explicitly by studying gravitational solutions with non-zero cosmological constant. We show that, when the background is flat, the constant charge density filling all space in the gauge theory that has been observed in previous works is a consequence of this curvature term. As an example of a solution with a curved background, we study the Lifshitz black hole with two different matter couplings. The curvature of the background, i.e., the Lifshitz spacetime, again yields a constant charge density; however, unlike the previous examples, it is canceled by the contribution from the matter fields. For one of the matter couplings, there remains no additional non-localized source term, providing an example for a non-vacuum gravity solution corresponding to a vacuum gauge theory solution in arbitrary dimensions.

Interactions of sodium ions with polyelectrolytes of constant charge density

1984 ◽  
Vol 17 (11) ◽  
pp. 2436-2441 ◽  
Author(s):  
Paul Ander ◽  
Mahmoud Kardan
Keyword(s):  
Charge Density ◽  
Sodium Ions ◽  
Constant Charge Density ◽  
Constant Charge

Hydroxyproline adsorption on a mercury electrode in neutral solution

1991 ◽  
Vol 69 (10) ◽  
pp. 1528-1534 ◽  
Author(s):  
M. M. Gómez
Keyword(s):  
Dipole Moment ◽  
Adsorption Process ◽  
Normal Component ◽  
Mercury Electrode ◽  
Hydroxyl Group ◽  
Neutral Solution ◽  
Pyrrolidine Ring ◽  
Adsorption Parameters ◽  
Gibbs Energies ◽  
Comparison Of The Results

The adsorption of hydroxyproline (HPRO) on mercury in aqueous solutions of 10−2 M KClO4 has been determined from electrocapillary and capacity measurements. Comparison of the results obtained for HPRO with those reported for proline (PRO) shows that the presence of a hydroxyl group in the molecule has a small effect on the adsorption process. The respective values for adsorption parameters are −7 and −5 μC cm−2 for the charges of maximum adsorption, −13.0 and −10.4 kj mol−1 for the standard Gibbs energies of adsorption at zero charge, and −1.28 and +0.6 for the α parameter in the Frumkin isotherms. According to the analysis carried out for the normal component of the dipole moment of HPRO, −0.8 D, the more probable orientation of this aminoacid adsorbed on mercury is with the pyrrolidine ring parallel to the electrode surface resting the OH group away from the surface. Key words: adsorption, double layer, aminoacids, hydroxyproline.

Electrocapillary measurements at low concentrations of surfactants: Adsorption of tetrabutylammonium cation

1983 ◽  
Vol 48 (4) ◽  
pp. 964-975 ◽  
Author(s):  
Ladislav Novotný ◽  
Ivan Smoler ◽  
Jaroslav Kůta
Keyword(s):  
Surface Tension ◽  
Maximum Energy ◽  
Tetrabutylammonium Perchlorate ◽  
Adsorption Parameters ◽  
Surface Tension Data ◽  
Frumkin Isotherm ◽  
Low Concentrations ◽  
Drop Time

Using drop-time technique with long drop-times achieved by means of a spindle-type capillary with the combination of a interrupted convection the surface tension data of tetrabutylammonium perchlorate in 0.1 mol l-1 NaClO4 in the concentration range 3 . 10-3 mol l-1 down to 10-7 mol l-1 could be measured. The corresponding adsorption parameters have been evaluated both from Langmuir (for Θ ⪬ 0.8) and Frumkin isotherm. The maximum energy of adsorption amounts to -48.1 kJ . mol-1. The dependence of E vs log c (Yesin-Markov plot) carried out in the concentration range 10-7 to 10-3 mol l-1 showed a S-shaped curve.

Adsorption of tetramethylthiourea in concentrated NaClO4 solutions

2009 ◽  
Vol 74 (9) ◽  
pp. 1309-1321 ◽  
Author(s):  
Dorota Sieńko ◽  
Dorota Gugała-Fekner ◽  
Jolanta Nieszporek ◽  
Zygmunt Fekner ◽  
Jadwiga Saba
Keyword(s):  
Double Layer ◽  
Interaction Parameter ◽  
Mercury Electrode ◽  
Differential Capacity ◽  
Surface Excess

Tetramethylthiourea electrosorption behaviour on the mercury electrode in 2, 3 and 4 mol l–1 NaClO4 was determined by means of double-layer differential capacity measurements. The relative surface excess Γ′ of the adsorbate calculated from the surface pressures depended on the NaClO4 concentration. A clear influence of NaClO4 concentration appeared in the changes of interaction parameter A obtained from the Flory–Huggins isotherm and in the permittivity parameter of the inner layer.

Adsorption of Iodide Ion from Aqueous NaI-NaClO4- Butan-1-ol at the Mercury-Electrolyte Interface

1999 ◽  
Vol 64 (12) ◽  
pp. 1925-1936 ◽  
Author(s):  
Jadwiga Saba ◽  
Kazimierz Sykut ◽  
Jolanta Nieszporek ◽  
Jan Szaran
Keyword(s):  
Surface Tension ◽  
Gibbs Energy ◽  
Adsorption Equilibrium ◽  
Standard Gibbs Energy ◽  
Mercury Electrode ◽  
Differential Capacity ◽  
Capacity Zero ◽  
Charge Potential ◽  
Adsorption Layers ◽  
Zero Charge Potential

Properties of the adsorption layers I--ClO4--H2O and I--ClO4--H2O-butan-1-ol on the mercury electrode were described using adsorption and kinetic parameters for the Zn(II) ion reduction. The systems were characterized by the measurements of differential capacity, zero charge potential and surface tension at this potential. The data were analysed to obtain the surface pressure and the charge due to specific adsorption of I- ions as a function of charge and concentration of I- ions. The standard Gibbs energy of adsorption ∆G0ad and parameter B obtained from the virial isotherm were compared. The rate constants of Zn(II) ion reduction as an ion affecting the adsorption equilibrium were determined.

Thermal Effect on Electroosmotic Flow in a Slit Microchannel

2013 ◽  
Author(s):  
Yi Zhou ◽  
Chun Yang ◽  
Cunlu Zhao
Keyword(s):  
Boltzmann Equation ◽  
Charge Density ◽  
Surface Charge ◽  
Thermal Effect ◽  
Electroosmotic Flow ◽  
Stokes Equations ◽  
Ion Distribution ◽  
Temperature Dependent ◽  
Constant Potential ◽  
Constant Charge

Electroosmotic flow (EOF) in microfluidic systems is frequently subjected to thermal effect because of temperature-dependent material properties. Boltzmann equation is usually used to describe the ion distribution in EOF. This study will compare the ion distribution under the thermal effect with the Boltzmann distribution. Moreover, for thin electrical double layer (EDL), constant potential model always be used to simplify the calculation of EOF at constant charge. In this study, the thermal effects on EOF at both constant potential and constant charge are analyzed. In addition, as the surface charge density increases largely with higher temperature, in this study efforts are also made to address the thermal effect on EOF induced by the temperature-dependent charge density. In particular, a numerical model is presented for investigating the steady EOF under the thermal effect. The proposed model involves several coupled governing equations including the Nernst-Planck equations, the Poisson equation, the modified Navier-Stokes equations, and the energy equation. The simulation results show that the Boltzmann equation cannot fully describe the ionic concentration distributions under the large thermal effect when EDL overlap. Moreover, for thin EDL, the electroosmotic velocity under the thermal effect at constant potential is lower than that at constant charge, due to the negative electrothermal force at constant potential. Furthermore, it is revealed that the temperature-dependence of surface charge can significantly modify the characteristics of EOF.

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