Electrosorption properties of dimethylalkyl and diethylalkyl phosphine oxides below and above the critical micelle concentration

Müller, E.; Emons, Hendrik; Dörfler, H.‐D.

doi:10.1016/0021-9797(81)90107-7

Cited by 25 publications

(6 citation statements)

References 26 publications

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“…The variation of the C vs E curves with time is even more pronounced at extreme polarizations where the shape, height, and position of the capacitance peaks are seen to be critically dependent on time. This suggests once again that if the characteristics of these peaks are to be correlated to the oleate bulk cmc according to the empirical criteria developed by Volldhart, Dörfler, and Müller − or interpreted according to the theory of phase transitions involving surface aggregates developed by Nikitas 24 and Nikitas et al, then only the long-time curves can safely be considered as near-equilibrium ones. This makes the use of a dropping mercury electrode (DME) whose mercury drop lifetime rarely exceeds 10 s and is usually never longer than 5 s, completely inadequate for the study of slowly proceeding adsorption/phase transition phenomena.…”

Section: Resultsmentioning

confidence: 99%

Study of Oleate Adsorption at the Mercury/Electrolyte Solution Interface as a Function of Electrode Potential and Time

Sotiropoulos¹,

Avranas²,

Papadopoulos³

1997

Langmuir

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The adsorption of sodium oleate from electrolyte solutions on a polarized mercury electrode can be studied by monitoring the differential capacitance of the electrode double layer. Its variation with potential and time can provide qualitative information on the state of the oleate adsorbate. A new experimental methodology, three-dimensional phase-sensitive ac voltammetry, is used to provide safer information on the equilibrium transition characteristics and also to follow the time evolution of the phenomenon. The steady-state differential capacitance vs electrode potential curve is interpreted by means of recently developed thermodynamic criteria for phase transitions of surfactants at charged interfaces. At concentrations below the bulk critical micelle concentration monolayer adsorption takes place at moderate and negative polarizations, whereas there is some evidence of multilayer adsorption at more positive potentials. At higher concentrations, multilayer adsorption occurs throughout the potential range studied. In both cases, the formation of a close-packed structure is likely to be restricted to the first layer and the phase transitions of the latter to be realized via aggregates formed by its interaction with the outer layers. In addition, a close-packed polylayer is also observed at extreme positive potentials for high bulk oleate concentrations. Analysis of the capacitance transients based on simple diffusion, adsorption, or Avrami formalisms cannot describe successfully the time dependence of oleate adsorption on mercury, indicating that the latter is under mixed control or/and a complex process.

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Section: Resultsmentioning

confidence: 99%

Study of Oleate Adsorption at the Mercury/Electrolyte Solution Interface as a Function of Electrode Potential and Time

Sotiropoulos¹,

Avranas²,

Papadopoulos³

1997

Langmuir

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“…Furthermore, they are hydrated in aqueous solution, revealing "ideal surface behavior". [1][2][3] Thus, they have been used repeatedly for studying various problems of interfacial science such as thermodynamic, 2,4-9 kinetic, [10][11][12][13][14][15][16][17][18] surface-rheological, [19][20][21] electrochemical, [22][23][24] analytical, 25 catalytic 26 and ecological 27 ones.…”

Section: Introductionmentioning

confidence: 99%

“…n -Alkyldimethylphosphine oxides are amphiphiles that represent a lot of advantages with respect to modeling adsorption properties because they are nonionic and chemically very stable compounds. Furthermore, they are hydrated in aqueous solution, revealing “ideal surface behavior”. − Thus, they have been used repeatedly for studying various problems of interfacial science such as thermodynamic, ,− kinetic, − surface-rheological, − electrochemical, − analytical, catalytic and ecological ones.…”

Section: Introductionmentioning

confidence: 99%

Novel Results on the Adsorption Properties of n-Alkyldimethylphosphine Oxides at the Air/Water Interface

1999

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The adsorption parameters of alkyldimethylphosphine oxides (from n-hexyl- to n-tetradecyl) at the air/water interface were calculated from equilibrium surface tension (σe) versus concentration (c) isotherms at 295 K. To guarantee absence of measurable surface-active impurities in the adsorption layers, stock solutions of the surfactants were purified until the state of surface-chemical purity was achieved. The evaluation of the σe vs c isotherms was performed by applying a two-state approach to the surface equation of state. All of them are described in the best way by ideal surface behavior. The critical micelle concentrations (cmc) and the calculated adsorption parameters, i.e., standard free energy of adsorption and limiting surface area demand per molecule adsorbed (A min), reveal distinct effects of alternation (even/odd phenomena). The A min values decrease with rising n-alkyl chain length. The results are discussed with respect to donor−acceptor interactions and surface conformational changes in the adsorption layer. As these surfactants' adsorption reveals ideal surface behavior, the data may serve as a reliable basis for modeling adsorption.

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“…We have described details of this method elsewhere [9][10][11]. We have described details of this method elsewhere [9][10][11].…”

Section: Methodsmentioning

confidence: 99%

Two-dimensional condensation in camphor-10-sulphonic acid films at the mercury/electrolyte interface

Dörfler

Dietrich

Müller

et al. 1990

Colloid & Polymer Sci

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The electrosorption properties of camphor-10-sulphonic acid (CS) in different electrolytes (Na2SO4, LiC104, KNO3, KCI, KBr, KJ) were investigated experimentally by ac polarographic measurements at different temperatures. Depending on the type of electrolyte and on the temperature, film condensation was observed. The Frumkin interaction coefficient, determined from the critical degree of coverage, does not depend linearly on the reciprocal temperature as would be the case in correspondence to the temperature dependence of the pit width. This contradiction does not occur if the interaction coefficient is determined from the critical degree of coverage using the lattice gas model. The temperature dependence of the pit width of the differential capacity-potential curves, found in the experiment, can be theoretically described by both these models. The interaction coefficient in the models is inversely proportional to the temperature. Furthermore, the parameters of the standard free energy of adsorption, the interaction energy, the interaction coefficient of the Frumkin isotherm, the adsorption coefficient, and the maximal surface concentration of CS in the film were estimated and compared.

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Electrosorption properties of dimethylalkyl and diethylalkyl phosphine oxides below and above the critical micelle concentration

Cited by 25 publications

References 26 publications

Study of Oleate Adsorption at the Mercury/Electrolyte Solution Interface as a Function of Electrode Potential and Time

Study of Oleate Adsorption at the Mercury/Electrolyte Solution Interface as a Function of Electrode Potential and Time

Novel Results on the Adsorption Properties of n-Alkyldimethylphosphine Oxides at the Air/Water Interface

Two-dimensional condensation in camphor-10-sulphonic acid films at the mercury/electrolyte interface

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