Wetting Equilibria of Hydrocarbon Droplets at an Electrified Interface

Abstract

Wetting equilibria of organic liquids at an electrified interfacesthe dropping mercury electrode/aqueous electrolytesare studied. The approach is based on measuring wetting as a function of electrical potential in aqueous dispersions by recording the double layer charge displacement current due to the attachment and spreading of organic droplets. The effects of chain length of n-alkanes, double bonds, and specific adsorption of inorganic anions on wetting have been measured. The potential range of wetting became wider with increasing chain length of n-alkanes; i.e., the critical interfacial tensions of wetting decreased in the sequence from decane to octadecane. The values of critical interfacial tension of wetting, obtained from electrocapillary curves, are in good agreement with the values calculated in the system mercury/ water/n-alkane using the Young-Dupre ´and Good-Girifalco-Fowkes relationships. The presence of a single double bond caused a decrease in critical interfacial tension of wetting by 3.5-4 mJ/m 2 , and the effect of conjugated double bonds in squalene seems to be additive. Critical interfacial tensions of wetting are equal at the positively and the negatively charged interface for n-alkanes and for unsaturated and branched squalene as well, showing the importance of dispersion forces in hydrocarbon interaction with the mercury and water interface. However, in the presence of specifically adsorbed bromide and iodide ions at the positively charged electrode, the critical interfacial tensions of wetting increase due to the additional interfacial energy required for displacement of the adsorbed anions. The obtained results on potential controlled wetting equilibria between the mercury electrode and hydrocarbon droplets offer a rationale for electrochemical studies of dispersed systems and adhesion-based electrochemical sensors for particle analysis.

The Electrochemistry of Liposomes

“…Following earlier observations of chronoamperometric spikes arising from the adhesion of cells and organic droplets on a dropping mercury electrode (DME), [156][157][158][159][160][161][162][163] and of similar signals upon adhesion of several other entities on the mercury surface, 164-168 a more detailed analysis of the nature of the interaction of liposomes in suspension and mercury electrodes was achieved by detecting chronoamperometric adhesion signals using multilamellar liposome suspensions and a static mercury drop electrode (SMDE). 169 These authors found that adhesion-spreading events lead to spike-shaped capacitive signals due to the changes of the double layer capacity and surface charge density at the area where the lipid island is formed.…”

Structural Features of the Algal Cell Determine Adhesion Behavior at a Charged Interface

“…To put this in a broader context, it is known that the general adhesion behavior of algal cells at the charged interface shows an analogy with the proposed adhesion mechanism of droplets of organic liquids in terms of attachment, deformation, spreading over the interface, taking into account that particle surface properties determine the dynamics of adhesion and the rate of spreading over the interface. Experimentally determined values of critical interfacial tensions (ɤ 12 ) c + , (ɤ 12 ) c − for adhesion of different hydrocarbon droplets were equal at the positively and negatively charged interfaces, which showed the importance of London dispersion forces in hydrocarbon interactions with the mercury and water interface and the agreement with the modified Young‐Dupré equation for the three‐phase systems [17, 18, 44]. On the other side, the Young‐Dupré equation shows limitations for adhesion of algal cells at the mercury interface due to the system complexity (cell surface charge, cell mechanics, physiological activity, age of the cell in culture, concomitant biochemical processes within the cell, etc).…”

In Situ Amperometric Characterization of Liposome Suspensions with Concomitant Oxygen Reduction

“…Based on amperometrically measured critical potentials of adhesion and electrocapillary data, critical interfacial tensions of adhesion at the positively (g 12 could be attributed to electrostatic interaction between liposome and mercury interface. In contrast, critical interfacial tensions of adhesion are equal at the positively and negatively charged electrode for non-polar liquids, pointing to the importance of dispersion forces in hydrocarbon interaction with mercury and water interface [6,33]. Minimum signal frequency was shifted negatively by 82 mV from the E pzc , i.e., to the potential of À 584 mV.…”