Interpreting diffusion coefficients of electrochemical probes in oil‐in‐water microemulsions

Abstract

The relationship between apparent diffusion coefficients, D', of electroactive probe and thc microstructure of an oil-in-water anionic microemulsion, sodium dodecyl sulfate (SDS)/dodecane/I-pentanol/0.1 M NaCI,, has been investigated. Three probes, ferroceiie (Fc), Fe(CN)i-and methyl viologen (MV2+) allowed the effect of ditrerent microstructure and interactions on the d-values to be investigated. The results indicate that the droplet as well as hicontinuous microemulsion structures can be identified and point to the effects of crossphase exchange, partitioning, and multiple binding on the D'-values.

The effect of structure of oil phase, surfactant and co-surfactant on the physicochemical and electrochemical properties of bicontinuous microemulsion

“…Different experimental approaches are being employed to study the individual microemulsion phases and phase transitions [7]. These include the conductivity measurements [8][9][10][11][12][13][14][15], viscosity measurements [8,9,14], the fluorescence probe studies [15][16][17], the cyclic voltammetry [1,10,16,[18][19][20], NMR self-diffusion studies [11], and the cryo TEM studies [11]. Conductivity for example tends to decrease with decrease in the water content that is from O/W through bicontinuous to W/O phase.…”

Study of the Electrochemical Behavior of Biodiesel Microemulsion

“…As can be clearly observed, there was a decrease in the Do of the MEs compared to that of the probe in the homogeneous aqueous solution medium. This decrease may either be attributed to the increase in the diffusional path of the probe in the presence of oil droplets in the aqueous phase or to an increase in viscosity . Furthermore, molecules confined in restricted spaces give rise to low diffusion coefficients .…”

“…Microemulsions (MEs) are defined as optically transparent and thermodynamically stable mixtures which are generally composed of water, hydrophobic organic liquid, a third component known to be responsible for stabilizing the mixture, reducing the interfacial tension between the two liquids, while significantly increasing the solubility and the contact surface between them, enabling their dispersion . The aforementioned third component may be a surfactant and/or a liquid miscible in both the aqueous phase and the organic liquid acting as a cosurfactant, cosolvent or consolute.…”

“…Some studies of electrochemical properties involving hydrocarbon microemulsions (oils) have been described in the literature , , . One of the first electrochemical characterization studies of ME that deserves mentioning was made by Chokshi et al.…”

Determination of the Electrostatic Potential of Oil-in-Water Emulsion Droplets by Combined Use of Two Membrane Potential-Sensitive Dyes

“…By referring to previous papers, [23][24][25][26] O/W emulsions were prepared as follows: 2 mL of DCE containing 5 mM TPrATClPB (or TEATClPB) and a certain concentration(s) of one or two PSDs and 50 mL of W containing 10 mM SDS and different concentrations of TPrACl (or TEACl) were added to a 100-mL glass bottle; the mixture was then homogenized by sonication at 21 kHz for 60 s using an ultrasonic homogenizer (VIOLAMO, SONICSTAR85; the output was set at 70% of the maximum level). The droplets of the O/W emulsions prepared were observed with a digital microscope (KEYENCE, VH-5500); the size of most droplets was about 2 μm, though much larger droplets were occasionally observed, as exemplified in Fig.…”