Monolayers and Thin Films
Zeta Potential of Stearic Acid Monolayer at the Air–Aqueous Solution Interface

https://doi.org/10.1006/jcis.2002.8340Get rights and content

Abstract

The zeta (ζ) potential of an insoluble monolayer of stearic acid at the air–water interface was measured as a function of pH in the presence of 0.0001, 0.001, and 0.01 M NH4NO3. The ζ potential was measured by means of the plane interface technique which involved the determination of the electrophoretic velocity profile of reference (polystyrene latex) particles along the solution depth in a rectangular open quartz cell. The ζ vs pH relationship at 0.001 and 0.01 M NH4NO3 was analyzed in terms of the Gouy–Chapman–Stern–Grahame model for electrical double-layer incorporating a simple site-binding model used previously for many oxide and latex colloid studies. The dissociation constant (pKa) of stearic acid monolayer and double-layer parameters such as integral capacitances of inner and outer Helmholtz layers and the complexation constant of counterion complexes were also estimated.

References (17)

  • S. Usui et al.

    J. Colloid Interface Sci.

    (2001)
  • J.A. Davis et al.

    J. Colloid Interface Sci.

    (1978)
  • R. Sprycha et al.

    J. Colloid Interface Sci.

    (1987)
  • R. Sprycha

    J. Colloid Interface Sci.

    (1989)
  • J. Glazer et al.

    Trans. Faraday Soc.

    (1953)
  • T. Ishino et al.

    Jpn. J. Appl. Phys.

    (1994)
  • R.W. Huddleston et al.
  • J.T. Davis et al.

    Interfacial Phenomena

    (1963)
There are more references available in the full text version of this article.

Cited by (20)

  • Forces between a hard surface and an air–aqueous interface with and without films

    2020, Current Opinion in Colloid and Interface Science
    Citation Excerpt :

    The repulsive forces increased in magnitude and range, when the pH of the water was increased from pH 5.8, 7.0 to 9.0. As the charge of an insoluble carboxylic acid monolayer at an air–aqueous interface increases with a pH increase [68] and as stearic acid contains a carboxylic acid headgroup, a pH increase causes the charge of the stearic acid monolayer at an air–aqueous interface to increase. This would increase the electrostatic repulsion.

  • Electrokinetic transport in liquid foams

    2017, Advances in Colloid and Interface Science
    Citation Excerpt :

    Then, finite size effects will be considered as they have been shown to be crucial in some situation. Many experiments since the 1970s [31–44] aim to measure the zeta-potential of surfactant laden interfaces by different techniques. A large amount of data has been generated from bubbles using commercial zetameters, where the electrophoretic velocity of small bubbles (800 nm to 50 μm) under AC electric field (∼20 Hz) is performed [33,36,40,42,43].

  • The use of zeta potential to investigate the pKa of saturated fatty acids

    2016, Advanced Powder Technology
    Citation Excerpt :

    This means that the ionisation of deposited mono or multilayers of stearic acid on chloroform is highly dependent on the concentration and nature of the cations present. Usui and Healy [22] measured the zeta potential of an insoluble monolayer of stearic acid at the air–water interface as a function of pH at temperatures of 20–23 °C in the presence of varying concentrations of ammonium nitrate (10−4–10−2 M). They produced curves showing that the negative zeta potential of the stearic acid monolayer steadily increased with increasing pH from pH 3 to 8, and then reduced slightly from pH 8 to 10.

  • The isoelectric point/point-of zero-charge of interfaces formed by aqueous solutions and nonpolar solids, liquids, and gases

    2007, Journal of Colloid and Interface Science
    Citation Excerpt :

    It is important to stress that all of the nonpolar interfaces in water summarized in Tables 1–3, yield electrokinetic potential data that are pH-dependent, i.e., H+ and OH− are the potential determining ions for these nonpolar–aqueous interfaces, in the same way as H+/OH− are potential determining for metal oxide–water and many other hydrophilic solid–water interfaces. Recently Usui and Healy [33,34] have quite successfully used standard site dissociation-site equilibria models with counter ion binding, to describe the electrical double layers at the insoluble alkyl alcohol and alkyl acid close packed monolayer–water interfaces, which also interestingly show very low pzc values of around pH 3 or lower. They argue that the water clusters that hydrate at the OH or COOH head group regions act as amphoteric sites to create the electrical double layer.

View all citing articles on Scopus
1

To whom correspondence should be addressed: 43-23 Hagurodai, Taihaku-ku, Sendai 982-0817, Japan.

View full text