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The electrical double layer on gold probed by electrokinetic and surface force measurements
Marcel Giesbers1, J Mieke Kleijn, Martien A Cohen Stuart
1Laboratory of Physical Chemistry and Colloid Science, Wageningen University, PO Box 8038, Wageningen, 6700 EK, The Netherlands.
Journal of Colloid and Interface Science
|November 18, 2005
Summary
This study characterizes gold surfaces in aqueous solutions using streaming potential and atomic force microscopy. Results show electric double-layer interactions dominate, with potential influenced by pH and surface oxides.
Area of Science:
- Surface science
- Electrochemistry
- Colloid science
Background:
- Gold surfaces are crucial in catalysis and electronics.
- Understanding gold's electrical double layer in solution is key for controlling surface interactions.
- Previous studies often lack direct force measurements combined with electrokinetic potentials.
Purpose of the Study:
- To characterize the electrical double layer potential of gold surfaces in aqueous solutions.
- To compare results from streaming potential and atomic force microscopy (AFM) force measurements.
- To investigate the influence of pH on the gold/electrolyte interface.
Main Methods:
- Vacuum deposition of thin gold films on glass and silica substrates.
- Streaming potential measurements to determine zeta-potential.
- Colloidal-probe AFM force measurements using gold-coated silica particles.
- Analysis using Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and nonlinear Poisson-Boltzmann equation.
Main Results:
- Streaming potential measurements yielded the zeta-potential of the gold surface.
- AFM force measurements provided the diffuse double-layer potential (ψd).
- Interactions were dominated by electric double-layer overlap; Van der Waals forces were negligible.
- The double-layer potential showed strong pH dependence, attributed to surface oxide species.
- Excellent agreement was found between streaming potential and AFM force measurements.
Conclusions:
- The electrical double layer potential of gold surfaces is accurately determined by combining streaming potential and AFM force measurements.
- Surface oxide species significantly influence the gold/electrolyte interface, particularly its pH dependence.
- This foundational understanding is vital for predicting and controlling adsorption behavior at polarized gold interfaces.
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