Evidence of surface charge at the air/water interface from thin-film studies on polyelectrolyte-coated substrates.
The stability of thin water films on silicon substrates coated with cationic and anionic polyelectrolytes was investigated by the thin film pressure balance technique. Depending on the surface charge of the substrate, the water films are either stable (on negatively charged wafers) or rupture rapidly (on positively charged wafers). It is supposed that this behavior is due to a negative surface charge of the free water surface. The underlying assumption that the films' stability is due to electrostatic interactions is supported by measurements of the disjoining pressure on silicon wafers with a native oxide layer, which indicates a decrease of the film thickness, and thus decreasing repulsive interaction between the two film interfaces, with increasing ionic strength.
Ciunel
Katarzyna
K
Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technical University Berlin, Strasse des 17. Juni 112, D-10623 Berlin, Germany.
Armélin
Marc
M
Findenegg
Gerhard H
GH
von Klitzing
Regine
R