AFM forces between mica and polystyrene surfaces in aqueous electrolyte solutions with and without gas bubbles.
J Colloid Interface Sci
; 410: 188-94, 2013 Nov 15.
Article
em En
| MEDLINE
| ID: mdl-23998373
Force curves between a flat mica substrate and a polystyrene microsphere were measured with an atomic force microscope (AFM) in carefully degassed water and aqueous NaCl, CaCl2, and AlCl3 solutions. The pH of the water used does not change significantly with degassing treatment, and its value remains close to 6. Electrolyte concentration ranges from 10-4 to 10-2M and pH from 4.7 to 5.1. We have found that the repulsive long-range electrostatic force between mica and polystyrene is attenuated by the presence of electrolytes and counterbalanced by a long-range attractive force, which we referred to as a hydrophobic force, which is longer-ranged than the ever present attractive van der Waals force. This force, which includes the adhesive bridging of residual air bubbles and newborn vapor cavities, and any other unknown forces, is reasonably well represented by a unique exponential law. Prefactor and decaying length are not very sensitive to electrolyte type, concentration, and pH, suggesting that any new force included in the law, in addition to adhesive bridges, should obey a non-classical electrostatic mechanism. However, we also know that liquid/solid contact angle and liquid/vapor surface tension increase with electrolyte concentration and valence increasing the stability of bubbles and cavities which in turn increase the bridging force. Clearly, these effects are hidden in the empirical force law.
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Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Poliestirenos
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Cloreto de Cálcio
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Cloreto de Sódio
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Cloretos
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Compostos de Alumínio
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Gases
Idioma:
En
Revista:
J Colloid Interface Sci
Ano de publicação:
2013
Tipo de documento:
Article
País de afiliação:
Chile
País de publicação:
Estados Unidos