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La orientación y la carga del agua en la interfaz entre la gota de aceite hidrofóbico y el agua
Robert Vácha1, Steven W Rick, Pavel Jungwirth
1Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Journal of the American Chemical Society
|May 17, 2011
Resumen
Los investigadores revelaron la carga superficial negativa en las interfaces aceite/agua utilizando el potencial zeta, la dispersión de frecuencia de suma (SFS, por sus siglas en inglés) y simulaciones. La orientación de las moléculas de agua y los desequilibrios de enlaces de hidrógeno explican este fenómeno de carga interfacial.
Área de la Ciencia:
- Química Física es la química física.
- Ciencias de la superficie Ciencias de la superficie.
- Los fenómenos interfaciales son fenómenos de las interfaces.
Sus antecedentes:
- Comprender la carga eléctrica y la estructura molecular en las interfaces aceite/agua es crucial para numerosos procesos químicos y físicos.
- Estudios anteriores han sugerido varios mecanismos para la carga interfacial, pero una explicación definitiva sigue siendo difícil de alcanzar.
Objetivo del estudio:
- Para aclarar el origen de la carga superficial en la interfaz aceite/agua.
- Para determinar la estructura y la orientación de las moléculas de agua en esta interfaz.
- Investigar el papel del enlace de hidrógeno y la transferencia de carga en los fenómenos interfaciales.
Principales métodos:
- Técnicas experimentales combinadas: mediciones de potencial zeta y dispersión de frecuencia de suma (SFS).
- Enfoque computacional: simulaciones de dinámica molecular (DM), incluidas aquellas con transferencia de carga intermolecular.
- Se ha investigado el comportamiento interfacial dependiente del pH.
Principales resultados:
- Los experimentos de dispersión por frecuencia de suma (SFS, por sus siglas en inglés) revelaron la orientación de las moléculas de agua en la interfaz gota de aceite/agua.
- La orientación media del agua en una interfaz limpia de gotas de aceite refleja la de una interfaz cargada negativamente.
- Las simulaciones de dinámica molecular (DM) indicaron que un equilibrio roto de la donación y aceptación de enlaces de hidrógeno en la capa interfacial conduce a la carga superficial.
- No se observó adsorción selectiva de iones de hidróxido en experimentos dependientes del pH.
Conclusiones:
- El estudio estableció con éxito la carga y la estructura de la interfaz aceite/agua.
- La carga interfacial se atribuye a la interrupción de la dinámica de enlace de hidrógeno dentro de la capa de agua interfacial.
- Los hallazgos proporcionan una explicación a nivel molecular para la carga superficial negativa experimentalmente observada en las interfaces aceite/agua.
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