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Constante dieléctrica anormalmente baja de agua confinada
L Fumagalli1,2, A Esfandiar3, R Fabregas4,5
1School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK. laura.fumagalli@manchester.ac.uk geim@manchester.ac.uk.
Science (New York, N.Y.)
|June 23, 2018
Resumen
Los investigadores midieron las propiedades dieléctricas del agua interfacial. Encontraron una capa eléctricamente muerta con una constante dieléctrica de ~ 2, de dos a tres moléculas de espesor, cerca de las superficies.
Área de la Ciencia:
- Química Física
- Ciencias de la superficie
- Propiedades dieléctricas
Sus antecedentes:
- La constante dieléctrica del agua a granel es aproximadamente 80.
- Se predice que la constante dieléctrica del agua interfacial es menor que el agua a granel debido a la reducida libertad de rotación del dipolo cerca de las superficies.
- La evidencia experimental de las propiedades dieléctricas del agua interfacial es limitada.
Objetivo del estudio:
- Investigar experimentalmente la constante dieléctrica del agua interfacial confinada entre superficies atómicamente planas.
- Para cuantificar el grosor y las propiedades dieléctricas de la capa eléctricamente muerta en el agua interfacial.
Principales métodos:
- Las mediciones de capacidad local se realizaron en agua confinada entre dos paredes atómicamente planas.
- Se realizaron experimentos con distancias variables entre las paredes, hasta 1 nanómetro.
Principales resultados:
- Se observó una capa interfacial con polarización significativamente reducida.
- La constante dieléctrica fuera del plano (ε) de esta capa interfacial se midió en aproximadamente 2.
- Se encontró que esta capa eléctricamente muerta tenía de dos a tres moléculas de espesor.
Conclusiones:
- Los resultados experimentales confirman la existencia de una capa eléctricamente muerta en el agua interfacial con una constante dieléctrica mucho más baja que el agua a granel.
- Estos hallazgos proporcionan datos cruciales para los modelos teóricos de las interacciones superficiales mediadas por el agua.
- El estudio demuestra un método para investigar las propiedades dieléctricas de fluidos y sólidos confinados.
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