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Iones en nanogotas acuosas seleccionadas por tamaño: energías de unión secuenciales de moléculas de agua y efectos
William A Donald1, Ryan D Leib, Maria Demireva
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|October 18, 2011
Resumen
Investigando el agua del agua.
Área de la Ciencia:
- Química Física es la química física.
- La espectroscopia es una técnica de espectroscopia.
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- Comprender la hidratación iónica es crucial para varios procesos químicos y biológicos.
- Las propiedades fotofísicas de los iones están significativamente influenciadas por las moléculas de disolvente que los rodean.
- Estudios previos han explorado las interacciones ion-agua, pero la medición directa de las energías de unión en nanopartículas controladas es un desafío.
Objetivo del estudio:
- Para investigar los efectos del agua en la fluorescencia iónica.
- Para medir las energías promedio secuenciales de unión de moléculas de agua a iones hidratados en nanotopas.
- Para determinar si las propiedades fotofísicas de las nanogotas imitan las de la solución a granel.
Principales métodos:
- Se empleó nanocalorimetría iónica para medir las energías de unión.
- Se crearon nanogotas que contienen iones específicos (colorantes de rodamina, Ce(3+), TrpH(+), [KYK + 2H](2+)) y moléculas de agua.
- Se utilizó la excitación a 248 nm para inducir la fluorescencia, y se registraron las longitudes de onda de emisión.
Principales resultados:
- Los tintes de rodamina y Ce ((3+) en nanotopas exhibieron una fluorescencia similar a las soluciones a granel.
- El rendimiento cuántico de fluorescencia se acercó a ~1 para iones en nanotopas con ≥ 8 moléculas de agua.
- Se determinaron las energías de unión secuenciales promedio de las moléculas de agua para los iones hidratados, acercándose a los valores asintóticos para TrpH ((+) y [KYK + 2H] ((2+).
Conclusiones:
- Las propiedades fotofísicas de los iones en las nanogotas se acercan a las de los iones totalmente hidratados en tamaños de racimo relativamente pequeños.
- La nanocalorimetría iónica proporciona un método sensible para estudiar las interacciones entre iones y agua y las energías de unión.
- Los hallazgos sugieren una estructura líquida del agua en estos entornos controlados de nanogotas.
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