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Reacción de hidratos de organosilicio con superficies sólidas: un ejemplo de autoensamblaje catalizado por superficie
Roy Helmy1, Robert W Wenslow, Alexander Y Fadeev
1Department of Chemistry and Biochemistry, Seton Hall University, South Orange, New Jersey 07079, USA.
Journal of the American Chemical Society
|June 17, 2004
Resumen
El octadecilsilano forma monocapas densas y horizontalmente entrelazadas en óxidos metálicos a través de la hidrólisis catalizada. La acidez y la basicidad de la superficie dictan la reactividad, con un injerto óptimo logrado a través de condiciones controladas.
Área de la Ciencia:
- Química de las superficies.
- Ciencia de los materiales Ciencia de los materiales.
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- El octadecilsilano (C18H37SiH3) es un precursor versátil para la modificación de la superficie.
- Las monocapas autoensambladas (SAM) son cruciales para adaptar las propiedades de los materiales.
- Comprender el mecanismo de reacción de los silanos con los óxidos metálicos es clave para la funcionalización de superficies controladas.
Objetivo del estudio:
- Para investigar las reacciones de la fase de solución del octadecilsilano con varios óxidos metálicos de gran superficie.
- Para caracterizar la estructura y las propiedades de las resultantes monocapas soportadas.
- Para aclarar el papel de las propiedades de la superficie del óxido metálico en el mecanismo de reacción.
Principales métodos:
- Reacción en la fase de solución del octadecilsilano con 10 óxidos metálicos diferentes.
- Espectroscopia de infrarrojos con transformación de Fourier (FTIR) para la caracterización química.
- (29) Espectroscopia de Resonancia Magnética Nuclear (RMN) de Si para el análisis estructural.
- Cromatografía de gases para cuantificar la evolución del hidrógeno.
Principales resultados:
- Alta densidad de injerto (4,5-5 grupos/nm2) de monocapas de octadecilsilano lograda en la mayoría de los óxidos metálicos.
- Formación de SAMs enlazados horizontalmente con enlaces Si-O-Si y Si-OH.HO-Si, y enlace vertical mínimo con el óxido.
- Hidrólisis completa del octadecilsilano, produciendo aproximadamente 3 mol de H2 por mol de silano injertado.
- La velocidad de reacción es catalizada por agua adsorbida en los sitios ácido/base de Lewis y Brønsted de los óxidos metálicos.
Conclusiones:
- La hidrólisis del octadecilsilano es el paso limitador de velocidad, catalizado por la acidez / basicidad de la superficie.
- Los materiales con propiedades ácidas/básicas débiles (sílice, carbono, polímeros) no reaccionan.
- La temperatura de reacción y el dopaje superficial con ácidos/bases mejoran significativamente la reactividad.
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