Espectroscopia de RMN 17O de alta resolución de la wadsleyita (beta-Mg2SiO4) obtenida por medio de la espectroscopia
Sharon E Ashbrook1, Andrew J Berry, William O Hibberson
1School of Chemistry, University of Exeter, Exeter EX4 4QD, United Kingdom.
Journal of the American Chemical Society
|September 25, 2003
Resumen
La espectroscopia de RMN de oxígeno-17 (17O) de alta resolución ahora analiza muestras de miligramos. Este avance permite un estudio detallado de la Tierra.
Área de la Ciencia:
- Espectroscopia de RMN en estado sólido.
- La geoquímica es la geoquímica.
- Física de los minerales física de los minerales.
Sus antecedentes:
- Las técnicas avanzadas de RMN mejoran la sensibilidad a los materiales sólidos.
- La síntesis de alta presión produce las fases cruciales del manto terrestre.
- La espectroscopia de RMN con oxígeno-17 (17O) requiere muestras enriquecidas para el análisis detallado.
Objetivo del estudio:
- Para demostrar la aplicación de la espectroscopia de RMN 17O de alta resolución a muestras pequeñas y sintetizadas.
- Para caracterizar la estructura de beta-Mg2SiO4, una fase clave del manto de la Tierra.
- Para determinar los parámetros químicos y cuadrupolares del oxígeno específicos del sitio en beta-Mg2SiO4.4.
Principales métodos:
- Síntesis de beta-Mg2SiO4 enriquecido con 17O utilizando un aparato de yunque múltiple a alta presión (16 GPa) y temperatura (1873 K).
- Experimentos de RMN de estado sólido 17O de alta resolución utilizando aleaciones de metales de transición superconductores (STMAS) y técnicas de hilado de ángulo mágico cuántico múltiple (MQMAS).
- Análisis de datos espectrales de RMN para resolver sitios de oxígeno cristalográficamente distintos y extraer sus parámetros.
Principales resultados:
- Adquisición exitosa de espectros de RMN 17O de alta calidad a partir de cantidades miligráficas de beta-Mg2SiO4.4 enriquecido.
- Resolución y asignación de los cuatro sitios de oxígeno distintos dentro de la estructura cristalina beta-Mg2SiO4.
- Determinación del desplazamiento químico preciso y los parámetros cuadrupolares para cada sitio de oxígeno.
Conclusiones:
- La espectroscopia de RMN 17O de alta resolución es ahora lo suficientemente sensible para el análisis detallado de pequeñas fases minerales sintetizadas a alta presión.
- El estudio proporciona la primera caracterización estructural detallada de RMN de beta-Mg2SiO4.4.
- Esta metodología abre nuevas vías para investigar la composición y la estructura de los materiales relevantes para el interior profundo de la Tierra.
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