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Electron paramagnetic resonance (EPR) investigation of TiO₂-delaminated clays

 

Investigación por resonancia paramagnética electrónica (EPR) de arcillas delaminadas con TiO₂

 

J.G. Carriazo¹*, A. Ensuncho-Muñoz² and O. Almanza³

 

¹ Departamento de Química, Universidad Nacional de Colombia, Sede Bogotá. Ciudad Universitaria, Carrera 30, N° 45-03, Bogotá, D. C. (Colombia). *Autor para la correspondencia. E-mail: jcarriazog@unal.edu.co.

² Departamento de Química, Facultad de Ciencias Básicas e Ingeniería, Universidad de Córdoba. Montería, Colombia.

³ Departamento de Física, Universidad Nacional de Colombia, Sede Bogotá. Ciudad Universitaria, Carrera 30, N° 45-03, Bogotá, D. C. (Colombia).

 

Received February 16, 2013.
Accepted March 15, 2014.

 

Abstract

In this paper a set of TiO₂ and Fe/TiO₂ delaminated clays, prepared by different synthesis procedures, was characterized by electron paramagnetic resonance (EPR) spectroscopy. EPR analyses revealed an important shift of the central g-value as consequence of Fe³⁺ insertion (substitution) in the TiO₂ structure by a sensitive and direct method of iron incorporation. A series of additional g-values, symmetrically distributed around the central absorption line, was attributed to some electron trapping sites (defects) remained in the TiO₂ framework. The spectroscopic characterizations carried out in this work contribute to understand the photo-catalytic properties previously observed for these solids.

Keywords: delaminated clay, titanium dioxide, EPR, iron-titanium modified clay, clay mineral.

 

Resumen

El presente artículo muestra la caracterización, mediante espectroscopía de resonancia paramagnética electrónica (EPR), de un conjunto de arcillas delaminadas con TiO₂ y Fe/TiO₂ obtenidas por diferentes procedimientos de síntesis. Los análisis de EPR mostraron un desplazamiento importante del valor "g" central como consecuencia de la inserción de Fe³⁺ por substitución en la estructura de TiO₂ mediante un método sensible y directo de incorporación de los iones hierro (III). Adicionalmente, se observó un conjunto de valores g simétricamente distribuidos alrededor de la línea del valor g central, las cuales se atribuyen a sitios de electrones atrapados en vacancias (defectos) de la estructura de TiO₂. La caracterización espectroscópica realizada en este trabajo contribuye a la comprensión de las propiedades fotocatalíticas previamente observadas para los sólidos sintetizados.

Palabras clave: arcilla delaminada, dióxido de titanio, EPR, arcilla modificada con hierro-titanio, mineral de arcilla.

 

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