Shifting to the red the absorption edge in TiO₂ films: a photoacoustic study

 

F. Gordillo-Delgado^*,º,ª, K. Villa-Gómezª y E. Marín^b

 

ª Laboratorio de Optoelectrónica, Universidad del Quindío Apdo. Postal 2639 Armenia, Colombia. ºfgordillo@uniquindio.edu.co

^{*, b} Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del I.P.N, Unidad Legaria Calz. Legaria 694. Col. Irrigación México D.F, México 11500.

 

Recibido: 4 de enero de 2010;
Aceptado: 22 de febrero de 2011

 

Abstract

When Titanium dioxide in contact with a polluted water sample is irradiated with ultraviolet light, electron-hole pairs can be generated, which can react with oxygen and water producing free radicals that can degrade the pollutants, changing them into harmless compounds for the environment. The ultraviolet component of the solar radiation is around 7%. Therefore, it is convenient to modify the TiO₂ films crystalline structure for obtaining photocatalytical processes with visible light. In this work we report on the growth of TiO₂ thin films by the Sol-gel technique considering the incorporation of AgNO₃ in the initial solution containing the precursor. The concentration of the AgNO₃ saline solution was changed between 5 and 30% to control the grain size of the grown TiO₂ nanocrystals, impregnating 6 layers over glass slide substrates and using a sintering temperature of 600 °C. The obtained films were characterized structurally by means of X-ray diffraction. The shift in the forbidden energy bandwidth value to the red part of the optical absorption spectrum was evidenced by Photoacoustic Spectroscopy. The photocatalytic activity was tested on a solution of methylene blue using also the Photoacoustic technique.

Keywords: Titanium dioxide; Thin films; Sol-gel; Photocatalysis; Photoacoustic.

 

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Acknowledgements

Authors acknowledge the partial financial support of COLCIENCIAS, "Universidad del Quindío" and SIP-IPN through projects number 20090477 and 20100780. This work was also supported by SEP-CONACyT Grant 83289.

We also thank the support from COFAA-IPN through the SIBE and PIFI Programs.

 

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Note

The Editors thank to the Physics Department of the Centro de Investigación y de Estudios Avanzados del IPN for the support in the publication of this issue, and the cooperation of M en C. Alejandra García Sotelo and Eng. Erasmo Gómez.