Plasma Induced Modifications in TiO 2 Films
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Plasma Induced Modifications in TiO2 Films D. A. Gutiérrez1, F. J. Avila1, P. Reyes2*, H. Martínez3, R. Romero1, R. Natividad1 1
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Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM Carretera TolucaAtlacomulco Km 14.5, C.P. 50200, Toluca, Estado de México, México.
Facultad de Ciencias, Universidad Autónoma del Estado de México, Instituto Literario 100, Col. Centro, C.P. 50000, Toluca, Estado de México, México. 3
Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, A.P. 48-3, C. P. 62251, Cuernavaca, Morelos, México. Email: [email protected]
ABSTRACT Titanium dioxide (TiO2) is an efficient photocatalyst. It is, however, fully activated only under ultraviolet (UV) radiation. Thus some research has been addressed to modify TiO2 so that it becomes sensitive to visible (Vis) light. The aim of this work was to modify the catalytic activation wavelength of TiO2 films by N2 plasma surface treatment. For such a purpose, sol-gel method was used to coat glass substrates with TiO2 films. The films so obtained were characterized by Raman Spectroscopy and SEM. For N2 plasma treatment, the films were exposed to N2 plasma and the effect of exposure time, N2 pressure and electric conditions on TiO2 photocatalytic activity under sunlight was studied. The photocatalytic activity was established via methylene blue (MB) degradation. Keywords: Absorption, catalytic, Raman spectroscopy, scanning electron microscopy (SEM), sol-gel. INTRODUCTION In heterogeneous photocatalysis, anatase TiO2 has been applied successfully either as powder or thin film in processes like organic compounds degradation [1-4]. Unfortunately, the photocatalytic materials can only absorb the radiation in the range of ultraviolet light which is less than 5% of the whole solar radiation spectrum [5-6], thus wasting most of the remaining radiation that could increase photocatalyst efficiency and maximize its use. This fact has aroused the interest of many researchers to elucidate the possibility of moving the absorption band gap towards the visible light range. It has been reported that doping with gases such as nitrogen can enhance the photocatalytic activity of TiO2 by shifting its range of absorption into the UV-visible light [7-8]. It has been confirmed [8-11] that the TiO2 catalyst doped with nitrogen or also named titanium oxinitrate (TiOx-Ny) causes physical changes in the catalyst such as the modification of the internal refraction, hardness and electrical conductivity [7]. Among these changes, the photocatalytic reactivity of the TiOx-Ny formed allows the activation energy interval to move closer to the visible absorption, using the primary part of sunlight.
Mater. Res. Soc. Symp. Proc. Vol. 1275 © Materials Research Society
The modification of TiO2 with gases has been attempted by different means as laser flash method, heat treatment, deposition by dispersion, plasma deposition, among others [12-13]. In this work, TiO2 films synthesized by sol-gel method were exposed to N2 plasma in order to modify the wavelength at whic
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