Synthesis and characterization of colloidal titania nanoparticles
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1074-I10-24
Synthesis and characterization of colloidal titania nanoparticles Ana-Lilia Díaz-Fonseca, and Juan-Carlos Cheang-Wong Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, México, D.F., 01000, Mexico ABSTRACT Spherical submicrometer-sized titanium dioxide (TiO2 or titania) particles were prepared by the sol-gel method from hydrolysis and condensation of titanium alkoxide using different basic catalysts in ethanol/acetonitrile at different annealing temperatures. A systematic study was performed in order to determine the effect on the particle size and shape of the different reagents. Subsequently, they were deposited onto silicon wafers, in order to form a monolayer of TiO2 monodisperse particles. The titania particles were characterized by scanning electron microscopy to determine size and shape, and by X-ray diffraction to find their crystal structure.
INTRODUCTION Titanium dioxide (TiO2 or titania) is the most widely used white pigment because of its brightness and very high refractive index (n = 2.7). TiO2 is also an effective opacifier in powder form, and it is employed as a pigment to provide whiteness and opacity to products such as paints, enamel or glazes of ceramics, coatings, cosmetics, plastics, papers, inks, foods, medicines (i.e. pills and tablets) as well as most toothpastes [1]. Titanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet light and it is thus added to paints, cements, windows, tiles, or other products for sterilizing, deodorizing and anti-fouling properties, and is also used as a hydrolysis catalyst. For all these applications, colloidal titania particles are being intensively studied in order to establish reliable preparation methods to obtain fine, spherical and monodisperse particles. Indeed, the properties of TiO2 particles depend strongly on its crystal structure, shape and size. Some of these properties can be perfectly controlled by appropriate synthesis conditions, but several alternative approaches must be still explored in order to modify, for instance, the shape of titania particles and determine its effect on the optical properties. Indeed, it has been observed that amorphous glassy materials can undergo extreme deformations under exposure to high-energy beams. Ion irradiation induces damage and structural changes in solids due to energy losses of multi-MeV heavy ions via ionization events and atomic collisions occurring in the near-surface region of the irradiated sample. This ionbeam induced anisotropic deformation of amorphous materials such as silica has been reported in the case of SiO2 films on Si substrates [2,3], as well as in colloidal silica particles [4,5]. In both cases the resulting effect is an increase of the sample dimensions perpendicular to the ion beam and a decrease in the direction parallel to the ion beam as a function of the fluence. This effect has been observed in several classes of amorphous materials, but never in crystalline samples. Therefore, the aim of the present work is to stud
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