Synthesis and Characterization of Nanoparticles of TiO 2
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Synthesis and Characterization of Nanoparticles of TiO2 Rosa M. Lima García and Rafael Quintero-Torres Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Juriquilla, Querétaro 76230, México ABSTRACT The first steps in the synthesis of nanostructures are followed through UV-Vis and correlated with photoluminescence and images taken by SEM and TEM. Colloids permit the control in the atomic arrangement and the formation of nanostructures used to build cluster of materials. The size of the cluster in the colloid is around 5 nm. After the formation of the colloid a hydrothermal growth and microwave heating allows the formation of an ensemble of nanosheet. This work is aim in the direction to controls the synthesis and the properties of materials with potential applications as active optical materials. INTRODUCTION It is documented that many synthetic strategies, physical and chemical are available to produce TiO2 nanostructured materials [1, 2]. In the same direction we must realize that considering the diverse set of variables involved for each process, important changes are always produced at molecular level. Applications for nanostructured materials are related with the complexities for processing the material and to direct the synthesis toward controlling the structure from subnanometric to microstructure. This study is directed towards the understanding of newly formed nanoparticles, the first stages in the hydrolysis of titanium isopropoxide with the intention of controlling the beginning of the structure. The motivation to work with nanoparticles is related to the importance that quantum confinement due to the small size brings to the use and control of the electronic properties and is aimed to improve potential applications [3, 4]. The passive applications only make use of the large area to volume ratio in this kind of material and on the intrinsic physical properties like the high refractive index; on the other hand, the applications requiring active behavior make use of the phenomena controlled by the energy levels. The search for routes to obtain the material and specific properties is pursued in this work, by mean of understanding the genesis of nanoparticles generated during the reaction and taking control of two conditions a) to control of the nucleation and growth and b) to avoid the agglomeration of particles. To arrive to both conditions we select to perform the reaction under very diluted conditions in presence of HNO3 to prevent agglomeration [5, 6]. The material evolution was recorded with the UV-Vis spectroscopy, photoluminescence, SEM and TEM. The colloid reaches a stable sol opalescent with blue hues, them moves by hydrothermal growth to stable clusters and by microwave heating or conventional heating to nanosheets. EXPERIMENTAL The formation of nanoparticles of TiO2 is intended through the colloidal route because the formation of colloids is an example of molecular self assembly and offer one strategy to
generate nanostructures. F
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