Analysis of Pt-Nanoparticles Embedded on Crystalline TiO 2 Studied by Transmission Electron Microscopy
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Analysis of Pt-Nanoparticles Embedded on Crystalline TiO2 Studied by Transmission Electron Microscopy Jordi Arbiol1,2, Ana Ruiz1, Albert Cirera1, Francisca Peiró1, Albert Cornet1, Joan R. Morante1, Abdelhadi Alimoussa2 and Marie-José Casanove2 1 Enginyeria i Materials Electrònics, Departament d’Electrònica, Universitat de Barcelona, C/. Martí i Franquès, 1, 08028 Barcelona, Spain. TN +34 93 4021141 e-mail: [email protected] 2 CEMES-CNRS, 29, rue Jeanne Marvig, BP 4347, 31055 Toulouse Cedex, France ABSTRACT In this work, we studied the Pt particles embedded on crystalline TiO2 nanopowders. As it is well known, metal nanoparticles distributed on TiO2 surface can improve dramatically the reaction rate and selectivity of reaction in gas sensing. We prepared a wide set of TiO2 samples with different nominal Pt concentration. The aim of this study was to analyse the Pt distribution on TiO2 surface (density of Pt, particle size distribution, etc.), as well as the Pt phases existing in our samples. We used High Resolution Transmission Electron Microscopy (HRTEM) as a powerful tool to study Pt particles morphology. The HRTEM images were compared with computer simulations to confirm the results obtained. The chemical composition of the material has been also investigated by Inductively Coupled Plasma (ICP). INTRODUCTION Nowadays, there is a great interest in developing semiconductor gas sensors for controlling air pollution and exhaust gases. Semiconductor gas sensors (such as SnO2 or TiO2) offer great advantages due to their simple implementation, low cost and good reliability for real-time control systems [1,2]. The semiconductor gas sensors implemented just with pure transition metal oxides, such as TiO2, work at quite high temperatures (from 400 ºC). In order to increase the material sensitivity and selectivity, decreasing the response time and operating temperature of the sensitive nanopowders it is common to introduce catalytic additives [3-8]. However, the sensing performance depends strongly on the additive characteristics: grain size, homogeneity of distribution, localisation (superficial or volumic), oxidation state, etc. So, to obtain the best sensing results we will have to select carefully the parameters involved in the technological steps followed for the additive introduction. The aim of this work is to study the influence of the Pt weight % concentration on the material structure, catalytic metal distribution and mean size of both TiO2 and Pt particles and nanoclusters after Pt introduction by impregnation method in TiO2. A study of the Pt nanoclusters mass, dispersed on TiO2 particles has been made by TEM. We have developed a simple quantitative method, using TEM images, in order to measure the Pt superficial mass proportion versus TiO2, and we have compared the values obtained with those obtained with a real quantitative technique as Inductively Coupled Plasma (ICP) to evaluate its effectiveness. High Resolution Electron Microscopy has been used to determine the structure of Pt nanoclusters.
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