Structural Characterization of Nanoparticles Obtained by a Polyol Synthesis in the Bimetallic System Pt-Pd
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Structural Characterization of Nanoparticles Obtained by a Polyol Synthesis in the Bimetallic System Pt-Pd A. F. García-Ruiz1,2, J. J. Velázquez Salazar2, R. Esparza2 and N. Castillo3. 1
UPIICSA-COFAA, Instituto Politécnico Nacional, Te 950, Col. Granjas-México, Iztacalco, C. P. 08400 México, D. F. México. E-mail: [email protected] 2 Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA. 3 ESIQIE-Instituto Politécnico Nacional, UPALM Zacatenco, 07738 México, D.F. ABSTRACT A modified polyol synthesis has been utilized to study the different structures obtained in the bimetallic system of platinum (Pt) and palladium (Pd). Some results are shown in this work. Thermal methods under refluxing, carrying on the reaction up to 285 ºC, have been assayed to reduce metallic salts using ethylene glycol (EG) as reducer and polyvinylpyrrolidone (PVP) as protective reagent of the formed bimetallic nanoparticles. The special core-shell structure has been observed in these bimetallic nanoparticles, whose synthesis was assisted by Ag, showing polyhedral shapes. The average diameter size of the core has been estimated at 10 nm, and the diameter size of the shell in 13 nm, consequently the thickness of the shell is around 1.5 nm. Nanoparticles were structurally characterized with transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) equipped with detector to generate high angle annular dark field (HAADF) images. This kind of structures have been studied and utilized to increase successfully the catalytic properties of monometallic nanoparticles of Pt or Pd according to other works. Here, the synthesis procedure is described; as the main results, several images are presented showing the obtained bimetallic core-shell structures and their fast Fourier transform (FFT), and also the size and the elemental analysis of the nanoparticles are reported, concluding that this synthesis method is very efficient for preparing bimetallic core shell structures. Keywords: Chemical synthesis, Core-shell, Nanostructure, Pt-Pd, STEM. INTRODUCTION In the recent years, it has had an increasing interest in the study of multimetallic nanoparticles [1-3]. The chemical synthesis and morphology control of nanoparticles of metals such as platinum, palladium, gold, etc., are attracting increasing attention [4,5]. Many researches have showed that several properties of nanoparticles are improved from that of monometallic nanoparticles when they are bimetallic nanoparticles [1, 6-10]. Such properties are, for example, catalytic properties for using in sustainable fuel cell technology and data storage and properties for other applications such as drugs delivery, diagnostics in biological tissues (e. g. cancer diagnostics and therapies) and others [1,11-13]. Particularly, in the preparation of bimetallic nanoparticles of platinum (Pt) and palladium (Pd) to improve those mentioned properties a lot of efforts have been dedicated, getting systems as monoparticles d
