title: Structural characterization of Pt-Pd core-shell nanoparticles by Cs-corrected STEM.
abstract: Pt-Pd core-shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 °C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core-shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM-EDS and STEM-EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.
authors.affiliation: Centra de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, 76230 Santiago de Querétaro, Querétaro, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Esparza
authors.affiliation: UPIICSA-COFAA, Instituto Politécnico Nacional, Te 950, Col. Granjas-México, Iztacalco, 08400 Mexico, D.F., Mexico.
authors.forename: Amado F
authors.initials: AF
authors.lastname: García-Ruiz
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
authors.forename: J J Velázquez
authors.initials: JJ
authors.lastname: Salazar
authors.affiliation: Centra de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, 76230 Santiago de Querétaro, Querétaro, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Pérez
authors.affiliation: Department of Physics and Astronomy, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
authors.forename: M
authors.initials: M
authors.lastname: José-Yacamán
keywords: Aberration corrected; Chemical synthesis; Core-shell; Electron microscopy; Nanostructure; Pt–Pd