Angle Resolved TEM Imaging of Pt Nanoparticles
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Angle Resolved TEM Imaging of Pt Nanoparticles N. Shukla • M. M. Nigra • M. A. Bartel T. Nuhfer • C. Phatak • A. J. Gellman
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Received: 29 July 2010 / Accepted: 13 September 2010 / Published online: 30 September 2010 Ó Springer Science+Business Media, LLC 2010
Abstract Particle shape and size are two of the most important characteristics of nanoparticulate catalysts that determined their activity and selectivity. In many studies, the shapes of nanoparticles are characterized using transmission electron micrographs obtained at a single nanoparticle orientation and thus, the shape determination is based on viewing a single cross-sectional profile of the nanoparticle. A full determination of particle shape should require viewing over a range of angles. In this work Pt nanoparticles with controlled shapes and sizes have been synthesized using a high pressure technique. Angle resolved transmission electron microscopy techniques (electron tomography) are necessary to view the crystals over a range of orientations and determine their three dimensional shapes. In this work, angle resolved TEM imaging of nanoparticles reveals information about the nanoparticle shape and orientation on substrates that cannot be determined from single cross-sectional TEM images. Angle resolved TEM imaging of nanoparticles will be very
N. Shukla (&) A. J. Gellman National Energy Technology Laboratory, 626 Cochran Mill Road, Pittsburgh, PA 15236, USA e-mail: [email protected] N. Shukla Institute for Complex Engineered Systems, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA M. M. Nigra M. A. Bartel A. J. Gellman Department of Chemical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA T. Nuhfer C. Phatak Department of Material Science and Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA 15213, USA
valuable in catalysis and in the fields where the shapes of nanoparticles play an important role. Keywords
Pt Nanoparticle Nanoparticle shape
1 Introduction The goal of catalysis science is to understand the factors influencing the rates and selectivities of reactions occurring on catalyst surfaces. Many conventional catalysts are transition metal particles supported on high surface area oxides. Such supported metal catalysts are typically prepared by impregnating the oxide support with metal salts or organometallic compounds which are then reduced to metallic form [1]. In this method of catalyst preparation, the metal particle size and shape are not well-controlled, and these catalysts represent inhomogeneous, suboptimal environments for catalytic selectivity. In order to tailor and optimize catalyst selectivity, it is necessary to develop methods to prepare highly uniform catalysts. Preparation and characterization of such catalysts is a key challenge in catalyst science. The most important design targets for catalysts are high activity, high selectivity, and high stability. A highly active catalyst must expose a high surface area and this often require
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