Au@Hg Nanoalloy Formation Through Direct Amalgamation: Structural,Spectroscopic, and Computational Evidence for Slow Nanoscale Diffusion |
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Authors: | Stijn F. L. Mertens Matthew Gara Alla S. Sologubenko Joachim Mayer Sönke Szidat Karl W. Krämer Timo Jacob David J. Schiffrin Thomas Wandlowski |
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Affiliation: | 1. Departement für Chemie und Biochemie, Universit?t Bern, Freiestrasse 3, 3012 Bern, Switzerland;2. School of Chemistry, Trinity College Dublin, Dublin 2, Ireland;3. Gemeinschaftslabor für Elektronenmikroskopie, RWTH Aachen University, 52074 Aachen, Germany;4. Institut für Elektrochemie, Universit?t Ulm, Albert‐Einstein‐Allee 47, 89081 Ulm, Germany;5. Chemistry Department, University of Liverpool, Liverpool L69 7ZD, UK |
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Abstract: | Dynamic core–shell nanoparticles have received increasing attention in recent years. This paper presents a detailed study of Au–Hg nanoalloys, whose composing elements show a large difference in cohesive energy. A simple method to prepare Au@Hg particles with precise control over the composition up to 15 atom% mercury is introduced, based on reacting a citrate stabilized gold sol with elemental mercury. Transmission electron microscopy shows an increase of particle size with increasing mercury content and, together with X‐ray powder diffraction, points towards the presence of a core–shell structure with a gold core surrounded by an Au–Hg solid solution layer. The amalgamation process is described by pseudo‐zero‐order reaction kinetics, which indicates slow dissolution of mercury in water as the rate determining step, followed by fast scavenging by nanoparticles in solution. Once adsorbed at the surface, slow diffusion of Hg into the particle lattice occurs, to a depth of ca. 3 nm, independent of Hg concentration. Discrete dipole approximation calculations relate the UV–vis spectra to the microscopic details of the nanoalloy structure. Segregation energies and metal distribution in the nanoalloys were modeled by density functional theory calculations. The results indicate slow metal interdiffusion at the nanoscale, which has important implications for synthetic methods aimed at core–shell particles. |
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Keywords: | gold mercury nanoalloys discrete dipole approximation density functional theory |
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