Au@Hg nanoalloy formation through direct amalgamation: Structural, spectroscopic, and computational evidence for slow nanoscale diffusion

Mertens, S.F.L. and Gara, M. and Sologubenko, A.S. and Mayer, J. and Szidat, S. and Krämer, K.W. and Jacob, T. and Schiffrin, D.J. and Wandlowski, T. (2011) Au@Hg nanoalloy formation through direct amalgamation: Structural, spectroscopic, and computational evidence for slow nanoscale diffusion. Advanced Functional Materials, 21 (17). pp. 3259-3267. ISSN 1616-301X

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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. Interaction of an 11-nm gold hydrosol with metallic mercury leads to Au@Hg particles with up to 15 atom% Hg, following zero-order kinetics. The large difference in cohesive energy between the alloying elements causes slow inward diffusion of Hg over ca. 3 nm, decreasing the coherent face-centered cubic (fcc)-Au lattice length (indicated in red) as observed by X-ray diffraction. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Item Type:
Journal Article
Journal or Publication Title:
Advanced Functional Materials
Additional Information:
Cited By :23 Export Date: 17 April 2019 CODEN: AFMDC
Subjects:
ID Code:
132992
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Deposited On:
22 Apr 2019 13:15
Refereed?:
Yes
Published?:
Published
Last Modified:
04 Jun 2020 06:32