Gold-copper nano-alloy, " tumbaga ", in the era of nano: Phase diagram and segregation

Grégory Guisbiers, Sergio Mejia-Rosales, Subarna Khanal, Francisco Ruiz-Zepeda, Robert L. Whetten, Miguel José-Yacaman

Research output: Contribution to journalArticlepeer-review

107 Scopus citations

Abstract

Gold-copper (Au-Cu) phases were employed already by pre-Columbian civilizations, essentially in decorative arts, whereas nowadays, they emerge in nanotechnology as an important catalyst. The knowledge of the phase diagram is critical to understanding the performance of a material. However, experimental determination of nanophase diagrams is rare because calorimetry remains quite challenging at the nanoscale; theoretical investigations, therefore, are welcomed. Using nanothermodynamics, this paper presents the phase diagrams of various polyhedral nanoparticles (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) at sizes 4 and 10 nm. One finds, for all the shapes investigated, that the congruent melting point of these nanoparticles is shifted with respect to both size and composition (copper enrichment). Segregation reveals a gold enrichment at the surface, leading to a kind of core-shell structure, reminiscent of the historical artifacts. Finally, the most stable structures were determined to be the dodecahedron, truncated octahedron, and icosahedron with a Cu-rich core/Au-rich surface. The results of the thermodynamic approach are compared and supported by molecular-dynamics simulations and by electron-microscopy (EDX) observations.

Original languageEnglish (US)
Pages (from-to)6718-6726
Number of pages9
JournalNano Letters
Volume14
Issue number11
DOIs
StatePublished - Nov 12 2014
Externally publishedYes

Keywords

  • binary phase diagram
  • congruent melting
  • nanoalloy
  • nanothermodynamics
  • polyhedra
  • size effect

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering

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