Gold–Copper Nano-Alloy, “Tumbaga”, in the Era of Nano: Phase Diagram and Segregation

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.

Antibacterial properties and toxicity from metallic nanomaterials

“…Shortly after reports identified copper as an antibacterial reagent, 92 synthesis techniques for producing nanosized copper were developed. 93 It has been reported that the antibacterial characteristics displayed by copper are a result of cellular damage after contact between released Cu 2+ ions and bacteria membrane. This section analyzes different synthesis, antibacterial properties of the structure nanoparticle, comparison of different shapes and sizes, promising composites, and toxicity properties of copper nanomaterial.…”

Structure and Reactivity of Cu-doped Au(111) Surfaces

“…From the catalytic point of view, supported copper and supported gold nanoparticles are very active for oxidation reaction and Cu/Au nanoparticulates have been reported to be catalytically active for a variety of reactions, in particular for the oxidation of CO and of alcohols to produce biofuels [70][71][72]. Moreover, supported gold catalytic systems can also operate as highly selective catalysts for the hydrogenation of important feedstocks such as benzaldehyde [73] and nitrobenzene [74].…”

Kinetic Monte Carlo approach to Schottky defects in noble metal nanoclusters

“…A nano-phase diagram of structure versus temperature has been developed for gold and silver from experiments and density functional theory (DFT) [11,12]. A phase diagram for copper has been produced as an alloy with gold for nanoclusters [13]. We model all three noble metals, gold, silver, and copper and use gold to present typical data, with tabular data compiled for silver and copper.…”