Successful synthesis and thermal stability of immiscible metal Au–Rh, Au–Ir andAu–Ir–Rh nanoalloys

Abstract

We successfully prepared face-centred cubic nanoalloys in systems of Au-Ir, Au-Rh and Au-Ir-Rh, with large bulk miscibility gaps, in one-run reactions under thermal decomposition of specially synthesised single-source precursors, namely, [AuEn][Ir(NO)], [AuEn][Ir(NO)] [Rh(NO)] and [AuEn][Rh(NO)]. The precursors employed contain all desired metals 'mixed' at the atomic level, thus providing significant advantages for obtaining alloys. The observations using high-resolution transmission electron microscopy show that the nanoalloy structures are composed of well-dispersed aggregates of crystalline domains with a mean size of 5 ± 3 nm. Еnergy dispersive x-ray spectroscopy and x-ray powder diffraction (XRD) measurements confirm the formation of AuIr, AuRh, AuIrRh, AuIrRh and AuIrRh metastable solid solutions. In situ high-temperature synchrotron XRD (HTXRD) was used to study the formation mechanism of nanoalloys. The observed transformations are described by the 'conversion chemistry' mechanism characterised by the primary development of particles comprising atoms of only one type, followed by a chemical reaction resulting in the final formation of a nanoalloy. The obtained metastable nanoalloys exhibit essential thermal stability. Exposure to 180 °C for 30 h does not cause any dealloying process.

Exploring AuRh Nanoalloys: A Computational Perspective on the Formation and Physical Properties

“…In a work from 2017, Shubin et al. studied the formation and stability of gold‐based nanoalloys exploring also the AuRh system [37] . Despite the investigated sizes and compositions were slightly different from the ones of our nanosystems, their analysis reflects what we observed in our simulations.…”

Monitoring in situ the colloidal synthesis of AuRh/TiO2 selective-hydrogenation nanocatalysts

“…32 The inuence of the relative Au/Rh molar ratio on the metal particle size in the AuRh/TiO 2 catalysts was also determined by TEM (Table 1). A gradual increase in the particle size with the Au concentration is evidenced, going from 2.4 nm for Rh and Au 13 Rh 87 , to 3.2 nm for Au 37 Rh 63 , and 4.0 nm for Au 57 Rh 43 . Above 60 at% Au, the average particle size somewhat decreases to 3.3 nm for Au 63 Rh 37 , and 2.8 nm for pure Au.…”

High-Efficiency Biocidal Solution Based on Radiochemically Synthesized Cu-Au Alloy Nanoparticles

“…As in the case of the synthesis of monometallic NPs, the morphology and crystal structure of metal alloy NPs can be controlled in particular by choosing appropriate methods of synthesis and control of some reaction parameters, such as the concentration of precursor ions and reducing agents, stabilizing agents, temperature, and time [6,7]. Thus, the metal alloy NPs can be obtained using both top-down and bottom-up approaches [8] by different methods, such as: chemical (e.g., chemical and electrochemical reduction [9], hydrothermal [10], precipitation [11], sol-gel [12], micro-emulsion [13]), physical (e.g., sputtering [14], thermal decomposition [15], microwaves [16], radiolytic [17], and sonochemical [18]) and biological (bacteria, fungi, plants, agricultural and industrial wastes) [19][20][21][22] procedures. Metal alloy NPs have an advantage over monometallic nanoparticle systems due to the synergism between the individual component alloy nanoparticle's characteristics and a more stable structure [8].…”