Tracking the restructuring of oxidized silver–indium nanoparticles under a reducing atmosphere by environmental HRTEM. Issue 36 (6th September 2017)

• Record Type: Journal Article
• Authors: Ramade, Julien; Langlois, Cyril; Pellarin, Michel; Piccolo, Laurent; Lebeault, Marie-Ange; Epicier, Thierry; Aouine, Mimoun; Cottancin, Emmanuel
• Is Part Of: Nanoscale. Volume 9:Issue 36(2017)
• Page Start: 13563
• Page End: 13574
• Publication Date: 2017-09-06
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c7nr02986a
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : Multimetallic nano-alloys display a structure and consequently physicochemical properties evolving in a reactive environment. Abstract : Multimetallic nano-alloys display a structure and consequently physicochemical properties evolving in a reactive environment. Following and understanding this evolution is therefore crucial for future applications in gas sensing and heterogeneous catalysis. In view hereof, the structural evolution of oxidized Ag25 In75 bimetallic nanoparticles under varying H2 partial pressures ( P H2 ) and substrate temperatures ( T s ) has been investigated in real-time through environmental transmission microscopy (E-TEM) while maintaining the atomic resolution. Small Ag25 In75 bimetallic nanoparticles, produced by laser vaporization, are found (after air transfer) to contain an indium–oxide shell surrounding a silver-rich alloyed phase. For high P H2 and T s, the direct reduction of the indium oxide shell, immediately followed by the melting or the diffusion onto the carbon substrate of the reduced indium atoms, is found to be the dominant mechanism. This reduction is concomitant with the growth of the core, indicating a partial diffusion of indium atoms from the shell towards the particle volume. The "surviving" particles therefore consist of a silver–indium alloy, very stable and remarkably resistant against oxidation contrary to native clusters. Interestingly, in the ( P H2, T s ) space, the transition from "soft" (core–shell particles for low ( P H2, T s ) values) to "strong" reduction conditions (silver-rich alloys for high ( P H2, T s ) products) defines an intermediate domain where the preferred formation of Janus structures is detected. These results are discussed in terms of thermodynamic driving forces in relation to alloying and interface energies. This work shows the potential of high-resolution ETEM for unravelling the mechanisms of nanoparticle reorganization in a chemically reactive environment.