Identification of a Critical Intermediate in Galvanic Exchange Reactions by Single-Nanoparticle-Resolved Kinetics

• Published in: Angewandte Chemie 2014-03, Vol.126 (11), p.2911-2916
• Main Authors: Smith, Jeremy G., Yang, Qing, Jain, Prashant K.
• Format: Article
• Language: eng ; ger
• Subjects: Chemistry; Einzelpartikelspektroskopie; Exchange; Galvanische Reaktionen; Kristallkeimbildung; Nanoparticles; Nanopartikel; Nanostructure; Nanostrukturen; Reaction kinetics; Trajectories; Transformations; Transmission electron microscopy; Vacancies; Voids
• ISSN: 0044-8249; 1521-3757
• DOI: 10.1002/ange.201309307

The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using a combination of plasmonic spectroscopy and scanning transmission electron microscopy. Single‐nanoparticle reaction trajectories showed that a Ag nanoparticle exposed to Au3+ makes an abrupt transition into a nanocage structure. The transition is limited by a critical structural event, which we identified by electron microscopy to comprise the formation of a nanosized void. Trajectories also revealed a surprisingly strong nonlinearity of the reaction kinetics, which we explain by a model involving the critical coalescence of vacancies into a growing void. The critical void size for galvanic exchange to spontaneously proceed was found to be 20 atomic vacancies. Mut zur Lücke: Untersuchungen des galvanischen Austauschs in Einzelpartikelauflösung (siehe Bild) offenbarten ein bisher unbekanntes kritisches Phänomen. Die Bildung eines kritischen Hohlraums von ungefähr 20 Atomfehlstellen in Ag‐Nanopartikeln war Triebkraft für einen schnellen spontanen galvanischen Austausch, der einen Au/Ag‐Nanokäfig lieferte.