Identification of a Critical Intermediate in Galvanic Exchange Reactions by Single‐Nanoparticle‐Resolved Kinetics |
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Authors: | Jeremy G. Smith Qing Yang Prof. Prashant K. Jain |
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Affiliation: | 1. Department of Chemistry, University of Illinois at Urbana Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (USA) http://www.nanogold.org;2. Present address: Department of Chemistry, University of California at Los Angeles, Los Angeles, CA 90095 (USA);3. Department of Physics and Materials Research Laboratory, University of Illinois at Urbana, Champaign, Urbana, IL 61801 (USA) |
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Abstract: | 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. |
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Keywords: | galvanic reactions nanoparticles nanostructures nucleation single‐particle spectroscopy |
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