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Download fileInitiation and Progression of Anisotropic Galvanic Replacement Reactions in a Single Ag Nanowire: Implications for Nanostructure Synthesis
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posted on 2021-11-11, 21:06 authored by Silvia Canepa, Murat Nulati Yesibolati, Jakob Schiøtz, Shima Kadkhodazadeh, Wei Huang, Hongyu Sun, Kristian MølhaveThe galvanic replacement reaction
(GRR) is a convenient method
for synthesizing hollow/porous noble metal nanostructures with energy,
health, and environmental applications. Understanding the reaction
mechanism is important for optimizing the produced nanostructures’
physicochemical properties. Using liquid-phase scanning transmission
electron microscopy (LPSTEM), we quantitatively analyzed the GRR process
in individual silver nanowires (AgNWs) reacting with an aqueous HAuCl4 solution. The experiments and atomic-scale simulations show
that GRR is a highly selective process with respect to the exposed
surface facets, and we discover that the process progression is influenced
by the internal crystal domains. We observe that the etching of AgNWs
starts preferentially from facets with high energy sites while not
favorable on low energy {111} facets, where even the internal twin
facets within the nanostructures are found to be temporarily stable.
The LPSTEM-observed etch rates in single or multiple crystal segments
in AgNWs are shown to approach diffusion-limited conditions. These
results provide intricate and detailed insights into the GRR process,
which are difficult to achieve by other methods, and such studies
will be beneficial for the understanding of how the surface energy
and number of available surface sites influence the initiation probability,
which will theoretically guide the synthesis of nanostructures, also
supported with the deeper understanding of how the internal structure
may influence the process.
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scale simulations showresults provide intricateobserved etch ratesmultiple crystal segmentsinternal crystal domainsindividual silver nanowiresgalvanic replacement reactionsingle ag nanowirehighly selective processhigh energy sitesagnws starts preferentially4 </ subexposed surface facetssurface energyreaction mechanismusing liquidtheoretically guidetemporarily stablesynthesizing hollowquantitatively analyzedlow energylimited conditionsenvironmental applicationsdetailed insightsconvenient methodaqueous hauclapproach diffusionalso supported