Exploiting core–shell and core–alloy interfaces for asymmetric growth of nanoparticles

Njoki, Peter N.; Lutz, Patrick; Wu, Wenjie; Solomon, Louis; Maye, Mathew M.

doi:10.1039/c2cc34184k

Cited by 10 publications

(20 citation statements)

References 28 publications

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“…Both, epitaxial and non-epitaxial shells have been synthesized for different applications [9-13]; however, epitaxial growth has not been thoroughly investigated in core-shell nanoparticles. Several works have studied the effect of elastic strain in the catalytic activity of metal films [14-17] and core-shell nanoparticles [4, 6, 18-22] as well as a substrate for surface-enhanced Raman scattering [23]. Therefore, it is necessary to study in detail the interface of these heterostructures to understand the growth of the shell and the appearance of defects that will alter the properties of such materials.…”

Section: Introductionmentioning

confidence: 99%

Strain-release mechanisms in bimetallic core–shell nanoparticles as revealed by Cs-corrected STEM

et al. 2013

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Lattice mismatch in a bimetallic core-shell nanoparticle will cause strain in the epitaxial shell layer, and if it reaches the critical layer thickness misfit dislocations will appear in order to release the increasing strain. These defects are relevant since they will directly impact the atomic and electronic structures thereby changing the physical and chemical properties of the nanoparticles. Here we report the direct observation and evolution through aberration-corrected scanning transmission electron microscopy of dislocations in AuPd core-shell nanoparticles. Our results show that first Shockley partial dislocations (SPD) combined with stacking faults (SF) appear at the last Pd layer; then, as the shell grows the SPDs and SFs appear at the interface and combine with misfit dislocations, which finally diffuse to the free surfaces due to the alloying of Au into the Pd shell. The critical layer thickness was found to be at least 50% greater than in thin films, confirming that shells growth on nanoparticles can sustain more strain due to the tridimensional nature of the nanoparticles.

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Section: Introductionmentioning

confidence: 99%

Strain-release mechanisms in bimetallic core–shell nanoparticles as revealed by Cs-corrected STEM

et al. 2013

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“…64 Briefly, a Au/Pd core/shell NP was prepared using a microwave mediated hydrothermal processing route we recently developed, 65 were thin Pd shells are deposited in a layer-by-layer manner at Au NP seeds at 120 o C. To these Au/Pd cores Ag was deposited in a similar layer-by-layer fashion, which produces the Au/Pd-Ag heterostructures that resemble dumbbells, where one side is Au/Pd, and the other Ag. 64 Briefly, a Au/Pd core/shell NP was prepared using a microwave mediated hydrothermal processing route we recently developed, 65 were thin Pd shells are deposited in a layer-by-layer manner at Au NP seeds at 120 o C. To these Au/Pd cores Ag was deposited in a similar layer-by-layer fashion, which produces the Au/Pd-Ag heterostructures that resemble dumbbells, where one side is Au/Pd, and the other Ag.…”

Section: Synthesismentioning

confidence: 99%

“…The 210 µC cm -2 charge density is the charge required for desorption a monolayer of hydrogen on a planar Pt surface, 69,70 and thus can used as only an approximate value for Pd, Au and Ag. 64,68 The Au/Pd core does not have a significant resonance in this region, and no Au signature is shown since it is the inner core and its SPR is attenuated by the Pd shell. The instrument was equipped with a STEM detector and an energy dispersive x-ray spectroscopy (EDS) detector.…”

Section: Synthesismentioning

confidence: 99%

“…The instrument was equipped with a STEM detector and an energy dispersive x-ray spectroscopy (EDS) detector. 64 Figure 2 is a set of TEM micrographs after [PtCl 6 ] 2reaction, which we denote as Au/Pd-Pt. The TGA samples were drop cast as neat solutions into platinum pans and allowed to fully dry before analysis.…”

Section: Synthesismentioning

confidence: 99%

“…[64][65][66][67][68] We hypothesized these NPs may be ideal substrates upon which to test the feasibility of combining heterostructure growth with galvanic exchange. [64][65][66][67][68] We hypothesized these NPs may be ideal substrates upon which to test the feasibility of combining heterostructure growth with galvanic exchange.…”

Section: Introductionmentioning

confidence: 99%

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Heterostructured Au/Pd–M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

2015

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The synthesis, processing, and galvanic exchange of three heterostructured nanoparticle systems is described. The surface accessibility and redox potential of a Au/Pd-Ag dumbbell nanoparticle, where a Au/Pd core/shell region, and a silver region make up the domains, was used to prepare the new nanostructures with controlled composition, morphology, and microstructure. Results indicate that the silver domain was particularly susceptible to galvanic displacement, and was exchanged to Au/Pd-M (M = Au, Pd, Pt). Interestingly, the dumbbell morphology remained after exchange, and the silver region was transformed to hollow, parachute, or concentric domains respectively. The morphology and microstructure change was visualized via TEM and HRTEM, and the composition changes were probed via STEM-EDS imaging and XPS. The electrocatalytic activity of the Au/Pd-M towards methanol oxidation was studied, with results indicating that the Au/Pd-Pt nanoparticles had high activity attributed to the porous nature of the platinum domains.

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Void Coalescence in Core/Alloy Nanoparticles with Stainless Interfaces

Maye

2013

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The oxidation properties of nanoparticles with core/alloy microstructure and stainless steel like interfaces is described. In particular, 15-nm Fe/FeCr nanoparticles with a stainless steel like interface are prepared. These particles show a unique morphological transformation that is induced by surface oxidation, oxide passivation, and vacancy coalescence. This Kirkendall diffusion results in a tailorable oxide layer thickness, Fe-core size, as well as void size and symmetry. Much like the interface of bulk stainless steel, the interfacial FeCr oxide passivates oxidation, resulting in self-limited diffusion. Because of this, a highly uniform and stable core-void-shell morphology is observed.

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Exploiting core–shell and core–alloy interfaces for asymmetric growth of nanoparticles

Cited by 10 publications

References 28 publications

Strain-release mechanisms in bimetallic core–shell nanoparticles as revealed by Cs-corrected STEM

Strain-release mechanisms in bimetallic core–shell nanoparticles as revealed by Cs-corrected STEM

Heterostructured Au/Pd–M (M = Au, Pd, Pt) nanoparticles with compartmentalized composition, morphology, and electrocatalytic activity

Void Coalescence in Core/Alloy Nanoparticles with Stainless Interfaces

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