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Abstract This article describes a systematic study of the oxidative etching and regrowth behaviors of Pd nanocrystals, including single‐crystal cubes bounded by {100} facets, single‐crystal octahedra and tetrahedra enclosed by {111} facets; and multiple‐twinned icosahedra covered by {111} facets and twin boundaries. During etching, Pd atoms are preferentially oxidized and removed from the corners regardless of the type of nanocrystal, and the resultant Pd2+ions are then reduced back to elemental Pd. For cubes and icosahedra, the newly formed Pd atoms are deposited on the {100} facets and twin boundaries, respectively, due to their relatively higher energies. For octahedra and tetrahedra, the Pd atoms self‐nucleate in the solution phase, followed by their growth into small particles. We can control the regrowth rate relative to etching rate by varying the concentration of HCl in the reaction solution. As the concentration of HCl is increased, 18‐nm Pd cubes are transformed into octahedra of 23, 18, and 13 nm, respectively, in edge length. Due to the absence of regrowth, however, Pd octahedra are transformed into truncated octahedra, cuboctahedra, and spheres with decreasing sizes whereas Pd tetrahedra evolve into truncated tetrahedra and spheres. In contrast, Pd icosahedra with twin boundaries on the surface are converted to asymmetric icosahedra, flower‐like icosahedra, and spheres. This work not only advances the understanding of etching and growth behaviors of metal nanocrystals with various shapes and twin structures but also offers an alternative method for controlling their shape and size.
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Facile Synthesis of Pd−Cu Bimetallic Twin Nanocubes and a Mechanistic Understanding of the Shape Evolution
Abstract This paper presents a facile synthesis of Cu twin cubes, with a yield ofca. 70%, from seeds based on Pd hexagonal nanoplates. The lattice mismatch, capping agent, and number of planar defects in the seeds all play important roles in directing the shape evolution of Cu on the Pd seeds. Initially, the Cu atoms are only deposited on one of the two basal planes of a Pd nanoplate in the form of small islands. As the growth continues, Cu {100} facets developed in the presence of hexadecylamine and Cl−, two capping agents with selectivity towards the Cu(100) surface. When switched to Pd triangular nanoplates, Cu right bipyramids instead of cubes are obtained and only three {100} facets are created from each side of the seed. Atomic‐resolution transmission electron microscopy analysis indicates that the correspondence between the type of the seed and the shape of the final product can be attributed to the number of planar defects along the vertical direction of the plate‐like seed, with two and one twin planes corresponding to cube and right bipyramid, respectively. By adjusting the experimental condition, this synthetic method can also be extended to Pd−Ag and other bimetallic systems.
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- Award ID(s):
- 1804970
- PAR ID:
- 10131074
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemNanoMat
- Volume:
- 6
- Issue:
- 3
- ISSN:
- 2199-692X
- Format(s):
- Medium: X Size: p. 386-391
- Size(s):
- p. 386-391
- Sponsoring Org:
- National Science Foundation
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