An official website of the United States government
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.
more »
« less
Carving growing nanocrystals: coupling seed-mediated growth with oxidative etching
This work presents multiple experimental evidences coherently showing that the versatile structural evolution of Au nanocrystals during seed-mediated growth under the guidance of foreign metal ions and halide-containing surfactants is essentially dictated by the dynamic interplay between oxidative etching and nanocrystal growth. Coupling nanocrystal growth with oxidative etching under kinetically controlled conditions enables the in situ surface carving of the growing nanocrystals, through which the surface topography of shape-controlled nanocrystals can be deliberately tailored on the nanometer length-scale.
more »
« less
- Award ID(s):
- 1655740
- PAR ID:
- 10093937
- Date Published:
- Journal Name:
- Nanoscale
- Volume:
- 10
- Issue:
- 39
- ISSN:
- 2040-3364
- Page Range / eLocation ID:
- 18457 to 18462
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)This article reviews the advancements and prospects of liquid cell transmission electron microscopy (TEM) imaging and analysis methods in understanding the nucleation, growth, etching, and assembly dynamics of nanocrystals. The bonding of atoms into nanoscale crystallites produces materials with nonadditive properties unique to their size and geometry. The recent application of in situ liquid cell TEM to nanocrystal development has initiated a paradigm shift, (1) from trial-and-error synthesis to a mechanistic understanding of the “synthetic reactions” responsible for the emergence of crystallites from a disordered soup of reactive species (e.g., ions, atoms, molecules) and shape-defined growth or etching; and (2) from post-processing characterization of the nanocrystals’ superlattice assemblies to in situ imaging and mapping of the fundamental interactions and energy landscape governing their collective phase behaviors. Imaging nanocrystal formation and assembly processes on the single-particle level in solution immediately impacts many existing fields, including materials science, nanochemistry, colloidal science, biology, environmental science, electrochemistry, mineralization, soft condensed-matter physics, and device fabrication.more » « less
-
Gamma alumina (γ-Al2O3) is widely used as a catalyst and catalytic support due to its high specific surface area and porosity. However, synthesis of γ-Al2O3 nanocrystals is often a complicated process requiring high temperatures or additional post-synthetic steps. Here, we report a single-step synthesis of size-controlled and monodisperse, facetted γ-Al2O3 nanocrystals in an inductively coupled nonthermal plasma reactor using trimethylaluminum and oxygen as precursors. Under optimized conditions, we observed phase-pure, cuboctahedral γ-Al2O3 nanocrystals with defined surface facets. Nuclear magnetic resonance studies revealed that nanocrystal surfaces are populated with AlO6, AlO5 and AlO4 units with clusters of hydroxyl groups. Nanocrystal size tuning was achieved by varying the total reactor pressure yielding particles as small as 3.5 nm, below the predicted thermodynamic stability limit for γ-Al2O3.more » « less
-
We report the successful synthesis of monodispersed Cu2S nanocrystals and the subsequent formation of highly ordered nanocrystal superlattices. The synthesis is performed under ambient air conditions using simple experimental setups, making the process both accessible and scalable. By systematically tuning the reaction temperature and duration, we demonstrate precise control over the nanocrystal size, which is crucial in achieving uniformity and monodispersity. Furthermore, we uncover a previously unidentified nanocrystal growth mechanism that plays a key role in producing highly monodisperse Cu2S nanocrystals. This insight into the growth process enhances our fundamental understanding of nanocrystal formation and could be extended to the synthesis of other semiconductor nanomaterials. The self-assembly of these nanocrystals into superlattices is carefully examined using electron diffraction techniques, revealing the presence of pseudo-crystalline structures. The ordered arrangement of nanocrystals within these superlattices suggests strong interparticle interactions and opens up new possibilities to tailor their collective optical, electronic, and mechanical properties for potential applications in optoelectronics, nanomedicine, and energy storage.more » « less
-
Seed-mediated synthesis is a versatile method to prepare multimetallic nanocrystals for diverse applications. However, many fundamental questions remain on how the structural and chemical properties of nanocrystal seeds control the reaction pathways, especially for nonaqueous synthesis at elevated temperatures. Herein, we elucidate the role of surface ligands and crystallinity of Au nanocrystal seeds on the heterometallic seeded growth of Cu-based nanocrystals. We found that weakly coordinating ligands are critical to facilitate the diffusion between Au and Cu, which enables subsequent one-dimensional growth of Cu. Replacing multiple-twinned Au seeds with single-crystalline ones switched the growth pathway to produce heterostructured nanocrystals. Our work illustrates the importance of precise control of seed characteristics for the predictive synthesis of structurally complex multimetallic nanocrystals.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c8nr06895j
