Shape control of metal nanocrystals

Why metal nanocrystals come out as cubes, cuboctahedra, octahedra, bipyramids, decahedra, icosahedra, wires or plates: single-crystal seeds take the shape set by the growth rates along ⟨111⟩ and ⟨100⟩, capping agents such as PVP, bromide and citrate pick the facet that is exposed, and twinned or faulted seeds grow into bipyramids, multiply twinned particles, wires and plates. After Xia et al. 2009.

1. Single-crystal seeds: From single-crystal seeds, octahedra, cuboctahedra or cubes form depending on the relative growth rates along ⟨111⟩ and ⟨100⟩; with uniaxial growth, cubic seeds give rectangular bars (Xia 2009). 2. Capping agents: A capping agent changes the order of free energies of the facets and thus their relative growth rates; the plane with a slower addition rate is exposed more (Xia 2009). 3. PVP and bromide on {100}: PVP binds most strongly to {100} of Ag and Pd: atoms add to the poorly passivated {111} facets, giving nanocubes larger than 25 nm; Br⁻ on {100} of Ag, Au, Pd and Pt gives smaller cubes (below 25 nm), bars and octagonal rods (Xia 2009). 4. Citrate on {111}: Citrate binds most strongly to {111}, at least for Pd, favouring octahedra, icosahedra and decahedra (Xia 2009). 5. Twinned seeds: Singly twinned seeds give right bipyramids enclosed by {100} facets (two right tetrahedra base to base); multiply twinned seeds give icosahedra, decahedra and pentagonal rods or wires, depending on whether the side {100} planes are stabilised (Xia 2009). With Br⁻ and high-molecular-weight PVP capping the {100} side faces, penta-twinned silver wires grow along their length only (da Silva 2016). 6. Plates: Seeds with stacking faults grow into thin plates with {111} top and bottom faces: hexagonal, then triangular as the {111} facets leave the sides (Xia 2009).

Starting materials: Seeds of silver, gold, palladium or platinum: single crystals, singly twinned, multiply twinned or with stacking faults. Product: Cubes, cuboctahedra, octahedra, right bipyramids, decahedra, icosahedra, pentagonal wires and triangular plates.

Xia et al., “Shape-controlled synthesis of metal nanocrystals: simple chemistry meets complex physics?”, Angew. Chem. Int. Ed. 2009 (doi:10.1002/anie.200802248); da Silva et al., “Facile synthesis of sub-20 nm silver nanowires through a bromide-mediated polyol method”, ACS Nano 2016 (doi:10.1021/acsnano.6b03806); Mendoza-Cruz et al., “Experimental high-resolution observation of the truncated double-icosahedron structure: a stable twinned shell in alloyed Au–Ag core@shell nanoparticles”, Nano Lett. 2024 (doi:10.1021/acs.nanolett.3c04435); Skrabalak et al., “Gold nanocages: synthesis, properties, and applications”, Acc. Chem. Res. 2008 (doi:10.1021/ar800018v).

Yes. Open it in the LabCanvas editor: all 47 layers are editable, including 8 generated objects (structures, plots, equipment) with their own settings. Change the text, colours and layout, then export PNG, TIFF, SVG or PDF.

Not to view it here. To open and edit it, sign in to LabCanvas or create a free account (the free plan keeps up to 3 designs). Downloading the figure is part of LabCanvas Pro (US$19 a month or US$199 a year).