Stability of Crystal Facets in Gold Nanorods

Abstract

Metal nanocrystals can be grown in a variety of shapes through the modification of surface facet energies via surfactants. However, the surface facets are only a few atoms wide, making it extremely challenging to measure their geometries and energies. Here, we locate and count atoms in Au nanorods at successive time intervals using quantitative scanning transmission electron microscopy. This enables us to determine the atomic-level geometry and the relative stability of the facets and to expound their relationship to the overall three-dimensional nanocrystal shape and size. We reveal coexisting high- and low-index facets with comparable stability and dimensions and find the geometry of the nanorods is remarkably stable, despite significant atom movements. This information provides unique insights into the mechanisms that govern growth kinetics and nanocrystal morphology.

Understanding the Effect of Iodide Ions on the Morphology of Gold Nanorods

“…In Figure c–e, 3D visualizations along different viewing directions and a slice through the reconstructed volume are presented. Although the reconstruction did not enable a direct indexing of the lateral facets due to surface roughness, the facets at the sides of the tip could be reliably investigated and were determined to correspond to {111} and {110} planes, in agreement with the findings reported by Katz‐Boon et al…”

Determination of the Surface Facets of Gold Nanorods in Wet‐Coated Thin Films with Grazing‐Incidence Wide Angle X‐Ray Scattering

“…[6] Reports on the crystalline structure of gold nanorod (AuNR) according to TEM data differ in their results. [2,[7][8][9][10][11][12][13][14] Wang et al reported an octagonal cross section with alternating (100)/(110) facets and tips covered with (110) and (111) facets. [12] Carbo-Argibay et al [10] suggested high-index surface facets such as (250) and (520).…”

“…Reports on the crystalline structure of gold nanorod (AuNR) according to TEM data differ in their results . Wang et al reported an octagonal cross section with alternating (100)/(110) facets and tips covered with (110) and (111) facets .…”

“…High‐index facets generally provide weaker scattering than the low‐index ones. The high‐index crystalline facets recently reported for AuNR and palladium show very low peak intensities ( I hkl ) due to the synergistic interactions of structural factor ( F hkl ), scale factor ( K ), multiplicity factor ( p hkl ), Lorentz factor ( L ϴ ), polarization factor ( P ϴ ), absorption multiplier ( A ϴ ), orientation factor ( T hkl ), and extinction multiplier ( E hkl ): I hkl = | F hkl | 2 × K × p hkl × L ϴ × P ϴ × A ϴ × T hkl × E hkl . The same problem limits electron diffraction detection of facets …”

From Gold Nanoseeds to Nanorods: The Microscopic Origin of the Anisotropic Growth

“…6) to nearly 100 %. [13] These recent studies point to the fact that the interaction with surfactants and ions can lead to ar eduction in the relative energy of ah igh-index facet. [11,12] An anorod geometry with eight identical high-index lateral Au(250) facets [11] is shown in Figure 1b.Ananorod that consists of octagonal Au(5120) side facets,terminating in pyramids with Au(130) facets at the two ends that are connected to the sides by four small Au(5120) "bridging" facets, [12] is reported in Figure 1c.Coexisting highand low-index facets,n amely an alternating sequence (1+ + ffiffi ffi 2 p ,1,0), (110), (1,1+ + ffiffi ffi 2 p ,0), (010), and so on, with comparable stability and dimensions have also been reported.…”