Atomic-Scale Determination of Surface Facets in Gold Nanorods(Bart Goris, Sara Bals, Wouter Van den Broek, Enrique Carbó-Argibay, Sergio Gómez-

Graña,

Luis M. Liz-Marzán and Gustaaf Van Tendeloo)Victoria Salinas, Nisha Verma12.12.2013

Introduction

Properties of Gold Nanorods

● well-defined anisotropy

● interaction between shape and optical response

● surface facets can influence reactivity and ligand adsorption

● important applications in nanoplasmonics

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Introduction

Aberration-Corrected Electron Microscopy: incomplete characterization

Electron Tomography: insufficient resolution

Compressive-Sensing-Based 3D Reconstruction Algorithm: ● high precision characterization● atomic-scale imperfections and surface relaxation can be studied● methodology applicable to a broad range of nanocrystals● structure-properties connection

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Methods and ResultsLow-Magnification Electron Tomography and Electron Diffraction

● faceted morphology for both types of rods● insufficient resolution for correct indexing of the side facets

Figure 1. (1) 4

Methods

High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM)

● images are formed by collecting scattered electrons with an annular dark-field detector

● signal collection efficiency

● signal is proportional to thickness of the specimen and to the atomic mass of the sample

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Methods and ResultsHAADF-STEM: ● high resolution HAADF-STEM projections along {110}A B

● intensity profile diagrams

Figure 2. (1) 6

Methods and Results

Figure 3. (1) 7

3D Reconstruction of Gold Nanorods

A B

• {110} & {100} – morphology of rods• tip rounded at {101}

• rounded morphology including {520}

• tip facets comparable to A

Methods and Results

Figure 4. (1) 8

3D Fourier Transform of Reconstructed CTAB Nanorod

A B C

projections of the calculated 3D Fourier transforms of the reconstructed nanorod obtained along the different directions fcc crystal structure

Methods and Results

3D Fourier Transform of Reconstructed CTAB Nanorod

A B Ctheoretical model corresponding to 3D reciprocal space bcc crystal structure

Figure 5. (1) 9

Methods and ResultsGeometrical Phase Analysis (GPA)

atomic-resolution reconstruction of a gold nanorod

Figure 6. (1) 10

• volume rendering of the reconstructed nanorod

• two selected slices through the reconstruction

• tip of the nanorod: {101} facets• surface step with a thickness of two

atoms is observed

Methods and Results

Geometrical Phase Analysis (GPA)

● reference region without strain in the middle of the nanorod

● considerable measurement error slight deviations from equilibrium value

● atomic outward relaxation at the tip of the nanorod

Figure 7. (1) 11

3D εzz Strain Field

Conclusions

● fcc crystal lattice of CTAB nanorods reproduced by high-resolution HAADF-STEM projection images

● rodsʼ side facets precisely determined

● 3D strain measurements obtained and correlated with the nano-objectsʼ atomic lattice

perspectives for 3D atomic visualization of different nanomaterials

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References

1. Goris, B. et al., Atomic-Scale Determination of Surface Facets in Gold Nanorods, Nature Materials 11, 930-935 (2012).

2. Guerrero-Martínez, A. et al., Inclusion Complexes between β-Cyclodextrin and a Gemini Surfactant in Aqueous Solution: An NMR Study, J. Phys. Chem. B 110, 13819-13828 (2006).

3. Nikoobakht, B. & El-Sayed, M. A., Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method, Chem. Mater. 15, 1957-1962 (2003).

4. Pecharroman, C. et al. Redshift of Surface Plasmon Modes of Small Gold Rods due to Their Atomic Roughness and End-Cap Geometry, Phys. Rev. B 77, 035418 (2008).

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