atomic-scale determination of surface facets in gold nanorods (final version)
TRANSCRIPT
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
2
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
3
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
5
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
12
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).
13