Abstracts Book - IMRC 2018

• SA2-O002 Invited Talk
ON THE INTERPRETATION OF NANOPARTICLES ELECTRON
DIFFRACTION PATTERNS
Reyes-Gasga Jose 1
1 Instituto de Física - Universidad Nacional Autónoma de México, Departamento de Materia
Condensada, Mexico.
Modern FEG transmission electron microscopes allow to obtain parallel- and
converging- beam diffraction patterns (SADP and CBED, respectively) of
nanoparticles. However, their interpretation requires to resolve the
corresponding reciprocal space, and the relationship with the Ewald sphere.
In the SADP, nanoparticles present forbidden spots, for example in the [111] and
[112] electron diffraction patterns of ï¬Â‚at gold triangular nanoparticles. The
forbidden spots were successfully indexed as corresponding to the interference
of the First Laue Zone (FOLZ) and the zero-order Laue zone (ZOLZ). The study of
the forbidden spots and their relation to the shape and incompleteness of layers
in nanoparticles will be commented.
In the CBED patterns, the transition 10-fold to 5-fold symmetry has been
observed in gold decahedral nanoparticles. The 10-fold symmetry predicted by
Friedel’s law is lost by the asymmetric shift of the diffraction spots. Dynamical
and kinematical diffraction calculations indicate this decrease in symmetry is
produced by double refraction effect coupled with the variation of the dynamical
diffraction conditions.
Acknowledgment:
I thank to Drs. L.D. Romeu, A. Gomez-Rodriguez, J. L. Elechiguerra, X. Gao, J. M.
Montejano-Carrizales and S. Tehuacanero-Cuapa as coauthors of the papers
where this work was partially reported, and S. Tehuacanero Nuñez for technical
help in the image processing. I also thank to DGAPA-UNAM (Project PAPIIT-
IN109516) for the partial financial support.
Keywords: Electron diffraction, Nanoparticles, Electron microscopy
Presenting authors email: jreyes@fisica.unam.mx