Ultrafast electron crystallography and nanocrystallography: For chemistry, biology and materials science. Part II. Ultrafast electron nanocrystallography

Abstract

This article shows the development of the Ultrafast Electron Nanocrystallography (UEnC), a specific implementation of Ultrafast Electron Crystallography (UEC), optimized for high sensitivity and high data acquisition efficiency and trained on the quantitative studies of different solid nanostructures with high temporal resolution ranging from pico- to femtoseconds. These achievements have opened up new possibilities for studying the coherent structural dynamics of the nanoparticles. Nanostructures are characterized by a number of unusual properties compared to their bulk counterparts. First of all, this is due to the manifestation of the quantumsize effect and the corresponding relatively-large percentage of structural units of the nanoparticle being on its surface. One of the structural features is the emergence of the so-called nanocrystallographic structure types, which have a tendency to form closed shells and are connected with the appearance of magic numbers in the size distribution. The morphology and lattice parameters of nanocrystals are strongly dependent on the substrate and the surface modification, which results in the contraction, and the formation of twin boundaries due to the relaxation of the surface deformations. The article describes UEnC experiment, the theory and data analysis, and sample preparation. The presented examples include the investigation of the structural dynamics of condensed phase, surfaces, and nanocrystals, the melting dynamics of gold nanoparticles and direct observation of coherent optical phonons generation in nanofilms. The results of several internationally renowned research groups are included and cited.