Argonne National Laboratory Center for Nanoscale Materials U.S. Department of Energy

High-pressure-induced tuning of the collective properties of supercrystals self-assembled from nanoparticles

SEM of 3d supercrystals

High-resolution SEM images of faceted three-dimensional supercrystals self-assembled from colloidal 7.0 nm spherical PbS nanocrystals (inset, scale bar 30 nm).

Precise ordering in two- and three-dimensional superlattices formed by the self-assembly of individual nanocrystals allows for the control of magnetic, optical, and electronic coupling that can lead to reversible metal-to-insulator transitions, enhanced conductivity, spin-dependent electron transport, enhanced ferro- and ferrimagnetism, tunable magnetotransport, and efficient charge transport. Precise positioning of the nanocrystals within a three-dimensional superlattice leads to the term “supercrystals” in analogy to crystals built by atoms. However, unlike the atomic crystals, supercrystals offer a much greater degree of flexibility in tuning interparticle distances.

A research team from Argonne (CNM NanoBio Interfaces and Nanophotonics Groups; and APS Sector 12) and the University of Chicago (GSECARS, Sector 13, APS) have reported for the first time combined quasi-hydrostatic high-pressure small-angle X-ray scattering (SAXS) and micro X-ray diffraction (XRD) studies on individual faceted, three-dimensional supercrystals self-assembled from colloidal 7.0-nm PbS nanocrystals. The combination of these two techniques allows for precise determination of the interparticle spacing during pressure cycling. Diamond anvil cell SAXS experiments in the pressure range from ambient to 12.5 GPa revealed nearly perfect structural stability of the supercrystals. XRD experiments demonstrated strong preferential orientation of individual nanocrystals in supercrystals up to ~55 GPa that is preserved during pressure cycling.

P. Podsiadlo et al., “High-pressure structural stability and elasticity of supercrystals self-assembled from nanocrystals.” NanoLetters, B, 579-588 (2011). (DOI:  10.1021/nl103587u)

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April 2011

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