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Nat Mater. 2014 Aug;13(8):807-11. doi: 10.1038/nmat3923. Epub 2014 Apr 6.

Hydrogen-bonded structure and mechanical chiral response of a silver nanoparticle superlattice.

Author information

1
School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA.
2
Department of Chemistry and School of Solar and Advanced Renewable Energy, University of Toledo, Toledo, Ohio 43606, USA.

Abstract

Self-assembled nanoparticle superlattices-materials made of inorganic cores capped by organic ligands, of varied structures, and held together by diverse binding motifs-exhibit size-dependent properties as well as tunable collective behaviour arising from couplings between their nanoscale constituents. Here, we report the single-crystal X-ray structure of a superlattice made in the high-yield synthesis of Na(4)Ag(44)(p-MBA)(30) nanoparticles, and find with large-scale quantum-mechanical simulations that its atomically precise structure and cohesion derive from hydrogen bonds between bundledp-MBA ligands. We also find that the superlattice's mechanical response to hydrostatic compression is characterized by a molecular-solid-like bulk modulus B(0) = 16.7 GPa, exhibiting anomalous pressure softening and a compression-induced transition to a soft-solid phase. Such a transition involves ligand flexure, which causes gear-like correlated chiral rotation of the nanoparticles. The interplay of compositional diversity, spatial packing efficiency, hydrogen-bond connectivity, and cooperative response in this system exemplifies the melding of the seemingly contrasting paradigms of emergent behaviour 'small is different' and 'more is different'.

PMID:
24705383
DOI:
10.1038/nmat3923

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