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Science. 2019 Jun 21;364(6446):1174-1178. doi: 10.1126/science.aaw8237.

Particle analogs of electrons in colloidal crystals.

Girard M#1,2,3, Wang S#3,4, Du JS#1,3, Das A#3,4, Huang Z1,3, Dravid VP1,3, Lee B5, Mirkin CA6,3,4, Olvera de la Cruz M6,2,3,4.

Author information

1
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA.
2
Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA.
3
International Institute for Nanotechnology, Northwestern University, Evanston, IL 60208, USA.
4
Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
5
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA.
6
Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208, USA. m-olvera@northwestern.edu chadnano@northwestern.edu.
#
Contributed equally

Abstract

A versatile method for the design of colloidal crystals involves the use of DNA as a particle-directing ligand. With such systems, DNA-nanoparticle conjugates are considered programmable atom equivalents (PAEs), and design rules have been devised to engineer crystallization outcomes. This work shows that when reduced in size and DNA grafting density, PAEs behave as electron equivalents (EEs), roaming through and stabilizing the lattices defined by larger PAEs, as electrons do in metals in the classical picture. This discovery defines a new property of colloidal crystals-metallicity-that is characterized by the extent of EE delocalization and diffusion. As the number of strands increases or the temperature decreases, the EEs localize, which is structurally reminiscent of a metal-insulator transition. Colloidal crystal metallicity, therefore, provides new routes to metallic, intermetallic, and compound phases.

PMID:
31221857
DOI:
10.1126/science.aaw8237

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