Density-Gradient Control over Nanoparticle Supercrystal Formation

Taegon Oh, Jessie C. Ku, Jae Hyeok Lee, Mark C. Hersam, Chad A. Mirkin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


With the advent of DNA-directed methods to form "single crystal" nanoparticle superlattices, new opportunities for studying the properties of such structures across many length scales now exist. These structure-property relationships rely on the ability of one to deliberately use DNA to control crystal symmetry, lattice parameter, and microscale crystal habit. Although DNA-programmed colloidal crystals consistently form thermodynamically favored crystal habits with a well-defined symmetry and lattice parameter based upon well-established design rules, the sizes of such crystals often vary substantially. For many applications, especially those pertaining to optics, each crystal can represent a single device, and therefore size variability can significantly reduce their scope of use. Consequently, we developed a new method based upon the density difference between two layers of solvents to control nanoparticle superlattice formation and growth. In a top aqueous layer, the assembling particles form a less viscous and less dense state, but once the particles assemble into well-defined rhombic dodecahedral superlattices of a critical size, they sediment into a higher density and higher viscosity sublayer that does not contain particles (aqueous polysaccharide), thereby arresting growth. As a proof-of-concept, this method was used to prepare a uniform batch of Au nanoparticle (20.0 ± 1.6 nm in diameter) superlattices in the form of 0.95 ± 0.20 μm edge length rhombic dodecahedra with body-centered cubic crystal symmetries and a 49 nm lattice parameter (cf. 1.04 ± 0.38 μm without the sublayer). This approach to controlling and arresting superlattice growth yields structures with a 3-fold enhancement in the polydispersity index.

Original languageEnglish (US)
Pages (from-to)6022-6029
Number of pages8
JournalNano letters
Issue number9
StatePublished - Sep 12 2018


  • DNA
  • assembly
  • colloidal crystals
  • density barrier
  • nanoparticle
  • uniform crystals

ASJC Scopus subject areas

  • Bioengineering
  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


Dive into the research topics of 'Density-Gradient Control over Nanoparticle Supercrystal Formation'. Together they form a unique fingerprint.

Cite this