@article{63b2f4ee829b486dbb81f1b8162abff4,
title = "Density-Gradient Control over Nanoparticle Supercrystal Formation",
abstract = "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.",
keywords = "DNA, assembly, colloidal crystals, density barrier, nanoparticle, uniform crystals",
author = "Taegon Oh and Ku, {Jessie C.} and Lee, {Jae Hyeok} and Hersam, {Mark C.} and Mirkin, {Chad A.}",
note = "Funding Information: This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550-17-1-0348. This work made use of the MatCI Facility, which receives support from the MRSEC Program (NSF DMR-1720139) of the Materials Research Center at Northwestern University, and the EPIC facility of Northwestern University's NUANCE Center, which receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR-1121262) at the Materials Research Center, the International Institute for Nanotechnology (IIN), and the State of Illinois, through the IIN. Use of the Dupont-Northwestern-Dow Collaborative Access Team beamline at the Advanced Photon Source (APS) in Argonne National Laboratory was supported by the U.S. Department of Energy (DE-AC02-06CH11357). T.O. acknowledges support from Kwanjeong Fellowship. J.C.K. acknowledges the Department of Defense for a National Defense Science and Engineering Graduate Fellowship. J.-H.L. and M.C.H. acknowledge the Northwestern University Materials Research Science and Engineering Center (NSF DMR-1121262). Funding Information: *E-mail: chadnano@northwestern.edu. Phone: 847-467-7302. ORCID Taegon Oh: 0000-0003-1981-7742 Mark C. Hersam: 0000-0003-4120-1426 Chad A. Mirkin: 0000-0002-6634-7627 Author Contributions T.O. and J.C.K. conceived the method. T.O., J.C.K., and J.-H.L screened suitable materials for the density layers. T.O. and J.C.K. designed and performed experiments. All authors wrote the manuscript. Funding This material is based upon work supported by the Air Force Office of Scientific Research under Award Number FA9550- 17-1-0348. This work made use of the MatCI Facility, which receives support from the MRSEC Program (NSF DMR-1720139) of the Materials Research Center at Northwestern University, and the EPIC facility of Northwestern University{\textquoteright}s NUANCE Center, which receives support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205), the MRSEC program (NSF DMR-1121262) at the Materials Research Center, the International Institute for Nanotechnology (IIN), and the State of Illinois, through the IIN. Use of the Dupont−Northwestern−Dow Collaborative Access Team beamline at the Advanced Photon Source (APS) in Argonne National Laboratory was supported by the U.S. Department of Energy (DE-AC02−06CH11357). T.O. acknowledges support from Kwanjeong Fellowship. J.C.K. acknowledges the Department of Defense for a National Defense Science and Engineering Graduate Fellowship. J.-H.L. and M.C.H. acknowledge the Northwestern University Materials Research Science and Engineering Center (NSF DMR-1121262). Notes The authors declare no competing financial interest. Publisher Copyright: {\textcopyright} 2018 American Chemical Society.",
year = "2018",
month = sep,
day = "12",
doi = "10.1021/acs.nanolett.8b02910",
language = "English (US)",
volume = "18",
pages = "6022--6029",
journal = "Nano Letters",
issn = "1530-6984",
publisher = "American Chemical Society",
number = "9",
}