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Title: Macroscopic and tunable nanoparticle superlattices

In this paper, we describe a robust method to assemble nanoparticles into highly ordered superlattices by inducing aqueous phase separation of neutral capping polymers. Here we demonstrate the approach with thiolated polyethylene-glycol-functionalized gold nanoparticles (PEG-AuNPs) in the presence of salts (for example, K 2CO 3) in solutions that spontaneously migrate to the liquid–vapor interface to form a Gibbs monolayer. We show that by increasing salt concentration, PEG-AuNP monolayers transform from two-dimensional (2D) gas-like to liquid-like phase and eventually, beyond a threshold concentration, to a highly ordered hexagonal structure, as characterized by surface sensitive synchrotron X-ray reflectivity and grazing incidence X-ray diffraction. Furthermore, the method allows control of the inplane packing in the crystalline phase by varying the K 2CO 3 and PEG-AuNPs concentrations and the length of PEG. Using polymer-brush theory, we argue that the assembly and crystallization is driven by the need to reduce surface tension between PEG and the salt solution. Our approach of taking advantage of the phase separation of PEG in salt solutions is general (i.e., can be used with any nanoparticles) leads to high-quality macroscopic and tunable crystals. In conclusion, we discuss how the method can also be applied to the design of orderly 3Dmore » structures.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Materials Science and Engineering
  2. Ames Lab., Ames, IA (United States). Division of Materials Sciences and Engineering
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Chemical and Biological Engineering
  4. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
Publication Date:
Grant/Contract Number:
AC02-07CH11358; AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Nanoscale
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2040-3364
Publisher:
Royal Society of Chemistry
Research Org:
Ames Lab. and Iowa State Univ., Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; 36 MATERIALS SCIENCE
OSTI Identifier:
1362278