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Title: Poly(N-isopropylacrylamide)-grafted gold nanoparticles at the vapor/water interface

Journal Article · · Journal of Colloid and Interface Science
 [1];  [2];  [1];  [2];  [3];  [2]
  1. Ames Lab., Ames, IA (United States)
  2. Ames Lab., Ames, IA (United States); Iowa State Univ., Ames, IA (United States)
  3. Iowa State Univ., Ames, IA (United States)

Hypothesis: Grafting nanoparticles surfaces with water-soluble polymers modify interparticle interactions that are pivotal for assembling them into ordered phases. By manipulating salt concentrations of gold nanoparticles (AuNPs) that are grafted with poly(N-isopropylacrylamide) (PNIPAM-AuNPs), we hypothesize that various aggregated phases form at the suspension/vapor interface or in the bulk that depend on the molecular weight (MW) of PNIPAM and on salt concentrations. Experiments: AuNPs are grafted with thiolated PNIPAM of molecular weights of 3 or 6 kDa, and grafting is confirmed by dynamic light scattering. Liquid-surfaces X-ray reflectivity and grazing incidence small-angle X-ray scattering are used to determine the density profiles of the suspension/vapor interface and their inplane structure as salt is added to the suspensions. Findings: We observe that surface enrichment is induced by adding NaCl to the suspensions, and that at low salt concentrations, the monoparticle layer formed is dispersed, and above a threshold salt concentration, depending on MW of PNIPAM, the PNIPAM-AuNPs order in a hexagonal structure. We show that the lattice constant of the two-dimensional hexagonal structure varies with salt concentration, and more significantly with MW of PNIPAM.

Research Organization:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division; USDOE
Grant/Contract Number:
AC02-07CH11358
OSTI ID:
1735334
Alternate ID(s):
OSTI ID: 1775885
Report Number(s):
IS-J-10,367
Journal Information:
Journal of Colloid and Interface Science, Vol. 585; ISSN 0021-9797
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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