Title

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

Publication Date

11-27-2020

Department

Chemical and Biological Engineering; Materials Science and Engineering; Neuroscience; Ames Laboratory; Physics and Astronomy

Campus Units

Ames Laboratory, Chemical and Biological Engineering, Materials Science and Engineering, Physics and Astronomy, Neuroscience

OSTI ID+

1735334

Report Number

IS-J 10367

DOI

10.1016/j.jcis.2020.11.080

Journal Title

Journal of Colloid and Interface Science

Volume Number

585

First Page

312

Last Page

319

Abstract

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 find 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.

DOE Contract Number(s)

AC02-07CH11358

Language

en

Publisher

Iowa State University Digital Repository, Ames IA (United States)

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