Chemical and Biological Engineering, Materials Science and Engineering, Neuroscience, Ames Laboratory, Physics and Astronomy
Research Focus Area
Advanced and Nanostructured Materials
Journal or Book Title
Journal of Colloid and Interface Science
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.
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.
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.
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Minier, Samuel; Kim, Hyeong Jin; Zaugg, Jonathan; Mallapragada, Surya K.; Vaknin, David; and Wang, Wenjie, "Poly(N-isopropylacrylamide)-grafted gold nanoparticles at the vapor/water interface" (2021). Chemical and Biological Engineering Publications. 451.
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