Publication Date

4-30-2021

Department

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

Campus Units

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

OSTI ID+

1787747

Report Number

IS-J 10498

DOI

10.1021/acs.jpcc.1c01354

Journal Title

Journal of Physical Chemistry C

Volume Number

125

Issue Number

18

First Page

10090

Last Page

10095

Abstract

We report on the assembly of gold nanoparticles grafted with poly(ethylene glycol) (PEG–AuNPs) in aqueous solutions into the face-centered cubic superlattice by synchrotron X-ray scattering. At sufficiently high salt concentrations, the lattice constant decreases with increasing temperature, i.e., it exhibits a negative thermal expansion (NTE) coefficient that is 2–4 orders (in magnitude) larger than previously reported in NTE materials. The generality of the effect is demonstrated with different salts and different PEG chain lengths. Theoretical calculations show that PEG–AuNP becomes more insoluble (with the Flory–Huggins parameter χ > (1/2)) as temperature increases through water dehydration, with a decrease in the volume of the superlattice and an increase in the entropy of the system. Implications on the formation of nanoparticle superlattices and NTE properties are also discussed.

DOE Contract Number(s)

AC02-07CH11358; AC02-06CH11357

Language

en

Publisher

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

IS-J 10498 SI.pdf (1174 kB)
Supporting Information

Available for download on Saturday, April 30, 2022

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