Abstract
The crucial roles of the ionization state and counterion presence on the phase behavior of fatty acid in aqueous solutions are well-established. However, the effects of counterions on the adsorption and morphological state of fatty acid on nanoparticle surfaces are largely unknown. This knowledge gap exists due to the high complexity of the interactions between nanoparticles, counterions, and fatty acid molecules in aqueous solution. In this study, we use adsorption isotherms, small angle neutron scattering, and all-atom molecular dynamic simulations to investigate the effect of addition of ethanolamine as a counterion on the adsorption and self-assembly of decanoic acid onto aminopropyl-modified silica nanoparticles. We show that the morphology of the fatty acid assemblies on silica nanoparticles changes from discrete surface patches to a continuous bilayer by increasing concentration of the counterion. This morphological behavior of fatty acid on the oppositely charged nanoparticle surface alters the interfacial activity of the fatty acid-nanoparticle complex and thus governs the stability of the foam formed by the mixture. Our study provides new insights into the structure-property relationship of fatty acid-nanoparticle complexes and outlines a framework to program the stability of foams formed by mixtures of nanoparticles and amphiphiles.
| Original language | English |
|---|---|
| Pages (from-to) | 3703-3712 |
| Number of pages | 10 |
| Journal | Langmuir |
| Volume | 36 |
| Issue number | 14 |
| DOIs | |
| State | Published - Apr 14 2020 |
Funding
The article is dedicated to the memory of Prof. Gerhard H. Findenegg (TU Berlin), who was a great scholar, scientist, and mentor. Authors thank Mr. Y. Guo for assistance with SEM imaging and Prof. Kerry Dooley for helping with nitrogen gas adsorption measurement. The research was supported by U.S. Department of Energy, Office of Science, Basic Energy Sciences, under EPSCoR grant no. DE-SC0012432 with additional support from the Louisiana Board of Regents. This research used resources at the High Flux Isotope Reactor, DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. Portions of this research were conducted with high-performance computing resources provided by Louisiana State University. Contributions to measurements and manuscript preparation by G. R. were supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division.