Issue 9, 2017

Ultraviolet photo-oxidation of polyvinylpyrrolidone (PVP) coatings on gold nanoparticles

Abstract

Polymeric coatings are commonly applied to impart functionality and colloidal stability to engineered nanoparticles. In natural environments, transformations of the coating can modify the particle transport behavior, but the mechanisms and outcomes of these transformations have not yet been thoroughly evaluated. This study investigates the photo-transformations of polyvinylpyrrolidone (PVP) coatings on gold nanoparticles (AuNPs) under ultraviolet (UV) irradiation, representing light exposure in surface waters or other sunlit environments, and the impact on the AuNP colloidal stability. Multiple orthogonal characterization methods were applied to interrogate UV-induced transformations and their consequences. Rapid oxidation of the PVP coating occurred upon UV exposure. The transformed PVP largely persisted on the AuNP surface, albeit in a collapsed polymer layer around the AuNP surface. This transformation resulted in drastically diminished colloidal stability of the AuNPs, consistent with loss of steric stabilization. While the residual coating modified the interaction of the AuNPs with calcium counterions, it did not prevent subsequent stabilization by humic acid. This study demonstrates the importance of both chemical and physical coating transformations on nanoparticles, and hence the need for orthogonal and complementary characterization methods to fully characterize the coating transformations. Finally, the specific transformations of the PVP-coated AuNPs investigated here are discussed more broadly with respect to generalizability to other polymer-coated NPs and the implications for their fate in sunlit or other reactive environments.

Graphical abstract: Ultraviolet photo-oxidation of polyvinylpyrrolidone (PVP) coatings on gold nanoparticles

Supplementary files

Article information

Article type
Paper
Submitted
10 May 2017
Accepted
28 Jul 2017
First published
28 Jul 2017

Environ. Sci.: Nano, 2017,4, 1866-1875

Ultraviolet photo-oxidation of polyvinylpyrrolidone (PVP) coatings on gold nanoparticles

S. M. Louie, J. M. Gorham, J. Tan and V. A. Hackley, Environ. Sci.: Nano, 2017, 4, 1866 DOI: 10.1039/C7EN00411G

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