Ion transfer reactions at Ag-nanoparticle/polymer interfaces
Final Report Abstract
In this project the mechanisms and kinetics of silver nanoparticle aging and ion release in polymer thin films have been investigated. Changes in the microstructure of the nanocomposite film upon immersion in water or buffer solutions were correlated with the kinetics of the silver ion release. The changes in the morphology are attributed to the expected dissolution of the silver nanoparticles after immersion in water and also to Ostwald ripening phenomena which led to particle coarsening. The Ostwald ripening process is in particular important if the nanoparticles are in electrochemical contact. It was demonstrated that a thin (several nm) polymer layer on top of the nanoparticles is sufficient to hinder the mobility of the nanoparticles on the polymer surface and their detachment into the ambient solution. PTFE thin coatings reduce the amount of the released Ag ions and the release rate due to the slow water diffusion through the polymer layer. Moreover, it was found that tailoring the thickness of the polymer barrier, allows tuning of the kinetics of the Ag ion release process. In case of alloy nanoparticles a negligible Au ion release is observed. The silver ion release is initially fast for all alloy nanocomposites but slows down in correlation to the gold fraction in the alloy and as the composition of the alloy nanoparticles becomes Au rich a saturation state is approached. However, no gold shell formation was observed even after prolonged silver ion release and the remaining silver is redistributed within the alloy nanoparticles. Samples coated by a HMDSO plasma polymer prepared with different amount of added oxygen allows to adjust the silver release without changing the barrier thickness. The different oxygen flow during the plasma polymerization process changes the composition of the formed films. With increasing oxygen flow they become more hydrophilic. In contrast, thin films obtained without oxygen flow have a polymeric chemical structure and are therefore highly hydrophobic making them exhibit high barrier properties for silver ion release. Measurements of water uptake of the films clearly confirmed the result that the water permeability of the HMDSO barrier was altered by the changed oxygen flow.
Publications
- “Combined in situ electrochemical impedance spectroscopy-UV/Vis and AFM studies of Ag nanoparticle stability in perfluorinated films,” Mater. Chem. Phys. 134(1) (2012) pp. 302–308
K. Yliniemi, B. Oezkaya, N. Alissawi, V. Zaporojtchenko, T. Strunskus, B. P. Wilson, F. Faupel, and G. Grundmeier
(See online at https://doi.org/10.1016/j.matchemphys.2012.02.069) - “Tuning of the ion release properties of silver nanoparticles buried under a hydrophobic polymer barrier,” J. Nanoparticle Res. 14(7) (2012) 928
N. Alissawi, V. Zaporojtchenko, T. Strunskus, T. Hrkac, I. Kocabas, B. Erkartal, V. S. K. Chakravadhanula, L. Kienle, G. Grundmeier, D. Garbe-Schoenberg, and F. Faupel
(See online at https://doi.org/10.1007/s11051-012-0928-z) - J. Nanoparticle Res. 15 (2013) 2080
N. Alissawi, T. Peter, T. Strunskus, C. Ebbert, G. Grundmeier and F. Faupel
- “Effect of gold alloying on stability of silver nanoparticles and control of silver ion release from vapor-deposited Ag-Au/polytetrafluoroethylene nanocomposites,” Gold Bull. 46(1) (2013) pp. 3–11
N. Alissawi, V. Zaporojtchenko, T. Strunskus, I. Kocabas, V. S. K. Chakravadhanula, L. Kienle, D. Garbe-Schoenberg, and F. Faupel
(See online at https://doi.org/10.1007/s13404-012-0073-6) - “Ion release from silver/polymer nanocomposites”, Dissertation, Kiel 2013
N. Alissawi
