Ion release from silver / polymer nanocomposites
The tuning of silver ion release is very important for biomedical applications of silver nanocomposite materials to reduce the potential toxicity effects towards human cells and the environment. The present work is based on developing different metal/polymer nanocomposites using several physical vapor deposition (PVD) techniques. Since the properties of the nanoparticles strongly depend on their size, distribution and shape, the determination of their exact morphology is important in order to understand and control their physical properties. Thus, in this work the metal nanoparticles are deposited on the surface of the polymer films or buried under a polymer barrier instead of being embedded into the polymer matrix. The model system consists of ensembles of silver nanoparticles (AgNPs) on sputtered polytetrafluoroethylene (PTFE) thin films. Sputtered PTFE films are suitable to host the AgNPs due to the high crosslinking and since PTFE is a hydrophobic polymer so the quick depletion of the AgNPs could be avoided. Besides, PTFE is known for its high resistance to chemicals, transparency, good dielectric properties and biocompatibility. We examined the morphology, the composition and the optical properties of these nanocomposites using various analytical methods to characterize them and to study the potential of the silver ion release of the samples after immersion in water for several periods of time. Inductively coupled plasma mass spectroscopy (ICP-MS) is used to measure the concentration of silver ions in water. Changes in the microstructure and the optical properties of the nanocomposite films upon immersion in water allow demonstrating the kinetics of the silver ion release. Different approaches to tune the silver ion release process are studied and demonstrated in this work. Adjusting the release of silver ions through variation of the initial amount of silver nanoparticles, particle size control and through barrier thickness control is presented. Tuning the silver ion release by alloying with gold is also discussed. Furthermore, we study the release of silver ions from Ag/PTFE nanocomposites covered by thin films of plasma polymerized hexamethyldisiloxane (HMDSO) and we show how varying the oxygen flow during the plasma polymerization process can adjust the silver ion release potential of the nanocomposites due to changes in the properties of the formed plasma polymerized HMDSO thin films.
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