Physico-Chemical nanomaterials science

Deposition and characterization of functional coatings based on PDPA/Ag nanostructured materials
Vyshnevska Yu.P.1, Brazhnyk I.V.2
1 National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute".
37K20, Peremohy Ave., Kyiv, 03056, Ukraine. 
E-mail: vishnevsk@ukr.net
2 Gimasi SA Ukraine R&D Centre
18, Via Luigi Lavizzari, Mendrisio, 6850, Switzerland.

Hybrid nanostructured materials with desired electrical, catalytic, magnetic and optical properties may be obtained via embedding inorganic nanoparticles into conducting polymeric matrices. From the fabrication perspective it is desired that such functionalization could be performed within a single step approach where the processes of polymerization and nanoparticles formation occur simultaneously. Establishing regularities of the nanoparticle formation processes in such systems is a key to efficient functionalization of the materials for wide range of applications.
The PDPA/Ag nanocomposite thin films have been prepared via in situ oxidative polymerization of diphenylamine monomers in presence of AgNO3 in 0.5M sulfuric acid in stationary conditions, as well as under cyclic polarization. Silver nanoparticles are found to be uniformly dispersed within polymeric matrices. The NPs are mostly spherically shaped with sizes in the range 25-40 nm, while some larger flakes and agglomerates may also be present.
The formation mechanism of such composite may include two cases. In the first case, diphenylamine monomers may be oxidized directly by Ag+ ions that triggers oxidative polymerization and leads to the formation of PDPA polymeric chain. At the same time, Ag+ ions will be reduced to a metallic state that will lead to the formation of silver nanoparticles.
In the second case, reduction of silver ions may occur on the surface of the nanoparticles while the electrons for the reaction may be provided via conducting polymeric matrices. High conductivity of PDPA doped with sulphate anions in this case will facilitate to the charge transfer toward a growing NPs seeds.
Optimization of the initial precursors concentration and the polarization regime while taking into account the nanocomposite formation mechanism allows one to control the resulted composite structure including polymer-monomer ratio and the NPs distribution.