Tereza Košutová, Lukáš Horák, Jan Hanuš, Ondřej Kylián, Hana Libenská, Zdeněk Krtouš, Amir Mohammad Ahadi, Jaroslav Kousal, Miroslav Cieslar, Milan Dopita, Charles University, Prague, Czech Republic
In presented work we investigated homogeneous silver nanoparticles and silver nanoparticles wrapped in titanium oxide shells, so called core-shell nanoparticles. The silver cores could extend the active region to visible light for photocatalytic properties of TiO₂. Therefore these core-shell nanoparticle films are attractive for optical applications.
Studied nanoparticles were prepared by gas aggregation cluster sources combined with magnetron sputtering of single metallic targets in different configurations. This physical preparation method is environmentally friendly, scalable to industry demands, provides high cleanness of the process and tunability of nanoparticles structure. The core-shell nanoparticles with varied thickness of TiOx shell were prepared by in-flight coating of primarily formed silver cores.
This study focuses on the thermal stability of described nanoparticles. The evolution of morphology, chemical and phase composition, size distribution and microstructure, of Ag and Ag@TiOx nanoparticles during the annealing was determined by combination of in-situ x-ray scattering methods (XRD, SAXS), ex-situ transmission and scanning electron microscopies, and x-ray photoelectron spectroscopy. Optical properties were investigated by UV-Vis spectroscopy. The measurements showed that Ag nanoparticles are not very thermally stable in the air atmosphere, their coalesce starts around 100 °C. Contrary, the titanium oxide shell formed around nanoparticles acts as a protection against sintering.