Highly Quasi-Monodisperse Ag Nanoparticles on Titania Nanotubes by Impregnative Aqueous Ion Exchange

Silver nanoparticles were homogenously dispersed on titania nanotubes (NT), which were prepared by alkali hydrothermal methodology and dried at 373 K. Ag+ incorporation was done by impregnative ion exchange of aqueous silver nitrate onto NT. First, Ag+ ions incorporate into the layers of nanotube walls, and then, upon heat treatment tinder N-2 at 573 and 673 K, they migrate and change into Ag2O and Ag-0 nanoparticles. respectively. In both cases, Ag nanoparticles are highly dispersed, decorating the nanotubes in a polka-dot pattern. The Ag particle size distribution is very narrow, being ca. 4 +/- 2 nm Without any observable agglomeration. The reduction of Ag2O into Ag-0 octahedral nanoparticles occurs spontaneously and topotactically when annealing, without the aid of any reducing agent. The population of Ag-0 nanoparticles can be controlled by adjusting the annealing temperature. An electron charge transfer from NT support to Ag-0 nanoparticles, because of a strong interaction, is responsible for considerable visible light absorption in Ag-0 nanoparticles supported on NT.