Effect of annealing on the phase transition and morphology of Ag NPs on/in TiO2 rods synthesized by a polyol method

In this study, we report the effect of annealing (250–700 oC) on the phase transition and morphology of silver (Ag) nanoparticles (NPs) on/in titanium dioxide (TiO2) rods prepared using a polyol method. The annealed samples showed not only morphological change, i.e., a solid-to-liquid (melting) transition of Ag NPs due to its partial dissolution into the TiO2 rods, but also early stage anatase crystallization and anatase–rutile transformation of TiO2 rods under low annealing temperatures. Such findings, together with XRD and FE-SEM analyses, confirm that, upon higher annealing treatment, diffusion and coalescence leads to changes in the size and shape of the metal particles not only in the outermost regions, but also a random distribution and progressive growth of Ag clusters in the inner interface region. Here, it was shown that annealing can induce changes in morphology, as well as the chemical state and structure of Ag–TiO2. The present polyol-synthesized Ag–TiO2 composite also showed improved thermal stability.