Multiphase TixOy nanoparticles by pulsed laser ablation of titanium in supercritical CO2

In this paper, we demonstrate pulsed laser ablation (PLA) in supercritical CO2 (scCO(2)) as a promising method to synthesize multiphase TixOy nanoparticles from a titanium target. These results are compared against PLA of titanium in H2O. By means of transmission electron microscopy, we observed spherical-shaped, well-dispersed non-agglomerate crystalline nanoparticles by PLA in scCO(2) while PLA in H2O produced spherical-shaped as well as randomly shaped nanoparticles that joined to form web-like networks. Raman spectroscopy and x-ray diffraction showed nanoparticles synthesized in scCO(2) consisted of anatase-TiO2, Ti2O3 and TiO0.89 while nano particles synthesized in H2O were mainly rutile-TiO2, with possibility of presence of brookite-TiO2. This indicates PLA in scCO(2) favours formation of metastable phases (anatase-TiO2, Ti2O3 and TiO0.89) while PLA in H2O results in mostly stable phase (rutile-TiO2).