One-step synthesis and optical properties of blue titanium suboxide nanoparticles

Spherical titanium suboxide nanoparticles (Ti5O9, Ti9O17, TiO) are synthesized by arc plasma. A mixture of Ar, H2 and H2O at 10 mbar pressure is used as the working gas. The variations of the proportion of H2O in the mixture gas during the synthesis induce a clear change in the size, color, composition, and optical properties of these nanoparticles. A reduction of H2O partial pressure reduces the grain size of the product. The titanium suboxide nanoparticles (Ti5O9, Ti9O17) show a blue luster. The UV-Vis-NIR absorption spectra present a substantial absorption in the range 400-800 nm. In particular, there is a uniform and stable absorption from 800 to 3000 nm. FT-IR spectra reveal the H2O partial pressure significantly affects the -OH groups content on the surface or in the bulk of the nanoparticles.