Synthesis, characterization, and phase stability of ultrafine TiO₂ nanoparticles by pulsed laser ablation in liquid media

We synthesized ultrafine TiO₂ nanoparticles by pulsed laser ablation of a titanium target immersed in an aqueous solution of surfactant sodium dodecyl sulfate (SDS) or deionized water. The surfactant concentration dependence of TiO₂ nanocrystal formation was systematically investigated by various characterization techniques. The maximum amount of ultrafine anatase nanocrystalline particles (with mean size of 3 nm in diameter) was obtained in an aqueous solution of 0.01 M SDS. A probable formation process was proposed based on the laser-induced reactive quenching and surfactant-mediated growth. The phase transformation and particle growth of as-prepared products were also investigated by heat treatment up to 500 °C. Single-phase anatase nanoparticles with a mean size of 8 nm were obtained by heat treatment of samples prepared in water or in a 0.01 M SDS solution. Particle size did not substantially increase through annealing, probably due to the relatively homogeneous size distribution and crystallinity of as-prepared titania nanoparticles.