Nonstoichiometric Titanium Oxides via Pulsed Laser Ablation in Water

Titanium oxide compounds TiO,Ti2O3, and TiO2 with a considerable extent of nonstoichiometry were fabricated by pulsed laser ablation in water and characterized by X-ray/electron diffraction, X-ray photoelectron spectroscopy and electron energy loss spectroscopy. The titanium oxides were found to occur as nanoparticle aggregates with a predominant 3+ charge and amorphous microtubes when fabricated under an average power density of ca. 1 × 108W/cm2 and 1011W/cm2, respectively followed by dwelling in water. The crystalline colloidal particles have a relatively high content of Ti2+ and hence a lower minimum band gap of 3.4 eV in comparison with 5.2 eV for the amorphous state. The protonation on both crystalline and amorphous phase caused defects, mainly titanium rather than oxygen vacancies and charge and/or volume-compensating defects. The hydrophilic nature and presumably varied extent of undercoordination at the free surface of the amorphous lamellae accounts for their rolling as tubes at water/air and water/glass interfaces. The nonstoichiometric titania thus fabricated have potential optoelectronic and catalytic applications in UV-visible range and shed light on the Ti charge and phase behavior of titania-water binary in natural shock occurrence.