TiO2 reduction by laser ablation in N,N-dimethyl formamide solvent and their photothermal properties

Abstract

In this work, reduced Titania (TiO2−x) was obtained by laser ablation of commercial rutile TiO2 powder dispersed in N,N-dimethyl formamide (DMF) using a pulsed Nd:YAG (Neodymium-doped Yttrium Aluminium Garnet) laser (532 nm, 10 ns, 10 Hz). It was observed that DMF solvent was able to promote change in the optical band gap of commercial TiO2 (P25). The Ultraviolet–Visible (UV–vis) absorption measurement showed a shoulder in the infrared region with maximum at 690 nm, characteristic of reduced metal oxide. The electron paramagnetic resonance (EPR) measurements confirmed the presence of oxygen vacancies by the characteristic signal in g = 2.002 g and more intense than water-reduced oxide commonly obtained in other works. The X-ray diffraction (XRD) results show the same crystalline phase to P25 and small shifts due to presence of vacancy’s distorting the TiO2 structure. Scanning electron microscopy (SEM) image have shown surface coalesced particles in comparison to commercial P25, agreeing with nitrogen adsorption measurements which indicated a decrease in the surface area from 10.6 to 6.9 m2/g. The photothermal conversion properties was investigated and the reduced TiO2 samples showed higher temperatures when excited with a laser 785 nm wavelength in function of the strong absorption band and higher vacancy’s concentration.