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Zinc oxide (ZnO) nanoparticles containing oxygen vacancies were synthesized by the French process modified with pulsed injection of nitrogen. Zinc vapor was generated by evaporation of zinc foil and carried by a carrier gas to react with co-currently supplied air. During the reaction, nitrogen gas was injected in pulse, perpendicular to the flow direction of both zinc vapor and air. Low partial pressure of oxygen and turbulence caused by pulsed injection yielded uniform ZnO nanotetrapods that contained oxygen vacancies. The content of oxygen vacancies depended upon the characteristics of the pulse, i.e. flowing and non-flowing period of the gas, pulsing cycle time, and the supplied pressure of the injected gas. Strong correlation between the presence of oxygen vacancies and the intensity of green emission in the photoluminescence spectra of ZnO was also observed.

Titanium dioxide nanoparticles were prepared using solvothermal methods in 1,4-butanediol and toluene. Three different crystallite sizes (10 nm, 13 nm, and 17 nm) of titania as anatase crystals were produced and were then employed as catalysts in photocatalytic oxidation of ethylene in gas phase. As the crystallite size of titania increased, more Ti3+ surface defects were observed. The amounts of surface defects on titania were determined by temperature-programmed desorption using carbon dioxide as a probe molecule. Despite the smaller specific surface area, titania with larger crystallite size exhibited higher photocatalytic activity, which was attributed to more surface defects in the catalyst.