In this study, ultrasonic spray pyrolysis combined with salt-assisted decomposition, a process that adds sodium nitrate (NaNO₃) into a titanium precursor solution, is used to synthesize nanosized titanium dioxide (TiO₂) particles. The added NaNO₃ prevents the agglomeration of the primary nanoparticles in the pyrolysis process. The nanoparticles are obtained after a washing process, removing NaNO₃ and NaF from the secondary particles, which consist of the salts and TiO₂ nanoparticles. The effects of pyrolysis temperature on the size, crystallographic characteristics, and bandgap energy of the synthesized nanoparticles are systematically investigated. The synthesized TiO₂ nanoparticles have a size of approximately 2–10 nm a bandgap energy of 3.1–3.25 eV, depending on the synthetic temperature. These differences in properties affect the photocatalytic activities of the synthesized TiO₂ nanoparticles.

Current synthesis processes for titanium dioxide (TiO₂) nanoparticles require expensive precursors or templates as well as complex steps and long reaction times. In addition, these processes produce highly agglomerated nanoparticles. In this study, we demonstrate a simple and continuous approach to synthesize TiO₂ nanoparticles by a salt-assisted ultrasonic spray pyrolysis method. We also investigate the effect of salt content in a precursor solution on the morphology and size of synthesized products. The synthesized TiO₂ nanoparticles are systematically characterized by X-ray diffraction, transmission electron micrograph, and UV-Vis spectroscopy. These nanoparticles appear to have a single anatase phase and a uniform particle-size distribution with an average particle size of approximately 10 nm. By extrapolating the plots of the transformed Kubelka-Munk function versus the absorbed light energy, we determine that the energy band gap of the synthesized TiO₂ nanoparticles is 3.25 eV.

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• Effect of Pyrolysis temperature on TiO₂ Nanoparticles Synthesized by a Salt-assisted Ultrasonic Spray Pyrolysis Process
  Jae-Hyun Yoo, Myeong-Jun Ji, Woo-Young Park, Young-In Lee
  Journal of Korean Powder Metallurgy Institute.2019; 26(3): 237.     CrossRef