Synthesis of TiO 2 nanoparticles containing Fe, Si, and V using multiple diffusion flames and catalytic oxidation capability of carbon-coated nanoparticles

Titanium dioxide (TiO 2 ) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C–TiO 2 ), carbon-coated with iron oxide (Fe/C–TiO 2 ), silica-coated (Si–TiO 2 ), and vanadium-doped (V–TiO 2 ) TiO 2 nanoparticles is demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flame, with titanium tetraisopropoxide (TTIP) as the precursor for TiO 2 . For the growth of Fe/C–TiO 2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si–TiO 2 and V–TiO 2 , TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy-filtered TEM for elemental mapping (of Si, C, O, and Ti), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C–TiO 2 , Fe/C–TiO 2 , and Si–TiO 2 nanoparticles, whereas rutile is the dominant phase for the V–TiO 2 nanoparticles. For C–TiO 2 and Fe/C–TiO 2 , the nanoparticles are coated with about 3-5-nm thickness of carbon. The iron-based TiO 2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470 °C (with iron) compared to 610 °C (without iron). Enhanced catalytic oxidation properties are also observed for model soot particles, Printex-U, when mixed with Fe/C-TiO 2 . With regards to Si–TiO 2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO 2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V–TiO 2 , vanadium is doped within the TiO 2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of V 4+ and V 5+ oxidation states.