Synthesis of Coated Titanium Dioxide Nanoparticles Using a Multi-Element Diffusion Flame

Synthesis of coated titanium dioxide nanoparticles using a multi- element diffusion flame burner

M.A. Ismail1, N.K. Memon1, D.H. Anjum2, and S.H. Chumg1 1Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955- 690, Saudi Arabia; 2Advanced Nanofabrication Imaging and Charaterization, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955- 690, Saudi Arabia. e: [email protected]

Titanium dioxide (TiO2) nanoparticles coated with oxides were manufactured by flame synthesis using a multi-element diffusion flame burner (MEDB). The growth of silica-coated TiO2 (SiO2-TiO2) and carbon-coated TiO2 is demonstrated using a single-step process. Hydrogen (H2), oxygen (O2), and argon (Ar) are utilized to establish the flame, whereas titanium tetraisopropoxide (TTIP) is used as the precursor for TiO2. Hexamethyldisiloxane (HMDSO) was mixed with TTIP for the SiO2 coated case, whereas ferrocene or ethylene was mixed for the carbon-coated cases. The nanoparticles were characterized using high-resolution transmission electron microscopy (HRTEM) with energy filtered TEM for elemental mapping (of Si, C, O, and Ti), x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. A uniform coating of 3 to 5 nm of carbon was observed around the TiO2 particles. The carbon coating was amorphous when using ethylene as the carrier gas. This coating layer thickness increased when ferrocene was used. It was observed that ferrocene increases the reactivity of the carbon layer and the specific surface area. Additionally a decrease in the band gab of TiO2 with changes to the bond energies was noticed. A uniform coating of 5 to 8 nm of silicon dioxide was observed around TiO2 particles when HMDSO was mixed with the precursor. Coating occurs only on crystalline nanoparticles, suggesting a possible growth mechanism of silica-coated and carbon-coated TiO2 nanoparticles. The change in the band gab of the TiO2 nanoparticles, as a result of the coating, could enhance its electrical and photocatalytic properties.