Synthesis of coated titanium dioxide nanoparticles using a multielement 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: mohamed.ismail@kaust.edu.sa
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.