Article

On the Sol-gel Synthesis and Characterization of Titanium Oxide Nanoparticles

ABSTRACT TiO2 nanoparticles have been prepared by sol-gel process using titanium isopropoxide as a
precursor with ethanol and water as solvents. The synthesis involves gel formation, digestion for
24h, drying at 100oC for 10h, and calcination in air at 500-800oC for 2h. The resulting powder
has been studied with respect to phase(s), morphology, optical absorption and photo -
luminescence (PL) behaviour. The calcination of dried sol-gel product at 500oC for 2h leads to
formation of anatase phase that possesses a tetragonal structure (a = 3.785 Å, c = 9.514 Å, Z =
4), average crystallite size ~ 11 nm and band gap of 3.34 eV. Further, increasing the time (t) of
calcination causes crystallite growth that follows the relation d = α – β exp (-t/τ), α = 18.1 nm, β
= 9.6 nm and τ = 6.9h. However, calcination of sol-gel product at 800oC for 2h gives rise to a
rutile phase (tetragonal a = 4.593Å, c = 2.959Å, Z = 2), average crystallite size ~ 25 nm and band
gap of 3.02 eV. The anatase phase exhibits strong PL emission peaks (excitation wavelength 405
nm) at 2.06 and 1.99 eV due to defect levels within the energy band gap. This observation has
been attributed to finite size effects occurring in nanoparticles.

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