Conference Paper

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

DOI: 10.1557/opl.2011.759 Conference: Materials Research Society symposia proceedings. Materials Research Society


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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Available from: Varun Chaudhary, Jan 14, 2015
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    ABSTRACT: In this study, anatase titanium dioxide nanoparticles were successfully prepared by a sol–gel method using two different precursors, titanium isopropoxide and titanium butoxide. Hydrochloric acid or nitric acid was added to adjust the pH of the solution. The sols obtained were dried at 80 °C and calcined at 450 °C for 3 h. The nanostructures were characterised by scanning electron microscopy, FTIR and ultraviolet–visible spectroscopy. The phase transformations were investigated by an X-ray diffractometer. Highly crystalline anatase titania nanoparticles could be obtained through the controlled hydrolysis reaction rate. The sizes of synthesized particles were in the range 5–13 nm, i.e. 9 nm on an average and with a regular shape. The size of nanoparticles was not affected by the choice of precursor. The broad view of the samples prepared using titanium isopropoxide showed film-like structures, whereas the samples prepared using titanium butoxide showed spherical granules. A red shift of 0.13 eV was observed in the band gap in the case of non-spherical particles compared to spherical ones.
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    ABSTRACT: Introducing defects into the intrinsic TiO2 structural framework with nitrogen enhanced the photocatalytic response towards the degradation of atrazine, as compared to undoped TiO2. Both catalysts, which were prepared in an analogous manner, demonstrated high crystallinity and anatase phase dominant with well defined {101} facets, which serves as a pioneer platform for good photocatalytic activity. The introduction of nitrogen increased the stability of the crystal structure which leads to the formation of pure active anatase phase. Although the optical response was shifted towards the visible region, initiated by the formation of new absorption defects and interstate energy levels, the chemical state of nitrogen in the doped TiO2 controls the overall catalyst photoreactivity. In this study, it was found that the surface area and degree of band gap reduction played a lesser role for photocatalysis enhancement, although they partly contributed, than the concentration of surface charge traps and the type of structural framework formed during nitrogen incorporation. The enhancement in the photocatalytic degradation of atrazine clearly was influenced by the loading and nature of the nitrogen dopant, which in turn, governed the types of chemical and optical properties of the final catalyst product.
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