1) Titania nanopowder was prepared using a sol-gel method with titanium butoxide and nitric acid as precursors and urea as a dopant to decrease the band gap, allowing for visible light absorption. 2) Characterization with XRD, FTIR, UV-Vis, and SEM showed the powders were nanocrystalline with a band gap below 2.5 eV. 3) In photocatalytic tests, the powders significantly degraded xylenes and ethylbenzene (70% and 60% respectively) under visible light, but degraded toluene to a lesser extent (7.44%), demonstrating their photocatalytic activity.

1. Doped titania nanopowders with photocatalytic and antimicrobial
properties under visible light irradiation
D. S. Tsoukleris1, C. Psarras1, M. Loizidou2, E. Α. Pavlatou1, G. Chousos3, P.
Panagopoulos3, Ch. Vasilakos3, Th. Maggos3
1
.General Chemistry Laboratory, School of Chemical Engineering, National Technical
University of Athens
2
Unit of Environmental Science and Technology, School of Chemical Engineering,
National Technical University of Athens
9 Heroon Polytechniou Str., Zografos Campus, Athens GR-15780, Greece
3
Environmental Research Laboratory, INRASTES, NCSR “Demokritos”, Ag. Parskevi,
Athens, Greece
One of the most prevalent synthetic routes for the production of doped
nanostructured titania has become the so called sol-gel process, widely known as
hydrolysis-condensation (SOLution-GELation) which falls into the broad class of wet
chemistry methods. In this work emphasis has been given to the study of this specific
synthesis route, since it has become the most frequently applied synthetic method providing
various advantages.
In this study, titania nanopowder was prepared by sol–gel method using titanium
butoxide (TBOT) and distilled water/ HNO3 as titanium precursor and hydrolyzing agent,
respectively. An alcoholic solutions were added and the solution was stirred under vigorous
stirring. Then, added the dopant urea and stirred overnight. The prepared sol-gel solution
deposited onto glass spherules with spray pyrolysis method and calcinated to 450o
C in order
to be produced the final TiO2 thin film. X-ray diffraction patterns (XRD) of the calcinated
powders were obtained with a Siemens D5000 X-ray diffractometer in the diffraction angle
range 2θ = 20o
-80o
using Cu Kα radiation. FT-Infrared spectra were obtained on a Jasco
4200 spectrophotometer and the spectra were recorded for a wave number range from 700 to
5000 cm-1
with a resolution of 8 cm-1
by using the ATR method. Diffuse reflectance UV-
Vis spectra from 200nm to 700nm with slit width of a few nm was collected on a Hitachi
3010 spectrophotometer. Moreover, morphology and particle size were studied by using
electron microscopy (SEM).
In order to enhance the efficiency of TiO2 under visible irradiation, the produced
nanomaterial was modified with non-metal dopants aimed to decrease the band gap that
facilitates visible light absorption. In terms of the use of TiO2 in semiconductors, band gap
was arguably one of the most important properties. In general, the band gap of the TiO2
nano-particles is from 3.0 to 3.2eV whereas in this study the band-gap was estimated to be
below 2.5 eV by the reflectance UV-Vis spectra. The XRD data demonstrate that all
powders could be characterized as nanocrystalline as well as the FEG-SEM results (Fig. 1).
The photocatalytic efficiency of the material was evaluated in a photoreactor by the
photo-degradation of benzene, toluene and o-, m-, p-, xylenes and ethylbenzene (BTEX).
0.03 m2
of the powder (spherules) were placed inside a pyrex (permitting radiation pass
when wavelength is over 320 nm) glass tube (50 cm in length and 1.5 cm in diameter),
which in turn was incorporated in the central axis of the photoreactor. A known
concentration of VOCs (approx. 20 ppb/v) with 0.2m3
/h flow rate passed from the glass
tube, while the 4 Vis-lamps were irradiating the system. The analysis of VOCs
concentration was conducted by an automated GC-PID (955 Syntec Spectras) providing

2. VOCs concentrations every 15 minutes interval. Preliminary results shown significant
degradation of xylenes and ethyl-benzene (70% and 60% respectively) while the
corresponding value for toluene was quite lower (7.44%).Accordingly the photocatalytic
rate (μg/m2
s) was calculated 0.03, 0.01 and 0.002 for xylene and ethyl-benzene and toluene
respectively.
Figure 1. SEM image of synthesized TiO2 nano-powders