The presentation deals with the use of conduction of photocatalytic reaction using the transition metal doped transparent semiconducting thinfilms. The precursor to film is prepared by the SILAR method, which is a chemical method.

1. P R A V E E N N . V A I D Y A
D e p a r t m e n t o f P h y s i c s , S D M C o l l e g e o f E n g i n e e r i n g
a n d T e c h n o l o g y , D h a r w a d ( K a r n a t a k a ) .
B y
Study of Absorption properties of Photo catalytic Titanium
Oxide thin films prepared by SILAR method
(NITTTR) National Institute of Technical Teachers Training & Research,
Chandigarh, India (MHRD, Govt. of India)
2nd International Conference
Research Trends in Engineering, Applied Science and Management
(ICRTESM-20117)
P r e s e n t a t i o n o n
At

2. Photo catalysis
o What is photo catalysis?
o Photo catalytic materials: Compound semiconductors like, ZnO, Fe2O3, GaP,
TiO2, CdS, SiC etc.,
o Different forms of photo catalysts a) powder form
b) Thin film structures.
Working
 Photo catalyst can be placed in contact with the reactants (water, VOC’s, any
solid, liquid or air pollutants).
 UV light is focused on its surface.
 The decomposition of pollutants yield water, oxygen and/or hydrogen or CO2
as the end Products.
 The Redox (Oxidation and Reduction) reaction is responsible for the above
process are explained in the following the reactions.

3. Decomposition process of TiO2 photo
catalyst
Band
Gap
Valance band
(holes)
(+vely
charged)
Conduction band
(electrons)(-vely
charged)
Reduction: O2 +
e→O2
—
Oxidation:
H2O + h→ OH +
H+
EM
energy
(UV) =h√

4. h+ (VB) + H2O • OH + H+
TiO2 – Photo catalytic Reactions
TiO2+ hν (=Eg of TiO2) h+ (VB) + e - (CB)
Oxidation reaction
Reduction reaction
H2O2 + e- OH • + OH-
O2+ e- O• -
O2
• - + H+ HO2
•
HO •
2+ HO •
2 H2O2 + O 2
O2
• - + HO •
2 +H+ H2O2 + O2
H2O2 + hν 2 • OH
H2O2 + O2
• - • OH + OH - + O2
h+ (VB) + OH- • OH
R-X+ + OH R-OH+X+
R-X + h+ R-X+
R-OH + OH CO2 + H2O

5. TiO2 – Photo catalytic Reactions
 Removal of Organic Pollutant from Water by Heterogenous Photocatalysis: A Review , Wankhade Atul V.1, Gaikwad G.
S.3, Dhonde M.G.2*, Khaty N. T.2 and Thakare S.R.
Research Journal of Chemistry and Environment, Vol.17 (1) January (2013) Res.J.Chem.Environ.

6. The Maximization Photo catalytic activity is based on
the,
 Absorption of Electromagnetic radiations and Band gap of semiconductor.
 Rate of recombination of excited electrons and holes (Diffusion length of the
carriers).
 Surface property of semiconducting film
 Adsorption of reactants through the film.
 Hydrofilicity of the surface of film
 Intensity of incident electromagnetic radiation.
 Temperature of the pollutants
 Pre-adsorption of oxygen
 Yan, S.C.; Ouyang, S.X.; Gao, J.; Yang, M.; Feng, J.Y.; Fan, X.X.; Wan, L.J.; Li, Z.S.; Ye, J.H.; Zhou, Y.; et al. A room-
temperature reactive-template route to mesoporous ZnGa2O4 with improved photocatalytic activity in reduction of CO2.
Angew. Chem. Int. Ed. 2010, 122, 6544–6548.
 81. Chang, H.T.; Wu, N.M.; Zhu, F. A kinetic model for photo catalytic degradation of organic contaminants in a thin-film
TiO2 catalyst. Water Res. 2000, 34, 407–416.
The rate of decomposition of the pollutant is based on these factors
•Film thickness
•Grain size
•Surface roughness
•porosity

7. Features of good photo catalyst
 It should inert in nature.
 It should be non toxic and it should not liberate toxic
products in environment.
 It should be activated by the application light.
 It should be cost effective
 It should be user friendly – synthesis and fabricate.
One semiconducting material among number
of alternatives is TiO2.

8. Features of TiO2 semiconductor
 Band gap 3.2 eV. And activated in UV range of spectrum.
 Anatase form of crystal is most favorable for the photo
catalysis.
 On annealing above 600k it convert into rutile form
loosing its crystalline.
 Compared other semiconductors it has favorable features
to used as photo catalyst.
 Photo catalytic activity is enhanced by doping with
transition metal and hybridizing.

9. Successive Ionic Layer and adsorption(SILAR) Method.
The 0.1M Ti(III)Cl3:15%HCl solution was used as a cationic and 0.01M NaOH
solution was used as an anionic precursors.
consists of four steps:
 Adsorption of titanium species for 20 s,
 Rinsing with distilled water for 5 s to remove excess adsorbed or loosely
bounded titanium species,
 Reaction with NaOH precursor solution for 10 s to form stable TiO2, and
 Rinsing with purified water for 5 s to remove excess species or powdery TiO2.
The higher concentration of precursor solutions resulted in to a higher growth rate
but the quality of the film was poor due to powdery deposit.
The films are dried in Sunlight for two hours and annealed for two hours in a
temperature 200o .
Features
 Excellent material utilization efficiency,
 Good control over the deposition process along with the film thickness.
 Cost effective and user friendly
 Large-scale deposition capability on virtually any type of substrate
Synthesis of TIO2 film by

10. SCHEMATICS OF ‘SILAR’ METHOD TO
DEPOSITE TiO2:
•S.S. Kale, R.S. Mane, H. Chung, M.Y. Yoon, C.D. Lokhande, S.H. Han, Appl. Surf. Sci., 253 (2006) 421.
•H.M. Pathan, S.K. Min, J.D. Desai, K.D. Jung, O.S. Joo, Mater. Chem. Phys., 97 (2006) 5.
•S. Park, E. Dimasi, Y. Kim, W. Han, P.M. Woodward, T. Vogt, Thin Solid Films, 515 (2006) 1250.
Adsorption
time20sec
Rinsing
time05sec
Rinsing
time05
sec
Reaction
time05sec
0.1M TiCl3
+15% HCl
Distilled
water
0.01N
NaOH
solution
Distilled
water
Glass
substrate

11. Result and Discussion
250 275 300 325 350 375 400 425 450 475 500 525 550 575 600
0.01
0.02
0.03
0.04
0.05
Absorbance
Wavelength (nm)
300 325 350 375 400 425 450 475 500 525 550 575 600
0.05
0.10
0.15
0.20
absorbance
wavelength
16:28:48 (1033)
300 325 350 375 400 425 450 475 500 525 550 575 600
0.0
0.1
0.2
Absorbance
Wavelength
16:33:04 (1033)
• From figs 1,2 and 3 represents the absorption peaks
of films with 10, 20 and 30 coatings respectively.
• All the films show absorption peaks at 320nm
•It is shown that absorption intensity go on increases
with increasing the number of coatings.
Fig. 2
Fig. 1
Fig. 3

12. Bibliography
1. Research Journal of Chemistry and Environment , Vol.17 (1) January (2013) Res.J.Chem.Environ. (84) Review Paper: Removal of Organic
Pollutant from Water by Heterogenous Photocatalysis: A Review, Wankhade Atul V, Gaikwad G. S., Dhonde M.G., Khaty N. T. and Thakare S.R. .
Xi, S.V. Geisen, Water Res. 35 (2001) 1256
2. CdS-Based Semiconductor Photocatalysts for Hydrogen Production from Water Splitting under Solar LightSheng Huang, Yu Lin, Jian-Hua Yang, Ying Yu*
Nanotechnology for Sustainable Energy Chapter 9, pp 219–241
3. Romanian Journal of Information science and Technology, Volume 10, Number 3, 2007, 269{277).H. Hsien, C. Chang, Y. Chen, S. Cheng, Appl. Catal. B:
Environ., 31 (2001) 241).
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8. S. Yang, L. Gao, J. Am. Ceram. Soc. 88 (2005) 968.
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11. 12. MacKenzie, J.D. Sol-gel research – achievements since 1981 and prospects for the Future. J.
12. Sol-Gel Sci. Techn. 2003, 26, 23–27
13. Photocatalytic activity of nanometer TiO2 thin films prepared by the sol–gel method Jiaguo Yu et al.- Materials Chemistry and Physics 69 (2001)
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