Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films
TiO₂ thin films were prepared by PECVD technique from vapors of Titanium-IV iso-propoxide mixed with oxygen at different temperatures. The films were deposited on substrates with system of special platinum electrodes and on glass substrates. Photoconductivity and capacitance at different humidit...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2006 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2006
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| Цитувати: | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films / A. Kolouch, M. Horáková, P. Hájková, E. Heyduková, P. Exnar, P. Spatenka // Вопросы атомной науки и техники. — 2006. — № 6. — С. 198-200. — Бібліогр.: 11 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859596679982874624 |
|---|---|
| author | Kolouch, A. Horáková, M. Hájková, P. Heyduková, E. Exnar, P. Spatenka, P. |
| author_facet | Kolouch, A. Horáková, M. Hájková, P. Heyduková, E. Exnar, P. Spatenka, P. |
| citation_txt | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films / A. Kolouch, M. Horáková, P. Hájková, E. Heyduková, P. Exnar, P. Spatenka // Вопросы атомной науки и техники. — 2006. — № 6. — С. 198-200. — Бібліогр.: 11 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | TiO₂ thin films were prepared by PECVD technique from vapors of Titanium-IV iso-propoxide mixed with oxygen
at different temperatures. The films were deposited on substrates with system of special platinum electrodes and on
glass substrates. Photoconductivity and capacitance at different humidity, photocatalytic activity and photo-induced
hydrophility under UV irradiation and surface morphology were evaluated on the films. The results revealed that the
photoconductivity is influenced by humidity and is connected to the photocatalytic activity.
|
| first_indexed | 2025-11-27T22:22:36Z |
| format | Article |
| fulltext |
198 Problems of Atomic Science and Technology. 2006, 6. Series: Plasma Physics (12), p. 198-200
RELATIONSHIP BETWEEN PHOTOCATALYTIC ACTIVITY,
HYDROPHILICITY AND PHOTOELECTRIC PROPERTIES
OF TiO2 THIN FILMS
A. Kolouch1, M. Horáková1, P. Hájková1, E. Heyduková2, P. Exnar1, P. patenka1,3
1Technical University of Liberec, Faculty of Mechanical Engineering,
Department of Material Science, Hálkova 6, 461 17 Liberec, Czech Republic;
2Technical University of Liberec, Faculty of Education,
Department of Chemistry, Hálkova 6, 461 17 Liberec, Czech Republic;
3University of South Bohemia, Pedagogical faculty,
Jeronýmova 10, 371 15 eské Bud jovice, Czech Republic
TiO2 thin films were prepared by PECVD technique from vapors of Titanium-IV iso-propoxide mixed with oxygen
at different temperatures. The films were deposited on substrates with system of special platinum electrodes and on
glass substrates. Photoconductivity and capacitance at different humidity, photocatalytic activity and photo-induced
hydrophility under UV irradiation and surface morphology were evaluated on the films. The results revealed that the
photoconductivity is influenced by humidity and is connected to the photocatalytic activity.
PACS: 68.47.Mm, 68.55.-a, 78.66.-w
INTRODUCTION
Titanium oxide thin films attract considerable attention of
many research teams due to their great variety of interesting
properties resulting in numerous applications such as optical
films, photoelectrochemical solar cell, photocatalyst, gas and
humidity sensors etc. Titanium dioxide has been considered
to be photoconductive material. It is one of the n-type
semiconductors potentially applicable to photochemical
electrodes for energy conversion from solar to other form
such as electricity [1,2,3]. Very interesting property is
photoinduced hydrophility. Wang et al. recently reported that
ultraviolet illumination of TiO2 surfaces could produce a
highly hydrophilic surface, which was denoted as
superhydrophilicity [4]. The originally less hydrophobic
TiO2 surface becomes highly hydrophilic (superhydrophilic)
by its bandgap excitation via UV light irradiation and
gradually reverts to originally less hydrophilic in the dark
[5]. Among different methods of film deposition the sol-gel
and plasma assisted deposition are the most frequently used.
Usual method how to test the photocatalytic activity is
decomposition of different organic compounds, but there
is no common standard developed for comparison of
photocatalytic activity [6]. Recently, a technique has been
proposed for quality comparison of the thin film
photocatalysts prepared by different methods, which uses
the photocurrent images [7]. The photoconductivity and
induced hydrophility is also crucial property for sensor
applications. Indeed, a correlation between
photoconductivity and photocatalytic activity had been
demonstrated in certain cases; in some films, however,
another author reported that an increase in
photoconductivity is not accompanied by an increase in
the contaminant degradation rate [8]. The aim of our
paper is characterization of electrical and photocatalytic
properties of thin films prepared by plasma enhanced
chemical vapor deposition.
EXPERIMENTAL
The depositions were performed in the capacitive
coupled homemade planar reactor. The bottom electrode
(12 cm in diameter) was connected to the RF power
generator with excitation frequency 13,56 MHz via the
matching unit and could be resistively heated up to
500°C. The temperature was measured by thermocouple
located on the inner side of the electrode and recalculated
on the upper side of the electrode according to calibration
curves. The electrode worked as substrate holder. The
single molecular precursor titanium (IV) iso-propoxide
(Ti[OCH(CH3)2]4, 97% purity, TTIP) was used as source
of titanium. The precursor was evaporated in the liquid
heated evaporator at temperature 50°C and the vapors
were transported through the showerhead upper electrode
into the chamber. The mixture of TTIP vapors and oxygen
was used as the working gas. The flow rate of TTIP
vapors and oxygen was independently controlled by a
needle valve and a mass flow controller, respectively. The
working pressure was held constant at 8 Pa using a
throttle valve controller. Based on other experiments we
used very low RF power about 2 W which results in
formation of a negative self bias as high as -50 V. The
depositions were carried out with respect to the substrate
temperature ranging between 20°C and 300°C, the
deposition time was 2 hours. The films were deposited on
glass and on special substrates with system of special
platinum electrodes (fig. 1.) on alumina plates. The
electrodes used for measurements of photoconductivity
and capacity were obtained from the Elceram company.
Fig. 1 Picture of special platinum electrode
The film photoconductivity and capacitance were
measured on the apparatus built on Technical University of
Liberec in dependence on ambient air humidity and
deposition temperature. AC signal of 10 MHz and 1 V in
the amplitude was used for our measurements. To eliminate
199
stray capacities, the apparatus was calibrated before
measurement of particular samples. The photocatalytic
activity was evaluated from decomposition speed of acid
orange II aqueous solution (podium salt of sulphonated azo
dye, AOII), exposed to UV. Irradiation was provided by a
fluoresced black light tube (Philips 60 cm, 20 W, 365 nm).
Photocatalytic efficiency was expressed by Photocatalytic
decomposition speed (r), calculated from the slope of AOII
concentration versus irradiation time curve in
semilogaritmic coordinates and was normalized to the
sample surface area, volume of the solution and UV
intensity. The hydrophility of the TiO2 thin films was
evaluated from the contact angle of water droplet. The
contact angle measurement was done by the home-made
arrangement consisting of table with the micro-feed and
CCD camera connected to the computer via a PCI card. For
each samples the contact angle was measured before UV
and after sample illumination by UV lights for 60 minutes.
To eliminate film inhomogenity the contact angle was
measured on five predefined position. The hydrophility of
the sample was characterized by the average value and
standard deviation calculated from these five values. The
film thickness was measured by the optical profiler
MicroProf® with CWL sensor from company FRT GmbH,
surface morphology was evaluated by AFM.
RESULTS AND DISCUSSION
The film thickness measured by optical profiler was
about 600 nm and was similar for all films. The surface
morphology investigated by AFM is shown on fig. 2. The
average grain size increased from about 100 nm to 250nm
with deposition temperature increased from 130°C to 280°C.
Fig.2. AFM pictures
The dependence of photocatalytic degradation speed
on the deposition temperature is shown on fig. 3. The
photocatalytic activity is low and very similar for all films
deposited at temperature up to 230°C. Rapid increase of
the photocatalytic activity has been observed for samples
deposited at temperature higher than 255°C. The
decomposition speed of AOII is approximately 4 times
higher at deposition temperature 255°C that at 230°C.
Photoinduced hydrophility (hydrophobic to
hydrophilic transition after UV irradiation) behaves very
similar as photocatalytic decomposition speed, see fig. 4.
The films deposited at temperature up to 200°C had all
similar initial contact angle about 80 degrees which didn’t
change after UV irradiation. Films deposited at
temperature 230°C and higher exhibited with lower initial
contact angle which decreases considerably after UV
irradiation. The transition between the hydrophobic and
hydrophilic properties of the TiO2 surfaces was attributed
to the formation and extinction of a surface hydroxyl
group.[9,10,11] UV irradiation caused reduction of Ti
ions from Ti4+ to Ti3+ and the production of oxygen
vacancies on TiO2 surfaces. Succeeding dissociative
adsorption of ambient water vapor at these oxygen
vacancies resulted in the formation of a surface hydroxyl
group [9,10].
Fig. 3 Variation of photocatalytic decomposition speed
with deposition temperature
Fig. 4. Variation of contact angle with deposition
temperature
The TiO2 is known to posses occurs in two crystalline
forms. It is known that the anatase crystalline structure
features higher fotoactivity than rutile. The XRD
measurements revealed first poor anatase structure at the
deposition temperature 230°C but well developed anatase
structure was found for the deposition temperature 280°C.
Thus our experimental results intimate that both the
enhancement in the photoactivity as well as in the
hydrophility are connected with formation of anatase
structure of the films deposited above 200°C.
The results from measurements of photoconductivity and
capacity are summarized in the fig. 5, 6. The
photoconductivity was measured on selected samples and for
two values of humidity, very low humidity 0,13% and high
humidity 75%. The films with low photocatalytic have very
low photoconductivity and capacity and have no sensitivity
on the humidity. The films exhibited high photocatalytic
activity exhibited also higher photoconductivity. The
increasing of the photoconductivity is not the same order as
photocatalytic activity, see fig. 4, 5. The highest
photoconductivity and capacity has the film deposited at
305°C, which is also the only the one with appreciable
sensitivity to the humidity. When this film is placed in the
200
environment with high humidity the water molecules are
absorbed on the surface and increased the photoconductivity.
Thus it can be concluded that photoconductivity is related to
the photocatalytic activity although there is no direct
relationship between these two properties.
Fig. 5. Time dependence of photoconductivity for
different humidity, A) humidity 0,13 %,
B) humidity 75%
Fig. 6. Time dependence of capacity for different
humidity, A) humidity 0,13 %, B) humidity 75%
CONCLUSIONS
- PECVD deposition method is convenient for low
temperature deposition of photocatalytic TiO2 thin films;
- the photocatalytic activity and photoinduced
hydrophility of PECVD TiO2 films is related to its
photoconductivity;
- photocatalytic activity, photoinduced hydrophility and
photoelectric properties have been found to be connected
with the formation of anatase structure.
ACKNOWLEDGEMENTS
This work was supported by projects of the MSMT
1M0577
REFERENCES
1. A. Brajsa, K. Szaniawska, R.J. Barczynski,
L. Murawski, B. Koscielska, A. Vomvas, K. Pomoni. The
photoconductivity of sol-gel derived TiO2 films // Optical
Materials. 2004, v.26, p. 151-155.
2. M.R. Hoffmann, S.T. Martin, D.W. Choi,
D.W. Bahnemann. Environmental applications of
semiconductor photocatalysis // Chem. Rev. 1995, v.95,
p.69-96.
3. B. O'Regan, M. Gratzel. A low-cost, high-efficiency
solar-cell based on dye-sensitized colloidal TiO2 films//
Nature. 1991, v.353, p.737-740.
4. M.Wark, J. Tschirch, O. Bartels, D. Bahnemann,
J. Rathousky. Photocatalytic activity of hydrophobized
mesoporous thin films of TiO2 // Thin Solid Films,1999,
v. 351, p.260-263.
5. Xiao-Ping WangU, Yun Yu, Xing-Fang Hu, Lian Gao.
Hydrophilicity of TiO films prepared by liquid phase
deposition // Thin Solid Films. 2000, v. 371, p.148-152.
6. V.G. Bessergenev, R.J.F. Pereira, M.C. Mateus,
I.V. Khmelinskii, D.A. Vasconcelos, R. Nicula,
E. Burkel, A.M. Botelho do Rego, A.I. Saprykin. Study of
physical and photocatalitic properties of titanium dioxide
thin films prepared from complex precursors by chemical
vapour deposition //Thin Solid Films. 2006, v.503,
p.29-39.
7. A. Hagen, A. Barkschat, J. K. Dohrmann, H. Tributsch.
Imaging UV photoactivity and photocatalysis of TiO2-
films // Sol. Energy Mater. Sol. Cells. 2003, v.77, p.1-13.
8. M.L. Hitchman, F. Tian // J. Electroanal. Chem. 2002,
v.165, p. 538-539.
9. N. Sakai, R. Wang, A. Fujishima, T. Watanabe,
K. Hashimoto, Effect of ultrasonic treatment on highly
hydrophilic TiO2 surfaces // Langmuir. 1998, v.14,
p.5918-5920.
10. R. Wang, N. Sakai, A. Fujishima, T. Watanabe,
K. Hashimoto. Studies of surface wettability conversion
on TiO2 single-crystal surfaces // J. Phys. Chem. 1999,
v. 103, pp.2188-2194.
11. M.A. Handerson // Surf. Sci. 1999, p.355.
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| id | nasplib_isofts_kiev_ua-123456789-82296 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-27T22:22:36Z |
| publishDate | 2006 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Kolouch, A. Horáková, M. Hájková, P. Heyduková, E. Exnar, P. Spatenka, P. 2015-05-27T14:58:55Z 2015-05-27T14:58:55Z 2006 Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films / A. Kolouch, M. Horáková, P. Hájková, E. Heyduková, P. Exnar, P. Spatenka // Вопросы атомной науки и техники. — 2006. — № 6. — С. 198-200. — Бібліогр.: 11 назв. — англ. 1562-6016 PACS: 68.47.Mm, 68.55.-a, 78.66.-w https://nasplib.isofts.kiev.ua/handle/123456789/82296 TiO₂ thin films were prepared by PECVD technique from vapors of Titanium-IV iso-propoxide mixed with oxygen at different temperatures. The films were deposited on substrates with system of special platinum electrodes and on glass substrates. Photoconductivity and capacitance at different humidity, photocatalytic activity and photo-induced hydrophility under UV irradiation and surface morphology were evaluated on the films. The results revealed that the photoconductivity is influenced by humidity and is connected to the photocatalytic activity. This work was supported by projects of the MSMT 1M0577 en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Low temperature plasma and plasma technologies Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films Article published earlier |
| spellingShingle | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films Kolouch, A. Horáková, M. Hájková, P. Heyduková, E. Exnar, P. Spatenka, P. Low temperature plasma and plasma technologies |
| title | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films |
| title_full | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films |
| title_fullStr | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films |
| title_full_unstemmed | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films |
| title_short | Relationship between photocatalytic activity, hydrophilicity and photoelectric properties of TiO₂ thin films |
| title_sort | relationship between photocatalytic activity, hydrophilicity and photoelectric properties of tio₂ thin films |
| topic | Low temperature plasma and plasma technologies |
| topic_facet | Low temperature plasma and plasma technologies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/82296 |
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