Third Day Poster Session, 17 June 2010 - NanoTR-VI

Poster Session, Thursday, June 17
Theme F686 - N1123
Humidity Sensing Properties of Titanium Dioxide (TiO 2 ) Thin Films
Mehmet KABADAYI 1 , Salih OKUR 1 ,Nesli T. YAĞMURCUKARDEŞ 1
1 Izmir Institute of Technology, Faculty of Science, Department of Physics, Gulbahce Koyu Kampusu, 35430,
Urla, Izmir, Turkey
Abstract- Humidity sensing properties of TiO 2 nanoparticle thin film that prepared by drop casting method were investigated
by quartz crystal microbalance (QCM) and electrical characterization. The results of our experiment show that TiO 2
nanoparticles have a great potential for humidity sensing applications at room temperature.
Pure titanium dioxide does not occur in nature but is
derived from ilmenite of leuxocene ores. The TiO 2
nanoparticles generally present in three crystal phases:
anatase, rutile, and brookite. Due to its high
photocatalytic activity, anatase is used as a photocatalyst
to treat various waste waters [2].
In our study we used commercially available millennium
PC 500 TiO 2 which has 5-10nm particle size, 99%
anatase form and 250 m 2 /gr BET surface area. 1gr TiO 2
dispersed in 20ml distilled water and kept into ultrasonic
cleaner for 30 minute at 50 0 C. After waiting 10 minutes
the semi-transparant part of the dispersion was taken.
And 5μl of the dispersion is coated over a glass substrate
by drop-casting method. The thickness of the film was
measured as 450 nm with Dektak 150 profilometer of
Veeco. SEM image of drop casted millenium PC 500
TiO 2 thin film is shown in Figure1.
(1)
where is resonant frequency (8MHz), A is the
area of the gold disk coated onto the crystal, ρ is
the density of the crystal (2.684g/cm 3 ), and μ is the
shear modulus of quartz (2.947x10 11 g/cms 2 ).
F/Hz
2
0
-2
-4
-6
11%
22%
43%
53%
84%
75%
94%
84%
94%
97%
-8
0 1000 2000 3000 4000 5000 6000
2
1
0
(a)
Time/sec
43%
53%
75%
22%
11%
y = 0,698 - 0,067407x R= 0,9972
y = 2,2276 - 0,077601x R= 0,99245
(b)
-1
f/Hz
-2
-3
-4
-5
upward
downward
-6
0 20 40 60 80 100
Relative Humidity (%)
Figure 2(aand b):Frequency change with different RH(%) values
Figure 1. SEM image of drop casted millenium PC 500 TiO2 thin film.
For the electrical characterizations, Au metal with
high purity (99.9%) was thermally evaporated on
the TiO 2 film with a separation of 17 μl. Keithly
2420 Sourcemeter was used to investigate
electronic parameters. To estimate the frequency
change due to mass loading of water molecules,
QCM with the model of CHI400A Series from CH
Instruments was used. Electrical characterization
and frequency changes were obtained with the
exposure of the film at different relative humidity
(RH) ratios. (11%, 22%, 43%, 55%, 75%, 84%,
94%, and 97% RH.)
To convert the measured frequency change to the
mass change, Sauerbrey Equation is used [3].
Figure 2 (a and b) shows the frequency changes due
to different relative humidity values .The frequency
of the TiO 2 film is decreasing and increasing
humidity values from 11% to 97%.
A positive frequency observed during the resonance
oscillations because of the behaviours of TiO 2
films.Our experimental results give that TiO2
nanoparticle sensor is sensitive to relative humidity
changes at room temperature
[1] S. Okur, M. Kus, F. Özel, V. Aybek, M. Yilmaz, Talanta,
81;1-2; 2010; 248.
[2] Tetsuro, K., Toshiaki, O., Mitsunobu, I., et al.,
Photocatalytic Activity of Rutile–Anatase Coupled TiO2
Particles Prepared by a Dissolution–Reprecipitation
Method, J.Colloid. Interf. Sci., 2003, vol. 267, no. 2, pp.
377–381.
[3] G. Sauerbrey, Z. Phys. 155 (1959) 206.
6th Nanoscience and Nanotechnology Conference, zmir, 2010 701