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Advances in Materials Physics and Chemistry, 2012, 2, 9-12
doi:10.4236/ampc.2012.24B003 Published Online December 2012 (http://www.SciRP.org/journal/ampc)
Antibacterial Activity of TiO2/Ti Composite Photocatalyst
Films Treated by Ultrasonic Cleaning
Yun Lu1, Lian Hao2, Yutaka Hiraka wa2, Hiromasa Sato2
1Graduate School & Faculty of Engineering, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
2Graduate School, Chiba University, Yayoi-cho, Inage-ku, Chiba, Japan
Email: email@example.com, firstname.lastname@example.org
In this work, TiO2/Ti composite films were fabricated by 2-setp MCT and the following high temperature oxidation. Antibacterial
activity of the composite films treated by ultrasonic cleaning to increase the performance reliability was examined. The prepared
TiO2/Ti composite films showed high photocatalytic activity in the degradation of methylene blue solution. It is obvious that TiO2/Ti
composite films have antibacterial activity under UV irradiation.
Keywords: Mechanical Coating Technique; TiO2/Ti Composite Film; Photocatatlyst; Antibacterial Activity
In recent years, TiO2 photocatalysts have showed a high poten-
tial in the environmental and energy fields, including self-
cleaning Surfaces, air and water purification systems, steriliza-
tion, hydrogen evolution and photoelectrochemical conversion,
among others [1-3]. To lower the recycling cost and increase
the degradation efficiency of pollutants, investigations of TiO2
photocatalysts are oriented toward the immobilization in the
form of films [4,5]. Numerous techniques including physical
vapor deposition (PVD), chemical vapor deposition (CVD), and
sol-gel method, among others have been used to fabricate TiO2
photocatalyst films to increase their photocatalytic activity [6-8].
However, some disadvantages limit the applications of these
techniques. For example, complicated and large scale equip-
ments are required and their processes can be operated only in
vacuum for PVD and CVD. In addition, the production cost is
In this condition, we developed ball milling and proposed a
novel coating technique called mechanical coating technique
(MCT) to fabricate TiO2 photocatalyst films on alumina (Al2O3)
balls [9-12]. In MCT, collision, friction and abrasion among Ti
powder, alumina balls and the inner wall of the bowl are util-
ized effectively to form Ti films on alumina balls. After that,
TiO2 films or TiO2/Ti composite films were fabricated by the
following high-temperature oxidation. Although the TiO2 re-
sultants had rutile crystal type, they showed relatively high
photocatalytic activity . Further, we developed 2-step MCT
based on the concept of MCT to prepare TiO2/Ti composite
films by coating nano-TiO2 powder particles on the Ti films
without oxidation process [9,12]. The TiO2/Ti composite films
showed high photocatalytic activity in the degradation of me-
thylene blue solution. It is expected that the TiO2/Ti composite
films on alumina balls are applied in the environmental and
In this work, TiO2/Ti composite films on alumna balls were
fabricated by 2-step MCT and the following high temperature
oxidation. Ultrasonic cleaning was performed for the alumina
balls with the TiO2/Ti composite films to increase the perform-
ance reliability. Photocatalytic activity and antibacterial activity
of the TiO2/Ti composite films were evaluated and discussed.
2.1. F abric ation of TiO2/Ti Composite Films
First, Ti powder with an average diameter of 30 μm and a pu-
rity of 99.1% was used as the coating material. Alumina (Al2O3)
balls with an average diameter of 1 mm were used as the sub-
strates. Ti powder and Al2O3 balls were charged into a bowl
made of alumina with a dimension of Φ75 × 70 mm (250 ml in
volume). Then the mechanical coating was carried out by a
planetary ball mill (Pulverisette 6, Fritsch). The rotation speed
of the ball mill was set at 300 rpm and the milling time was 10
h. During the fabrication, milling operation was performed 10
min followed by 2 min intermittence to avoid the overheating
of the bowl and the contents. The schematic diagram of MCT
can be found in our published work .
Secondly, TiO2/Ti composite films were fabricated. The
Al2O3 balls coated with Ti films and anatase TiO2 nanopowder
of 7 nm in average diameter (ST-01, purity: 99.99 %, Ishihara
Sangyo) were used as the substrate and the coating material,
respectively. The rotation speed of planetary ball mill was 300
rpm. MCT was carried out for 3 h. Planetary ball mill (Pulver-
isette 6, Fritsch) was also employed for MCT in the second step.
Further, to enhance the photocatalytic activity and, the alu-
mina balls with TiO2/Ti composite films were heat-treated at
773 K in air for 10 h. Subsequently, all the samples were cleaned
in acetone by ultrasonic (frequency: 28 kHz) for 1.5 h to remove
the unstrong adhesions on the surface of the samples to increase
the performance reliability.
2.2. Characteri zatio n of TiO 2/Ti Composite Films and
Evaluation of Phot o catalytic Activity
Copyright © 2012 SciRes. AMPC
Y. LU ET AL.
The morphologies and the microstructures of the samples were
observed by SEM (JSM-6510, JEOL).
Photocatalytic activity of the samples was evaluated by
measuring the degradation rate of methylene blue (MB) solu-
tion at room temperature. The samples were spread uniformly
on the bottom of a cylinder-shaped cell with Φ20 × 50 mm. To
obtain the same initial conditions of evaluating photocatalytic
activity for all the samples, pre-adsorption of MB solution was
carried out using 3 ml MB solution with a concentration of 20
μmol/l before evaluating photocatalytic activity. Subsequently,
the samples after the pre-absorption were spread uniformly on
the bottom of the cell again and 7 ml MB solution with a con-
centration of 10 μmol/l was poured into the cell. Then photo-
catalytic activity was evaluated under UV light irradiation with
an intensity of 1 mW/cm2 for 24 h. These evaluation conditions
were referenced to Japanese Industrial Standard (JIS R 1703-2).
The absorbance of MB solution was measured by a colorimeter
(Sanshin Industrial Co., Ltd) with UV irradiation. The gradient,
k (nmol·l-1·h-1) of MB solution concentration-irradiation time
curve was calculated by the least-squares method with the data
from 1~12 h and used as the degradation rate constants. The
details of the evaluation can be found in our published work
3. Evaluation of Antibactiral Activity
Antibacterial activity of the alumina balls with TiO2/Ti com-
posite films was evaluated by using Escherichia coli test re-
ferred to JIS R 1702 for the flat film sample. The Ti film alu-
mina balls by MCT were used for the control sample. First, the
alumina balls (5 g) with TiO2/Ti composite films were washed
by alcohol and air-dried, then spread uniformly on the bottom
of a petri dish with Φ50 × 12 mm as shown in Figure 1. Sub-
sequently, 0.8 ml solution of Escherichia coli (NBRC3972)
culture with 1.3~5 × 105 colony/ml was dropped uniformly onto
the the alumina balls on the bottom of the petri dish. In order to
count the starting colonies of Escherichia coli, the control
samples of the Ti film alumina balls were immediately washed
away by using 9.2 ml SCDLP medium as shown in Figure 2
and the medium was diluted by 10 fold dilution. Besides, the
samples of the alumina balls with TiO2/Ti composite films were
placed in the dark and under UN irradiation (by FL15BL-B)
with 0.1 mW/cm2 (by UV-340A) for 8 h respectively as shown
in Figure 3. Afterwards, the samples were washed away by
using 9.2 ml SCDLP medium and the medium was diluted by
One layer sample
on the bottom
Figure 1. One layer of the alumina balls with TiO2/Ti composite
films spread uniformly on the bottom of petri dish.
10 fold dilution as the control samples for counting the colonies
of Escherichia coli. The all test were carried out at 25.4ºC.
4. Reasults and Discussion
4.1. Surface Mor phologies a nd Photoca taly tic Act ivit y
of the TiO2/Ti Films
Figure 4 shows the surface morphologies of the TiO2/Ti films.
Petri dish with
one layer sample
Figure 2. Wash-out of the culture medium in antibacterial activity
Figure 3. Antibacterial activity test under UV irradiation .
Figure 4. SEM images of surfaces of the films, (a) TiO2/Ti compos-
ite films and (b) TiO2/Ti composite films after ultrasonic cleaning.
Copyright © 2012 SciRes. AMPC
Y. LU ET AL.
Copyright © 2012 SciRes. AMPC
was reported [13,14]. However, the applications of TiO2 proba-
bly are limited by the shapes of plat films and powder. In this
work, the TiO2/Ti composite film balls with the sterilization
performance of Escherichia coli will lead new applications.
It can be found that the adhered some TiO2 particles on the
surface of the Ti films were removed by ultrasonic cleaning. It
must be that the removed TiO2 particles had relative weak ad-
hesion strength and the performance reliability of the TiO2/Ti
films will be increased by ultrasonic cleaning. Figure 5 gives
the concentration evolution of MB solution as a function of UV
irradiation time. After ultrasonic cleaning, although the degra-
dation rate constants k was lower rather than that (k = 574
nmol·l-1h-1) without ultrasonic cleaning, still kept relative large
value, 486 nmol·l-1h-1. It hints that there is enough TiO2, which
has strong adhesion on the Ti film base after ultrasonic cleaning.
Besides, the photokilling process of Escherichia coli on
TiO2 photocatalyst can be understood as follows . The ini-
tial reaction is a partial decomposition of the outer membrane
by the reactive species produced by TiO2 photocatalysis. Cor-
respondingly, the permeability change of the outer membrane
enables reactive species to easily reach the cytoplasmic mem-
brane. Thus, the cytoplasmic membrane is attacked by reactive
species, leading to the peroxidation of membrane lipid.
4.2. Antiba ctrial Activi t y of T iO2/Ti Composite Films
UV irradiation time / h
MB solution concentration /μmol·l
Figure 6 shows photographs of the poured plate cultures sam-
ples used the collected bacterial culture liquid. Compared of
these photographs, it is obvious that the quantity of the bacillus
coli in the case (Figure 6(d)) of TiO2/Ti films is less than that
of the Ti films used for the control samples. It shows that
TiO2/Ti films has antibacterial activity. Table 1 gives antibac-
terial test conditions and results. The average count of Es-
cherichia coli of the control samples had a starting average
count, 3.6 × 105, however, after 8 h, reached 18.0 × 105 and
11.3×105 in the dark place and under UV irradiation respec-
tively. On the other hand, the average count of Escherichia coli
for the TiO2/Ti films were less than these of the control samples
of the Ti films, 9.3 × 105 and 1.7 × 105 in the dark place and
under UV irradiation respectively. The TiO2/Ti composite films
shown obvious antibacterial activity.
Table 2 shows the decision of the antibacterial test validity.
In order to all the evaluation conditions, the antibacterial tests
in this work passed all the evaluation conditions.
In these years, the antibacterial performance of TiO2 photo-
catalysts have been paid close attention. The sterilization perform-
ance of Escherichia coli for TiO2 plat films and nano-powder
Figure 5. Concentration evolution of MB solution as a function of
UV irradiation time for TiO2/Ti composite films.
Table 1. The antibacterial test conditions and results of TiO2/Ti
(a)In the dark place for Ti film balls(b)Under UV irradiation for Ti
(d) Under UV irradiation for
/Ti composite film balls
(c)In the dark place for TiO
composite film balls
in the dark place
in the dark place
Figure 6. The samples of the standing plate culture used the col-
lected bacterial culture liquid after antibacterial test for 8 h of Ti
and Ti/TiO2 composite films (The white points and circle bodies:
Y. LU ET AL.
TiO2/Ti composite films on alumna balls were fabricated by
2-step MCT and the following high temperature oxidation. Ul-
trasonic cleaning was performed for the alumina balls with the
TiO2/Ti composite films to increase the performance reliability.
Photocatalytic activity and antibacterial activity of the TiO2/Ti
composite films were evaluated respectively. After ultrasonic
cleaning, although the degradation rate constants k still kept
high photocatalytic activity in the degradation of methylene
blue solution. TiO2/Ti composite films has obvious antibacte-
The authors gratefully acknowledge JFE Techno-Research cor-
poration of Japan for providing the antibacterial test.
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Copyright © 2012 SciRes. AMPC