researchers adopted different methodologies to improve the surface area of the TiO 2
based structures and studied its role in improving antibacterial efficacy. Joost et al.
(2015) prepared high surface area TiO 2 nanoparticles to construct a nanostructured
thin film and demonstrated the antimicrobial activity using viable bacterial cells and
bacterial plasma membrane fatty acids. They observed the destruction of saturated
and unsaturated fatty acids in the bacterial plasma membrane in 10 minutes by fast
formation of peroxide through photocatalytic activity. A comparison between silicone substrate and nano TiO 2 thin film in E. coli destruction proved the mechanism
and is shown in Fig. 2.3A.
Another way of nanostructuring is construction of TiO 2 nanotube in thin film
form by electrochemical anodization and rapid break down anodization (Antony
et al. 2011, 2012b). Podporska-Carroll et al. (2015) studied the antibacterial activity
of TiO 2 nanotubes prepared by rapid break down anodization process and compared
with that of commercial Degussa-P25 TiO 2 powder. The fabricated nanotube powders showed excellent antimicrobial activity towards E. coli and S. aureus under
light irradiation for 24 hours. The improved nanostructuring and specific surface area
played an important role in increasing the rate of formation of reactive oxygen
species in the case of nanotubular structure (Fig. 2.3B). Also, the improved surface
area can improve the bacterial adsorption which enhances the bacterial killing. Bai
and coworkers fabricated TiO 2 nanorod spheres in large scale by a non-hydrothermal
route (Bai et al. 2013) (Fig. 2.3C). Intrinsic antibacterial properties for these structures were observed under dark conditions due to the spikes present on the TiO 2
nanostructure which pierce the bacterial cell wall and kill the bacteria. Under solar
light irradiation, bacterial destruction ability was increasing with increase in calcination temperature and 82.12% of bacterial destruction was obtained for sample
calcined at 900
C (Fig. 2.3D). The increase in photocatalytic activity with increase
in calcination temperature is attributed to enhanced crystallization leading to redshift
thereby narrowing the band gap of TiO 2 .
2.5.1.2 Doped TiO 2
The pristine TiO 2 is a wide band gap material and can absorb light in the UV region.
In order to make it visible light active, an important strategy adopted in the case of
TiO 2 is doping by cations and anions. The present section discusses the bacterial
disinfection of doped TiO 2 . The photocatalytic property of TiO 2 is utilized for E coli
disinfection in wastewater by Majeda and coworkers (Khraisheh et al. 2015). For
this activity, Cu doped TiO 2 was prepared by sol gel and wet impregnation method.
It was observed that, Cu-TiO 2 prepared by incorporating 10% of CuCl 2 as precursor,
was showing 100% E. coli destruction. The synergistic effect of oxidative attack of
TiO 2 and leaching out of Cu was found to be responsible for the remarkable
performance and the photocatalytic disinfection process is shown in Fig. 2.4. Raut
et al studied the sunlight induced antibacterial effect of TiO 2 À x À 3y N 2y thin films
deposited on Si(100), quartz and glass substrates by a single step ultrasonic spray
pyrolysis route (Raut et al. 2012). The precursor used for N doping was hexamine.
38
R. P. Antony et al.
based structures and studied its role in improving antibacterial efficacy. Joost et al.
(2015) prepared high surface area TiO 2 nanoparticles to construct a nanostructured
thin film and demonstrated the antimicrobial activity using viable bacterial cells and
bacterial plasma membrane fatty acids. They observed the destruction of saturated
and unsaturated fatty acids in the bacterial plasma membrane in 10 minutes by fast
formation of peroxide through photocatalytic activity. A comparison between silicone substrate and nano TiO 2 thin film in E. coli destruction proved the mechanism
and is shown in Fig. 2.3A.
Another way of nanostructuring is construction of TiO 2 nanotube in thin film
form by electrochemical anodization and rapid break down anodization (Antony
et al. 2011, 2012b). Podporska-Carroll et al. (2015) studied the antibacterial activity
of TiO 2 nanotubes prepared by rapid break down anodization process and compared
with that of commercial Degussa-P25 TiO 2 powder. The fabricated nanotube powders showed excellent antimicrobial activity towards E. coli and S. aureus under
light irradiation for 24 hours. The improved nanostructuring and specific surface area
played an important role in increasing the rate of formation of reactive oxygen
species in the case of nanotubular structure (Fig. 2.3B). Also, the improved surface
area can improve the bacterial adsorption which enhances the bacterial killing. Bai
and coworkers fabricated TiO 2 nanorod spheres in large scale by a non-hydrothermal
route (Bai et al. 2013) (Fig. 2.3C). Intrinsic antibacterial properties for these structures were observed under dark conditions due to the spikes present on the TiO 2
nanostructure which pierce the bacterial cell wall and kill the bacteria. Under solar
light irradiation, bacterial destruction ability was increasing with increase in calcination temperature and 82.12% of bacterial destruction was obtained for sample
calcined at 900
C (Fig. 2.3D). The increase in photocatalytic activity with increase
in calcination temperature is attributed to enhanced crystallization leading to redshift
thereby narrowing the band gap of TiO 2 .
2.5.1.2 Doped TiO 2
The pristine TiO 2 is a wide band gap material and can absorb light in the UV region.
In order to make it visible light active, an important strategy adopted in the case of
TiO 2 is doping by cations and anions. The present section discusses the bacterial
disinfection of doped TiO 2 . The photocatalytic property of TiO 2 is utilized for E coli
disinfection in wastewater by Majeda and coworkers (Khraisheh et al. 2015). For
this activity, Cu doped TiO 2 was prepared by sol gel and wet impregnation method.
It was observed that, Cu-TiO 2 prepared by incorporating 10% of CuCl 2 as precursor,
was showing 100% E. coli destruction. The synergistic effect of oxidative attack of
TiO 2 and leaching out of Cu was found to be responsible for the remarkable
performance and the photocatalytic disinfection process is shown in Fig. 2.4. Raut
et al studied the sunlight induced antibacterial effect of TiO 2 À x À 3y N 2y thin films
deposited on Si(100), quartz and glass substrates by a single step ultrasonic spray
pyrolysis route (Raut et al. 2012). The precursor used for N doping was hexamine.
38
R. P. Antony et al.