452
S. Das et al.
tive stress may also result in change in membrane fatty acid components in bacteria
and their corresponding membrane fluidity, which are studied using Fourier transmission infrared spectroscopy (FTIR) and analysis of Fatty acid methyl esters (FAME)
(Kiwi and Nadtochenko 2005; Misra et al. 2018). The development of oxidative
stress and its impact on the bacterial cell membrane can be observed using Transmission electron microscopy (TEM), Field emission scanning electron microscopy
(FESEM) and advanced atomic force microscopy (AFM) or attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) (Choi et al. 2016; Kiwi and
Nadtochenko 2005; Longo and Kasas 2014). After membrane, bacterial intracellular
components like nucleic acids and proteins are primary targets for ROS attack. The
damage in protein and nucleic acids could be studied using Sodium Dodecyl Sulfate
Poly Acrylamide Gel Electrophoresis (SDS-PAGE) and Agarose Gel Electrophoresis
respectively (Carré et al. 2014; Misra et al. 2018). The rate of photocatalyst adsorption on bacterial surface and the ultimate photocatalytic inactivation shows positive
correlation to the ROS generation and bactericidal effect of semiconductor metal
oxide-based photocatalysts. These interactions could be the rate-determining step in
bacterial PCD (Das et al. 2017).
2 Innovation in Photocatalyst Technology
TiO 2 electrode had been used first in 1972 (Fujishima and Honda 1972) for water
splitting applications. Since then researchers have been synthesizing TiO 2 of different sizes, characteristics, and physical and chemical properties to be exploited
for numerous photocatalytic applications (Fujishima and Honda 1972; Kondo et al.
2008; Wang et al. 1998). Nanosized TiO 2 with its light opaque properties in comparison to its bulkier form was reported to have a superior oxidation competency
(Siddiquey et al. 2008). Still problems regarding their morphology, particle size,
and vulnerability in harsh chemical environment, remain the biggest challenge for
large-scale photocatalytic applications and post-reaction separability (Byrne et al.
1998). However, the most important drawback of TiO 2 photocatalysis is mismatching between its bandgap energy and the sunlight spectra. The TiO 2 bandgap overlap
only with the UV (320–400 nm) ranges, as a consequence of which it can only take
benefit of less than 5% of the solar spectrum reaching the earth’s surface, and thus its
less likely to be used for real-time photocatalytic applications for sustainable development (Chong et al. 2010). This has intensely influenced research in photocatalyst
development, to make better usage of the visible spectrum. In this perspective, the
feasibility of using ZnO and CdS photocatalysts has been re-evaluated with respect
to recent advances in nanotechnology. ZnO, possessing a wide bandgap energy of
3.37 eV and hefty exciton binding energy up to 60 meV, has gained high consideration in the past decade because of its ease of synthesis and exceptional optical,
photovolatic, photocatalytic, high photochemically active and biocompatible properties (Chong et al. 2010). In contrast, the immobilization of the photocatalysts in
inert substrate or matrices drastically reduces the active site of catalyst and will
S. Das et al.
tive stress may also result in change in membrane fatty acid components in bacteria
and their corresponding membrane fluidity, which are studied using Fourier transmission infrared spectroscopy (FTIR) and analysis of Fatty acid methyl esters (FAME)
(Kiwi and Nadtochenko 2005; Misra et al. 2018). The development of oxidative
stress and its impact on the bacterial cell membrane can be observed using Transmission electron microscopy (TEM), Field emission scanning electron microscopy
(FESEM) and advanced atomic force microscopy (AFM) or attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) (Choi et al. 2016; Kiwi and
Nadtochenko 2005; Longo and Kasas 2014). After membrane, bacterial intracellular
components like nucleic acids and proteins are primary targets for ROS attack. The
damage in protein and nucleic acids could be studied using Sodium Dodecyl Sulfate
Poly Acrylamide Gel Electrophoresis (SDS-PAGE) and Agarose Gel Electrophoresis
respectively (Carré et al. 2014; Misra et al. 2018). The rate of photocatalyst adsorption on bacterial surface and the ultimate photocatalytic inactivation shows positive
correlation to the ROS generation and bactericidal effect of semiconductor metal
oxide-based photocatalysts. These interactions could be the rate-determining step in
bacterial PCD (Das et al. 2017).
2 Innovation in Photocatalyst Technology
TiO 2 electrode had been used first in 1972 (Fujishima and Honda 1972) for water
splitting applications. Since then researchers have been synthesizing TiO 2 of different sizes, characteristics, and physical and chemical properties to be exploited
for numerous photocatalytic applications (Fujishima and Honda 1972; Kondo et al.
2008; Wang et al. 1998). Nanosized TiO 2 with its light opaque properties in comparison to its bulkier form was reported to have a superior oxidation competency
(Siddiquey et al. 2008). Still problems regarding their morphology, particle size,
and vulnerability in harsh chemical environment, remain the biggest challenge for
large-scale photocatalytic applications and post-reaction separability (Byrne et al.
1998). However, the most important drawback of TiO 2 photocatalysis is mismatching between its bandgap energy and the sunlight spectra. The TiO 2 bandgap overlap
only with the UV (320–400 nm) ranges, as a consequence of which it can only take
benefit of less than 5% of the solar spectrum reaching the earth’s surface, and thus its
less likely to be used for real-time photocatalytic applications for sustainable development (Chong et al. 2010). This has intensely influenced research in photocatalyst
development, to make better usage of the visible spectrum. In this perspective, the
feasibility of using ZnO and CdS photocatalysts has been re-evaluated with respect
to recent advances in nanotechnology. ZnO, possessing a wide bandgap energy of
3.37 eV and hefty exciton binding energy up to 60 meV, has gained high consideration in the past decade because of its ease of synthesis and exceptional optical,
photovolatic, photocatalytic, high photochemically active and biocompatible properties (Chong et al. 2010). In contrast, the immobilization of the photocatalysts in
inert substrate or matrices drastically reduces the active site of catalyst and will