Designing Novel Photocatalysts for Disinfection of Multidrug-Resistant …
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electron–hole interaction of thicker CdS shell, facilitating a greater magnitude in
involvement of photoexcited electrons during the charge separation.
Photocatalytic applications involve decontamination of an extensive range of
organic refractory pollutants. This also involves various microbes like waterborne
bacteria and fungus. Das et al. (2015) for the first time, reported the utilization of
colloidally-synthesized (chemically precipitated) Ag@ZnO Core-shell NCs for the
complete PCD of V. Cholerae in 90 min. Reports of the efficient PCD of E. coli and
S. aureus were reported displayed by the same group using sonochemically synthesized Ag@ZnO core-shell NCs (Das et al. 2018). In both the cases, the structural
integrity of the core-shell NCs were found to be properly maintained during and postreaction as confirmed from the Atomic Absorption Spectroscopy studies (AAS) or
Microwave plasma atomic emission spectroscopy (MP-AES). Moreover, application of these NCs in real water conditions and reusability has also set a benchmark
for their real-time application to get rid of waterborne bacteria. Though core-shell
NCs were reported as suitable photocatalysts (Das et al. 2017), their potentials as
antimicrobial agents have been convincing too. Das et al. (2016) reported for the first
time biologically synthesized Ag@ZnO core-shell NCs for complete inactivation of
Candida krusei fungus without the involvement of any light (Das et al. 2016). Thus,
tuning the structural properties of these semiconductors may help these core-shell
NCs as potential antimicrobial agents against both water and skin borne pathogens.
2.3 Clay-Based Nanocomposites for Photocatalytic
Disinfection of Microbes
Clays are naturally occurring layered plates of aluminosilicates stacked or mound
together. Their broad classification includes as montmorillonite-smectite, kaolinite,
illite, and chlorite types. Clays might be also be grouped as phyllosilicates that fit
into three standard groups: montmorillonite, illite, and kaolinite. Phyllosilicates are
two-dimensional arrays of silicon–oxygen tetrahedral and two-dimensional arrays
of aluminum or magnesium–oxygen–hydroxyl octahedral. Montmorillonite-layered
silicates and illite have 2:1 layered configuration whereas and kaolinite has 1:1 layered configuration. The physicochemical characteristics differ but are principally
eminent for their hydrous alumina-silicates contents. Clays generally have intersected silicates sheet joint with a second sheet-like alignment of metal atoms, oxygen, and hydroxyl ions (Bergaya and Lagaly 2006; Weaver and Pollard 2011). The
fundamental configuration units are divided into silica sheets and brucite or gibbsite
sheets (Miranda-Trevino and Coles 2003). The 1:1 configuration type consists of
one tetrahedral sheet and one octahedral sheet; (Miranda-Trevino and Coles 2003;
Yaya et al. 2012). Octahedron consists of two planes of hydroxyl ions amidst which
a plane of magnesium or aluminum ions is situated that is usually synchronized by
hydroxyl sheets octahedrally. These octahedrons called octahedral sheets are also
457
electron–hole interaction of thicker CdS shell, facilitating a greater magnitude in
involvement of photoexcited electrons during the charge separation.
Photocatalytic applications involve decontamination of an extensive range of
organic refractory pollutants. This also involves various microbes like waterborne
bacteria and fungus. Das et al. (2015) for the first time, reported the utilization of
colloidally-synthesized (chemically precipitated) Ag@ZnO Core-shell NCs for the
complete PCD of V. Cholerae in 90 min. Reports of the efficient PCD of E. coli and
S. aureus were reported displayed by the same group using sonochemically synthesized Ag@ZnO core-shell NCs (Das et al. 2018). In both the cases, the structural
integrity of the core-shell NCs were found to be properly maintained during and postreaction as confirmed from the Atomic Absorption Spectroscopy studies (AAS) or
Microwave plasma atomic emission spectroscopy (MP-AES). Moreover, application of these NCs in real water conditions and reusability has also set a benchmark
for their real-time application to get rid of waterborne bacteria. Though core-shell
NCs were reported as suitable photocatalysts (Das et al. 2017), their potentials as
antimicrobial agents have been convincing too. Das et al. (2016) reported for the first
time biologically synthesized Ag@ZnO core-shell NCs for complete inactivation of
Candida krusei fungus without the involvement of any light (Das et al. 2016). Thus,
tuning the structural properties of these semiconductors may help these core-shell
NCs as potential antimicrobial agents against both water and skin borne pathogens.
2.3 Clay-Based Nanocomposites for Photocatalytic
Disinfection of Microbes
Clays are naturally occurring layered plates of aluminosilicates stacked or mound
together. Their broad classification includes as montmorillonite-smectite, kaolinite,
illite, and chlorite types. Clays might be also be grouped as phyllosilicates that fit
into three standard groups: montmorillonite, illite, and kaolinite. Phyllosilicates are
two-dimensional arrays of silicon–oxygen tetrahedral and two-dimensional arrays
of aluminum or magnesium–oxygen–hydroxyl octahedral. Montmorillonite-layered
silicates and illite have 2:1 layered configuration whereas and kaolinite has 1:1 layered configuration. The physicochemical characteristics differ but are principally
eminent for their hydrous alumina-silicates contents. Clays generally have intersected silicates sheet joint with a second sheet-like alignment of metal atoms, oxygen, and hydroxyl ions (Bergaya and Lagaly 2006; Weaver and Pollard 2011). The
fundamental configuration units are divided into silica sheets and brucite or gibbsite
sheets (Miranda-Trevino and Coles 2003). The 1:1 configuration type consists of
one tetrahedral sheet and one octahedral sheet; (Miranda-Trevino and Coles 2003;
Yaya et al. 2012). Octahedron consists of two planes of hydroxyl ions amidst which
a plane of magnesium or aluminum ions is situated that is usually synchronized by
hydroxyl sheets octahedrally. These octahedrons called octahedral sheets are also