Merits of photocatalytic and antimicrobial applications of gamma-irradiated Co: XNi1- xFe2O4/SiO2/TiO2; X = 0.9 nanocomposite for pyridine removal and pathogenic bacteria/fungi disinfection: Implication for wastewater treatment

Article abstract of DOI:10.1039/c9ra10505k

In this paper, we report a layer-by-layer approach for the preparation of a concentric recyclable composite (Co_xNi_1-xFe₂O₄/SiO₂/TiO₂; x = 0.9) designed for wastewater treatment. The prepared composite was investigated by X-ray diffraction spectroscopy, high-resolution transmission electron microscopy and scanning electron microscopy (SEM) supported with energy dispersive X-ray (EDX) spectroscopy to analyze crystallinity, average particle size, morphology and elemental composition, respectively. The antimicrobial activities of the prepared composite have been investigated against multi-drug-resistant bacteria and pathogenic fungi using a variety of experiments, such as zone of inhibition, minimum inhibitory concentration, biofilm formation and SEM with EDX analysis of the treated bacterial cells. In addition, the effects of gamma irradiation (with different doses) and UV irradiation on the antibacterial abilities of the prepared composite have been evaluated. Moreover, the effect of gamma irradiation on the crystallite size of the prepared composite has been studied under varying doses of radiation (25 kGy, 50 kGy and 100 kGy). Finally, the photocatalytic efficiency of the prepared composite was tested for halogen-lamp-assisted removal of pyridine (artificial wastewater). Various parameters affecting the efficiency of the photocatalytic degradation, such as photocatalyst dose, pyridine concentration, pH, point of zero charge and the presence of hydrogen peroxide, have been studied. Our results show that the synthesized composite has a well-crystallized semi-spherical morphology with an average particle size of 125.84 nm. In addition, it possesses a high degree of purity, as revealed by EDX elemental analysis. Interestingly, the prepared composite showed promising antibacterial abilities against almost all the tested pathogenic bacteria and unicellular fungi, and this was further improved after gamma and UV irradiation. Finally, the prepared composite was very efficient in the light-assisted degradation of pyridine and its degradation efficiency can be tuned based on various experimental parameters. This work provides a revolutionary nanomaterial-based solution for the global water shortage and water contamination by offering a new wastewater treatment technique that is recyclable, cost effective and has an acceptable time and quality of water.

Full text of DOI:10.1039/c9ra10505k

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PAPER
Merits of photocatalytic and antimicrobial
applications of gamma-irradiated CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite for pyridine
removal and pathogenic bacteria/fungi
Cite this: RSC Adv., 2020, 10, 5241
disinfection: implication for wastewater treatment†
a
bc
Ahmed M. El-Khawaga,d
*
*
‡
Gharieb S. El-Sayyad,
‡
M. Abd Elkodous,
Mohamed A. Elsayed,d Ahmed I. El-Batal
and Mohamed Gobara
a
d
In this paper, we report a layer-by-layer approach for the preparation of a concentric recyclable composite
(CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9) designed for wastewater treatment. The prepared composite was
investigated by X-ray diffraction spectroscopy, high-resolution transmission electron microscopy and
scanning electron microscopy (SEM) supported with energy dispersive X-ray (EDX) spectroscopy to
analyze crystallinity, average particle size, morphology and elemental composition, respectively. The
antimicrobial activities of the prepared composite have been investigated against multi-drug-resistant
bacteria and pathogenic fungi using a variety of experiments, such as zone of inhibition, minimum
inhibitory concentration, biofilm formation and SEM with EDX analysis of the treated bacterial cells. In
addition, the effects of gamma irradiation (with different doses) and UV irradiation on the antibacterial
abilities of the prepared composite have been evaluated. Moreover, the effect of gamma irradiation on
the crystallite size of the prepared composite has been studied under varying doses of radiation (25 kGy,
50 kGy and 100 kGy). Finally, the photocatalytic efficiency of the prepared composite was tested for
halogen-lamp-assisted removal of pyridine (artificial wastewater). Various parameters affecting the
efficiency of the photocatalytic degradation, such as photocatalyst dose, pyridine concentration, pH,
point of zero charge and the presence of hydrogen peroxide, have been studied. Our results show that
the synthesized composite has a well-crystallized semi-spherical morphology with an average particle
size of 125.84 nm. In addition, it possesses a high degree of purity, as revealed by EDX elemental
analysis. Interestingly, the prepared composite showed promising antibacterial abilities against almost all
the tested pathogenic bacteria and unicellular fungi, and this was further improved after gamma and UV
irradiation. Finally, the prepared composite was very efficient in the light-assisted degradation of pyridine
and its degradation efficiency can be tuned based on various experimental parameters. This work
Received 13th December 2019
Accepted 17th January 2020
provides
a revolutionary nanomaterial-based solution for the global water shortage and water
DOI: 10.1039/c9ra10505k
contamination by offering a new wastewater treatment technique that is recyclable, cost effective and
rsc.li/rsc-advances
has an acceptable time and quality of water.
1 Introduction
aDrug Microbiology Laboratory, Drug Radiation Research Department, National
Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy
Authority, Cairo, Egypt. E-mail: Gharieb.Elsayyad@eaea.org.eg
bDepartment of Electrical and Electronic Information Engineering, Toyohashi
University of Technology, Toyohashi, Aichi 441-8580, Japan. E-mail: mohamed.
hamada.abdlekodous.xi@tut.jp
Water contamination is one of the most serious factors affecting
public health and terrestrial and aquatic environments.1 In
addition, the percentage of available potable water on Earth, on
which all living organisms rely, is tiny (only about 1%).2 More-
over, 6–8 million people die every year due to water-borne
pathogens, which cause serious diseases, such as typhoid
fever, diarrhea and hepatitis A.3–5 Wastewater contains different
kinds of pollutants, such as heavy metals, dissolved and non-
dissolved chemicals, phenols, dyes and other miscellaneous
substances.6,7
cCenter for Nanotechnology (CNT), School of Engineering and Applied Sciences, Nile
University, Sheikh Zayed, Giza 16453, Egypt
dChemical Engineering Department, Military Technical College, Egyptian Armed
Forces, Cairo, Egypt
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra10505k
‡ Equal contribution.
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Among these pollutants, pyridine receives continuous the crystallite size of the prepared composite have also been
attention due to the severity of its effects.8 Pyridine (C5H5N) is studied. Moreover, the photocatalytic ability of the prepared
an organic compound with a basic heterocyclic structure.9,10 It is composite was tested for the degradation of pyridine solution
a colorless, volatile and ammable liquid possessing an (as an articial wastewater). Different parameters controlling
unpleasant odor and high toxicity.11 Pyridine exposure has the photocatalytic efficiency, such as photocatalyst dose, pH,
critical effects on the human immune system and may lead to pyridine concentration and the presence of H2O2 have been
carcinogenicity.12 In addition, pyridine derivatives exhibit studied.
toxicity to aquatic life and produce irritation due to their
unpleasant smell.13 Currently, more than 25 000 tons per year of
pyridine derivatives are produced worldwide because of their
2 Materials and methods
widespread use as herbicides and insecticides in cultivation and
2.1. Materials
in some industrial activities, including textile manufacture,
chemical and pharmaceutical synthesis.14
Tetraethyl orthosilicate (TEOS) 98% [Si(OC2H5)4], titanium(IV)
isopropoxide 97% (C12H28O4Ti), ammonium hydroxide
(NH4OH), nickel chloride (NiCl2), ferric chloride (FeCl3$6H2O),
absolute ethanol (C2H5OH), ꢁ80 000 MW hydroxypropyl cellu-
lose, sodium hydroxide (NaOH), cobalt chloride (CoCl2), and
pyridine (C5H5N) were purchased from Sigma-Aldrich (Ger-
many). Precursors for this study were used as received without
further purication. Materials are commercially available and
of extra-pure grade.
Thus, wastewater treatment and strategies for water preser-
vation should be a global consideration. Chemical and micro-
bial removal of various kinds of pollutants are currently
employed in traditional wastewater treatment plants.15
However, the efficiency of degradation of pollutants, the
capacity of wastewater treatment plants and the treatment time
all have serious limitations. To overcome these limitations
more effective and satisfactory techniques for wastewater
treatment are required. Advances in nanotechnology using
nanomaterials provides a revolutionary solution for these issues
and can also improve the efficacy of traditional wastewater
treatment plants.16
2.2. Methods
The nanocomposite under investigation was prepared and fully
Nanomaterials possess relatively higher degrees of chemical, characterized according to the methods reported in our
physical and biological activities due to their large surface area previous paper.24 We briey present the preparation steps below
with respect to their bulk counterparts.17–21 Among nano- and list the new experiments performed, such as new charac-
materials, titanium dioxide (TiO2) is still a very promising terization data, degradation of pyridine, study of the parameters
candidate for light-assisted photocatalysis and degradation of affecting degradation efficiency (photocatalyst dose, contami-
many kinds of pollutant present in wastewater.22
nant concentration, pH, presence of H2O2), antimicrobial
TiO2 nanoparticles (NPs) are chemically active, abundant, activities against multi-drug-resistant bacteria and pathogenic
non-toxic and possess satisfactory photocatalytic activity.23 fungi and the effect of gamma and UV irradiation on the anti-
However, nanoparticles are too small to adsorb large quantities microbial activity of the prepared composite.
of pollutants and collection and reusability of the particles are
2.2.1. Preparation of the core cobalt–nickel ferrite nano-
very important considerations in terms of the overall cost. Thus, particles (CoxNi1ꢀxFe2O4; x ¼ 0.9). Nanoparticles of CoxNi1ꢀx
-
designing efficient and reusable photocatalytic systems for Fe2O4; x ¼ 0.9 were prepared via a coprecipitation approach.
wastewater treatment based on nanomaterials is of critical First, nickel chloride (12.5 mg), cobalt chloride (12.5 mg) and
importance.
ferric chloride 45% (0.05 ml) were dissolved in deionized (DI)
ꢂ
Herein, we report the preparation of an improved recyclable water (50 ml) under slight heating to 80 C. Then, the pH was
nanocomposite (CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9) synthesized raised to 8 by adding drops of aqueous sodium hydroxide
by a layer-by-layer approach. The CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs are solution (2 M) to the mixture, which lead to the formation and
employed as a magnetic core for reusability (Fig. S1†) and easy precipitation of CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs. DI water was used
collection of the material aer successive wastewater treatment to wash the obtained precipitateꢂ several times. Then, the
operations, while the SiO2 layer was used to separate the precipitate was ꢂdried for 3 h at 70 C. Finally, the powder was
magnetic core from the photoactive TiO2 layer, so as not to calcined at 300 C for 4 h.
reduce its quantum efficiency. Finally, the TiO2 layer was used
2.2.2. Preparation of a core–shell structure (CoxNi1ꢀxFe2-
as a photoactive catalyst for the removal of pollutants present in O4; x ¼ 0.9/SiO2). First, CoxNi1ꢀxFe2O4; x ¼ 0.9 powder (180 mg)
wastewater. The antimicrobial activities of the prepared obtained as in Section 2.2.1 was dispersed in DI water (64 ml)
composite were tested against pathogenic bacteria and unicel- via sonication for 45 min in an ultrasonic water bath. Then,
lular fungi, such as Klebsiella pneumoniae, Proteus vulgaris, ammonia solution (25%) (8 ml) and absolute ethanol (320 ml)
Proteus mirabilis, Salmonella typhi, Staphylococcus aureus, were dropped directly into the mixture under constant stirring
Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, at room temperature. Aer that, TEOS (3.2 ml) was added drop-
Candida tropicalis and Candida albicans. In addition, the effect by-drop to the mixture, which was then le under constant
of both gamma (with different doses) and UV irradiation on the stirring for 16 h. The precipitate was isolated by centrifugation
antimicrobial activities of the prepared composite have been and then washed with DI water and absolute ethanol many
ꢂ
analyzed. The effects of different doses of gamma irradiation on times. Finally, the precipitate was dried at 50 C for 4 h.
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2.2.3. Preparation of the sandwich structure nano-
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2.2.6. Gamma irradiation. All prepared samples were
composite (CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9). First, CoxNi1ꢀx
-
gamma-irradiated at NCRRT, Cairo, Egypt. The irradiation
Fe2O4; x ¼ 0.9/SiO2 powder obtained as in Section 2.2.2 was source was the 60Co-Gamma Chamber 4000-A-India. The
dispersed in 100 ml absolute ethanol, 0.2 g hydroxypropyl applied dose rate was xed at 2.10 kGy hꢀ1. Gamma irradiation
cellulose and 0.48 ml DI water with sonication for 30 min in an displays hydrated and/or free radicals and solvated electrons
ultrasonic water bath. Then, titanium(IV) isopropoxide (4 ml) aer water radiolysis.26
was dissolved in absolute ethanol (18 ml) in a separate vessel
2.2.7. Antimicrobial activity of CoxNi1ꢀxFe2O4/SiO2/TiO2; x
and was dripped directly into the mixture at a rate of 0.5 ¼ 0.9 nanocomposite. Each layer of the fabricated composite
ml minꢀ1. Aer that, the stirring speed was raised to 900 rpm (the core CoxNi1ꢀxFe2O4 NPs and the two shells of SiO2 and TiO2
and the temperature to 85 ꢂC, and the reaction was le for NPs) and the full nanocomposite (CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼
100 min under reuxing conditions. The precipitate produced 0.9) were dispersed in dimethyl sulfoxide (DMSO) to prepare
was collected and washed with ethanol many times, aer which a net concentration of 10 mg mlꢀ1. Then, they were separately
it was redispersed in 20 ml of DI water. For partial etching of the examined for their antimicrobial potential using the agar disc
silica layer and to form the hollow structure of the composite, distribution technique.27 Additionally, the CoxNi1ꢀxFe2O4/SiO2/
the dispersion was mixed with 2 M NaOH solution (3.5 ml) TiO2; x ¼ 0.9 nanocomposite was irradiated with gamma rays at
under constant stirring for 1 h at room temperature. The various doses (25.0, 50.0 and 100.0 kGy) in order to investigate
powder was then collected, washed many times with DI water the effect on its antimicrobial activity.
ꢂ
and ꢂdried at 90 C for 4 h. Finally, the powder was calcined at
All prepared samples (each layer of the composite and the
whole nanocomposite) were examined against distinct isolates
550 C for 4 h.
2.2.4. Characterization of the prepared nanocomposite. of pathogenic bacteria, such as Staphylococcus aureus
Phase, crystallinity and crystallite size were investigated by X-ray (methicillin-resistant S. aureus (MRSA)), Escherichia coli, Bacillus
diffraction (XRD) spectroscopy using a Brucker Axis D8 subtilis, Pseudomonas aeruginosa, Salmonella typhi, Klebsiella
diffractometer operating at 30 mA current, 40 kV voltage and pneumoniae, Proteus vulgaris, and P. mirabilis. In addition, the
˚
using CuKa radiation (l ¼ 1.540598 A). The average size of the antifungal activity was examined against unicellular pathogenic
particles was calculated using a JEM2100 (Jeol, Japan) high- fungi such as Candida tropicalis and C. albicans. The tested
resolution transmission electron microscope (HRTEM). microorganisms were obtained from the culture collection of
Furthermore, the morphology, elemental composition and the Drug Microbiology Laboratory, Drug Radiation Research
purity of the particles were analyzed using a Zeiss, EVO-MA10 Department, NCRRT, Cairo, Egypt. It is worth mentioning that
scanning electron microscope (SEM) supported with an energy the 0.5 McFarland standard of all tested inoculums was set at 2–
dispersive X-ray (EDX) spectroscopy unit (Bruker Nano GmbH 5 ꢄ 108 CFU mlꢀ1 (for bacteria) and 1–4 ꢄ 107 CFU mlꢀ1 (for
D-12489, 410-M, Berlin, Germany). Finally, the zeta potential of yeast). The repression of the tested bacteria and yeast was
the prepared composite at different pH values was measured determined by the zone of inhibition (ZOI) method aer 24 h of
using an ELS-Z1NT analyzer (Photal OTSUKA ELECTRONICS, incubation.28
Japan).
Standard antibiotic discs (diameter of 6.0 mm), such as
2.2.5. Photocatalytic degradation of pyridine using Cox- amoxicillin/clavulanic acid (AMC) and nystatin (NS), were used
Ni1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. The nano- for comparison of the action of the examined samples.29
composite (10 mg) obtained as in Section 2.2.3 was added to
The minimum inhibitory concentration (MIC) was deter-
50 ml of an aqueous solution of pyridine with initial concen- mined using Luria–Bertani (LB) broth with appropriate serial
tration C0 ¼ 100 mg lꢀ1, under constant stirring at ambient dilution.30,31 The microorganism and the nutrient served as
temperature (24.0 ꢃ 2 ꢂC) for 30 min in the dark, until a positive control, and the nutrient alone was used as a negative
adsorption–desorption equilibrium was attained between pyri- control. The CoxNi1ꢀxFe2O4; x ¼ 0.9/SiO2/TiO2 nanocomposite
dine and the prepared photocatalyst (nanocomposite). Aer (starting with a concentration of 100 mg ml; 100 ppm) was
that a halogen lamp (500 W) was used as simulated visible light tested. MIC values were calculated aer 24 h of incubation at
8
to irradiate the solution containing the photocatalyst and 37 C.32,33 The tested bacterial inoculums were set at 3–4 ꢄ 10
ꢂ
pyridine, which was axially located and held in a quartz CFU mlꢀ1, and at 2–4 ꢄ 107 CFU mlꢀ1 for the tested yeasts. MIC
immersion tube. At constant time intervals of irradiation, values were determined through enzyme-linked immunosor-
a syringe equipped with a lter (2.5 mm pore size) was used to bent assay (ELISA) aer xing the absorption wavelength at
draw out a sample of the pyridine suspension (1 ml). The 600 nm.33,34
sample was then centrifuged for 10 min at 5000 rpm to separate
the photocatalyst.
2.2.8. Antibiolm activity of CoxNi1ꢀxFe2O4; x ¼ 0.9/SiO2/
TiO2 nanocomposite. A semi-quantitative study of bacterial and
The degradation rate of pyridine was calculated by deter- yeast biolm development was assessed according to the
mining the variation in pyridine concentration versus irradia- approach described by Christensen et al.35 Observations of the
tion time using
a
UV-vis spectrophotometer (Agilent bacterial and yeast biolm created throughout the interior walls
Technologies Cary 60 UV-vis) at lmax ¼ 256 nm. DI water was of the test tubes were recorded, without and with the Cox-
used as a ref. 25.
Ni1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. The antibiolm
action of the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite
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Fig. 1 HRTEM analysis of the prepared CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 hybrid nanocomposite concentric structure, where yellow and black
arrows display the two shell layers and the white circles represent the core CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs.
at a concentration of 10.0 mg mlꢀ1 was tested against pathogenic
In addition, nutrient broth (5.0 ml) was added to the test
bacteria and Candida species and was compared with a control tubes aer setting the 0.5 McFarland standard at 1–2 ꢄ 107 CFU
sample (a test tube without CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 mlꢀ1 (for the examined bacteria) and the tubes were then
nanocomposite).
incubated for 24 h at 37 ꢂC. The content of the control and
treated tubes was discarded, and then all tubes were cleaned
Fig. 2 SEM and corresponding EDX elemental analysis of the synthesized CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. [A–C] Different
magnifications of the core–multi-shell structure. [D] The corresponding EDX elemental analysis of the synthesized nanocomposite.
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Fig. 3 SEM-EDX elemental mapping of the synthesized CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite.
and rinsed with phosphate-buffered saline (PBS) with a pH of 10 min, and then tubes were rinsed with DI water. Bacterial and
7.5. Finally, all tubes were dried.36,37 The disciple bacterial and yeast biolms were stained with crystal violet (CV; 0.1%) for
yeast lms were xed using sodium acetate (3%; 5 ml) for 10 min and then soaked with DI water to remove excess CV.38
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Subsequently, 4 ml of absolute ethanol was added to disinte-
grate the CV. The developed biolms were recognized by the
notable stained bands at the inner walls and the bottom of the
test tubes.39 The bacterial and yeast biolms were examined
using a UV-vis spectrophotometer at 570 nm, and the biolm
repression percentage (%) was dened using eqn (1).37,40
Percentage of bacterial and yeast biofilm inhibitionð%Þ
OD of the control sample ꢀ OD of the treated sample
¼
OD of the control sample
ꢄ 100
(1)
2.2.9. Effect of UV irradiation. To dene the impact of UV
irradiation on the antimicrobial activity of CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 nanocomposite against the tested microbes, the
percentage inhibition was determined using the optical density
(OD) method.41 Three sensitive organisms were tested,
including E. coli (Gram-negative bacterium), S. aureus (Gram-
positive) and C. albicans (unicellular fungi). For each microbe,
four test tubes were prepared. The rst one was the control tube,
which contained only tested microbes and was not irradiated
with UV, the second control tube contained both microbes and
the synthesized CoxNi1ꢀxFe2O4;
composite and was not irradiated by UV, and the third tube
contained only microbes and was irradiated by UV. Finally, the
x
¼
0.9/SiO2/TiO2 nano-
fourth tube contained both microbes and the tested CoxNi1ꢀx
-
Fe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite and was UV-irradiated.
All test tubes contained nutrient broth and a xed count of
microorganisms (0.5 McFarland; CFU mlꢀ1). The UV-emitting
tube (10 W low-pressure mercury lamp; 90% emittance at
254.0 nm) was located horizontally and xed in the laminar
ow, and the tested tubes were exposed to UV irradiation for 1 h
at a distance of 2 feet (60.96 cm).
It is worth mentioning that the bacterial and yeast count was
calculated every 10 min by UV-vis spectrophotometry at 600 nm
(for bacteria) and 630 nm (for Candida species) for about 1 h and
the inhibition percentage was measured according to eqn (1).
2.2.10. Reaction mechanism using SEM and EDX analysis
of treated bacterial cells. Bacterial cells obtained from the
biolm-creating experiment were rinsed with PBS and tted
with a 3.0% glutaraldehyde suspension. The dried bacterial
samples were repeatedly cleaned by PBS and dried smoothly
with different concentrations of ethanol (30.0%, 50.0%, 70.0%,
80.0%, 95.0%, and 100%) for 15 min at 28.0 ꢃ 2.0 ꢂC, which was
a signicant feature for dehydrating.36 Then, bacterial cells were
set on an aluminum grip for SEM analysis.36 The morphological
features of the control (non-treated bacterial cells) and cells
treated with the fabricated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite were examined through SEM and EDX
investigations.
2.2.11. Statistical analysis. Statistical analysis of our data
was implemented by using the one-way analysis of variance
(ANOVA) test (at P < 0.05) applying Duncan's multiple range
considerations and the least signicant difference report
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(LSD).42 The results and data obtained were analyzed by SPSS fabricated nanocomposite are presented in Fig. 2, where Cox-
soware (version 15).
Ni1ꢀxFe2O4; x ¼ 0.9 NPs are located at the core, and the
following two layers (of SiO2 and TiO2 NPs) are shells around
this core, producing a core–multi-shell system.
3 Results and discussion
3.1. Characterization of the synthesized CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite
Fig. 2 shows SEM and EDX analysis of the synthesized Cox-
Ni1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite revealing its
particle dispersion with high purity through the appearance of
C, O, Si, Ti and Fe atoms and the lack of any foreign elements
(impurities). The recorded carbon atoms are attributed to the
sample holder used in the SEM imaging.47 The corresponding
EDX elemental analysis conrmed the presence of all the
constituent atoms of the nanocomposite. The absence of Ni and
Co atoms is attributed to their location at the deep core of the
composite and their smaller ratios.
3.1.3. Chemical mapping of the synthesized CoxNi1ꢀxFe2-
O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. Elemental mapping of
the integrated composite is shown in Fig. 3. The models were Si,
Ti, Fe, O, and C. Fig. 3 veried the formation of the composite in
terms of its components (Si, Ti, O, and Fe atoms). Interestingly,
the images of elemental mapping conrmed the creation of
a core–multi-shell system, revealed by the brightness and
darkness of its layers. CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs, which are
located at the core, were relatively darker than both the SiO2 and
3.1.1. High-resolution transmission electron microscopy.
HRTEM images of the concentric composition of the developed
nanocomposite (CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9) are pre-
sented in Fig. 1. The integrated composite has a semi-spherical
construction with diameters varying from 90.56 nm to
155.50 nm, and an average diameter of 125.84 nm. It is worth
noting that the compressed particles (white circles) are assigned
to the magnetic core NPs (CoxNi1ꢀxFe2O4; x ¼ 0.9). Also, the
hazy layers (black and yellow arrows) are attributed to the shell
layers (SiO2 and TiO2 NPs), respectively. The construction of the
composite and the arrangement of its layers were fully validated
by SEM color mapping.
3.1.2. Scanning electron microscopy and energy dispersive
X-ray spectroscopic analysis of the synthesized nanocomposite.
SEM was used to examine the formation and morphology of the
nanocomposite,43 while EDX examination was performed for
elemental analysis and purity estimation.44–46 SEM images of the
Fig. 4 Antibacterial and antifungal activities of gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite against pathogenic
microbes for [A] E. coli, [B] Staphylococcus aureus and [C] C. albicans, measured as ZOI (mm).
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TiO2 layers shielding that core.48 The brightest relative intensity
of the Ti atoms showed that the TiO2 layer is the external layer
and has the highest ratio (yellow arrow), followed by another
relatively less bright layer attributed to Si atoms (yellow arrow).
Finally, Fe atoms have a faint red color due to their location at
the core with the smallest ratio (white circle; Fig. 3). Further-
more, both Co and Ni atoms (the principal metals in the ferrite)
disappeared because they are located at the core.
This is one of the rst times elemental mapping has been
used as a tool to illustrate the development of a concentric
structure, giving a promising explanation about the distribution
and purity of the atoms and layers forming the
nanocomposites.49–51
3.2. In vitro antimicrobial activity of the synthesized
CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite
The disc agar spread method (which was performed as
a screening step) revealed that the synthesized CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite displayed a relatively high
antimicrobial activity against all examined bacteria and
Candida species pathogens. Screening results conrmed that
the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite exhibited
the highest antibacterial ability against E. coli (16.0 mm ZOI)
and S. aureus (MRSA) (11.0 mm ZOI) as shown in Table 1.
It is of interest to note that the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼
0.9 nanocomposite has more powerful potential in terms of anti-
microbial abilities than its separate layers (CoxNi1ꢀxFe2O4; x ¼ 0.9
NPs, SiO2, TiO2 NPs), DMSO and standard antimicrobial agents
(AMC). It is also worth noting that the synthesized CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite was more active against Gram-
negative bacteria than against Gram-positive species. The reasons
for this effect may be due to the fact that the cell walls of Gram-
negative species essentially consist of layers of peptidoglycan,
lipopolysaccharide, and lipid, while the cell walls of Gram-positive
species just have thick peptidoglycan structures.52
In addition, the produced CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite was very promising as an antifungal agent,
conferring great antifungal efficiency towards C. albicans
(10.0 mm ZOI), as presented in Table 1.
The MIC results for the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite against all examined pathogenic bacteria and
Candida species were in the range 12.5–3.125 mg mlꢀ1, as shown
in Table 1. The CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nano-
composite possesses a promising MIC value of 3.125 mg mlꢀ1
against E. coli and 6.25 mg mlꢀ1 against S. aureus.
Subsequently, following gamma irradiation with doses of
25.0, 50.0 and 100.0 kGy, the antimicrobial activity of the
synthesized CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite
was evaluated. Gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼
0.9 nanocomposite was more active against E. coli (30.0 mm
ZOI; Fig. 4A), S. aureus (MRSA) (25.0 mm ZOI; Fig. 4B) and C.
albicans (24.0 mm ZOI; Fig. 4C), as presented in Table 2.
Interestingly, the MIC values decreased with increasing dose
of gamma rays and a superior MIC result was recorded at 0.024
mg mlꢀ1 against E. coli for the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite irradiated by 100.0 kGy.
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Fig. 5 XRD pattern showing the effect of gamma irradiation, with doses of 25, 50 and 100 kGy, on the crystal size of the prepared
CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite, compared with the non-irradiated composite.
The enhanced activity of the prepared nanocomposite
From Fig. 5, it can be seen that crystallite size was reduced by
against all tested microorganisms aer gamma irradiation was increasing the gamma radiation dose from 25 to 100 kGy. This
due to the reduction in crystallite size (from 44.2 nm to 17.4 nm) inuence may be due to the movement of gamma rays inside
aer 100 kGy irradiation.53,54 The XRD patterns of non- the materials, transporting its power in a compact time interval
irradiated and gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x within exible contact with particles,53 which leads to modi-
¼ 0.9 nanocomposite with different doses (25 kGy, 50 kGy and cation in the irradiated material by forcing the atoms from their
100 kGy) are shown in Fig. 5.
initial conditions, and dividing particles.54
The XRD patterns presented in Fig. 5 show the crystallinity of
Additionally, with increase in irradiation dose the samples
the non-irradiated and gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/ showed a tendency to become amorphous (Fig. 5) and this is
TiO2; x ¼ 0.9 nanocomposite. Characteristic peaks of TiO2 NPs, because the crystallite size is independent of the crystallinity of
SiO2 NPs and CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs were clearly recorded. the sample. Crystallization of a material means that there are
Many sharp, strong and intense peaks were observed at 2q long arrangements of atoms. This can be indicated by the
values of 25.8ꢂ (reection 101), 38.0ꢂ (reection 112), 48.0ꢂ intensity of the XRD lines. For XRD, the smallest crystallite size
(reection 200), 54.3ꢂ (reection 105), and 60.3ꢂ (reection 213), caused obvious broadening of the XRD peaks, but crystallite
while the principal peak was observed at 2q ¼ 25.8ꢂ. Recorded size gives information about the formed sample.60 A perfect
peaks matched those of TiO2 NPs (JCPDS 04-0477).24
crystal would extend innitely in all directions; hence, no
An amorphous extended peak was recorded at 2q ¼ 22.1ꢂ, crystals are perfect because of their nite crystal size. This
which is associated with the interatomic lengths in SiO2 deviation from perfect crystallinity leads to broadening of the
NPs.55–58 Finally, sharp and intense peaks were observed at 2q ¼ diffraction peaks.61 The two principal properties obtained from
38.0ꢂ (reection 311), 45.2ꢂ (reection 400), 54.3ꢂ (reection peak width analysis are the crystallite size and lattice strain.
422), and 62.3ꢂ (reection 440), while a promising peak
Crystallite size is a measure of the size of coherently dif-
appeared at 38.0ꢂ, registering the appearance of both Ni Fe2O4 fracting domains. The crystallite size of the particles is not
(JCPDS 10-325) and Co Fe2O4 (JCPDS 1-1121), indicating the usually the same as the particle size due to the production of
development of CoxNi1ꢀxFe2O4; x ¼ 0.9 NPs.59
polycrystalline aggregates.62 Lattice strain is a measure of the
The average crystallite size was calculated using the Debye– distribution of lattice constants resulting from crystal imper-
Scherrer equation as:
fections, such as lattice dislocations. Other sources of strain
include the grain boundary triple junction, contact or sinter
stresses, stacking faults, and coherency stresses.63 Crystallite
size and lattice strain affect the Bragg peak in different ways.
Both these effects extend the peak width and intensity and shi
the 2q peak position accordingly.
Kl
D ¼
b cos q
where K ¼ 0.9 and is known as the shape factor, l is the wave-
˚
length of the X-ray (1.54060 A for CuKa), b is the full width at
half maximum (FWHM) and q is the diffraction angle.
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Interestingly, there is a relationship between the physical
properties of the fabricated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite and its recorded antimicrobial abilities, with
surface area playing a signicant role in the antimicrobial
action of the synthesized CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite against all tested pathogenic microbes.
The calculated surface area was 46.13 m2 gꢀ1, with a broad
spread of pore sizes of TiO2 NPs, with an average value of
3.71 nm and an average pore volume of about 0.19 cm3 gꢀ1, as
previously calculated in our recent paper,24 implying the
appearance of two kinds of pores in the external layer of the
composite TiO2 NPs: mesopores and macropores.64
The high surface area and broad pore size of the produced
nanocomposite increased the contact area to the microbial cell
and hence the antimicrobial activity of the CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 nanocomposite was increased.
The gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite had a more stable prole, with relatively lower
crystal size (19.6 nm, 19.3 nm and 17.4 nm aer gamma irra-
diation with 25 kGy, 50 kGy and 100 kGy, respectively; Fig. 5)
compared to the non-irradiated composite. These physical
properties were critical in improving its antimicrobial efficacy
even at a low concentration (0.024 mg mlꢀ1) against all examined
pathogenic bacteria and Candida species.
3.3. Antimicrobial potential of UV-irradiated CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite in liquid media
A comparative study of the inhibition percentage of E. coli, S.
aureus, and C. albicans by non-irradiated CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 nanocomposite and UV-irradiated CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite was performed and is pre-
sented in Fig. 6.
As shown in Fig. 6A–C, the inhibition percentage of the
tested pathogens increased with time upon treatment with the
CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite, meaning that
the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite showed
antimicrobial activities against colonies of E. coli, S. aureus and
C. albicans. Interestingly, the UV-irradiated CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite exhibited superior antimi-
crobial activities compared with the non-irradiated nano-
composite, as shown in Fig. 6. The maximum inhibition
percentage of non-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite and UV-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x
¼ 0.9 nanocomposite against E. coli was 22.30% and 70.45%,
respectively, and the inhibition was 40.45% and 60.50% for S.
aureus and 30.10% and 50.85% for C. albicans, aer 60 min
(experiment time).
Fig. 6 Antimicrobial abilities of UV-irradiated CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 nanocomposite against different pathogens: [A] E. coli,
[B] S. aureus and [C] C. albicans.
It was found that the CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite was more active under UV irradiation, con-
rming the presence of photogenerated reactive oxygen species
cells and the nanocomposite. The OH radicals can destroy
bacterial cells causing a reduction in cell coenzyme content.65
In addition, it has been reported that metal oxides (MO)
display a positive charge in slightly acidic medium, while
microbes possess a negative charge. This creates an electro-
magnetic affinity between microbes and the MO, leading to
oxidization of microbial cells and their subsequent
(ROS) that can decompose bacterial cells. Here, the CoxNi1ꢀx
-
Fe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite was shown to have
good antimicrobial abilities attributed to its high UV absorption
intensity. Hydroxyl (OH) radicals can also be generated by
irradiating CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite
with ultraviolet light, due to electron transfer between microbial
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destruction.66 Additionally, nanomaterials can destroy cellular
E. coli inoculated in the absence of gamma-irradiated Cox-
proteins and DNA by adhering to electron-donating structures, Ni1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite exhibited a thick
such as carbohydrates, thiols, indoles, amides, and hydroxyls. whitish-yellow mat throughout the air–liquid interface. This
In addition, they can create holes in the bacterial cell walls, mat was totally adhered to the wall of the test tubes and
making them outwardly permeable and nally resulting in cell appeared as a blue ring aer CV staining. A blue suspension was
loss.67 We have previously reported that our composite developed aer dissolving the CV-stained ring with absolute
possessed negative charge, but the media of the microbes is ethanol, as displayed in Fig. 7A.
slightly acidic (pH ¼ 6.0), which can change the surface charge
On the other hand, E. coli-inoculated test tubes that were
of the composite to positive, and this is in a good agreement treated with gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼
with our results (see Fig. 14B later).
0.9 nanocomposite (10.0 mg mlꢀ1) exhibited a suppressed effect
where the development of bacterial rings was limited. In addi-
tion, the blue color representing CV-stained adherent bacterial
cells was light and, aer CV dissolution by ethanol, no blue
color was observed, as shown in Fig. 7A. A similar effect was
recorded for the biolm repression of C. albicans (as an example
of a sensitive yeast), as presented in Fig. 7B.
3.4. Antibiolm activity of CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
nanocomposite gamma-irradiated with 100 kGy
Biolm creation has been recognized in several
exopolysaccharide-forming microbes.36,50 Biolm production by
common pathogenic bacteria and yeast microorganisms in the
absence and presence of gamma-irradiated (with 100 kGy)
CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite was assessed
using a test tube method.68
Fig. 7A shows the antibiolm activity of 100 kGy gamma-
irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite
against E. coli bacteria (as a model for susceptible bacteria).
To determine the repression percentage (%) of bacterial and
yeast biolm, a UV-vis spectrophotometer was used (at 570.0
nm). The optical density was determined aer separating CV-
stained bacterial and yeast biolms with ethanol. Table 3
shows the inhibition percentage of the biolms formed by the
tested bacteria and yeast strains. The highest percentage
Fig. 7 Antibiofilm activity of 100 kGy gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite using the test tube method against
[A] E. coli and [B] C. albicans. The steps were reported as follows. (a) Growth of the bacterial and yeast cells and biofilm formation (rings) without
treatment with the synthesized CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite and the inhibition of bacterial and yeast growth after
treatment with CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. (b) Staining of the adherent bacterial and yeast cells with crystal violet. (c)
Removing and dissolving the adherent bacterial and yeast cells by ethanol for determination of semi-quantitative biofilm inhibition (%) (as shown
in Table 3).
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Table 3 Semi-quantitative inhibition (%) of the biofilm formation for non-treated and treated bacterial and yeast pathogens with 100 kGy
gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocompositea
OD of crystal violet stain at 570.0
nm (treated with 10.0 mg mlꢀ1
OD of crystal violet
stain at 570.0 nm (control)
CoxNi1ꢀxFe2O4/SiO2/TiO2
nanocomposite)
Inhibition
(%)
Bacterial and yeast strains
Escherichia coli
0.992j ꢃ 0.0017
0.598e ꢃ 0.0030
0.645f ꢃ 0.0026
0.574d ꢃ 0.0023
0.411a ꢃ 0.0045
0.897i ꢃ 0.0005
0.708h ꢃ 0.0010
0.666g ꢃ 0.0030
0.519c ꢃ 0.0026
0.501b ꢃ 0.0026
0.01700
0.071d ꢃ 0.0023
0.089d ꢃ 0.0020
0.060c ꢃ 0.0026
0.098f ꢃ 0.0010
0.088e ꢃ 0.0047
0.499b ꢃ 0.0001
0.166h ꢃ 0.0020
0.313i ꢃ 0.0015
0.040a ꢃ 0.0025
0.111g ꢃ 0.0040
0.00767
92.82%
85.11%
90.69%
82.92%
78.58%
44.37%
76.55%
53.00%
92.29%
77.84%
—
Pseudomonas aeruginosa
Staphylococcus aureus (MRSA)
Bacillus subtilus
Proteus mirabilis
Salmonella typhi
Proteus vulgaris
Klebsiella pneumoniae
Candida albicans
Candida tropicalis
LSD
a
Values are presented as mean ꢃ SD (n ¼ 3). a–eData within the groups were analyzed using one-way analysis of variance (ANOVA) followed by
Duncan's multiple range test (DMRT). LSD, least signicant difference.
inhibition was observed against E. coli (92.82%; Fig. 7A and (Table 2). When the exopolysaccharide assembly is restricted
Table 3) followed by C. albicans (92.29%; Fig. 7B and Table 3) (the principal molecules for biolm development), E. coli
and S. aureus (90.69%; Table 3) aer treatment with 10.0 mg cannot make a biolm.36,68
mlꢀ1 of gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9
To further explain the antibiolm abilities of the 100 kGy
gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nano-
nanocomposite.
The synthesized 100 kGy gamma-irradiated CoxNi1ꢀxFe2O4/ composite, we propose a mechanism of action against biolm
SiO2/TiO2; x ¼ 0.9 nanocomposite was used to restrain the production by E. coli from SEM and EDX studies.37,71 The SEM
development of biolm at its adhesion step (identied as the images show the bacterial cell morphologies before and aer
primary step).69
treatment with 100 kGy gamma irradiation of the prepared
The variance in the percentage inhibition may be attributed nanocomposite. In the control (non-treated bacterial cells),
to various circumstances, such as antimicrobial action, bio- bacterial cultures were normally developed and had denite
sorption (because of the large surface area of the synthesized normal cellular morphology with a normal cell exterior and
nanocomposite), physical characteristics (particle size of the compressed biolm production, as displayed in Fig. 8A.
nanocomposite), invasion capabilities and different chemical
Aer treatment, morphological modications were recog-
features controlling the interaction of the nanocomposite and nized on E. coli cells (Fig. 8). There was an obvious change at the
the biolms.68,70 It was also found that the 100 kGy gamma- surface, followed by a deformation and decrease in the viable
irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite count of E. coli cells. Moreover, biolm formation was arrested.
inhibited E. coli by greater than 98% at 0.024 mg mlꢀ1 MIC SEM investigation also showed shrinkage of the bacterial cell
Fig. 8 SEM and corresponding EDX elemental analysis of E. coli. [A] Normal bacterial cell without treatment with 100 kGy gamma-irradiated
CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite. [B] The depressed and deformed bacterial cell after treatment with 100 kGy gamma-irra-
diated CoxNi1ꢀxFe2O4; x ¼ 0.9/SiO2/TiO2 nanocomposite (yellow square represents complete lysis of E. coli cells). [C] The corresponding EDX
elemental analysis of the treated E. coli cell, confirming the cellular internalization of the 100 kGy gamma-irradiated CoxNi1ꢀxFe2O4; x ¼ 0.9/
SiO2/TiO2 nanocomposite.
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walls71 (Fig. 8B), while the EDX elemental study showed the
appearance of Ti and Si atoms (atoms of the outer shell of the
prepared nanocomposite) at the shrinkage area and the external
surface of the tested E. coli cells, conrming the reason for the
recorded effect, namely nanocomposite treatment (Fig. 8C).
One probable cause for the reported activity against E. coli
could be due to the large surface area (46.13 m2 gꢀ1) enabling
better static communication between the negatively charged
cell walls of the examined bacteria,72,73 as exhibited in Fig. 8B.
This conclusion is in a reasonable agreement with several
published reports conrming the interaction between MO NPs
and pathogens through electrostatic power, leading to bacterial
membrane separation.72,74,75 Recent research affirms that MO
NPs increase the oxidative pressure against pathogens76 and
rapidly destroy their cell membranes because of the high level
of ROS generated. Additionally, detailed reaction mechanisms
for MO NPs against pathogenic bacteria and yeast cells have
been described in our previous studies.37,77
Fig. 10 Effect of initial concentration of pyridine solution on the
degradation efficiency (10 mg of composite, 50 ml Py solution, 25 ꢂ
C
and pH 7).
Herein, the prepared nanocomposite interacted externally
with E. coli cells by means of electrostatic affinity and reduced
the bacterial cell counts through membrane leakage.74 The
Fig. 9 illustrates the decline in absorption with irradiation
proposed reaction mechanism begins with adhesion of the time for the photocatalytic degradation of pyridine solution
nanocomposite onto the surface of E. coli. Aer that, Ti2+ and (50 ml, 100 mg lꢀ1) using 10 mg of the prepared nanocomposite.
Si2+ ions (from the outer shell) enter the tested bacterial cell and With increasing irradiation period, the strong absorption bands
destroy its biological molecules, such as mitochondria and of pyridine recorded at 256 nm (indicating the maximum
DNA. Then, cellular toxicity due to oxidative stress through the wavelength, lmax, for the pyridine) are continuously reduced.
production of ROS develops. The nanocomposite can certainly The absorbance of the pyridine solution was reduced by 85%
block the signal transduction cycle of the examined bacterial aer 100 min of visible light irradiation at the specied exper-
cells.78
imental conditions.
3.5.1. Effect of the initial concentration of pyridine on
degradation efficiency. The degradation efficiency of the
prepared nanocomposite against pyridine at different initial
concentrations (10–150 ppm) is shown in Fig. 10. The results
show that the degradation efficiency is inversely proportional to
the concentration of pyridine, which can be effectively removed
in the presence of the prepared nanocomposite under visible
light irradiation even at high initial concentrations.
Table 4 gives the percentage degradation of pyridine at
a range of high initial concentrations (300–1000 ppm) and also
indicates the effectiveness of pyridine degradation over this
range. Upon increasing the initial concentration from 300 to
1000 ppm, a minor decrease in degradation efficiency was
observed. The measured degradation efficiencies exceeded
86%. The pyridine concentration removed from wastewater
increases upon increasing the initial concentration without
affecting the degradation efficiency.
3.5. Photocatalytic activity of CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼
0.9 nanocomposite
The photocatalytic activity of the synthesized CoxNi1ꢀxFe2O4/
SiO2/TiO2; x ¼ 0.9 nanocomposite was determined using pho-
tocatalytic degradation of pyridine solution (Py) under visible
light illumination.
The degradation rate of pyridine can be calculated using the
following equation:
ln Ct/C0 ¼ ꢀKt
(2)
Table 4 Removal of pyridine solution at high initial concentrations
Concentration (mg mlꢀ1
Fig. 9 UV-visible spectra of pyridine showing its degradation with
time (10 mg of nanocomposite, 50 ml Py solution (100 ppm), 25 ꢂC and
pH 7).
)
300
88.2
500
87.4
800
87.1
1000
86.3
Degradation percentage (%)
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10 mg and 30 mg at a pyridine concentration of 100 mg lꢀ1, as
shown in Fig. 13. Our results reveal that upon increasing the dose
of catalyst (CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9) from 10 to 30 mg in
100 ml of aqueous pyridine, the value of Ct/C0 ꢄ 100 decreased
from 40 to 19, which shows an increase in degradation efficiency.
This direct proportionality between the degradation efficiency
and the dose of the reaction medium photocatalyst can be
attributed to the increase in the active sites and large surface area
available for pyridine degradation.81
3.5.3. Effect of pH on degradation efficiency. The effect of
initial pH values of the pyridine solution was studied for
100 min under specied experimental conditions (10 mg of
prepared nanocomposite, 50 ml Py solution (100 mg lꢀ1), 25 ꢂC).
Our results reveal that the optimal pH, which led to degradation
of 86.5% of the pyridine, was 9. At pH 5 and 7 degradation
efficiencies of only 46.5% and 60.5%, respectively, were recor-
ded. In addition, no increase in pyridine degradation was
noticed when the pH was further increased above pH 9, as
shown in Fig. 14A, and the degradation efficiency was
substantially decreased at pH < 5.
Fig. 11 The first-order kinetics of pyridine degradation (10 mg of
composite, 50 ml Py solution, 25 ꢂC and pH 7).
To better understand the relationship between pH and
degradation efficiency, the point of zero charge was determined
by measuring the zeta potential of the composite at different pH
values, from 2 to 10, in the presence of 0.01 M NaCl (electrolyte),
as shown in Fig. 14B.
where Ct and C0 are the remaining and initial concentrations of
pyridine, respectively, t is the irradiation time and K represents
the degradation rate constant.
Fig. 11 shows the relationship of ꢀln Ct/C0 vs. time. The
results show that the kinetics of the degradation reaction follow
the laws of a rst-order rate (R2 > 98) at initial concentrations.
Moreover, as revealed by Fig. 12, there is an inverse relationship
between the apparent rst-order rate constants and initial
pyridine concentration, which indicates the non-elementary
nature of the photocatalytic reaction. This recorded depen-
dence of the reaction rate constants on initial concentration is
in a good agreement with the literature.79,80
3.5.2. Effect of the dose of photocatalyst on degradation
efficiency. The impact of the photocatalyst dose on the efficiency
of degradation of pyridine under visible light irradiation was
studied by tuning the amount of photocatalyst used between
It is clear that when the pH is equal to 7 (neutral media) and
when it is more than 7 (alkaline media) the composite exhibited
a negative charge (zeta potential ¼ ꢀ35.19 mV at pH 7), which
stabilized at pH 9 (zeta potential ¼ ꢀ47.39). In acidic media (pH
less than 7), the composite showed a positive charge, which
stabilized at pH 2 (zeta potential ¼ +19.37 mV).
Moreover, the point of zero charge (PZC) was been found to
equal 6.1, which is in good agreement with the literature for
TiO2 NPs (the outer layer of the composite).82 It was previously
reported that at a pH of more than 8, TiO2 NPs are stabilized,
with no agglomeration, which is very important for photo-
catalytic degradation, and this supports the enhanced
Fig. 12 Apparent first-order rate constants vs. initial concentration of Fig. 13 Effect of photocatalyst dose on pyridine degradation effi-
pyridine.
ciency (50 ml Py solution (100 mg lꢀ1), 25 ꢂC and pH 7).
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solution as a result of absorption of visible light (eqn (3)) can
form hydrogen peroxide (H2O2) in the reaction medium.
However, increased amounts of hydrogen peroxide may have
a critical effect on the total contaminant degradation (eqn (4)).
Therefore, a study was performed at different concentrations of
H2O2, as shown in Fig. 15.
Herein, experiments were repeated with pyridine solutions
containing H2O2 to study its effect on the photocatalytic
degradation of pyridine (100 mg lꢀ1 and 50 ml) with H2O2
concentrations of 100 ppm and 200 ppm in the solution.
H2O2 + visible light / 2cOH
cH + H2O2 / cOH + H2O
(3)
(4)
The amount of H2O2 that can be formed by the absorbed
visible light is too small to dissociate into signicant amounts
of cOH. Therefore, further quantities of H2O2 are needed to
foster the degradation process. Addition of H2O2 will increase
and accelerate the generation of cOH in two ways; either
through self-decomposition due to the absorption of visible
light, or by H2O2 reduction at the conduction band, as illus-
trated in eqn (3) and (4), respectively.14,86
Generally, to improve the photocatalytic removal of organic
compounds, several researchers have investigated the effect of
adding external oxidants, such as H2O2, to improve the process.
Under certain conditions, cOH is formed by the ready decom-
position of H2O2, as the O–O bond dissociation energy in H2O2
is only 213 kJ molꢀ1, which is smaller than that of the O–H bond
in H2O at 418 kJ molꢀ1
.
However, aer analyzing various
14
studies that suggest the use of H2O2 to improve the degradation
rate of organic pollutants, it is clear that the optimal value for
H2O2 is strongly dependent on the type of organic compound,
the equipment conguration and the operating conditions, all
of which were identied as having a direct effect on the
production rate of cOH.
Fig. 14 [A] Influence of initial pH on the removal of pyridine (50 ml
pyridine (100 mg lꢀ1), 10 mg nanocomposite and 100 min irradiation
time) and [B] the point of zero charge (PZC) of CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 at different pH values.
photocatalytic activity of the prepared composite (with the TiO2
outer layer) at pH ¼ 9.83 Pyridine is a heterocyclic compound
containing nitrogen and, with degradation and upon mineral-
ization, the N atom in the ring is released as ammonia, which
can be detected easily by its unpleasant odor.84
Generally, it can be proposed that at high values of acidity for
the reaction medium, and due to the higher electronegativity of
the pyridine N atom compared with the sp2 hybridized C atoms
in the ring, ammonium salt develops and is released into the
solution, which is more stable and leads to a decrease in
degradation efficiency. However, in alkaline medium, the
anionic state of pyridine supports the absorption of visible
light. In addition, the formation of more hydroxyl radicals from
hydroxyl ions (OHꢀ / OHc) in the solution may lead to
improvement in the degradation efficiency.14,85
3.5.4. Effect of hydrogen peroxide on degradation effi-
ciency. Hydroxyl radicals generated in the pyridine aqueous
Fig. 15 Effect of H2O2 on pyridine degradation (initial concentration of
pyridine C0 ¼ 100 ppm, 50 ml, 10 mg of nanocomposite and pH 9).
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Fig. 16 Photocatalyst mechanisms of pyridine using CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nanocomposite and a possible degraded product.
To sum up, it is worth noting that the H2O2 concentration 4.435 min. The HPLC results also show the response aer 3 min
should not exceed a certain optimal value as it could then irradiation time for the same sample. The chromatogram shows
recombine with the cOH formed, leading to a decrease in the two other peaks which could be attributed to the pyridine
total degradation rate.14,86,87
In the literature on degradation of pyridine and pyridine discussion.
degradation intermediate products according to the above
derivatives there are inconsistencies concerning the reaction
Finally, as can be seen in the GC-MS analysis,14 the N atom in
mechanism by means of holes or hydroxyl radicals, as shown in the pyridine ring is released as NH3 upon mineralization and
Fig. 16. Agrios and Pichat88 suggest that pyridine reacts over then stripped from solution by aeration.94 The ammonium
TiO2 predominantly via formation of a radical centered on the nitrogen (NH3–N) is oen monitored as a measure of pyridine
pyridine ring. Some researchers report that free radicals would degradation.94,95
be generated by applying visible light simultaneously with
oxidants (air bubbling).89,90 Wang et al.91 showed that hydroxyl
4 Conclusion
radicals (cOH) could be generated indirectly from the applica-
tion of visible light. Therefore, the degradation relies on the
generation of reactive free radicals, especially hydroxyl radicals
(cOH), which is a powerful oxidizing agent having an oxidation
In this work, a recyclable nanocomposite (CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9) was designed and fabricated using a layer-by-layer
approach. The crystallinity and the effect of gamma radiation
potential of 2.33 V, which can undergo rapid and non-selective
on the crystal size of the prepared nanocomposite were identi-
reaction with most organic and many inorganic solutes.92
ed by XRD, while the average particle size was measured
through HRTEM, which revealed the semi-spherical shape of
According to our previous work,14 detection of the pyridine
intermediate decomposition product by gas chromatography-
the concentric nanocomposite. The synthesized CoxNi1ꢀxFe2O4/
mass spectrometry (GC-MS) and high-performance liquid
SiO2/TiO2; x ¼ 0.9 nanocomposite possesses good purity, as
chromatography (HPLC) supports a mechanism by means of
holes, as shown in Fig. 16, whereas the increase in the degra-
revealed by elemental EDX analysis. The core–multi-shell
structure was evaluated using SEM-EDX mapping techniques.
dation rate on bubbling air (O2) through the solution evidences
The antimicrobial abilities of the nanocomposite, gamma-
the important role played by hydroxyl and superoxide anion
irradiated nanocomposite and UV-irradiated nanocomposite
were then studied. The whole composite was more powerful in
terms of its antimicrobial abilities than its separated layers
(separate core and two shells). It was active even at low
(cO2ꢀ) radicals.
Pyridine wastewater consists of a large amount of molecular
H2O and ammonia. In addition, N–H/O and O–H/N inter-
molecular hydrogen bonds can exist in the wastewater.93,94
Molecular H2O and ammonia are both polar molecules and can
be polarized by visible light in the presence of H2O2, which
causes the dipoles to rotate and line up rapidly (2450 million
times per s). Therefore, the frequent pendulum vibration of
molecular H2O and ammonia leads to breaking and weakening
of the intermolecular hydrogen bond between ammonia and
H2O, which is benecial for escape of the pyridine decomposi-
tion product from the liquid phase to the gas phase (Fig. 16).
In order to conrm the degradation of pyridine, different
samples were analyzed by HPLC (direct injection) as mentioned
in our previous work.14 The results in ref. 14 show the HPLC
response of the pyridine sample injection subjected to micro-
wave (MW) radiation for 1 min. The pyridine retention time was
concentrations (10.0 mg mlꢀ1) against all tested pathogens. Our
results show that the gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/
TiO2; x ¼ 0.9 nanocomposite was effective against all tested
pathogenic microbes as a result of its high surface area and
reduction in crystal size due to the gamma rays. The gamma-
irradiated nanocomposite exhibited more enhanced antimi-
crobial abilities than the non-irradiated composite, and this
ability increased proportionally with increasing radiation dose
(the 100 kGy gamma-irradiated composite was the most active,
for example, causing E. coli growth inhibition even at 0.024 mg
mlꢀ1 MIC; Table 2). Biolm examination also revealed that 100
kGy gamma-irradiated CoxNi1ꢀxFe2O4/SiO2/TiO2; x ¼ 0.9 nano-
composite inhibited biolm formation by 92.82%, 92.29%, and
90.69% against E. coli, C. albicans and S. aureus, respectively.
5256 | RSC Adv., 2020, 10, 5241–5259
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Interestingly, the results for the antimicrobial abilities of UV-
irradiated nanocomposite also revealed higher antimicrobial
activity of the composite with time, conrming the generation
of ROS that can decompose bacterial cells. In addition, SEM-
EDX analysis of the treated bacterial cells conrmed the
cellular internalization by the nanocomposite in E. coli cells and
an observable external cell roughness, with subsequent defor-
mation and a decrease in the viable count of E. coli cells being
observed. Finally, the visible light-assisted photocatalytic
degradation of pyridine by the prepared nanocomposite was
studied taking into account many parameters that can affect its
degradation abilities, such as pyridine initial concentration,
photocatalyst dose (nanocomposite dose), different pH values
and the presence of H2O2. The prepared composite showed
promising visible light-assisted photodegradation abilities
against pyridine. Our work provides a new nanocomposite-
based solution for degradation of toxic pollutants and disin-
fection of water-borne pathogens, which cause serious diseases,
and thus offers a new wastewater treatment technique to over-
come the problems of global water shortage and water
contamination.
References
1 E. Hill and R. DiSalvo, Environmental Epidemiology, 2019, 3,
159.
2 B. Nath, Resonance, 2019, 24, 575–582.
3 M. Forde, R. Izurieta and B. Ormeci, Water Quality in the
ˆ
Americas, 2019, vol. 27.
4 P. I. Ritter and R. Sanchez, Prenatal Exposure to Acute
Diarrheal Diseases and Childhood Mortality, 2019.
5 K. Ravindra, S. Mor and V. L. Pinnaka, Environ. Sci. Pollut.
Res., 2019, 1–11.
´
6 C. A. Martınez-Huitle and M. Panizza, Curr. Opin.
Electrochem., 2018, 11, 62–71.
7 M. A. Elkodous, A. Hassaan, A. Ghoneim and Z. Abdeen,
Characterization and Application of Nanomaterials, 2018, 1,
1–9.
8 R. A. Abramovitch, Pyridine and Its Derivatives, Supplement,
John Wiley & Sons, 2009.
9 C. Xu, Q. Xiao, W. N. Leung, P. Wang and H. Lee, Chem. Eng.
Commun., 2019, 206(9), 1199–1217.
10 B. Bak, L. Hansen-Nygaard and J. Rastrup-Andersen, J. Mol.
Spectrosc., 1958, 2, 361–368.
11 C. Patel, M. Mohnike, M. C. Hilton and A. McNally, Org. Lett.,
2018, 20, 2607–2610.
Funding
12 Y. B. Poudel, L. He, S. Gangwar, S. L. Posy and
P. Sivaprakasam, US Pat., US10494370B2, 2019.
13 N. Gupta, E. J. O'Loughlin and G. K. Sims, in Microbial
Metabolism of Xenobiotic Compounds, Springer, 2019, pp. 1–
31.
Not applicable.
Research involving human
participation and/or animals
14 O. Zalat and M. Elsayed, J. Environ. Chem. Eng., 2013, 1, 137–
143.
Not applicable.
15 A. K. Choubey and Y. Shukla, J. Water Pollut. Purif. Res., 2019,
6, 24–36.
Informed consent
´
´
16 M. Salar-Garcıa and V. Ortiz-Martınez, in Advanced Research
in Nanosciences for Water Technology, Springer, 2019, pp.
341–362.
Not applicable.
17 G. Govindasamy, K. Pal, M. Abd Elkodous, G. S. El-Sayyad,
K. Gautam and P. Murugasan, J. Mater. Sci.: Mater.
Electron., 2019, 30, 16463–16477.
Ethical approval
Not applicable.
18 C. W. Wong, Y. S. Chan, J. Jeevanandam, K. Pal,
M. Bechelany, M. Abd Elkodous and G. S. El-Sayyad, J.
Cluster Sci., 2019, DOI: 10.1007/s10876-019-01651-3.
19 M. Abd Elkodous, G. S. El-Sayyad, M. I. A. Abdel Maksoud,
I. Y. Abdelrahman, F. M. Mosallam, M. Gobara and A. I. El-
Batal, Biol. Trace Elem. Res., 2019, DOI: 10.1007/s12011-
019-01894-1.
Conflicts of interest
The authors declare that they have no conict of interest.
Acknowledgements
The authors would like to thank the Nanotechnology Research
Unit (P. I. Prof. Dr Ahmed I. El-Batal), Drug Microbiology
Laboratory, Drug Radiation Research Department, NCRRT,
Egypt, for supporting this study under the project “Nutraceut-
icals and Functional Foods Production by using Nano/
Biotechnological and Irradiation Processes”. The authors
would also like to thank the Zeiss microscope team in Cairo for
their invaluable advice during this study. Finally, the author M.
Abd Elkodous would like to express his deep gratitude to Nile
University's vice president for research (Prof. Dr Ahmed Rad-
wan) for his continued support.
20 J. Jeevanandam, A. Sundaramurthy, V. Sharma, C. Murugan,
K. Pal, M. H. Abdel Kodous and M. K. Danquah, in
Sustainable Nanoscale Engineering, ed. G. Szekely and A.
Livingston, Elsevier, 2020, pp. 83–113, DOI: 10.1016/B978-
0-12-814681-1.00004-7.
21 M. A. Elkodous, G. S. El-Sayyad, H. A. Nasser, A. A. Elshamy,
M. Morsi, I. Y. Abdelrahman, A. S. Kodous, F. M. Mosallam,
M. Gobara and A. I. El-Batal, J. Cluster Sci., 2019, 30, 531–540.
22 A. Meng, L. Zhang, B. Cheng and J. Yu, Adv. Mater., 2019,
1807660.
This journal is © The Royal Society of Chemistry 2020
RSC Adv., 2020, 10, 5241–5259 | 5257

View Article Online
RSC Advances
Paper
23 K. Nakata and A. Fujishima, J. Photochem. Photobiol., C, 2012, 47 M. A. Maksoud, A. El-ghandour, G. S. El-Sayyad, A. Awed,
13, 169–189.
A. Ashour, A. I. El-Batal, M. Gobara, E. Abdel-Khalek and
24 M. A. Elkodous, G. S. El-Sayyad, A. E. Mohamed, K. Pal,
M. El-Okr, J. Sol-Gel Sci. Technol., 2019, 90, 631–642.
N. Asthana, F. G. de Souza Junior, F. M. Mosallam, 48 P. Dobrowolska, A. Krajewska, M. Gajda-R˛aczka,
M. Gobara and A. I. El-Batal, J. Mater. Sci.: Mater. Electron.,
2019, 30, 8312–8328.
B. Bartosewicz, P. Nyga and B. Jankiewicz, Materials, 2015,
8, 2849–2862.
25 A. I. El-Batal, G. S. El-Sayyad, A. El-Ghamry, K. M. Agaypi, 49 M. A. Maksoud, A. El-ghandour, G. S. El-Sayyad, A. Awed,
M. A. Elsayed and M. Gobara, J. Photochem. Photobiol., B,
2017, 173, 120–139.
R. A. Fahim, M. Atta, A. Ashour, A. I. El-Batal, M. Gobara
and E. Abdel-Khalek, J. Mater. Sci.: Mater. Electron., 2019,
1–12.
26 M. S. Attia, G. S. El-Sayyad, S. S. Saleh, N. M. Balabel and
A. I. El-Batal, J. Cluster Sci., 2019, 30, 919–935.
27 L. Boyanova, G. Gergova, R. Nikolov, S. Derejian, E. Lazarova,
N. Katsarov, I. Mitov and Z. Krastev, J. Med. Microbiol., 2005,
54, 481–483.
28 S. Rothenburger, D. Spangler, S. Bhende and D. Burkley,
Surg. Infect., 2002, 3, s79–s87.
29 A. El-Batal, B. M. Haroun, A. A. Farrag, A. Baraka and G. S. El-
Sayyad, Br. J. Pharm. Res., 2014, 4, 1341.
50 M. A. Maksoud, G. S. El-Sayyad, A. Ashour, A. I. El-Batal,
M. A. Elsayed, M. Gobara, A. M. El-Khawaga, E. Abdel-
Khalek and M. El-Okr, Microb. Pathog., 2019, 127, 144–158.
51 A. I. El-Batal, M. S. Attia, M. M. Nofel and G. S. El-Sayyad, J.
Cluster Sci., 2019, 30, 687–705.
52 Z.-X. Tang and B.-F. Lv, Braz. J. Chem. Eng., 2014, 31, 591–
601.
53 M. B. Ali, K. El Maalam, H. El Moussaoui, O. Mounkachi,
M. Hamedoun, R. Masrour, E. Hlil and A. Benyoussef, J.
Magn. Magn. Mater., 2016, 398, 20–25.
30 A. I. El-Batal, N. E. Al-Hazmi, F. M. Mosallam and G. S. El-
Sayyad, Microb. Pathog., 2018, 118, 159–169.
31 A. I. El-Batal, G. S. El-Sayyad, A. El-Ghamery and M. Gobara, 54 M. Veena, A. Somashekarappa, G. Shankaramurthy,
J. Cluster Sci., 2017, 28, 1083–1112.
32 G. S. El-Sayyad, F. M. Mosallam and A. I. El-Batal, Adv.
Powder Technol., 2018, 29, 2616–2625.
H. Jayanna and H. Somashekarappa, J. Magn. Magn.
Mater., 2016, 419, 375–385.
55 A. C. Wright, J. Non-Cryst. Solids, 1990, 123, 129–148.
33 A. I. El-Batal, G. S. El-Sayyad, F. M. Mosallam and 56 R. Mozzi and B. Warren, J. Appl. Crystallogr., 1969, 2, 164–
R. M. Fathy, J. Cluster Sci., 2019, 31(1), 79–90. 172.
34 A. Baraka, S. Dickson, M. Gobara, G. S. El-Sayyad, 57 Q. Mei, C. Benmore and J. Weber, Phys. Rev. Lett., 2007, 98,
M. Zorainy, M. I. Awaad, H. Hatem, M. M. Kotb and
A. F. Tawc, Chem. Pap., 2017, 71, 2271–2281.
35 G. D. Christensen, W. A. Simpson, A. L. Bisno and
E. H. Beachey, Infect. Immun., 1982, 37, 318–326.
36 M. A. Ansari, H. M. Khan, A. A. Khan, S. S. Cameotra and
R. Pal, Appl. Nanosci., 2014, 4, 859–868.
37 A. I. El-Batal, G. S. El-Sayyad, N. E. Al-Hazmi and M. Gobara,
J. Cluster Sci., 2019, 30(4), 947–964.
38 G. S. El-Sayyad, H. S. El-Bastawisy, M. Gobara and A. I. El-
Batal, Biol. Trace Elem. Res., 2019, DOI: 10.1007/s12011-
019-01842-z.
057802.
58 Q. Mei, C. Benmore, S. Sen, R. Sharma and J. Yarger, Phys.
Rev. B: Condens. Matter Mater. Phys., 2008, 78, 144204.
59 T. P. Almeida, M. W. Fay, Y. Zhu and P. D. Brown, Phys. E,
2012, 44(6), 1058–1061.
60 N. Patil, N. Dweltz and T. Radhakrishnan, Text. Res. J., 1962,
32, 460–471.
61 M. I. A. Abdel Maksoud, G. S. El-Sayyad, A. Abokhadra,
L. I. Soliman, H. H. El-Bahnasawy and A. H. Ashour, J.
Mater. Sci.: Mater. Electron., 2020, 31, 2598–2616.
62 K. Ramakanth, Basics of X-ray Diffraction and its Application,
IK, New Delhi, 2007.
63 J.-M. Zhang, Y. Zhang, K.-W. Xu and V. Ji, Solid State
Commun., 2006, 139, 87–91.
64 W. Wang, J. Yu, Q. Xiang and B. Cheng, Appl. Catal., B, 2012,
119–120, 109–116.
65 G. Zhang, D. Wang, J. Yan, Y. Xiao, W. Gu and C. Zang,
Materials, 2019, 12, 2010.
39 S. H. Abidi, S. K. Sherwani, T. R. Siddiqui, A. Bashir and
S. U. Kazmi, BMC Ophthalmol., 2013, 13, 57.
40 T. Mathur, S. Singhal, S. Khan, D. Upadhyay, T. Fatma and
A. Rattan, Indian J. Med. Microbiol., 2006, 24, 25.
41 K. F. El-Nemr, H. R. Mohamed, M. A. Ali, R. M. Fathy and
A. S. Dhmees, Int. J. Environ. Anal. Chem., 2019, 1–25.
42 K. Brownlee, J. Am. Stat. Assoc., 1952, 47(260), 687–691.
43 S. Elbasuney, Y. H. El-Sharkawy, G. S. El-Sayyad and 66 M. Haghi, M. Hekmatafshar, M. B. Janipour, S. Gholizadeh,
M. Gobara, Talanta, 2020, 211, 120695.
44 F. M. Mosallam, G. S. El-Sayyad, R. M. Fathy and A. I. El-
Batal, Microb. Pathog., 2018, 122, 108–116.
M. Faraz, F. Sayyadifar and M. Ghaedi, Int. J. Adv. Biotechnol.
Res., 2012, 3, 621–624.
67 H. A. Abdel-Rahman, E. H. Awad and R. M. Fathy, J. Compos.
Mater., 2019, 54(3), 331–343.
45 M. A. Maksoud, G. S. El-Sayyad, A. Ashour, A. I. El-Batal,
M. S. Abd-Elmonem, H. A. Hendawy, E. Abdel-Khalek, 68 A. I. El-Batal, N. M. Balabel, M. S. Attia and G. S. El-Sayyad, J.
S. Labib, E. Abdeltwab and M. El-Okr, Mater. Sci. Eng., C,
2018, 92, 644–656.
46 A. Ashour, A. I. El-Batal, M. A. Maksoud, G. S. El-Sayyad,
Cluster Sci., 2019, DOI: 10.1007/s10876-019-01707-4.
69 C. Ashajyothi, K. H. Harish, N. Dubey and
R. K. Chandrakanth, J. Nanostruct. Chem., 2016, 6, 329–341.
S. Labib, E. Abdeltwab and M. El-Okr, Particuology, 2018, 70 H.-J. Park, H. Y. Kim, S. Cha, C. H. Ahn, J. Roh, S. Park,
40, 141–151.
S. Kim, K. Choi, J. Yi and Y. Kim, Chemosphere, 2013, 92,
524–528.
5258 | RSC Adv., 2020, 10, 5241–5259
This journal is © The Royal Society of Chemistry 2020

View Article Online
Paper
RSC Advances
71 S. Priyadarshini, A. Mainal, F. Sonsudin, R. Yahya, 81 A. G. Agrios and P. Pichat, J. Photochem. Photobiol., A, 2006,
A. A. Alyousef and A. Mohammed, Res. Chem. Intermed.,
2019, 1–13.
180, 130–135.
82 G. A. Parks, Chem. Rev., 1965, 65, 177–198.
72 A. I. El-Batal, F. M. Mosalam, M. Ghorab, A. Hanora and 83 F. Loosli, P. Le Coustumer and S. Stoll, J. Nanopart. Res.,
A. M. Elbarbary, Int. J. Biol. Macromol., 2018, 107, 2298–2311. 2015, 17, 44.
73 A. El-Batal, A. El-Baz, F. Abo Mosalam and A. Tayel, J. Chem. 84 K. V. Padoley, A. S. Rajvaidya, T. V. Subbarao and
Pharm. Res., 2013, 5, 1–15. R. A. Pandey, Bioresour. Technol., 2006, 97, 1225–1236.
74 P. K. Stoimenov, R. L. Klinger, G. L. Marchin and 85 L. Zechmeister and E. F. Magoon, J. Am. Chem. Soc., 1956, 78,
K. J. Klabunde, Langmuir, 2002, 18, 6679–6686. 2149–2150.
75 A. I. El-Batal, F. M. Mosallam and G. S. El-Sayyad, J. Cluster 86 D. R. Stapleton, R. J. Emery, D. Mantzavinos and
Sci., 2018, 29(6), 1003–1015. M. Papadaki, Process Saf. Environ. Prot., 2006, 84, 313–316.
76 M. F. Khan, A. H. Ansari, M. Hameedullah, E. Ahmad, 87 D. R. Stapleton, D. Mantzavinos and M. Papadaki, J. Hazard.
F. M. Husain, Q. Zia, U. Baig, M. R. Zaheer, M. M. Alam
and A. M. Khan, Sci. Rep., 2016, 6, 27689.
77 M. Abd Elkodous, G. S. El-Sayyad, I. Y. Abdelrahman,
Mater., 2007, 146, 640–645.
88 A. G. Agrios and P. Pichat, J. Photochem. Photobiol., A, 2006,
180, 130–135.
H. S. El-Bastawisy, A. E. Mohamed, F. M. Mosallam, 89 X. Bi, P. Wang, C. Jiao and H. Cao, J. Hazard. Mater., 2009,
H. A. Nasser, M. Gobara, A. Baraka, M. A. Elsayed and
A. I. El-Batal, Colloids Surf., B, 2019, 180, 411–428.
78 G. S. El-Sayyad, F. M. Mosallam, S. S. El-Sayed and A. I. El-
Batal, J. Cluster Sci., 2019, 31(1), 147–159.
168, 895–900.
90 Y. Liu, L. Fang, H. Lu, Y. Li, C. Hu and H. Yu, Appl. Catal., B,
2012, 115, 245–252.
91 X. Wang and M. Liu, Appl. Surf. Sci., 2019, 485, 353–360.
79 D. L. Currell, G. Wilheim and S. Nagy, J. Am. Chem. Soc., 92 N. Remya and J.-G. Lin, Chem. Eng. J., 2011, 166, 797–813.
1963, 85, 127–130. 93 L. Perreux and A. Loupy, Tetrahedron, 2001, 57, 9199–9223.
80 A. K. Mathur, C. B. Majumder, S. Chatterjee and P. Roy, J. 94 M. Hamid, Heat Tran. Eng., 1992, 13, 73–84.
Hazard. Mater., 2008, 157, 335–343.
95 C. Eskicioglu, N. Terzian, K. J. Kennedy, R. L. Droste and
M. Hamoda, Water Res., 2007, 41, 2457–2466.
This journal is © The Royal Society of Chemistry 2020
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