Graphene oxide-metal oxide nanocomposites: Fabrication, characterization and removal of cationic rhodamine B dye

Article abstract of DOI:10.1039/c8ra00977e

The fabrication and characterization of graphene oxide (GO) nanosheets and their reaction with Fe₃O₄ and ZrO₂ metal oxides to form two nanocomposites, namely graphene oxide-iron oxide (GO-Fe₃O₄) and g

Full text of DOI:10.1039/c8ra00977e

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Graphene oxide–metal oxide nanocomposites:
fabrication, characterization and removal of
cationic rhodamine B dye†
Cite this: RSC Adv., 2018, 8, 13323
c
bc
Nagi M. El-Shafai,ab Mohamed E. El-Khouly,
Maged El-Kemary,
*
*
*
a
a
Mohamed S. Ramadan and Mamdouh S. Masoud
The fabrication and characterization of graphene oxide (GO) nanosheets and their reaction with Fe3O4 and
ZrO2 metal oxides to form two nanocomposites, namely graphene oxide–iron oxide (GO–Fe3O4) and
graphene oxide–iron oxide–zirconium oxide (GO–Fe3O4@ZrO2), have been examined. The fabricated
nanocomposites were examined using different techniques, e.g.transmission electron microscopy, X-ray
diffraction, zeta potential measurement and Fourier transform infrared spectroscopy. Compared to GO, the
newly fabricated GO–Fe3O4 and GO–Fe3O4@ZrO2 nanocomposites have the advantage of smaller band
gaps, which result in increased adsorption capacity and photocatalytic effects. The results also showed the
great effect of the examined GO–metal oxide nanocomposites on the decomposition of cationic
rhodamine B dye, as indicated by steady-state absorption and fluorescence, time correlated single photon
counting and nanosecond laser photolysis techniques. The antibacterial activity of the fabricated GO and
GO–metal oxides has been studied against Gram-positive and Gram-negative bacteria.
Received 31st January 2018
Accepted 26th March 2018
DOI: 10.1039/c8ra00977e
rsc.li/rsc-advances
Among the utilized metal oxides, zero valent iron (ZVI) has been
widely used for separating water from harmful heavy metals12,13
and organic species.14–22 The fabricated graphene oxide–iron
1. Introduction
Water pollution has been a vital environmental issue for the last
few decades.1,2 Industrial organic dyes and heavy metals are
considered to be the most important sources of water pollu-
tion.1,2 For this purpose, membrane technologies based on
nanomaterials have been extensively examined for water puri-
cation and desalination over the last few decades. Among the
utilized nanomaterials in water treatment, graphene oxide (GO),
with its fascinating 2D carbon framework with a honeycomb-
like structure, has attracted much attention in the last decade
for its unique specic surface area, high charge carrier mobility
and electron conductivity.3–5
oxide nanocomposites showed high efficiency in the removal of
tiny concentrations of chromium ions from water and indus-
trial waste water.23–28 In addition, the zirconium oxide (ZrO2)
nanoparticles showed unique electrochemical properties when
combined with graphene oxide.29–36 Compared with the widely
used TiO2, zirconium oxide (ZrO2) is less expensive and insol-
uble in water. According to the preparation method, ZrO2
exhibited a band gap ranging from 3 to 5 eV. Such a wide band
gap renders ZrO2 a promising photocatalyst for the production
of hydrogen in water decomposition.37
Taking these unique properties into consideration, we report
herein the fabrication and characterization of GO, graphene
oxide–iron oxide (GO–Fe3O4) and graphene oxide–iron oxide–
zirconium oxide (GO–Fe3O4@ZrO2). This combination of gra-
phene oxide with Fe3O4–ZrO2 metal oxide and its application in
the degradation of organic species is rare in the literature. Pho-
tocatalytic studies of the examined nanocomposites on the
degradation of cationic rhodamine B dye (RhB) have been exam-
ined in detail using TEM, XRD, FTIR, steady-state absorption and
uorescence and nanosecond laser ash photolysis techniques.
Recently, there has been great interest in fabricating and
utilizing novel graphene oxide–metal oxide nanocomposites for
environmental remediation by the degradation and elimination
of toxic organic contaminants and heavy metals, and for anti-
bacterial applications.6–8 Compared with graphene oxide, gra-
phene oxide–metal oxide nanocomposites show a unique
structural morphology and photochemical properties which
render them good candidates for water treatment projects.9–11
aDepartment of Chemistry, Faculty of Science, Alexandria University, Alexandria, Egypt
bInstitute of Nanoscience and Nanotechnology, Kafrelsheikh University, Kafr El-Sheikh
33516, Egypt
2. Experimental section
2.1. Chemicals and materials
cDepartment of Chemistry, Faculty of Science, Kafrelsheikh University, Kafr El-Sheikh
33516, Egypt. E-mail: mohamedelkhouly@yahoo.com
All of the chemicals and reagents were from Aldrich Chemicals
and used without any further purication.
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c8ra00977e
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 13323–13332 | 13323

View Article Online
RSC Advances
Paper
from a starting model based on information given in the Inor-
ganic Crystal Structure Database (ICSD). The morphology of the
synthesized GO was examined using transmission electron
microscopy (TEM, JEOL 2100) under a maximum acceleration
voltage of 200 kV.
2.2. Characterization techniques
UV-vis absorption and uorescence measurements were taken
using a Shimadzu UV-2450 spectrophotometer and a Shimadzu
RF-5301PC spectrouorometer, respectively. Picosecond time-
resolved uorescence lifetimes were recorded on a Fluo300
(PicoQuant, Germany). Lifetimes were evaluated using FluoFit
soware, which was attached to the equipment. Nanosecond
transient absorption studies were recorded using a nanosecond
laser ash photolysis technique (LP980, Edinburgh Instru-
ments, UK). The instrument was connected with a tunable laser
source (NT342B-10, Ekspla). Fourier transform infrared (FT-IR)
spectra were obtained using a JASCO spectrometer 4100, using
a KBr pellet technique. The X-ray diffraction (XRD) measure-
ments were conducted using a Shimadzu 6000 model with Cu
2.4.2 Synthesis of the GO–Fe3O4@ZrO2 nanocomposite.
0.04 g GO sheets were dispersed in 100 ml water for around 30
minutes. Then, 100 ml of the prepared solution (ZrOCl2$8H2O,
0.064 M FeCl2$4H2O and 0.129 M FeCl3$6H2O) was added. To
the resulting mixture, KOH solution in ethanol (1 M, 90 ꢂC) was
added dropwise under stirring for 1 hour at 100 ꢂC. At the end,
we obtained a black precipitate that was harvested using
centrifugation and washed with both water and ethanol. The
formed GO–Fe3O4@ZrO2 nanocomposite was dried under
ꢂ
vacuum at 45 C.
˚
Ka (l ¼ 1.5418 A) as the incident radiation. Transmission
2.4.3 Synthesis of the GO–Fe3O4 nanocomposite. 0.04 g GO
sheets were dispersed in 100 ml water for 30 minutes using
ultrasound and 100 ml aqueous solution (FeCl2$4H2O and
FeCl3$6H2O) was then added. To this mixture, KOH in ethanol
(1 M) was added dropwise under stirring for 1 h at 100 ꢂC. The
obtained black precipitate (GO–Fe3O4) was harvested using
centrifugation and washed with water and ethanol. ꢂThe GO–
Fe3O4 nanocomposite was dried under vacuum at 45 C.
electron microscopy (TEM) images were taken using a JEOL
2010 microscope operating under a maximum acceleration
voltage of 200 kV. Zeta potential results were obtained using
a Brookhaven zeta potential/particle size analyzer.
2.3. Photocatalytic activity
The photocatalytic activities of GO, GO–Fe3O4@ZrO2 and GO–
Fe3O4 nanocomposites were evaluated for the adsorption of
dyes, such as rhodamine B, without light and their efficiency for
the degradation of rhodamine B (RhB) dye under visible light
irradiation (simulator of sunlight; 150 W Xenon lamp, l > 420
nm). 1 ꢀ 10ꢁ4 M RhB dye and 2 mg nanocomposite were
dispersed in 10 ml H2O. Measurements were performed every
5 min aer exposure to visible light. This experiment was
repeated using UV light at 256 nm. OHc radicals were generated
more during the reaction, which can result in the rapid degra-
dation of RhB dye molecules.38 The photo degradation of RhB
by graphene oxide–metal oxide nanocomposites was analyzed
using steady-state absorbance and uorescence, time-resolved
uorescence and nanosecond laser photolysis techniques.
3. Results and discussion
3.1. Characterization of GO, GO–Fe3O4 and GO–Fe3O4@ZrO2
nanocomposites
Fig. 1 and S1† show the XRD patterns of the fabricated GO–
Fe3O4 and GO–Fe3O4@ZrO2 nanocomposites, in addition to
those of pure graphite powder, GO, Fe3O4 and ZrO2. The XRD
pattern of GO exhibited a diffraction peak at 10.9ꢂ,41,42 which is
signicantly larger than that found in the XRD pattern of pure
graphite (26.0ꢂ). This can be rationalized by the presence of
oxygenated functional groups on the carbon sheets of GO.43,44
XRD analysis of GO–Fe3O4 showed diffraction peaks at 29.6ꢂ,
35.3ꢂ, 43.5ꢂ, 56.5ꢂ and 63.5ꢂ,45 while GO–Fe3O4@ZrO2 showed
peaks at 44.0ꢂ, 64.2ꢂ and 77.3ꢂ, as observed from the database,
and a single phase with a monoclinic structure was formed. The
main crystallite sizes of the GO and metal oxide nano-
composites were calculated based on the Debye–Scherrer
formula (eqn (1)).46
2.4. Synthesis of nanocomposites based on graphene oxide
(GO)
2.4.1 Synthesis of the GO nanostructure. Water dispersions
and solid graphite oxide were prepared from natural graphite
powder using a modied Hummers and Offeman’s method.39,40
In a typical reaction, 8 g graphite akes (Sigma Aldrich), 8 g
NH4NO3 and 368 ml 98% (w/w) H2SO4 were mixed under stir-
D ¼ Kl/b cos q
(1)
ring in an ice bath for 1 h. Then, 40 g KMnO4 was slowly added where K is a constant representing the shape factor (ꢃ0.9), l is
ꢀ
to the mixture in the ice bath until the solution became green. the wavelength of the X-ray source (1.5405 A), b is the full width
The beaker was placed in a water bath at 35 ꢂC and the solution at half maximum of the diffraction peak and q is the angular
was stirred for about 1 h to form a thick paste. 640 ml high- position of the peak. The average crystallite sizes of GO–Fe3O4
purityꢂ water was then added to the formed paste and stirred and GO–Fe3O4@ZrO2 were determined to be 8 and 10 nm,
at 90 C for 1 h. The formed solution turned brown. With the respectively.
slow addition of 48 ml H2O2 (30%), the color changed from dark
Fig. 2 shows the TEM images of the fabricated GO, GO–Fe3O4
brown to yellow. The solid was ltered, washed with 10% HCl and GO–Fe3O4@ZrO2 nanocomposites with different magni-
aqueous solution (3.2 L) to remove metal ions and washed with cations. From the images, GO appeared as nano-sheets, while
water several times. The resulting graphene oxide was dried at GO–Fe3O4 and GO–Fe3O4@ZrO2 appeared as nano-spherical
ꢂ
45 C for 24 h. The crystalline structure of the GO powder was shapes. The samples were analyzed using EDX with uniform
identied using an XRD technique. Renement was carried out particle morphology (Fig. S2†). The average size of the observed
13324 | RSC Adv., 2018, 8, 13323–13332
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
bands at 390 and 360 nm correspond to GO–Fe3O4@ZrO2 and
GO–Fe3O4, respectively. The band gap values of the nano-
composites were determined using eqn (2):49,50
ahy ¼ A(hy ꢁ Eg)n
(2)
where a is the absorption coefficient, y is the frequency of light,
h is Planck’s constant, hy is the photon energy, A is a pro-
portionality constant, Eg is the band gap and n ¼ 1/2 for the
direct transitions.51 From the plot of (ahy)2 versus hy (the insets
of Fig. S3†), the band gaps for GO, GO–Fe3O4@ZrO2 and GO–
Fe3O4 were found to be 4.00, 3.20 and 3.66 eV, respectively.
A zeta potential technique has been used to predict the long
term stability of the nanoparticles in solution and to under-
stand the state of the nanoparticle surface. As shown in Fig. 3,
the spectra show negatively charged particles for GO (ꢁ33), GO–
Fe3O4@ZrO2 (ꢁ41) and GO–Fe3O4 (ꢁ52). These negative values
are related to the stability of the colloidal dispersions in water.
Fig. 4 shows a thermogravimetric analysis (TGA) diagram for
GO, GO–Fe3O4@ZrO2 and GO–Fe3O4 in the range of 25–700 ꢂC.
As seen from the TGA steps, the diagram shows that the
decomposition steps of GO with changing temperature match
the decomposition steps of GO–Fe3O4@ZrO2 and GO–Fe3O4,
suggesting the successful loading of the metal oxides over the
GO surface.
Fig. 1 XRD patterns of: (a) graphite, (b) graphene oxide, (c) GO–Fe3O4
and (d) GO–Fe3O4@ZrO2.
metal oxides on the surface of graphene oxide was ꢃ8 to 10 nm,
which is in good agreement with that observed using XRD.
The absorption spectra of fabricated GO–Fe3O4 and GO–
Fe3O4@ZrO2 were recorded in water, as shown in Fig S3.† The
absorption spectra exhibited an absorption peak with
a maximum at ꢃ228 nm, which was attributed to the p / p*
transitions of the aromatic C]C bonds.47,48 The absorption
Fig. 5 shows the FTIR spectra of the GO, GO–Fe3O4–ZrO2 and
GO–Fe3O4 nanocomposites. The peaks observed at 508 cmꢁ1
correspond to the characteristic stretching vibrations of the
Fig. 2 TEM images of: (a) GO, (b) GO–Fe3O4@ZrO2 and (c) GO–Fe3O4.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 13323–13332 | 13325

View Article Online
RSC Advances
Paper
Fig.
5
FT-IR spectra of: (a) GO, (b) GO–Fe3O4 and (c) GO–
Fe3O4@ZrO2.
Fig. 3 The zeta potentials of GO, GO–Fe3O4@ZrO2 and GO–Fe3O4 in
water.
presence of GO nanocomposites. In a control experiment, the
absorption band of RhB at 554 nm showed no signicant
changes under irradiation in the absence of GO nano-
composites (Fig. S5†).
The observed rate constants for the photocatalytic degrada-
tion of RhB with GO nanocomposites were determined using
eqn (3):
ln(C/Co)¼ ꢁkobs
t
(3)
where Co (mg lꢁ1) is the initial dye concentration and kobs
depends on the initial dye concentration (Co).55,56 From the
linear plot of ln(C/Co) with irradiation time, the degradation
rates (k) of RhB in the presence of GO, GO–Fe3O4@ZrO2 and
GO–Fe3O4 were determined to be 0.0479, 0.0997 and
0.05328 minꢁ1, respectively. This nding indicates a higher rate
constant in the case of the GO–Fe3O4@ZrO2 nanocomposite
compared to that of GO.
The efficiency of the photocatalytic degradation process was
determined using eqn (4):
D (%) ¼ [A(RhB)o ꢁ A(RhB)t]/A(RhB)o
(4)
Fig. 4 TGA of: (a) GO, (b) GO–Fe3O4@ZrO2 and (c) GO–Fe3O4.
where A(RhB)o and A(RhB)t are the absorbance changes of RhB
at 554 nm with time, in the dark and under light irradiation,
respectively.57,58 Fig. 7 illustrates that 80% of the RhB dye was
degraded in the presence of GO within around 90 minutes. This
percentage was increased to 90% and 98% of RhB in the pres-
ence of Fe3O4 and Fe3O4@ZrO2, respectively, suggesting the
signicant effect of the examined metal oxides (Fe3O4 and
Fe3O4@ZrO2) in increasing the photocatalytic degradation of
RhB/GO composites. This high efficiency for RhB degradation
by GO–Fe3O4@ZrO2 (98%) is found to be considerably higher
compared to that reported for TiO2–rGO (81%).59 The proposed
C–O bond in GO nanoparticles.52 The characteristic peaks of GO
vibration were recorded at 984 to 506 cmꢁ1. The broad
absorption band observed at ꢃ3455 cmꢁ1 corresponds to the
stretching vibration of the O–H band of physically absorbed
water.53 The recorded peaks at 573 cmꢁ1 (for GO–Fe3O4@ZrO2)
and 587 cmꢁ1 (for GO–Fe3O4) correspond to the characteristic
vibrations of the M–O bond.54
3.2. Photocatalytic study of rhodamine B
3.2.1 Photocatalytic study of RhB under UV irradiation. mechanism for the photodegradation of cationic RhB dye using
Fig. 6 and S4† show the absorption spectra of the photocatalytic GO–metal oxide nanocomposites is shown in Scheme 1,60–63
degradation of RhB using GO, GO–Fe3O4@ZrO2 and GO–Fe3O4 where the surface of GO has the ability to receive electrons from
nanocomposites under UV irradiation at 256 nm. As shown, the the high conduction band (CB) of ZrO2, which reacts with
characteristic absorption band of RhB dye was recorded at oxygen to produce superoxide anion radicals (O2cꢁ) and OHc
554 nm. With increasing irradiation time, the absorption band radicals, leading to the rapid oxidation of the organic
of RhB at 554 nm is greatly decreased and red-shied in the molecules.
13326 | RSC Adv., 2018, 8, 13323–13332
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
Fig. 6 UV-absorbance spectra of RhB in the presence of: (a) GO and (b) GO–Fe3O4@ZrO2 in water at the indicated time intervals under UV
irradiation at 256 nm.
Fig. 7 (Left) Pseudo-first-order plots for the photodegradation of RhB with GO, GO–Fe3O4@ZrO2 and GO–Fe3O4, with increasing irradiation time.
(Right) The photo-degradation efficiency (%) of RhB with GO, GO–Fe3O4@ZrO2 and GO–Fe3O4, with changing irradiation time (l ¼ 256 nm).
GO showed a low efficiency that may be explained by the
adsorption process of the dye over the GO surface.
3.2.2 Photocatalytic study of RhB under a sunlight simu-
lator. The photocatalytic degradation of RhB was examined with
GO, GO–Fe3O4@ZrO2 and GO–Fe3O4 nanocomposites under
visible light irradiation (sunlight simulator, UXL-151D-O, Xe
150 W, l > 420 nm). As shown in Fig. 8 and S6,† the results
showed no photocatalytic activity from the GO–Fe3O4@ZrO2
and GO–Fe3O4 nanocomposites toward RhB. On the other hand,
3.3. Adsorption process of RhB on the surface of GO
nanocomposites
Dye molecules were entrapped on the surface of GO and GO-
nanocomposites in aqueous solution. From Fig. 9 and S7,†
Scheme 1 The proposed mechanism for the photodegradation of cationic dye by graphene oxide–metal oxide nanocomposites.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 13323–13332 | 13327

View Article Online
RSC Advances
Paper
Fig. 8 Absorbance spectra of RhB dye in the presence of: (a) GO and (b) GO–Fe3O4@ZrO2 at the indicated time intervals under irradiation.
Fig. 9 Absorption spectra of RhB (1.7 ꢀ 10ꢁ5 M) with different concentrations of (a) GO and (b) GO–Fe3O4@ZrO2 in water.
one can see that the absorption band of RhB at 550 nm
decreased gradually with increasing amounts of GO (0.2 g lꢁ1).
For GO–Fe3O4 and GO–Fe3O4@ZrO2, different features were
observed where the absorption band of RhB was considerably
increased with increasing amounts of GO–Fe3O4 and GO–
Fe3O4@ZrO2. The uorescence measurements showed the
same trend as observed for the absorption studies. As seen in
Fig. 10 and S8,† the uorescence maximum band of RhB at
579 nm was signicantly decreased in the presence of GO, but
not in the presence of GO–Fe3O4 or GO–Fe3O4@ZrO2. The
adsorption process could be explained by the dye binding with
GO through hydrogen bonding, and electrostatic
interactions.64,65
3.4. Laser studies of the photodegradation process of RhB by
GO composites
Fluorescence lifetime measurements showed the same trend as
observed for the uorescence measurements (Fig. 11 and S9†).
Upon exciting RhB with 470 nm laser light, the uorescence
decay–time prole of the singlet-excited state of RhB (1RhB*)
decayed with a monoexponential decay, from which the uo-
1
rescence lifetime of RhB* was determined to be 1.7 ns. With
increasing amounts of GO, the substantial quenching of the
uorescence lifetime was considerable and the decay could be
tted satisfactorily to a biexponential decay. The fast decaying
component had a lifetime of 120 ps (58%), while the slow
decaying component had a lifetime of 1.9 ns (42%). The lifetime
Fig. 10 Fluorescence changes of RhB (1.7 ꢀ 10ꢁ5 M) with the addition of different concentrations of (a) GO and (b) GO–Fe3O4@ZrO2 in water.
13328 | RSC Adv., 2018, 8, 13323–13332
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
Fig. 11 Fluorescence decay profiles of the singlet-excited state of RhB in the presence of (a) GO and (b) GO–Fe3O4@ZrO2 in water; lex
420 nm; lem ¼ 580 nm.
¼
of the slow decaying component is close to that of the free RhB.
Nanosecond transient absorption spectroscopy was used to
Based on the change in the recorded uorescence lifetimes of obtain further insight into the excited state interactions of RhB
RhB in the absence and presence of GO, the rate and efficiency with GO, GO–Fe3O4@ZrO2 and GO–Fe3O4, to corroborate the
of the quenching process were determined to be 7.74 ꢀ 109 sꢁ1 observed interaction by both steady-state and time-resolved
and 93%, respectively.66–68 For GO–Fe3O4 and GO–Fe3O4@ZrO2, uorescence techniques. To achieve this, RhB dye was probed
it was observed that the uorescence lifetime of 1RhB* was kept with excitation at l ¼ 550 nm in an oxygen-free water solution.
almost the same with increasing concentrations of both GO– The nanosecond transient absorption spectrum of RhB in water
Fe3O4 and GO–Fe3O4@ZrO2. These measurements are in good was dominated by pronounced bleaching between 540 and
agreement with the steady-state uorescence measurements. 600 nm, which was due to the depletion of the singlet ground
These measurements suggest a higher adsorption of RhB over state (Fig. 12 and S10†). In the case of RhB–GO, it was observed
the surface of GO, but not GO–Fe3O4 and GO–Fe3O4@ZrO2.
that the singlet state of RhB recovered quickly with increasing
Fig. 12 Nanosecond transient absorption spectra of RhB dye in the presence of (a) GO and (b) GO–Fe3O4@ZrO2 in an oxygen-free water
solution; lex ¼ 550 nm.
Fig. 13 Zone of inhibition tests against E. Coli and Steph strains in the presence of GO, GO–Fe3O4@ZrO2 and GO–Fe3O4, at a concentration of
0.5 mg mlꢁ1
.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 13323–13332 | 13329

View Article Online
RSC Advances
Paper
amounts of GO, conrming the quenching of the singlet state of
RhB by the GO. In the case of RhB with GO–Fe3O4@ZrO2, the
intensity of the ground state bleaching remained almost
unchanged with increasing amounts of GO–Fe3O4@ZrO2, sug-
gesting that there was no interaction between RhB and
Fe3O4@ZrO2.
2 C. Santhosh, V. Velmurugan, G. Jacob, S. K. Jeong,
A. N. Grace and A. Bhatnagar, Role of nanomaterials in
water treatment applications: a review, Chem. Eng. J., 2016,
306, 1116–1137.
3 R. K. Joshi, S. Alwarappan, M. Yoshimura, V. Sahajwalla and
Y. Nishina, Graphene oxide: the new membrane material,
Mater. Today, 2015, 1, 1–12.
4 D. Cohen-Tanugi and J. C. Grossman, Nanoporous graphene
as a reverse osmosis membrane: recent insights from theory
and simulation, Desalination, 2015, 366, 59–70.
5 X. F. Sun, J. Qin, P. F. Xia, B. B. Guo, C. M. Yang, C. Song and
S. G. Wang, Graphene oxide–silver nanoparticle membrane
for biofouling control and water purication, Chem. Eng. J.,
2015, 281, 53–59.
6 Y. Chen, C. Tan, H. Zhang and L. Wang, Two-dimensional
graphene analogues for biomedical applications, Chem.
Soc. Rev., 2015, 44, 2681–2701.
7 P. Gao, Z. Liu, M. Tai, D. Delai and W. Ng, Multifunctional
graphene oxide–TiO2 microsphere hierarchical membrane
for clean water production, Appl. Catal., B, 2013, 138–139,
17–25.
8 K. Nair Abhinav and P. Jagadeesh Babu, TiO2 nanosheet-
graphene oxide based photocatalytic hierarchical
membrane for water purication, Surf. Coating. Technol.,
2017, 320, 259–262.
9 Q. Li, Z. Zhan, S. Jin and B. Tan, Wettable magnetic hyper
crosslinked microporous Nano particle as an efficient
adsorbent for water treatment, Chem. Eng. J., 2017, 326,
109–116.
10 L. Gonggang, H. Kai, Y. Hongqi, Z. Chenyuan, G. Yupei,
L. Yong and Z. Yonghua, Graphene oxide/triethanolamine
modied titanate nanowires as photocatalytic membrane
for water treatment, Chem. Eng. J., 2017, 320, 74–80.
11 J. Gao, C. Liu, L. Maio, X. Wang, Y. Peng and Y. Chen,
Enhanced power factor in exible reduced graphene oxide/
nanowires hybrid lms for thermoelectrics, RSC Adv., 2016,
6, 31580–31587.
12 M. Gheju, Hexavalent chromium reduction with zero-valent
iron (ZVI) in aquatic systems, Water, Air, Soil Pollut., 2011,
222, 103–148.
13 R. Rangsivek and M. R. Jekel, Removal of dissolved metals by
zero-valent iron (ZVI): Kinetics, equilibria, processes and
implications for stormwater runoff treatment, Water Res.,
2005, 39, 4153–4163.
3.5. Antibacterial activity of GO and nanocomposites
Antibacterial activity was tested against Gram-positive and
Gram-negative bacteria using BHI agar plates and the agar
diffusion method. The GO, GO–Fe3O4@ZrO2 and GO–Fe3O4
samples were evaluated. The resulting antibacterial effect could
be rationalized by the diffusion of GO, Fe3O4@ZrO2 and GO–
Fe3O4 over the agar surface, preventing bacterial growth in the
specic area occupied by the nanocomposite. As seen from
Fig. 13, we observed only a small zone of inhibition around GO,
indicating limited bacterial toxicity against E. coli.69 In contrast,
the GO–Fe3O4 sample showed a signicant inhibitory effect
against E. coli. The presence of clear zones on the BHI agar
surface proves that the GO–Fe3O4 composite was able to inhibit
the growth of E. coli, whereas no antibacterial activity was
detected for raw GO and GO–Fe3O4@ZrO2 against E. coli. The
GO, Fe3O4@ZrO2 and GO–Fe3O4 samples showed no antibac-
terial activity against Steph. The experiment was conducted to
characterize bacterial killing with concentration (0.5 mg mlꢁ1
and the cellular viability was measured aer 24 h exposure time.
)
4. Conclusion
Novel nanocomposites of graphene oxide with iron oxide (GO–
Fe3O4) and iron oxide–zirconium oxide (GO–Fe3O4@ZrO2) were
fabricated and characterized using XRD, TGA, FTIR, and TEM
techniques. From the optical absorption measurements, the
energy band gap values were found to be 4.00, 3.66, and 3.20 eV
for GO, GO–Fe3O4 and GO–Fe3O4@ZrO2, respectively. All of the
steady-state absorption and uorescence, time-resolved uo-
rescence and nanosecond transient absorption spectroscopy
results conrmed that RhB is efficiently adsorbed over the
surface of graphene oxide (ꢃ93%). Different features were
observed in the presence of metal oxides (Fe3O4 and Fe3O4@-
ZrO2) over the surface of graphene oxide. GO and Fe3O4@ZrO2
had a small zone of inhibition against E. coli and in contrast, the
GO–Fe3O4 sample showed a signicant inhibitory effect against
E. coli. GO, GO–Fe3O4@ZrO2 and GO–Fe3O4 showed no anti-
bacterial activity against Steph.
¨
14 A. S. Ruhl, N. Unal and M. Jekel, Evaluation of two-
component Fe(0) xed bed lters with porous materials for
reductive dechlorination, Chem. Eng. J., 2012, 209, 401–406.
15 C. Della Rocca, V. Belgiorno and S. Meriç, Overview of in situ
applicable nitrate removal processes, Desalination, 2007,
204, 46–62.
16 J. Farrell, M. Kason, N. Melitas and T. Li, Investigation of the
long-term performance of zero-valent iron for reductive
dechlorination of trichloroethylene, Environ. Sci. Technol.,
2000, 34, 514–521.
Conflicts of interest
The authors declare no conict of interest.
References
1 M. Elimelech and W. A. Phillip, The future of seawater 17 I. Hussain, Y. Zhang, S. Huang and X. Du, Degradation of p-
desalination: energy, technology, and the environment,
chloroaniline by persulfate activated with zero-valent iron,
Science, 2011, 33, 712–717.
Chem. Eng. J., 2012, 203, 269–276.
13330 | RSC Adv., 2018, 8, 13323–13332
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
18 M. Kallel, C. Belaid, T. Mechichi, M. Ksibi and B. Elleuch,
Removal of organic load and phenolic compounds from
using zirconium oxide nanowires as high dielectric-
constant gate dielectrics, Adv. Mater., 2010, 22, 1941–1945.
olive mill wastewater by Fenton oxidation with zero-valent 32 D. Du, J. Liu, X. Zhang, X. Cui and Y. Lin, One-step
iron, Chem. Eng. J., 2009, 150, 391–395.
electrochemical
nanocomposite:
application for detection of organophosphorus agents, J.
Mater. Chem., 2011, 21, 8032–8037.
deposition
preparation,
of
a
graphene-ZrO2
and
19 F. Gong, L. Wang, D. Li, F. Zhou, Y. Yao, W. Lu, S. Huang and
W. Chen, An effective heterogeneous iron-based catalyst to
activate peroxymonosulfate for organic contaminants
removal, Chem. Eng. J., 2015, 267, 102–110.
20 D. Li, D. Chen, Y. Yao, J. Lin, F. Gong, L. Wang, L. Luo,
Z. Huang and L. Zhang, Strong enhancement of dye
removal through addition of sulte to persulfate activated
characterization
33 B. H. Cho and W. B. Ko, Preparation of graphene-ZrO2
nanocomposites by heat treatment and photocatalytic
degradation of organic dyes, J. Nanosci. Nanotechnol., 2013,
13, 7625–7630.
by a supported ferric citrate catalyst, Chem. Eng. J., 2016, 34 S. Rani, M. Kumar, S. Sharma, D. Kumar and S. Tyagi, Effect
288, 806–812.
of graphene in enhancing the photocatalytic activity of
21 C. Shi, J. Wei, Y. Jin, K. E. Kniel and P. C. Chiu, Removal of
zirconium oxide, Catal. Lett., 2014, 144, 301–307.
viruses and bacteriophages from drinking water using zero- 35 Q. Xiang, J. Yu and M. Jaroniec, Graphene-based
valent iron, Sep. Purif. Technol., 2012, 84, 72–78.
22 Y. You, J. Han, P. C. Chiu and Y. Jin, Removal and
semiconductor photocatalysts, Chem. Soc. Rev., 2012, 41,
782–796.
inactivation of waterborne viruses using zerovalent iron, 36 S. Rani, M. Aggarwal, M. Kumar, S. Sharma and D. Kumar,
Environ. Sci. Technol., 2005, 39, 9263–9269.
Removal of methylene blue and rhodamine B from water
23 M. Ghazaghi, H. Z. Mousavi, A. M. Rashidi, H. Shirkhanloo
byzirconium oxide/graphene, Water Science, 2016, 30, 51–60.
and
R.
Rahighi,
Innovative
separation
and 37 A. Emeline, G. V. Kataeva, A. S. Litke, A. V. Rudakova,
preconcentration technique of coagulating homogenous
dispersive micro solid phase extraction exploiting
graphene oxide nanosheets, Anal. Chim. Acta, 2016, 902,
33–42.
V. K. Ryabchuk and N. Serpone, Spectroscopic and
photoluminescence studies of a wide band gap insulating
material: powdered and colloidal ZrO2 sols, Langmuir,
1998, 14, 5011–5022.
24 K. Pytlakowska, Speciation of inorganic chromium in water 38 C. Singh, S. Jauhar, V. Kumar, J. Singh and S. Singhal,
samples by energy dispersive X-ray uorescence
spectrometry, J. Anal. At. Spectrom., 2016, 31, 968–974.
25 K. Pytlakowska, V. Kozik, M. Matussek, M. Pilch, B. Hachula
and K. Kocot, Glycine modied graphene oxide as a novel
Synthesis of zinc substituted cobalt ferrites via reverse
micelle technique involving in situ template formation:
a study on their structural, magnetic, optical and catalytic
properties, Mater. Chem. Phys., 2015, 156, 188–197.
sorbent for preconcentration of chromium, copper, and 39 W. S. Hummers Jr and R. E. Offerman, Preparation of
zinc ions from water samples prior to energy dispersive X- graphite oxide, J. Am. Chem. Soc., 1958, 80, 1339.
ray uorescence spectrometric determination, RSC Adv., 40 L. J. Cote, F. Kim and J. X. Huang, Langmuir-Blodgett
2016, 6, 42836–42844.
26 A. Islam, H. Ahmad, N. Zaidi and S. Kumar, A graphene oxide
assembly of graphite oxide single layers, J. Am. Chem. Soc.,
2009, 131, 1043–1049.
decorated with triethylenetetramine-modied magnetite for 41 X. Ji, Y. Song, J. Han, L. Ge, X. Zhao, C. Xu, Y. Wang, D. Wu
separation of chromium species prior to their sequential
speciation and determination via FAAS, Microchim. Acta,
2016, 183, 289–296.
and H. Qiu, Preparation of a stable aqueous suspension of
reduced graphene oxide by green method for
applications in biomaterials, J. Colloid Interface Sci., 2017,
497, 317–324.
a
´
´
˜
´
27 I. Lopez-Garcıa, M. J. Munoz-Sandoval and M. Hernandez-
´
Cordoba, Cloud point microextraction involving graphene 42 M. M. Shahid, P. Rameshkumar, W. J. Basirun, J. J. Ching
oxide for the speciation of very low amounts of chromium
in waters, Talanta, 2017, 172, 8–14.
28 H. Su, Z. Ye and N. Hmidi, High-performance iron oxide–
graphene oxide nanocomposite adsorbents for arsenic
removal, Colloids Surf., A, 2017, 522, 161–172.
29 J. Liu, X. Meng, Y. Hu, D. Geng, M. N. Banis, M. Cai, R. Li and
X. Sun, Controlled synthesis of zirconium oxide on graphene
nanosheets by atomic layer deposition and its growth
mechanism, Carbon, 2013, 52, 74–82.
30 J. Gong, X. Miao, H. Wan and D. Song, Facile synthesis of
zirconia nanoparticles decorated graphene hybrid
nanosheets for an enzymeless methyl parathion sensor,
Sens. Actuators, B, 2012, 162, 341–347.
and N. M. Huang, Cobalt oxide nanocubes interleaved
reduced graphene oxide as an efficient electrocatalyst for
oxygen reduction reaction in alkaline medium, Electrochim.
Acta, 2017, 237, 61–68.
43 J. V. Rojas, M. C. Molina Higgins, M. Toro Gonzalez and
C. E. Castano, Single stepradiolytic synthesis of iridium
nanoparticles onto graphene oxide, Appl. Surf. Sci., 2015,
357, 2087–2093.
44 B. Ouadila, O. Cherkaoui, M. Sa and M. Zahouily, Surface
modication of knit polyester fabric for mechanical,
electrical and UV protection properties by coating with
graphene
oxide,
graphene
and
graphene/silver
nanocomposites, Appl. Surf. Sci., 2017, 414, 292–302.
31 L. Liao, J. Bai, Y.-C. Lin, Y. Qu, Y. Huang and X. Duan, High- 45 Y.-X. Ma, Y.-L. Kou, D. Xing, P.-S. Jin, W.-J. Shao, X. Li,
performance top-gated graphene-nanoribbon transistors
X.-Y. Du and P.-Q. La, Synthesis of magnetic graphene
oxide graed polymaleicamide dendrimer nanohybrids for
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 13323–13332 | 13331

View Article Online
RSC Advances
Paper
adsorption of Pb(II) in aqueous solution, J. Hazard Mater., 58 E. Abdelkader, L. Nadjia, B. Naceur and B. Noureddine, SnO2
2017, 340, 407–416.
foam
grain-shaped
nanoparticles:
Synthesis,
46 B. Cullity, Elements of X-ray Diffraction, A. W. R. C. Inc.,
Massachusetts, 1967.
characterization and UVA light induced photocatalysis, J.
Alloy. Comp., 2016, 679, 408–419.
47 V. H. Pham, T. V. Cuong, S. H. Hur, E. Oh, E. Jung Kim, 59 J.-J. Zhang, X. Liu, T. Ye, G.-P. Zheng, X.-C. Zheng, P. Liu and
E. W. Shin and J. S. Chung, Chemical functionalization of
graphene sheets by solvothermal reduction of
a grapheneoxide suspension in N-methyl-2-pyrrolidone, J.
Mater. Chem., 2011, 21, 3371–3377.
X.-X. Guan, Novel assembly of homogeneous reduced
graphene oxide-doped Meso porous TiO2 hybrids for
elimination of Rhodamine-B dye under visible light
irradiation, J. Alloy. Comp., 2017, 698, 819–827.
48 S. Woo, Y.-R. Kim, T. D. Chung, Y. Piao and H. Kim, 60 M. Sundararajana, L. J. Kennedya, P. Nithyab, J. J. Vijayac
Synthesis of a grapheme-carbon nanotube composite and
its electrochemical sensing of hydrogen peroxide,
Electrochim. Acta, 2012, 59, 509–514.
and M. Bououdinad, Visible light driven photocatalytic
degradation of rhodamine B using Mg doped cobalt ferrite
spinel nanoparticles synthesized by microwave combustion
method, J. Phys. Chem. Solids, 2017, 108, 61–75.
49 M. El-Kemary, N. Nagy and I. El-Mehasseb, Nickel oxide
nanoparticles: Synthesis and spectral studies of inter 61 S. Huang, Y. Xu, M. Xie, H. Xu, M. He, J. Xia, L. Huang and
actions with glucose Materials Science in Semiconductor
Processing, 2013 inter actions with glucose, Mater. Sci.
Semicond. Process., 2013, 16, 1747–1752.
H. Li, Synthesis of magnetic CoFe2O4/g-C3N4 composite and
its enhancement of photocatalytic ability under visible-light,
Colloid. Surface. Physicochem. Eng. Aspect., 2015, 478, 71–80.
50 R. Lopez and R. Gomez, Band-gap energy estimation from 62 S. Issarapanacheewin, K. Wetchakun, S. Phanichphat,
diffuse reectance measurements on sol-gel and
commercial TiO2: a comparative study, J. Sol. Gel Sci.
Technol., 2012, 61, 1–7.
W. Kangwansupamonkon and N. Watchakun, A novel
CeO2/Bi2WO6 composite with highly enhanced
photocatalytic activity, J. Mater. Sci. Lett., 2015, 156, 28–31.
51 A. Hagfeldt and M. Gratzel, Light-induced reactions in 63 S. Thennarasu, K. Rajasekar and K. B. Ameen, Hydrothermal
nanocrystalline systems, Chem. Rev., 1995, 95, 49–68.
52 K. Krishnamoorthy and S. J. Kim, Growth, characterization
and electrochemical properties of hierarchical CuO
nanostructures for supercapacitor applications, Mater. Res.
Bull., 2013, 48, 3136–3139.
53 D. B. Dubal, D. S. Dhawale, R. R. Salunkhe, V. S. Jamdade
and C. D. Lokhande, Fabrication of copper oxide
multilayer nanosheets for supercapacitor application, J.
Alloy. Comp., 2010, 492, 26–30.
temperature as a morphological control factor: Preparation,
characterization and photocatalytic activity of titanate
nanotubes and nanoribbons, J. Mol. Struct., 2013, 1049,
446–457.
64 W. Konicki, M. Aleksandrzak and E. Migowska, Equilibrium,
kinetic and thermodynamic studies on adsorption of
cationic dyes from aqueous solutions using graphene
oxide, Chem. Eng. Res. Des., 2017, 123, 35–49.
65 Y. Yang, S. Song and Z. Zhao, Graphene oxide (GO)/
polyacrylamide (PAM) composite hydrogels as efficient
cationic dye adsorbents, Colloids Surf., A, 2017, 513, 315–324.
54 V. A. J. Silva, P. L. Andrade, M. P. C. Silva, A. D. Bustamante,
L. D. S. Valladares and J. Albino Aguiar, Synthesis and
characterization of Fe3O4 nanoparticles, coated with fucan 66 V. Bandi, M. E. El-Khouly, K. Ohkubo, V. N. Nesterov,
poly saccharides, J. Magn. Magn Mater., 2013, 343, 138–143.
55 E. Bizani, K. Fytianos, I. Poulios and V. Tsiridis,
Photocatalytic decolorization and degradation of dye
solutions and wastewaters in the presence of titanium
dioxide, J. Hazard. Mater., 2006, 136, 85–94.
M. E. zandler and S. Fukuzumi, Bisdonor-azaBODIPY-
fullerene supramolecules: syntheses, characterization, and
light-induced electron-transfer Studies, J. Phys. Chem. C,
2014, 118, 2321–2332.
67 M. E. El-Khouly, P. Padmawar, Y. Araki, S. Chiang and O. Ito,
56 M. Sundararajan, L. John Kennedya, P. Nithy, J. Judith Vijaya
and M. Bououdin, Visible light driven photocatalytic
degradation of rhodamine B using Mg doped cobalt ferrite
Photoinduced processes in a tricomponent molecule
consisting of diphenylaminouorene-dicyanorthylene-
methanofullerene, J. Phys. Chem. A, 2006, 110, 884–891.
spinel nanoparticles synthesized by microwave combustion 68 F. D`Souza, M. E. El-Khouly, S. Gadde, M. E. Zandler,
method, J. Phys. Chem. Solids, 2017, 108, 61–75.
A. L. McCarty, Y. Araki and O. Ito, Supramolecular triads
57 N. Sreelekha, K. Subramanyam, D. A. Reddy, G. Murali,
K. Rahul Varma and R. P. Vijayalakshmi, Efficient
photocatalytic degradation of rhodamine-B by Fe doped
bearing porphyrin and fullerene via two-point binding
involving
coordination
and
hydrogen
bonding,
Tetrahedron, 2006, 62, 1967–1978.
CuS diluted magnetic semiconductor nanoparticles under 69 Q. Bao, D. Zhang and P. Qi, Synthesis and characterization of
the simulated sunlight irradiation, Solid State Sci., 2016,
62, 71–81.
silver nanoparticle and graphene oxide nanosheet
composites as a bactericidal agent for water disinfection, J.
Colloid Interface Sci., 2011, 360, 463–470.
13332 | RSC Adv., 2018, 8, 13323–13332
This journal is © The Royal Society of Chemistry 2018