A novel nanocomposite with superior electrocatalytic activity: A magnetic property based ZnFe2O4 nanocubes embellished with reduced graphene oxide by facile ultrasonic approach

Article abstract of DOI:10.1016/j.ultsonch.2019.05.007

Herein, a novel Zinc Ferrite nanocubes (ZnFe₂O₄ NCs) decorated reduced graphene oxide (rGO) nanocomposite have been designed through a sonochemical method. After then, as-synthesized ZnFe₂O₄ NCs/rGO was characterized by XPS, XRD, HRTEM and EIS. Furthermore, the ZnFe₂O₄ NCs/rGO nanocomposite modified GCE (glassy carbon electrode) shows excellent electrochemical sensing performance towards biomarker of 4-nitroquinoline N-oxide (4-NQ) with fast detection. 4-NQ is one of the important cancer biomarker. Moreover, the fabricated sensor showed a wide linear window for 4-NQ between 0.025 and 534.12 μM and nanomolar detection limit (8.27 nM). Further, the as-prepared ZnFe₂O₄ NCs/rGO/GCE has been applied to the determination of 4-NQ in human blood and urine samples with excellent recovery results.

Full text of DOI:10.1016/j.ultsonch.2019.05.007

Accepted Manuscript
A Novel Nanocomposite with Superior Electrocatalytic Activity: A Magnetic
Property Based ZnFe2O4 Nanocubes Embellished with Reduced Graphene Ox-
ide by Facile Ultrasonic Approach
Tse-Wei Chen, Umamaheswari Rajaji, Shen-Ming Chen, Muneerah Mogren Al
Mogren, Majdi Hochlaf, Sarah Dhaif Allah Al Harbi, R. Jothi Ramalingam
PII:
S1350-4177(19)30280-9
DOI:
https://doi.org/10.1016/j.ultsonch.2019.05.007
ULTSON 4590
Reference:
Ultrasonics Sonochemistry
To appear in:
Received Date:
Revised Date:
Accepted Date:
21 February 2019
6 May 2019
7 May 2019
Please cite this article as: T-W. Chen, U. Rajaji, S-M. Chen, M.M.A. Mogren, M. Hochlaf, S.D.A. Harbi, R.J.
Ramalingam, A Novel Nanocomposite with Superior Electrocatalytic Activity: A Magnetic Property Based
ZnFe2O4 Nanocubes Embellished with Reduced Graphene Oxide by Facile Ultrasonic Approach, Ultrasonics
Sonochemistry (2019), doi: https://doi.org/10.1016/j.ultsonch.2019.05.007
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers
we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and
review of the resulting proof before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

A Novel Nanocomposite with Superior Electrocatalytic Activity: A Magnetic Property
Based ZnFe2O4 Nanocubes Embellished with Reduced Graphene Oxide by Facile
Ultrasonic Approach
Tse-Wei Chena,b,‡, Umamaheswari Rajajia, ‡, Shen-Ming Chena,*, Muneerah Mogren Al
Mogrenc, Majdi Hochlafd, Sarah Dhaif Allah Al Harbic, R. Jothi Ramalingame
aDepartment of Chemical Engineering and Biotechnology, National Taipei University of
Technology, No.1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan
bResearch and Development Center for Smart Textile Technology, National Taipei
University of Technology, No.1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan
cChemistry Department, Faculty of Science, King Saud University, P.O. Box 2455, Riyadh
11451, Kingdom of Saudi Arabia
dLaboratoire Modelisation et Simulation Multi Echelle, MSME UMR 8208 CNRS,
University Paris-Est, ´5 Blvd. Descartes, 77454 Marne-la-Vallee, France
eSurfactant Research Chair, Chemistry Department, College of Science, King Saud
University, P.O. Box-2455, Riyadh-11451, Kingdom of Saudi Arabia
Corresponding author: Email: smchen78@ms15.hinet.net, (S.-M. Chen) ‡-equal contribution.
1

Abstract
Herein, a novel Zinc Ferrite nanocubes (ZnFe2O4 NCs) decorated reduced graphene
oxide (rGO) nanocomposite have been designed through a sonochemical method. After then,
as-synthesized ZnFe2O4 NCs/rGO was characterized by XPS, XRD, HRTEM and EIS.
Furthermore, the ZnFe2O4 NCs/rGO nanocomposite modified GCE (galssy carbon electrode)
shows excellent electrochemical sensing performance towards biomarker of 4-nitroquinoline
N-oxide (4-NQ) with fast detection. 4-NQ is one of the important cancer biomarker.
Moreover, the fabricated sensor showed a wide linear window for 4-NQ between 0.025-
534.12 µM and nanomolar detection limit (8.27 nM). Further, the as-prepared ZnFe2O4
NCs/rGO/GCE has been applied to the determination of 4-NQ in human blood and urine
samples with excellent recovery results.
Keywords: Zinc Ferrite; 4-nitroquinoline N-oxide; Toxic chemical detection, Reduced
graphene oxide; Biological samples.
1. Introduction
Zinc ferrite (ZnFe2O4), a common transition bimetal oxide, has been widely utilized as
an electro-catalyst to prepare highly effective nanocomposite for the electrochemical
applications such as water splitting, supercapacitors, batteries, electro and photocatalysis, due
to their unique structural properties, including ordered crystal structure, large surface area and
stability [1-8]. Since, it has used various applications and various fields [9-14]. Although, few
studies have focused on using zinc ferrites based nanocomposites as novel modified electrode
2

materials due to their aggregation. In this aspect, integrating zinc ferrites and high conductive
nanomatrix into nanocomposites have been developing as a precious approach to improve the
non-aggregativity and conductivity of the electrocatalyst [15-21].Furthermore, various nano-
layers matrix as a graphene based high conductive nanomaterials have been widely applied to
establish with zinc ferrites to improve their electrochemical performances [22, 23]. The
reduced graphene oxide (rGO) is one of the novel layered nanomaterial that possess good
conductivity, large electrocatalytic surface area and porosity [24-27]. Therefore, we can
focused the synthesis of zinc ferrites (ZnFe2O4) decorated reduced graphene oxide based
nanocomposite is considered as an effective way to enhance the electrochemical sensing
performances towards the biomarker application.
3

Scheme 1. Schematic diagram of the work
Cancer is an important disease in human life that has become a serious and increasing
global health problem. Moreover, 4-nitroquinoline N-oxide (4-NQ) has considerable research
attention due to tumorigenic properties and 4-NQ is one of the toxic biomarker in cancer
research and which is find from the tumorigenic part or cells [28]. When increase the
oxidative stress and DNA mutations in the human body, it has produced to 4-NQ biomarker
[28]. In addition, 4-NQ is induced cancer-causing DNA mutations [28-30]. Since, when
increasing the concentration of 4-NQ, its causing high carcinogenesis effect in the human
system such as mutagenicity and genotoxicity [28, 31-33]. Therefore, the determination of 4-
NQ marker in various biological system is of highly great potential for analytical and
research applications. Moreover, few detection methods are reported such as microbial assay,
high-performance liquid chromatography-MC (HPLC) and electron paramagnetic resonance
spectrometry [34-36]. Moreover, these methods are expensive and long-time process.
Nevertheless, the electrochemical methods are inexpensive, more efficient and fast than other
detection methods [37-44]. Therefore, we can develop the electrochemical sensing method
based ZnFe2O4/rGO nanocomposite in this work for the electrochemical detection of 4-NQ
marker.
In this study, reveals that the nanocubes based ZnFe2O4 nanocatalyst enhance the
electrocatalytic and sensing performance towards 4-NQ. Furthermore, to the best of our
knowledge, the electrochemical sensing application of ZnFe2O4/rGO nanocomposite has not
been published yet. Moreover, we have synthesized the ZnFe2O4/rGO nanocatalyst by an
ultrasound based sonochemical process. In addition, ZnFe2O4 based rGO companied
nanomaterials that are exhibited the excellent electrochemical sensing properties towards
4

biomarker. Moreover, ZnFe2O4 nanocubes decorated carbon nanosheets were successfully
synthesized and fabricated using the simple sonochemical approach. In the present work, the
synthesized ZnFe2O4/rGO was fabricated on GCE and characterized. Then the fabricated
electrode was used to determination of 4-NQ biomarker in biological samples. Furthermore,
the sensitivity of the ZnFe2O4/rGO nanocomposite modified GCEs were evaluated by
electrochemical techniques (Scheme 1).
Scheme 2. Facile sonochemical synthesis of ZnFe2O4/rGO nanocomposite.
5

2. Experimental section
2.1 Synthesis of ZnFe2O4 NCs/rGO nanocomposite
All chemicals and reagents were purchased from Sigma-Aldrich with analytical grade
and used without any further purification (chemical and methods given in supporting
information). A typical synthesized 25 mg of graphene oxide were subsequently added to the
pre-prepared mixture solution of 0.2 M (Zn(NO3)2·6H2O) and 0.4 M (Fe(NO3)3·9H2O in 50
mL of deionized water. Then, pH of the prepared suspension was adjusted to 8.0 pH by
slowly adding 0.1ꢀM of NH4OH solution under the stirring and then ultrasonicated for 15
min. After the suspension was sonicated in ultrasonic bath of 100 W at 40 kHz for 1 h.
Finally, ZnFe2O4/rGO nanocomposite was obtained by filtrating and drying at 80°C for 24ꢀh
(Scheme 2). For controlled experiments, pure ZnFe2O4 and rGO were also prepared using the
procedure described above but without an addition of graphene oxide and metal oxide
sources respectively.
2.2. Fabrication of ZnFe2O4 NCs/rGO modified electrode
The hybrid nanomaterials dispersed solution (2 mg/mL; ethanol) about 8 µL was drop
casted on the pre-cleaned electrode surface. Finally, the ZnFe2O4 NCs/rGO modified
electrode was dried in the oven at room temperature. Furthermore, same produce was applied
to fabricate for control electrodes such as rGO and ZnFe2O4 NCs. The fabricated and
unmodified electrodes were applied for the electrochemical determination of the 4-NQ.
6

3. Results and discussion
3.1. Morphological characterization
Evidently, the well-shaped morphologies and uniform nanocube structures are observed
in Figure 1B and C. and HRTEM image of reduced graphene oxide nanosheets shown in
Figure 1A and it’s like layered multi-carbon nanosheets and reduced nanosheets. As shown
in Figure D-E, the rGO nanosheets were comprised of non-aggregated, winkled, highly thin
and transparent nanosheets randomly, which agrees well arrangements of the nanocomposite.
As HRTEM shows, the nanocubes as structure were obtained for the synthesized ZnFe2O4
nanoparticles on the sonochemically reduced carbon nanosheets. These results were
confirmed that the formation of ZnFe2O4 NCs/rGO.
(A)
(B)
(C)
ZnFe2O4
rGO
ZnFe2O4
100 nm
100 nm
200 nm
(D)
(E)
(F)
rGO
ZnFe2O4/rGO
rGO
ZnFe2O4
ZnFe2O4
500 nm
100 nm
50 nm
Figure 1. HRTEM images of rGO (A) and ZnFe2O4 nanocubes (B-C). HRTEM images of
ZnFe2O4 NCs/rGO nanocomposite (D) and high magnification images (E-F).
7

3.2. XRD and XPS analysis
The XRD patterns of ZnFe2O4 NCs (blue line) and ZnFe2O4 NCs/rGO (green line) was
displayed in Figure 2A. The XRD pattern of the ZnFe2O4 NCs/rGO shows, several
diffraction peaks at 30.08°, 35.64°, 43.32°, 54.28°, 57.26° and 62.16° are observed that are
correlated to (220), (311), (400), (422), (511) and (440) crystal planes. This diffraction
patterns were matched with the orthorhombic ZnFe2O4 NCs (JCPDS No. 22-1012) [45-47].
Therefore, the XRD pattern indicates the successful formation of ZnFe2O4 NCs. Besides, the
rGO exhibited the diffraction peaks assigned for the miller indices plane is (002).
Furthermore, formation of ZnFe2O4 NCs are evaluated by Figure 2A. Finally, this
information is regenerated in the ZnFe2O4 NCs/rGO confirms the composite formation.
(311)
(B)
(A)
(C)
Zn 2p
Survey
C 1s
(002)
O 1s
(220)
C 1s
(440)
(400)
(511)
(422)
Fe 2p
ZnFe2O4 NCs/rGO
(311)
JCPDS No. 22-1012
(220)
(400)
(511) (440)
(422)
ZnFe2O4 NCs
ZnFe2O4 NCs/rGO
2θ (degree)
Binding energy (eV)
Bindingenergy (eV)
Fe 2p
(E)
Zn 2p
(D)
(F)
Zn 2p3/2
Fe 2p3/2
Fe 2p1/2
Zn 2p1/2
O 1s
Bindingenergy (eV)
Bindingenergy (eV)
Binding energy (eV)
8

Figure 2. XRD analysis of ZnFe2O4 NCs and ZnFe2O4 NCs/rGO (A). XPS survey spectrum
of ZnFe2O4 NCs/rGO (B) and de-conventional peaks of C1s (C), O1s (D), Fe 2p (E) and Zn
2p (F).
X-ray photoelectron spectroscopy (XPS) characterization is one of the specific tool for
the evaluation of chemical states and composition of the nanocomposites. The full survey
XPS analysis of ZnFe2O4 NCs/rGO nanocomposites shows in Figure 2B. The peak of C 1s O
1s, Fe 2p and Zn 2p were detected in the full scan XPS spectrum. As can be seen that the
characteristic peak for C 1s, O 1s, Zn 2p and Fe 2p levels were observed at their correlated
binding energies. As shown in Figure 2C, the high resolutions scan of the C 1s represents the
four major peak due to ring carbon (C-C/-C=C, -C-O, -C=O and -C-C=O). Then Figure 2D,
the XPS spectrum of the O 1s present in the ZnFe2O4 NCs/rGO reveals the primary peak
denotes the metal-oxygen bonds located. As shown in Figure 2E, two dominant peaks of Fe
2p bounded with the metal that exhibited the Fe 2p3/2 and Fe 2p1/2 located at the (158.8 eV)
and (163.4 eV). In Figure 2F, the XPS spectrum of the Zn 2p present in the nanocomposite
reveals the two peaks denoted the Zn 2p3/2 and Zn 2p1/2 at (1025 to 1055 eV) which
demonstrate the Zn present in the form of ZnFe2O4 NCs/rGO nanocomposite.
3.3. Electrochemical characterization of modified and unmodified electrodes
The electrochemical properties of interfacial electron transport behavior are
evaluated by CV [48-50]. The conductivity and interfacial character of bare GCE (a),
rGO/GCE (b), ZnFe2O4 NCs/GCE (c), and ZnFe2O4 NCs/rGO/GCE (d) were investigated in
Figure 3A and B. The CV analysis was carried out by 0.1 M KCl containing 5 mM
[Fe(CN)6]-3/-4 solution at a fixed scan rate (50 mV/s). In Figure 3A, shows the CVs of
modified and unmodified electrodes such as bare GCE (a), rGO/GCE (b), ZnFe2O4 NCs/GCE
9

(c) and ZnFe2O4 NCs/rGO/GCE (d). The catalyst modified and unmodified electrodes shows
the redox peak, for the comparison the bare GCE, rGO/GCE and ZnFe2O4 NCs/GCE were
low and modulator peak current. Mainly, the nanocomposite modified GCE has higher peak
current with low peak potential. In Figure 3B, shows that the scan rate of the nanocomposite
modified GCE and the results was plot to the corresponding calibration analysis (20 to 300
mV/s). Furthermore, the randles sevcik equation (1) has applied into the slope of the
electrochemical analysis in Figure 3C. In addition, the electrochemical active surface area of
the modified and unmodified electrode as bare GCE, rGO/GCE, ZnFe2O4 NCs/GCE, and
ZnFe2O4 NCs/rGO/GCE has been calculated as 0.086 cm2, 0.126 cm2, 0.158 cm2 and 0.179
cm2 respectively. Therefore, the results show that the ZnFe2O4 NCs/rGO modified GCE is the
higher surface area and high conductivity. Due to the properties of rGO and ZnFe2O4
nanocubes.
Ip = 2.69×105n3/2AD1/2Cv1/2
(1)
10

A
B
c
o
a
d
b
a
C
D
Z’ (ohm)
Figure 3. (A) CVs of bare GCE (a), rGO/GCE (b), ZnFe2O4 NCs/GCE (c) and ZnFe2O4
NCs/rGO/GCE (d) in 0.1 M KCl containing 5 mM [Fe(CN)6]-3/-4 solution. (B) Scan rate of
the nanocomposite modified electrode. (C) Calibration plot of (scan rate vs Vs-1)1/2. (D) EIS
spectra of bare GCE (a), ZnFe2O4 NCs/GCE (b) and ZnFe2O4 NCs/rGO/GCE (c).
The electrochemical properties of interfacial electron transport behavior are evaluated
by electrochemical impedance spectroscopy (EIS). The Nyquist plot exposed the various
modified and unmodified electrodes including bare GCE (a), ZnFe2O4 NCs/GCE (b) and
ZnFe2O4 NCs/rGO/GCE (c) shown in (Figure 3A). The EIS analysis was carried out by 0.1
M KCl containing 5 mM [Fe(CN)6]-3/-4 solution then the frequency ranges of 100 MHz to 100
kHz. The Nyquist plot explained the linear and semicircular, which described the lower and
11

higher frequencies on the modified and unmodified electrodes. The results were compared
with the bare GCE and ZnFe2O4 NCs/GCE and its depicts the higher semicircular and larger
Rct value around 736.48 Ω and 249.62 Ω than ZnFe2O4 NCs/rGO/GCE. Because, the
ZnFe2O4 NCs/rGO modified GCE shows the small semicircular and low Rct value of 106.25
Ω. Therefore, the nanocomposite has high conductive nanomaterials due to the properties of
rGO. Thus, the EIS results also indicated the formation of the nanocomposite with the rGO.
3.4. Electrochemical catalysis of 4-NQ on ZnFe2O4 NCs/rGO/GCE
The capability of the electrocatalyst modified and unmodified GCE towards the
electrochemical sensing of 4-NQ was analyzed by using CV method in Figure 4. In Figure
4A shows the CV curves of the bare GCE (a), rGO/GCE (b), ZnFe2O4 NCs/GCE (c) and
ZnFe2O4 NCs/rGO/GCE (d) in 100 µM 4-NQ in 0.05 M PB of pH 7.0. In all electrodes were
scanned from a potential of 0.25 V to -0.65 V at a scan rate of 50 mV/s. The poor sensitivity
and peak current exhibited by the bare GCE towards reduction reaction of 4-NQ was
improved considerably upon modification. Then, the rGO and ZnFe2O4 NCs modified GCE
are moderately improved towards the reduction of 4-NQ. Because, both electrodes have good
electrocatalytic ability due to their unique properties. In addition, commercial ZnFe2O4
nanoparticles modified GCE was checked and it has low peak current compared with
sonochemically synthesized ZnFe2O4 NCs modified GCE (Figure S1). Mainly, the developed
ZnFe2O4 NCs/rGO modified electrode, the reduction peaks current of the 4-NQ enhanced up
to 9.21 µA. The enhancement in the electrochemical performance has attributed to the
synergistic activity of rGO and ZnFe2O4 NCs. Moreover, the electrochemical sensing
mechanism of 4-NQ is converted into 4-hydroxyaminoquinoline N-oxide are given in
Scheme 3 and then, the 4-hydroxyaminoquinoline N-oxide has converted into 4-
12

nitrosoquinoline N-oxide (step-2). Higher sensitivity of the ZnFe2O4 NCs/rGO fabricated
electrode were attributed to the fact that the 4-NQ could interact through the conductive
electrocatalyst onto the GCE.
B’
A
B
e
a
d
c
b
a
C
D
j
a
Figure 4. (A) CVs of bare GCE (a), rGO/GCE (b), ZnFe2O4 NCs/GCE (c) and ZnFe2O4
NCs/rGO/GCE (d) containing 100 µM 4-NQ in 0.05 M PB (50 mV/s). (B) Various
concentration of 4-NQ (25 to 125 µM) and (Inset) shows the plot between 4-NQ
concentration versus cathodic peak current. (C) CV curves of different scan rate study ranges
from (20 to 200 mV/s) on ZnFe2O4 NCs/rGO/GCE for the reduction of 100 µM 4-NQ in 0.05
M PB. (D) The calibration plot between the cathodic current (Ipc) vs. the square root of the
scan rates.
13

Scheme 3. The electrochemical reduction reaction and mechanism of 4-NQ based on
ZnFe2O4 NCs/rGO modified GCE.
3.5. Effect of concentration, scan rate and pH
Figure 4B, shows the CVs of ZnFe2O4 NCs/rGO modified electrode in 0.05 M PB
containing various concentration of 4-NQ (a to e). When increase the concentration of 4-NQ,
a considerable increase in cathodic or reduction peak current. Furthermore, increase the 4-NQ
concentration, the cathodic peak current increased linearly. As shown in Figure 4A (inset),
the cathodic peak currents were increased linearly for the increasing concentration 4-NQ
from 25 to 125 µM and the electrochemical reduction linear regression equation y= 0.0908x-
0.37 and the correlation co-efficient is calculated as R2= 0.9953. These result reveals that the
nanocompsite modified electrode has great potential to electrochemically reduced the 4-NQ
to 4-NQ-NHOH and its evidences proved the good electrochemical performance of the
ZnFe2O4 NCs/rGO/GCE.
The effect of the scan rates (20 to 200 mV/s) were evaluated on ZnFe2O4 NCs/rGO
modified GCE containing 100 µM of 4-NQ in pH 7.0 (Figure 4C). Furthermore, the cathodic
peak currents were increase with the increasing the scan rates from 20 to 200 mV/s and the
obtained cathodic peak currents was plotted with different square root of the scan rates. As
14

shown in Figure 5D, cathodic peak currents are linearly increased with the square root of the
scan rates and the correlation coefficient of R2=0.9978. This results reveals that the
electrochemical reduction of 4-NQ at ZnFe2O4 NCs/rGO/GCE is diffusion controlled
process.
Figure 5. (A) CVs of the ZnFe2O4 NCs/rGO/GCE in the presence of 100 µM 4-NQ in
various pH solutions of (3.0, 5.0, 7.0, 9.0 and 11.0). (B) Plot of pH versus cathodic peak
current (Ipc).
The effect of pH on the voltammetric detection of 4-NQ with ZnFe2O4 NCs/rGO
modified GCE was examined over various pH ranges from pH 3.0 to 11.0. From Figure 5A,
it is found that the reduction peak current on the various pH of PB. The calibration plot of pH
versus cathodic peak current reveals that, as pH solution changes from lower to higher pH, a
peak potential were shift to negative side and it is also observed that the peak current
increases with increasing pH. Nevertheless, maximum peak current and response is obtained
in pH 7.0 (Figure 5A). Therefore, PB 7.0 is chosen as the optimum pH for the
electrochemical determination of 4-NQ on the ZnFe2O4 NCs/rGO modified GCE.
15

3.6. Electrochemical determination of 4-NQ by DPV techniques
A
B
534.12 µM
0.025 µM
Figure 6. (A-B) DPV responses for the successive additions of 4-NQ in 0.05 M PB (pH 7.0)
and various concentration ranges from (0.05 to 574.2 µM) at ZnFe2O4 NCs/rGO/GCE. (C-D)
The linear plot of 4-NQ concentrations versus current response.
The DPV (differential pulse voltammetry) is one of the electrochemical technique and
its highly sensitive technique compare then the CV method. Hence, the DPV technique was
employed to check the analytical performance of the ZnFe2O4 NCs/rGO/GCE towards the
biomarker of 4-NQ in 0.05 M PB at scan rate 50 mV/s. In Figure 6A shows the DPV for the
determination of 4-NQ for the different concentrations additions from 0.025 to 534.12 µM.
Moreover, Figure 6B depicts the corresponding calibration plot between peak current verses
concentration of 4-NQ. The electrocatalytic peak current response was increased for each
addition of 4-NQ based ZnFe2O4 NCs/rGO/GCE. Furthermore, the linear regression equation
y = 0.5238x +0.1446 with the correlation co-efficient is R2= 0.9985. Moreover, the peak
current responses were increased linearly proportional to the different concentration of 4-NQ.
In addition, the linear range was calculated as 0.025 to 534.12 µM and the detection limit is
8.27 nM and sensitivity 7.377 µA µM-1 cm-2 was observed. Besides, limit of quantification is
calculated to be 0.025 µM. These results reveals that the excellent electrochemical
16

performance of the proposed ZnFe2O4 NCs/rGO nanomaterials modified GCE for the
determination of 4-NQ.
3.7. Selectivity, stability and reproducibility of the sensor
A
B
C
D
Figure 7. (A) DPV responses of ZnFe2O4 NCs/rGO/GCE towards 50 μM of 4-NQ with 0.5
mM of interfering compounds. (B) Stability of the sensor as its continuous usage for 25 days
containing 100 µM 4-NQ in 0.05 M pH 7.0. (C) Plot for repeatability and (D) reproducibility
of ZnFe2O4 NCs/rGO/GCE containing 100 µM of 4-NQ.
Selectivity is one of the most important parameter for the detection of different
biologically important molecules. Hence, we have studied the interference effect for the
detection of 4-NQ in presence of some common biomolecules, co-existing and potentially
interfering molecules. Figure 7A. exhibited the DPV responses for the additions of 0.5 mM
of ascorbic acid, dopamine, uric acid, folic acid, glucose, H2O2, Na+, K+ and Fe2+ in presence
17

of 50 µM of 4-NQ. Moreover, the obtained DPV results reveals that the important
biomolecules are not affects much of the 4-NQ response. Therefore, these results are
exemplifying the good selectivity of the ZnFe2O4 NCs/rGO/GCE towards the determination
of 4-NQ.
In addition, the stability of the ZnFe2O4 NCs/rGO/GCE was explored by DPV
technique. Figure 7B depicts the DPV current response for the addition of 100 µM 4-NQ in
0.05 M PB (pH 7.0) at ZnFe2O4 NCs/rGO/GCE. The stability study shows that the initial
peak current value of the 4-NQ reduction was decreased to only 6.18% over 25 days. For the
reproducibility analysis five different ZnFe2O4 NCs/rGO modified GCE were prepared and
the DPV were recorded in presence of 100 µM of 4-NQ with the obtained results RSD were
calculated to be 3.57% (Figure 7D). The ZnFe2O4 NCs/rGO modified electrode was tested
for ten times and the RSD value were calculated to be 3.47% (Figure 7C). As a results,
ZnFe2O4 NCs/rGO/GCE shows the good selectivity, stability, repeatability and
reproducibility towards the detection of 4-NQ.
3.8. Real sample analysis
The practicality of the ZnFe2O4 NCs/rGO/GCE modified electrode was investigated
DPV method. The real sample of human serum and urine samples were collected from the
medical hospital (Taipei). Prior to the analysis, the human serum and urine samples were
diluted with buffer and spiked with known concentration of 4-NQ by using the standard
addition method. Later, the real samples were used to explore the practicality of the proposed
sensor. DPV responses for the addition of human serum and urine samples spiked with 100
nM, 200 nM and 500 nM concentration of 4-NQ. Then, the peak current responses were
18

increased for each addition of 4-NQ spiked samples. The obtained peak current responses
have calculated against the concentration. Moreover, the RSD (n=3) results were calculated
and tabulated in Table 1. It can be seen that the appreciable recovery results were obtained
for the determination of 4-NQ in human serum and urine samples.
Table 1. Determination of 4-NQ in real samples based on ZnFe2O4 NCs/rGO/GCE
Added/nM Found/nM Recovery/% *RSD/%
Real Samples
0
-
-
-
100
200
500
0
98.36
188.23
491.35
-
98.36
94.11
98.27
-
3.68
3.37
3.71
-
Blood serum
100
200
500
95.91
191.34
484.32
95.91
95.67
96.86
3.26
3.48
3.35
Urine
* Related standard deviation (RSD) of n=3 independent experiments.
4. Conclusion
In summary, the ZnFe2O4 NCs decorated rGO was synthesized by facile
sonochemical method. Further, the resultant nanomaterial was characterized through the
appropriate spectrophotometric techniques including HR-TEM, XRD, XPS, EIS and CV. As-
prepared ZnFe2O4 NCs/rGO nanocomposite was used to fabricate the modified GCE for the
19

determination biomarker. The electrocatalytic activity of the ZnFe2O4 NCs/rGO/GCE for the
detection of 4-NQ was evaluated using CV and DPV methods. Furthermore, the DPV study
reveals the wide linear range 0.025-534.12 µM and the LOD is 8.27 nM towards the
determination of 4-NQ. Besides, the interference study proved that our proposed sensor has
good selectivity towards the detection of 4-NQ. Mainly, our proposed sensor ZnFe2O4
NCs/rGO nanomaterial exhibited an excellent stability and reproducibility. Furthermore, we
have successfully demonstrated the practical ability of the 4-NQ sensor in human blood and
urine samples.
Acknowledgments
The authors extend their appreciation to the International Scientific Partnership
Program ISPP at King Saud University for funding this research work through ISPP# 0045.
This project was also supported by the Ministry of Science and Technology (MOST 107-
2113-M-027-005-MY3), Taiwan (ROC).
References
[1] J. Li, Q. Meng, Y. Zhang, L. Peng, G. Yu, A.C. Marschilok, L. Wu, D. Su, K.J.
Takeuchi, E.S. Takeuchi, Size-dependent kinetics during non-equilibrium lithiation of
nano-sized zinc ferrite, Nature communications, 10 (2019) 93.
[2] S. Gupta, C. Chang, C.-H. Lai, N.-H. Tai, Hybrid composite mats composed of
amorphous carbon, zinc oxide nanorods and nickel zinc ferrite for tunable
electromagnetic interference shielding, Composites Part B: Engineering, 164 (2019)
447-457.
20

[3] M.S. Javed, Z. Jiang, Q. Yang, X. Wang, X. Han, C. Zhang, X. Gu, C. Hu, Exploring
Li-ion hopping behavior in zinc ferrite and promoting performance for flexible solid-
state supercapacitor, Electrochimica Acta, 295 (2019) 558-568.
[4] Q. Zhang, Z. Li, X. Li, L. Yu, Z. Zhang, Z. Wu, Zinc ferrite nanoparticle decorated
boron nitride nanosheet: Preparation, magnetic field arrangement, and flame retardancy,
Chemical Engineering Journal, 356 (2019) 680-692.
[5] L. Yang, C. Sun, H. Lin, X. Gong, T. Zhou, W.-T. Deng, Z. Chen, J. Gao, Sensitive
Contrast-Enhanced MR Imaging of Orthotopic and Metastatic Hepatic Tumors by
Ultralow Doses of Zinc Ferrite Octapods, Chemistry of Materials, (2019).
[6] K. Sakthivel, G. Mani, S.-M. Chen, S.-H. Lin, A. Muthumariappan, V. Mani, A novel
synthesis of non-aggregated spinel nickel ferrite nanosheets for developing non-
enzymatic reactive oxygen species sensor in biological samples, Journal of
Electroanalytical Chemistry, 820 (2018) 161-167.
[7] S.-M. Chen, R. Umamaheswari, G. Mani, T.-W. Chen, M.A. Ali, A.-H. Fahad, M.
Elshikh, M.A. Farah, Hierarchically structured CuFe 2 O 4 ND@ RGO composite for
the detection of oxidative stress biomarker in biological fluids, Inorganic Chemistry
Frontiers, 5 (2018) 944-950.
[8] S. Kogularasu, M. Govindasamy, S.-M. Chen, M. Akilarasan, V. Mani, 3D graphene
oxide-cobalt oxide polyhedrons for highly sensitive non-enzymatic electrochemical
determination of hydrogen peroxide, Sensors and Actuators B: Chemical, 253 (2017)
773-783.
[9] M. Govindasamy, S. Shanthi, E. Elaiyappillai, S.-F. Wang, P.M. Johnson, H. Ikeda, Y.
Hayakawa, S. Ponnusamy, C. Muthamizhchelvan, Fabrication of hierarchical
NiCo2S4@ CoS2 nanostructures on highly conductive flexible carbon cloth substrate as
a hybrid electrode material for supercapacitors with enhanced electrochemical
performance, Electrochimica Acta, 293 (2019) 328-337.
[10] M. Govindasamy, S. Manavalan, S.-M. Chen, R. Umamaheswari, T.-W. Chen,
Determination of oxidative stress biomarker 3-nitro-L-tyrosine using CdWO4 nanodots
decorated reduced graphene oxide, Sensors and Actuators B: Chemical, 272 (2018)
274-281.
21

[11] S. Manavalan, M. Govindasamy, S.-M. Chen, U. Rajaji, T.-W. Chen, M.A. Ali, F.M.
Al-Hemaid, M. Elshikh, M.A. Farah, Reduced graphene oxide supported raspberry-like
SrWO4 for sensitive detection of catechol in green tea and drinking water samples,
Journal of the Taiwan Institute of Chemical Engineers, 89 (2018) 215-223.
[12] T.-W. Chen, U. Rajaji, S.-M. Chen, M. Govindasamy, S.S.P. Selvin, S. Manavalan, R.
Arumugam, Sonochemical synthesis of graphene oxide sheets supported Cu2S nanodots
for high sensitive electrochemical determination of caffeic acid in red wine and soft
drinks, Composites Part B: Engineering, 158 (2019) 419-427.
[13] M. Govindasamy, S.-F. Wang, S. Kumaravel, R.J. Ramalingam, H.A. Al-lohedan,
Facile synthesis of copper sulfide decorated reduced graphene oxide nanocomposite for
high sensitive detection of toxic antibiotic in milk, Ultrasonics sonochemistry, (2018).
[14] M.H. Sousa, F.A. Tourinho, J. Depeyrot, G.J. da Silva, M.C.F. Lara, New electric
double-layered magnetic fluids based on copper, nickel, and zinc ferrite nanostructures,
The Journal of Physical Chemistry B, 105 (2001) 1168-1175.
[15] V. Mani, B. Devadas, S.-M. Chen, Direct electrochemistry of glucose oxidase at
electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid
material modified electrode for glucose biosensor, Biosensors and Bioelectronics, 41
(2013) 309-315.
[16] V. Mani, B. Dinesh, S.-M. Chen, R. Saraswathi, Direct electrochemistry of myoglobin
at reduced graphene oxide-multiwalled carbon nanotubes-platinum nanoparticles
nanocomposite and biosensing towards hydrogen peroxide and nitrite, Biosensors and
Bioelectronics, 53 (2014) 420-427.
[17] R. Devasenathipathy, V. Mani, S.-M. Chen, Highly selective amperometric sensor for
the trace level detection of hydrazine at bismuth nanoparticles decorated graphene
nanosheets modified electrode, Talanta, 124 (2014) 43-51.
[18] B. Unnikrishnan, V. Mani, S.-M. Chen, Highly sensitive amperometric sensor for
carbamazepine determination based on electrochemically reduced graphene oxide–
single-walled carbon nanotube composite film, Sensors and Actuators B: Chemical, 173
(2012) 274-280.
[19] V. Mani, R. Devasenathipathy, S.-M. Chen, S.-F. Wang, P. Devi, Y. Tai,
Electrodeposition of copper nanoparticles using pectin scaffold at graphene nanosheets
22

for electrochemical sensing of glucose and hydrogen peroxide, Electrochimica Acta,
176 (2015) 804-810.
[20] M. Govindasamy, S.-F. Wang, W.C. Pan, B. Subramanian, R.J. Ramalingam, H. Al-
lohedan, Facile Sonochemical Synthesis of Perovskite-Type SrTiO3 Nanocubes with
Reduced Graphene Oxide Nanocatalyst for an Enhanced Electrochemical Detection of
α-Amino Acid (Tryptophan), Ultrasonics Sonochemistry, (2019).
[21] M. Govindasamy, B. Subramanian, S.-F. Wang, S. Chinnapaiyan, R.J. Ramalingam, H.
Al-lohedan, Ultrasound-Assisted Synthesis of Tungsten Trioxide Entrapped with
Graphene Nanosheets for Developing Nanomolar Electrochemical (Hormone) Sensor
and Enhanced Sensitivity of the Catalytic Performance, Ultrasonics Sonochemistry,
(2019).
[22] M. Govindasamy, R. Umamaheswari, S.-M. Chen, V. Mani, C. Su, Graphene oxide
nanoribbons film modified screen-printed carbon electrode for real-time detection of
methyl parathion in food samples, Journal of The Electrochemical Society, 164 (2017)
B403-B408.
[23] V. Mani, T.-W. Chen, S. Selvaraj, MWCNTs/MoS2 Decorated Cobalt Oxide
Polyhedrons Composite Film Modified Electrode for Electrochemical Determination of
Dopamine in Rat Brain and Human Blood Serum Samples, Int. J. Electrochem. Sci, 12
(2017) 7435-7445.
[24] M. Govindasamy, S.-M. Chen, V. Mani, M. Akilarasan, S. Kogularasu, B. Subramani,
Nanocomposites composed of layered molybdenum disulfide and graphene for highly
sensitive amperometric determination of methyl parathion, Microchimica Acta, 184
(2017) 725-733.
[25] V. Mani, M. Govindasamy, S.-M. Chen, B. Subramani, A. Sathiyan, J.P. Merlin,
Determination of folic acid using graphene/molybdenum disulfide nanosheets/gold
nanoparticles ternary composite, Int. J. Electrochem. Sci, 12 (2017) e267.
[26] V. Mani, M. Govindasamy, S.-M. Chen, T.-W. Chen, A.S. Kumar, S.-T. Huang, Core-
shell heterostructured multiwalled carbon nanotubes@ reduced graphene oxide
nanoribbons/chitosan, a robust nanobiocomposite for enzymatic biosensing of hydrogen
peroxide and nitrite, Scientific reports, 7 (2017) 11910.
23

[27] M. Govindasamy, V. Mani, S.-M. Chen, T. Maiyalagan, S. Selvaraj, T.-W. Chen, S.-Y.
Lee, W.-H. Chang, Highly sensitive determination of non-steroidal anti-inflammatory
drug nimesulide using electrochemically reduced graphene oxide nanoribbons, RSC
Advances, 7 (2017) 33043-33051.
[28] T. Nunoshiba, B. Demple, Potent intracellular oxidative stress exerted by the
carcinogen 4-nitroquinoline-N-oxide, Cancer Research, 53 (1993) 3250-3252.
[29] M. Govindasamy, S.-M. Chen, V. Mani, A. Sathiyan, J.P. Merlin, F.M. Al-Hemaid,
M.A. Ali, Simultaneous determination of dopamine and uric acid in the presence of
high ascorbic acid concentration using cetyltrimethylammonium bromide–
polyaniline/activated charcoal composite, RSC Advances, 6 (2016) 100605-100613.
[30] M. Govindasamy, V. Mani, S.-M. Chen, T.-W. Chen, A.K. Sundramoorthy, Methyl
parathion detection in vegetables and fruits using silver@graphene nanoribbons
nanocomposite modified screen printed electrode, Scientific reports, 7 (2017) 46471.
[31] J. Zheng, T. Gao, H. Shi, Y. Huang, Y. Xiang, G. Li, Electrochemical analysis of 8-
hydroxy-2’-deoxyguanosine with enhanced sensitivity based on exonuclease-mediated
functional nucleic acid, Talanta, (2019).
[32] A.R. Khandelwal, T. Moore-Medlin, O. Ekshyyan, X. Gu, F. Abreo, C.-A.O. Nathan,
Local and systemic Curcumin C3 complex inhibits 4NQO-induced oral tumorigenesis
via modulating FGF-2/FGFR-2 activation, American Journal of Cancer Research, 8
(2018) 2538.
[33] Y.C. Fann, C.A. Metosh-Dickey, G.W. Winston, A. Sygula, D. Ramakrishna Rao, M.B.
Kadiiska, R.P. Mason, Enzymatic and nonenzymatic production of free radicals from
the carcinogens 4-nitroquinoline N-oxide and 4-hydroxylaminoquinoline N-oxide,
Chemical research in toxicology, 12 (1999) 450-458.
[34] S. Kailasam, K. Rogers, A fluorescence-based screening assay for DNA damage
induced by genotoxic industrial chemicals, Chemosphere, 66 (2007) 165-171.
[35] F. Blasi, L. Dominici, M. Moretti, M. Villarini, S. Maurelli, M.S. Simonetti, P.
Damiani, L. Cossignani, In vitro genotoxicity/antigenotoxicity testing of some
conjugated linoleic acid isomers using comet assay, European journal of lipid science
and technology, 114 (2012) 1016-1024.
24

[36] I. Bobeldijk, A. Brandt, B. Wullings, T. Noij, High-performance liquid
chromatography–ToxPrint: chromatographic analysis with a novel (geno) toxicity
detection, Journal of Chromatography A, 918 (2001) 277-291.
[37] S.-M. Chen, S. Manavalan, U. Rajaji, M. Govindasamy, T.-W. Chen, M.A. Ali, A.K.
Alnakhli, F.M. Al-Hemaid, M. Elshikh, Determination of the antioxidant propyl gallate
in meat by using a screen-printed electrode modified with CoSe2 nanoparticles and
reduced graphene oxide, Microchimica Acta, 185 (2018) 520.
[38] M. Govindasamy, S. Manavalan, S.-M. Chen, U. Rajaji, T.-W. Chen, F.M. Al-Hemaid,
M.A. Ali, M.S. Elshikh, Determination of Neurotransmitter in Biological and Drug
Samples Using Gold Nanorods Decorated f-MWCNTs Modified Electrode, Journal of
The Electrochemical Society, 165 (2018) B370-B377.
[39] M. Govindasamy, V. Mani, S.-M. Chen, A. Sathiyan, J.P. Merlin, G. Boopathy,
Polyaniline/nickel Composite Film Modified Electrode for Sensitive Electrochemical
Determination of Ascorbic Acid, International Journal of Electrochemical Science, 11
(2016) 10806-10814.
[40] M. Govindasamy, V. Mani, S.-M. Chen, B. Subramani, R. Devasenathipathy, S.
Tamilarasan, Highly Sensitive Amperometric Sensor for Nitrobenzene Detection Using
Functionalized Multiwalled-Carbon Nanotubes Modified Screen Printed Carbon
Electrode, International Journal of Electrochemical Science, 11 (2016) 10837-10846.
[41] M. Govindasamy, U. Rajaji, S.-M. Chen, S. Kumaravel, T.-W. Chen, F.M. Al-Hemaid,
M.A. Ali, M.S. Elshikh, Detection of pesticide residues (Fenitrothion) in fruit samples
based on niobium carbide@ molybdenum nanocomposite: an electrocatalytic approach,
Analytica chimica acta, 1030 (2018) 52-60.
[42] V. Mani, A.P. Periasamy, S.-M. Chen, Highly selective amperometric nitrite sensor
based on chemically reduced graphene oxide modified electrode, Electrochemistry
Communications, 17 (2012) 75-78.
[43] V. Mani, S. Shanthi, T.-K. Peng, H.-Y. Lin, H. Ikeda, Y. Hayakawa, S. Ponnusamy, C.
Muthamizhchelvan, S.-T. Huang, Real-time quantification of hydrogen peroxide
production in living cells using NiCo2S4@CoS2 heterostructure, Sensors and Actuators
B: Chemical, (2019).
25

[44] G. Boopathy, M. Keerthi, S.-M. Chen, M. Umapathy, M. Govindasamy, T.-W. Chen,
M.A. Ali, F.M. Al-Hemaid, M. Elshikh, Graphene Oxide/α-MnO2 Binary Nanosheets
Based Non-Enzymatic Biosensor for Pico-Molar Level Electrochemical Detection of
Biomarker (Guanine) in DNA Sample, Journal of The Electrochemical Society, 165
(2018) B651-B658.
[45] F. Liu, X. Chu, Y. Dong, W. Zhang, W. Sun, L. Shen, Acetone gas sensors based on
graphene-ZnFe2O4 composite prepared by solvothermal method, Sensors and Actuators
B: Chemical, 188 (2013) 469-474.
[46] C.-H. Chen, Y.-H. Liang, W.-D. Zhang, ZnFe2O4/MWCNTs composite with enhanced
photocatalytic activity under visible-light irradiation, Journal of Alloys and
Compounds, 501 (2010) 168-172.
[47] P. Uniyal, K. Yadav, Synthesis and study of multiferroic properties of ZnFe2O4–BiFeO3
nanocomposites, Journal of Alloys and Compounds, 492 (2010) 406-410.
[48] S. Manavalan, U. Rajaji, S.-M. Chen, M. Govindasamy, S.S.P. Selvin, T.-W. Chen,
M.A. Ali, F.M. Al-Hemaid, M. Elshikh, Sonochemical synthesis of bismuth (III) oxide
decorated reduced graphene oxide nanocomposite for detection of hormone
(epinephrine) in human and rat serum, Ultrasonics sonochemistry, 51 (2019) 103-110.
[49] U. Rajaji, K. Murugan, S.-M. Chen, M. Govindasamy, T.-W. Chen, P.H. Lin, Graphene
oxide encapsulated 3D porous chalcopyrite (CuFeS2) nanocomposite as an emerging
electrocatalyst for agro-hazardous (methyl paraoxon) detection in vegetables,
Composites Part B: Engineering, 160 (2019) 268-276.
[50] T.-W. Chen, U. Rajaji, S.-M. Chen, R.J. Ramalingam, A relative study on
sonochemically synthesized mesoporous WS2 nanorods & hydrothermally synthesized
WS2 nanoballs towards electrochemical sensing of psychoactive drug (Clonazepam),
Ultrasonics sonochemistry, (2019).
Research Highlights
1) Facile sonochemical synthesis of Bimetal ferrite catalyst (BFC) based zinc ferrite
nanocubes decorated on multi-layered reduced graphene oxide (ZnFe2O4 NCs/rGO)
nanocomposite have been developed.
26

2) The ZnFe2O4 NCs/rGO nanocomposite was applied to the electrochemical sensor.
3) The ZnFe2O4 NCs/rGO has detected nanomolar level with broad dynamic range
towards 4-NQ.
4) The nanocomposite of ZnFe2O4 NCs/rGO was successfully applied real sample
analysis.
27