Ultrasonic-assisted preparation and characterization of magnetic ZnFe2O4/g-C3N4 nanomaterial and their applications towards electrocatalytic reduction of 4-nitrophenol

Article abstract of DOI:10.1016/j.ultsonch.2020.105071

Nanoball-structured ferromagnetic zinc ferrite nanocrystals (ZnFe₂O₄ NPs) entrapped with graphitic-carbon nitride (g-C₃N₄) was produced via straightforward and facile sonochemical synthetical technique (titanium

Full text of DOI:10.1016/j.ultsonch.2020.105071

Journal Pre-proofs
Ultrasonic-assisted Preparation and Characterization of Magnetic ZnFe2O4/g-
C3N4 Nanomaterial and their Applications towards Electrocatalytic Reduction
of 4-Nitrophenol
Sathishkumar Chinnapaiyan, Tse-Wei Chen, Shen-Ming Chen, Z. Abdullah
Alothman, M. Ajmal Ali, S.M. Wabaidur, Fahad Al-Hemaid, Shih-Yi Lee,
Wen-Han Chang
PII:
S1350-4177(19)31893-0
DOI:
Reference:
https://doi.org/10.1016/j.ultsonch.2020.105071
ULTSON 105071
To appear in:
Ultrasonics Sonochemistry
Received Date:
Revised Date:
Accepted Date:
11 January 2020
13 March 2020
19 March 2020
Please cite this article as: S. Chinnapaiyan, T-W. Chen, S-M. Chen, Z. Abdullah Alothman, M. Ajmal Ali, S.M.
Wabaidur, F. Al-Hemaid, S-Y. Lee, W-H. Chang, Ultrasonic-assisted Preparation and Characterization of
Magnetic ZnFe2O4/g-C3N4 Nanomaterial and their Applications towards Electrocatalytic Reduction of 4-
Nitrophenol, Ultrasonics Sonochemistry (2020), doi: https://doi.org/10.1016/j.ultsonch.2020.105071
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover
page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version
will undergo additional copyediting, typesetting and review before it is published in its final form, but we are
providing this version to give early visibility of the article. 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.
© 2020 Published by Elsevier B.V.

Ultrasonic-assisted Preparation and Characterization of Magnetic ZnFe2O4/g-C3N4
Nanomaterial and their Applications towards Electrocatalytic Reduction of 4-Nitrophenol
Sathishkumar Chinnapaiyana, Tse-Wei Chenb Shen-Ming Chena,*, Z. Abdullah Alothmanc,
,
M. Ajmal Alid, S. M. Wabaidurc, Fahad Al-Hemaidd , Shih-Yi Leee*, Wen-Han Changf,g,h
aDepartment of Chemical Engineering and Biotechnology, National Taipei University of
Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan, Republic of China
bDepartment of Materials, Imperial College London, London, SW7 2AZ, United Kingdom.
cAdvanced Materials Research Chair, Department of Chemistry, College of Science, King Saud
University, Riyadh 11451, Saudi Arabia.
dDepartment of Botany and Microbiology, College of Science, King Saud University, P.O. Box
2455, Riyadh, 11451, Saudi Arabia.
eDivision of Pulmonary and Critical Care Medicine, MacKay Memorial Hospital; MacKay
Medicine, Nursing and Management College.
fMacKay Memorial College Department of Cardiology, MacKay Memorial Hospital, Taiwan.
gDepartment of Emergency Medicine, MacKay Memorial Hospital, Taiwan.
hGraduate Institute of Injury Prevention and Control, Taipei Medical University; Department of
Medicine, Taiwan.
Corresponding Author:
*E-mail: smchen1957@gmail.com (S.-M.Chen), leesyi5538@yahoo.com.tw (S.-Y. Lee).

Abstract:
Nanoball-structured ferromagnetic zinc ferrite nanocrystals (ZnFe2O4 NPs) entrapped with
graphitic-carbon nitride (g-C3N4) was produced via straightforward and facile sonochemical
synthetical technique (titanium probe; 100 W/cm2 and 50 KHz). The morphological (SEM),
elemental (EDS), diffraction (XRD), XPS, and electrochemical studies (CV) have been carry out
to verify the nanostructure and shape of the materials. The ZnFe2O4 NPs/g-C3N4 electrode (GCE)
was constructed which displayed outstanding electrochemical ability towards toxic 4-nitrophenol
(NTP). A sensitive, selective, reproducible, and durable electrochemical NTP sensor was
developed by ZnFe2O4 NPs/g-C3N4 modified electrode. The modified sensor exhibited a high
sensitivity and 4.17 nanomolars of LOD. It’s greater than the LOD of previously reported NTP
modified sensors. The real-time experiments of the modified electrochemical (ZnFe2O4 NPs/g-
C3N4 electrode) sensor were successfully explained in various water (river and drinking) samples
and its showed high standard recoveries. Therefore, sonochemical synthetical method and
fabrication of modified electrode were developed this work based on environmental analysis of
NTP sensor.
Keywords: Sonochemical approach; Graphitic Carbon Nitride; Electrochemical detection;
Bimetal oxide; ZnFe2O4; Toxic chemical sensor.

1. Introduction
Ultrasound is an acoustic wave, which paves the route for several chemical reactions by
inducing chemical damage during the sonication process which leads to the growth, formation
and bubbles implosion within the liquid solution by its acoustic cavitation phenomenon [1-3]. On
sonication, the reaction condition such as a change in vapor pressure, collapsing of bubbles with
transient pressure and temperature were observed with the utilization of ultrasound waves [4-8].
In today’s world, the ultrasonication assisted synthesis of nanocomposite has attracted the
researchers due to its wide range of applications in various fields such as medical, chemical,
industrial and environmental fields [8-10]. Recently, a great deal of research has been addressed
to develop the hierarchical nanostructure of transition bimetal oxide such as nanorods,
nanoflowers, nanotubes, nanoparticles, nanosphere and layered sheets using facile sonochemical
approach due to its optical, and electronic properties [4, 11].
g-C3N4
Fe(NO3)3·9H2O
Zn(NO3)2·6H2O
sonicated/30 min
Stirred/12h
ZnFe2O4/g-C3N4 NC
Sonochemical
process
Scheme 1. Sonochemical synthesis of ZnFe2O4@g-C3N4 nanomaterials and sensor.
The spinel ferrites with chemical composition (MFe2O4, M = Zn, Ni, Co, and Cd) has
gained attention among researchers because of its excellent magnetic, chemical, catalytic and

physical properties [12-14]. Among these, the synergistic action of Zn and Fe in zinc ferrite
(ZnFe2O4) enrich the redox reaction in electrochemistry and was extensively applied in diverse
fields like photocatalysis, solar cells, photochemical hydrogen production, chemical sensors and
batteries [15-18]. Hence, ZnFe2O4 is an excellent candidate owing to its high abundance, low
cost, less toxic, environmental friendly, high electrochemical activity and high active surface
area [19, 20]. The synthesis of ZnFe2O4 with various structural morphologies like ZnFe2O4
nanoparticles, ZnFe2O4 nanobelts [21], and ZnFe2O4 nanorods has been reported [22]. One of the
fascinating methods to attain high electrochemical performance is to incorporate carbon-based
conductive material like CNT, graphene or graphitic carbon nitride (g-C3N4) with ZnFe2O4 [23,
24]. Besides, the polymeric 2D semiconductor, g-C3N4 has emerged as a potential candidate due
to its distinct electronic structure, low-cost, high stability, facile synthesis, high thermal stability,
low density, electrocatalytic and photochemical properties which have been exhaustively
employed in various fields such as sensing, photo-catalysis, and bio-imaging [25-29].
The significant advances in industrialization and technology over the globe have created a
huge demand to detect hazardous environmental pollutants such as heavy metals, dyes, and
pesticides from industrial wastewater. These harmful chemicals have a deleterious impact on the
ecology as well as mankind [30-33]. Among them, phenolic derivative 4-nitrophenol (NTP) is a
toxic, non-degradable nitro aromatic compound that is extensively employed in dyes, explosives,
pharmaceuticals, petroleum, textile, and paper industries [34]. Owing to its toxicity, the US
environmental protection agency (EPA) has categorized NTP as a priority pollutant with a
permissible limit of less than 20 ppb in water. Intake or inhalation of NTP leads to severe health
impacts on human, which affects the kidney, nervous and blood system by causing nausea,
inflammation, cyanosis, drowsiness and methemoglobinemia [34-36]. Therefore, a simple,

effective, rapid, cheap and sensitive methodology for detecting NTP in water and food samples is
of urgent need. To date, several methodologies, such as capillary electrophoresis, fluorescence,
high-performance liquid chromatography, spectrophotometry, flow injection, and gas
chromatography, have been widely used for the quantitative and qualitative detection of NTP.
Nonetheless, these methods are highly sensitive but are time-consuming, require complicated
operations with trained operators, high cost and need substantial sample manipulation. Moreover,
the electrochemical method is identified as a promising analysis tool for its low cost, high-speed
measurement, simple implementation, easy handling, reduced instrument size, and ultrasensitive
detection.
OH
NO2
ZnFe2O4/g-C3N4
g-C3N4
e-
OH
Drop casting
method
G
C
E
HNOH
ZnFe2O4
Electrochemical
cell setup
ZnFe2O4/ g-C3N4
Scheme 2. Fabrication of modified electrode and its application in water samples
In this work, we aimed to synthesize g-C3N4 incorporated on highly stable ZnFe2O4 for
effective electrochemical detection of NTP using the facile sonochemical approach. The
ZnFe2O4/g-C3N4 modified glassy carbon electrode (GCE) exhibits beneficial sensing ability over
NTP with a lower limit of detection, broad dynamic range, high reproducibility, stability, and
sensitivity. The as described modified electrode delivers excellent practicability in biological
samples.

2. Experimental section
2.1. Preparation of ZnFe2O4/g-C3N4 nanocomposites
One mol of zinc source (Zn(NO3)2·6H2O) and two mol of iron nitrate nonahydrate were
dissolved in 50 mL of Milli-Q water to form suspension (materials and method given in
supporting information file). Then, 100 mg of carbon nitride (C3N4) powder was subsequently
added to the pre-prepared mixture solution under magnetic stirrer. The suspension was ultrasonic
agitated for 1 h (100 W/cm2 and 50 KHz) and then mechanically stirred for 30 minutes at 30 °C
temperature. Finally, the obtained precipitate (PPT) was collected using centrifuged and washed
process with Milli-Q water and ethanol thoroughly and heated in vacuum dry oven at 80 °C for
12 h. For controlled material, pure ZnFe2O4 electro-catalyst was also prepared using same
procedure without an addition of graphitic carbon nitride powder. Then, it also using for
electrochemical experiments
2.2. Electrode modification using ZnFe2O4/g-C3N4 nanocomposite
The alumina powders (0.3 μm) were applied to polish (clean) the glassy carbon electrode
(GCE), and then the glassy carbon electrode was cleaned with water and ethanol sequentially.
After, washed glassy carbon electrode was dried, at electric oven for 30 min. Then, 8 μL
ZnFe2O4/C3N4 suspensions (2 mg/mL) were drop casted on GCE (glassy carbon electrode) and
then, composite drop casted electrode was dried at electric oven for 30 min. Furthermore, the
C3N4 modified GCE and ZnFe2O4 modified GCE were prepared with a similar way. Then, all the
modified electrodes were applied to electrochemical analysis.

(A)
(B)
(E)
(C)
(D)
(F)
g-C3N4
ZnFe2O4
Figure 1. TEM analysis of g-C3N4 nanosheets (A-B), TEM analysis of g-C3N4/ZnFe2O4 (C-E)
and graphical structure (stick and ball) of the g-C3N4/ZnFe2O4 nanocomposite (F).
3. Results and discussions
3.1. Characterizations of ZnFe2O4/g-C3N4 nanocomposite
Figure 1A, shows the TEM analysis of graphitic carbon nitride (A-B) and g-C3N4/ZnFe2O4
composite (C-E). Pure graphitic carbon nitride shows an aggregated multi-layered nanostructure
with smooth surface in Figure 1A-B. ZnFe2O4 particles are 200 nanometers larger and also its
nano-balls like shaped (Figure 1C). Moreover, ZnFe2O4 particles are covered with graphitic
carbon nitride sheets and it’s like multilayered nanocomposite (Figure 1D-E). Figure 1F depicts
the synthetic model of nanocatalyst (g-C3N4/ZnFe2O4) and the ball-stick model structure of the
graphitic carbon nitride with ZnFe2O4 catalyst.

(A)
Figure 2. X-ray powder diffraction analysis of graphitic carbon nitride/ZnFe2O4 composite.
Figure 2, explained the X-ray powder diffraction patterns of g-C3N4/ZnFe2O4 composite.
Furthermore, the X-ray powder diffraction peaks at 29.34°, 35.01°, 36.24°, 43.19°, 53.21°,
56.42°, and 63.34° with much intensity, can be assigned to (200), (311), (222), (400), (422),
(511), and (440) diffraction planes of spinel-type zinc ferrite (JCPDS 22–1012) [37-39]. Figure
2, can be seen the graphitic carbon nitride has two distinct peaks in XRD analysis. A week peak
at 28.71°, correspond to (002) plane with in-planar distance of graphitic carbon nitride (JCPDS
87–1526) and it is attributed to the long-range in-planar and stacking of aromatic units with one
more peak at 13.74°. Its high-intensity and can be designated to (100) XRD peak, which
correspond to tri-s-triazine part and also the interlayer stacking of graphitic carbon nitride.
Moreover, the ZnFe2O4 nanoparticles combined with g-C3N4 was confirmed by XRD analysis in
Figure 2. Therefore, the formation of nanocomposite has been achieved from X-ray powder
diffraction examination.

(C)
(A)
(B)
(D)
(E)
(F)
Figure 3. X-ray photoelectron spectroscopy (XPS) analysis of g-C3N4 nanosheets@ZnFe2O4
nanocomposite.
In this study, we are used X-ray photo-electron spectroscopy (XPS) method to analyses the
physical and chemical properties of the g-C3N4/ZnFe2O4 nanocomposite with surface and
structural character. Figure 3A shows the Zn 2p, Fe 2p, O 1s, N 1s and C 1s spectra of g-
C3N4/ZnFe2O4 catalysts [41]. Zn 2p3/2 was deconvoluted into two XPS peaks. That is binding
energy of 1020 to 1055ꢀeV and it’s due to Zn2+ as shown in Figure 3B. Furthermore, Fe 2p3/2 was
deconvoluted into two XPS peaks. That is binding energy of 710 to 735ꢀeV and it’s due to Fe3+
as shown in Figure 3C. Moreover, the peak intensity of the higher oxidation state Fe3+ is
enhancing with the increase of graphitic carbon nitride in the g-C3N4/ZnFe2O4 nanocomposite
[41]. Then, O 1s XP-spectra contains four distinct XPS peaks. Two low binding energy peaks are
located at 528.3ꢀeV and 530.2ꢀeV and it’s ascribed to the lattice oxygen O2− species in the
ZnFe2O4 nanoparticles (Figure 3D). The N 1s XPS spectrum of the g-C3N4 shown in Figure 3F
can be fitted into three peaks at 397.8 to 406.3ꢀeV, corresponding to pyridine and pyrrole-like N

and then, a peak emerged at 285 to 294.2ꢀeV, which also corresponds to C 1s in the g-
C3N4/ZnFe2O4 [42, 43]. It suggests that through sonochemical treating ZnFe2O4 could be
combined with g-C3N4, which promoted the formation of bimetal oxide on the surface of the
nanocomposite electrocatalyst. According to previous XPS literatures, the existence of bimetal
oxide in nanocomposite is used to electrochemical activities of the material.
3.2. Electrocatalysis of NTP based on g-C3N4/ZnFe2O4/GCE
(B)
(A)
25 µM
a
b
c
250 µM
[4-NP]µM
Figure 4. CVs at bare electrode (a), g-C3N4 modified electrode (b) and ZnFe2O4/g-C3N4
modified electrode (c) in presence of 150 µM NTP at 50 mVs-1 (pH 5.0; phosphate buffer; N2).
(B) CVs obtained at ZnFe2O4/C3N4 modified GCE in pH 5.0 phosphate buffer (with
nitrogen gas) with different concentrations of NTP and inset diagram is cathodic peak
current/µA and [NTP]/µM.

OH
OH
+ 4e- + 4H+
H O
+
2
NO2
HNOH
4-NP
4-Hydroxyminophenol
H
O
O
O
H+
+
N
N
N
O
O
O
O
O
O
Figure 5. Electrochemical reduction mechanism of 4-nitrophenol (NTP) based on ZnFe2O4/g-
C3N4 composite modified GCE in pH 5.0 (phosphate buffer; N2; 50 mV/s).
Figure 4A is explore, the CV analysis for unmodified electrode (a), g-C3N4/GCE (b) and
ZnFe2O4/g-C3N4/GCE (c) (0.1 M; phosphate buffer; pH 5.0) containing 150 µM of NTP. The
potential range was applied between 0.1 V and –0.8 V and the scan rate is 50 mV per second.
ZnFe2O4/g-C3N4 modified GCE offered more advantageous to NTP electrochemical reduction
due to the properties of electrocatalytic ability and fast electron transfer. It’s based on
electrochemical ability of ZnFe2O4 and graphitic carbon nitride sheets. Furthermore, the
electrochemical mechanism of the NTP is given in Figure 5 [44-46] and it’s clearly explained 4-
nitropheonl is converted into 4-hydroxyminopheonl by ZnFe2O4/g-C3N4 electrocatalyst. The
electrochemical reduction current is obtained at ZnFe2O4/g-C3N4/GCE and it’s higher than that
obtained at unmodified electrode (a) and g-C3N4 modified GCE (b). In addition, the
overpotential also reduced at ZnFe2O4/g-C3N4 modified GCE compare to unmodified GCE.
Therefore, the improved electrocatalytic ability of ZnFe2O4/g-C3N4 can be manifested and it has
excellent electro-catalytic activity based on graphitic carbon nitride. Figure 4B, presented the

CVs obtained at ZnFe2O4/g-C3N4 modified GCE in 0.1 M phosphate buffer (pH 5.0; 50 mV/s)
containing various concentrations of NTP (with nitrogen gas 15 seconds). A cathodic peak
current was linearly increased as the concentration of NTP increased (inset to Figure 4B).
(A)
(B)
20 mV/s
240 mV/s
Figure 6. (A) CVs obtained at ZnFe2O4/C3N4 modified GCE in pH 5.0 phosphate buffer with
different scan rate (20 to 240 mV/S) of NTP, the inset is the linear relationship between cathodic
peak current and square root of the scan rate.
The electrochemical current responses were increased linearly with concentrations of NTP
chemical, which is reveal for the anti-fouling potential of the ZnFe2O4/g-C3N4 modifier. Further,
the calibration plot is good linearity (inset). The electrochemical effect of the scan rate (kinetic
analysis) toward electro-catalytic NTP reduction was studied by ZnFe2O4/g-C3N4 at different
scan rates (20 to 240 mV/s; Figure 6A). Moreover, the plot between the cathodic peak current of
NTP and the square root of the scan rate which is applied and its exhibits good linearity.
Therefore, these results are suggesting a diffusion-controlled process based on surface of
ZnFe2O4/g-C3N4 modified glassy carbon electrode (Figure 6B). Then, the influence of electrolyte
was checked (pH) on ZnFe2O4/C3N4 modified electrode towards 100 μM NTP chemical at 0.1 M
phosphate buffer (Figure 7A). The pH of electrolyte is changes and the peak current with

potential (V; Ag/AgCl) of NTP cathodic peaks is also changed due to properties of
ZnFe2O4/C3N4. The reduction peak current increases as the pH increases from 3 to 5 and reached
maxima at pH 5.0 (Figure 7B). For pH 7 and 11, the cathodic peak current progressively
decreases. Thus, the reduction of NTP is more favorable at pH 5.0 (phosphate buffer) based on
ZnFe2O4/C3N4 modified GCE at 50 mV/s.
(A)
(B)
Figure 7. (A) CVs are carried out in (pH range: 3.0 to 11.0) phosphate buffer containing (100
μM) NTP at ZnFe2O4/C3N4 modified GCE (50 mV/s; 0.1 M PB). (B) Plot is peak current/μA and
different pH (3.0 to 11.0).
3.3. Amperometric determination towards NTP chemical
Figure 8A displayed, the amperometric (i-t) analysis of ZnFe2O4/C3N4 modified (RDE)
rotating electrode (rotation speed=1100 RPM) with injections of NTP into phosphate buffer (pH
5.0) at a regular intervals of 50 seconds. Moreover, the electrode operational potential (Eapp) is –
0.58 V (Ag/AgCl). Furthermore, well–defined and fast responses of NTP were obtained and
steady–state current was reached within six seconds. The electrochemical sensor and
amperometric working range is 0.015–724.17 µM (Figure 8B) and limit of detection (LOD) is
calculated as 4.17 nM. In addition, the electrochemical sensitivity of the work was calculated to

1.68 μA µM–1 cm–2. Further, the electrochemical sensor parameters are superior over existing
ZnFe2O4/C3N4 incorporated and modified (RDE) electrodes (Table 1). Mainly, the detection
limit is attained very lower at ZnFe2O4/C3N4 film modified electrode has surpassed that of many
previous electrochemical (NTP) and other sensors.
15 nM
(B)
(A)
724.17 µM
[4-NP]/µM
Figure 8. (A) Amperometric responses obtained at ZnFe2O4/C3N4/GCE after successive
injection of NP (4-nitrophenol; NTP); (B) The plots of amperometric responses current vs NTP
concentration/. Base solution: pH 7.0 PB (Applied potential: -0.58 V).
Table 1. Comparison of electro-analytical parameters obtained at ZnFe2O4/C3N4 film modified
rotation disc electrode (RDE) towards NTP with previous reports.
Limit of
detection/µM
8.0
Linear
range/µM
10–100
Modified Electrode
Ref.
Au NPs/aGCE
bGO sheets
[47]
[48]
[49]
0.02
0.04
0.1–120
0.1–10
cMWCNTs/Nafion

Graphene sheets/Nafion/dSPCE
erGOS–Au NPs
0.6
10–620
0.05–2
[50]
[51]
0.01
Ag NPs/chitosan
fMMIPs/Au/AuEg
0.07
0.1
0.07–2.0
0.1–140
[52]
[53]
[54]
hDTD/Ag NPs/iCPE
jHA NPs
0.25
1.0–100
1.0–300
0.60
4.07
[55]
ZnFe2O4/g-C3N4/GCE
0.015–724.17
This work
b
c
aGCE= Glassy-carbon electrode, GOS= Graphene oxide sheets, MWCNTs= Multiwall carbon
d
e
nanotubes, SPCE= Screen-printed carbon electrode, rGOS= Reduced graphene oxide sheets,
fMMIPs=
Molecularly
imprinted
polymers,
gAuE=
gold
electrode,
hDTD=
i
j
trioxadiazacyclonanodecine–dione, CPE= Carbon-paste electrode, HA NPs= Hydroxyapatite
nanoparticles.
The selectivity (anti-interference ability) of the modified sensor was examined by
performing experiments in presence of likely interfering agents. Figure S1 (A) showed the
amperometric response of the modified electrode towards 50 μM of NTP, and 0.5 mM of
ascorbic acid (AA), catechol (CT), serotonin (ST), histamine (His), metronidazole (MTZ), zinc
ion (Zn), hydroquinone (HQ), Tryptophan (TRP), acetaminophen (AC), potassium (K+) and
lysine (Lys). Besides, the modified electrode has quickly responded to NTP at ZnFe2O4/g-C3N4
in pH 5.0 (phosphate buffer; N2 gas). However, it was insensitive (maybe no peak) to the other
species (biomolecules, drugs and metal ions). Therefore, ZnFe2O4/g-C3N4 modified electrode
high recognizes to detect NTP in phosphate buffer.
3.4. Durability, Reproducibility and Reproducibility of ZnFe2O4/g-C3N4 modified electrode

In order to examine, the durability of the ZnFe2O4 and g-C3N4 modified electrochemical
sensor. The sensor performance of the ZnFe2O4/g-C3N4 modified electrode was monitored every
day towards 100 µM NTP at phosphate buffer (pH 7.0; 0.1 M), and then the modified electrode
was stored at 5°C. Similar experiments were studied and the sensor performance was retained
95.62% after 30 days, compare to initial sensor response. Therefore, ZnFe2O4/g-C3N4 modified
sensor has the excellent durability property (Figure S1B). Moreover, repeatability analysis was
performed using one electrode and 10 repeated measurements based on ZnFe2O4/g-C3N4 film
modified electrode and the R.S.D of the 10 repeated measurements is 3.41% (Figure S2A).
Finally, the reproducibility experiments were tested using five individual ZnFe2O4/g-C3N4
modified electrodes and data were recorded by CV method in phosphate buffer (pH 5.0; N2 gas)
containing 100 µM NTP. The R.S.D of the five measurements at five modified electrodes was
3.29% (Figure S2B). According to those results, the electrochemical sensor and ZnFe2O4/g-C3N4
modified electrode exhibited acceptable range of stability, repeatability and reproducibility.
3.5. Real time analysis of ATP at ZnFe2O4/g-C3N4 modified electrode
The practical analysis of the ZnFe2O4/g-C3N4 fabricated sensor was analyzed in different
water samples. Drinking water collected from National Taipei University of Technology, Taiwan
and river water collared form near river (New Taipei City). These samples were analyzed
directly and then known amounts of NTP were spiked into water samples (drinking water and
river water) and amperometric analysis was tested by optimized electrochemical experimental
conditions (like Figure 8 experiment). The electrochemical sensor performance was calculated
using standard addition method (SAM) and data are given in Table 2. Therefore, the ZnFe2O4/g-
C3N4 modified electrode (carbon based) has high potential to be used in practical applications.

Table 2. Electrochemical determination of NTP in water samples based on ZnFe2O4/g-
C3N4/GCE. *Relative standard deviation (RSD) of n=3 experiments.
Added
(µM)
10
Found
(µM)
9.83
Recovery
(%)
*RSD
(%)
Water Samples
Drinking water
98.30
99.20
99.48
97.4
3.51
2.62
3.26
3.21
3.22
3.71
20
19.84
49.74
9.74
50
10
River Water
20
19.68
48.19
98.40
96.38
50
4. Conclusions
In this work, a facile and robust sonochemical and solvothermal synthetical routes were
developed to prepare a nano-ball like ZnFe2O4 particles decorated graphitic carbon nitride
nanocomposite. The chemical structures and shape of the nanomaterials were confirmed by
morphological (TEM), elemental (EDS), spectral (XPS) and electrochemical methods (CV and
amperometric). The ZnFe2O4/g-C3N4 film modified electrode (carbon based) shown excellent
electrocatalytic performances by amperometric method. It was demonstrated which showed wide
working range (0.015–724.17 µM) and low detection limit (4.07 nM). The electrochemical
detection at nanomolar range is revealed and its good sensitivity in the quantification of NTP.

Acknowledgements
Authors are grateful to the Researchers Supporting Project No. (RSP-2019/1) King Saud
University, Riyadh, Saudi Arabia. This work was supported by the Ministry of Science and
Technology, Taiwan (MOST 107-2113-M-027-005-MY3). The authors gratefully acknowledge
the financial support of the National Taipei University of Technology, and Mackay Memorial
Hospital Joint Research Program(NTUT-MMH-109-01).
Reference
[1] M. Vinatoru, T.J. Mason, Can sonochemistry take place in the absence of cavitation?–A
complementary view of how ultrasound can interact with materials, Ultrasonics
sonochemistry, 52 (2019) 2-5.
[2] V. Grosjean, C. Julcour, O. Louisnard, L. Barthe, Axial acoustic field along a solid-liquid
fluidized bed under power ultrasound, Ultrasonics sonochemistry, 56 (2019) 274-283.
[3] B. Zhu, C. Fei, C. Wang, Y. Zhu, X. Yang, H. Zheng, Q. Zhou, K.K. Shung, Self-focused
AlScN film ultrasound transducer for individual cell manipulation, ACS sensors, 2 (2017)
172-177.
[4] V.R. Midathana, V.S. Moholkar, Mechanistic studies in ultrasound-assisted adsorption for
removal of aromatic pollutants, Industrial & engineering chemistry research, 48 (2009)
7368-7377.
[5] S. Ahmed, D.T. Gentekos, C.A. Fink, T.E. Mallouk, Self-assembly of nanorod motors into
geometrically regular multimers and their propulsion by ultrasound, ACS nano, 8 (2014)
11053-11060.

[6] S. Sabrina, M. Tasinkevych, S. Ahmed, A.M. Brooks, M. Olvera de la Cruz, T.E. Mallouk,
K.J. Bishop, Shape-directed microspinners powered by ultrasound, ACS nano, 12 (2018)
2939-2947.
[7] S. Vinoth, M. Govindasamy, S.-F. Wang, S. Anandaraj, Layered Nanocomposite of Zinc
Sulfide Covered Reduced Graphene Oxide and Their Implications for Electrocatalytic
Applications, Ultrasonics Sonochemistry, (2020) 105036.
[8] 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, 52 (2019) 382-
390.
[9] J.K. Rajput, P. Arora, G. Kaur, M. Kaur, CuFe2O4 magnetic heterogeneous nanocatalyst:
Low power sonochemical-coprecipitation preparation and applications in synthesis of 4H-
chromene-3-carbonitrile scaffolds, Ultrasonics sonochemistry, 26 (2015) 229-240.
[10] C. Karunakaran, S. SakthiRaadha, P. Gomathisankar, P. Vinayagamoorthy, Nanostructures
and optical, electrical, magnetic, and photocatalytic properties of hydrothermally and
sonochemically prepared CuFe 2 O 4/SnO 2, RSC Advances, 3 (2013) 16728-16738.
[11] S. Anandan, G.-J. Lee, J.J. Wu, Sonochemical synthesis of CuO nanostructures with
different morphology, Ultrasonics sonochemistry, 19 (2012) 682-686.
[12] H.Y. Hafeez, S.K. Lakhera, P. Karthik, M. Anpo, B. Neppolian, Facile construction of
ternary CuFe2O4-TiO2 nanocomposite supported reduced graphene oxide (rGO)
photocatalysts for the efficient hydrogen production, Applied Surface Science, 449 (2018)
772-779.

[13] L. Su, J. Feng, X. Zhou, C. Ren, H. Li, X. Chen, Colorimetric detection of urine glucose
based ZnFe2O4 magnetic nanoparticles, Analytical chemistry, 84 (2012) 5753-5758.
[14] F. Zou, X. Hu, Z. Li, L. Qie, C. Hu, R. Zeng, Y. Jiang, Y. Huang, MOF‐derived porous
ZnO/ZnFe2O4/C octahedra with hollow interiors for high‐rate lithium‐ion batteries,
Advanced materials, 26 (2014) 6622-6628.
[15] X. Zhou, X. Li, H. Sun, P. Sun, X. Liang, F. Liu, X. Hu, G. Lu, Nanosheet-assembled
ZnFe2O4 hollow microspheres for high-sensitive acetone sensor, ACS applied materials &
interfaces, 7 (2015) 15414-15421.
[16] Y. Sharma, N. Sharma, G.S. Rao, B. Chowdari, Li-storage and cyclability of urea
combustion derived ZnFe2O4 as anode for Li-ion batteries, Electrochimica Acta, 53 (2008)
2380-2385.
[17] P. Laokul, V. Amornkitbamrung, S. Seraphin, S. Maensiri, Characterization and magnetic
properties of nanocrystalline CuFe2O4, NiFe2O4, ZnFe2O4 powders prepared by the Aloe
vera extract solution, Current Applied Physics, 11 (2011) 101-108.
[18] S.-W. Cao, Y.-J. Zhu, G.-F. Cheng, Y.-H. Huang, ZnFe2O4 nanoparticles: microwave-
hydrothermal ionic liquid synthesis and photocatalytic property over phenol, Journal of
Hazardous materials, 171 (2009) 431-435.
[19] 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.
[20] 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.
[21] G. Song, F. Xin, X. Yin, Photocatalytic reduction of carbon dioxide over ZnFe2O4/TiO2
nanobelts heterostructure in cyclohexanol, Journal of colloid and interface science, 442
(2015) 60-66.
[22] M.M. Rahman, S.B. Khan, M. Faisal, A.M. Asiri, K.A. Alamry, Highly sensitive
formaldehyde chemical sensor based on hydrothermally prepared spinel ZnFe2O4
nanorods, Sensors and Actuators B: Chemical, 171 (2012) 932-937.
[23] B. Sriram, M. Govindasamy, S.-F. Wang, R.J. Ramalingam, H. Al-Lohedan, T.
Maiyalagan, Novel sonochemical synthesis of Fe3O4 nanospheres decorated on highly
active reduced graphene oxide nanosheets for sensitive detection of uric acid in biological
samples, Ultrasonics sonochemistry, 58 (2019) 104618.
[24] M. Tang, F. Xia, C. Gao, H. Qiu, Preparation of magnetically recyclable CuFe2O4/RGO
for catalytic hydrolysis of sodium borohydride, International Journal of Hydrogen Energy,
41 (2016) 13058-13068.
[25] A.H. Mady, M.L. Baynosa, D. Tuma, J.-J. Shim, Heterogeneous activation of
peroxymonosulfate by a novel magnetic 3D γ-MnO2@ ZnFe2O4/rGO nanohybrid as a
robust catalyst for phenol degradation, Applied Catalysis B: Environmental, 244 (2019)
946-956.
[26] X. Huang, Z. Nan, Formation of octahedron-shaped ZnFe2O4/SiO2 with yolk–shell
structure, Journal of Physics and Chemistry of Solids, (2020) 109410.
[27] C.A. Huerta-Aguilar, A.A. Ramírez-Alejandre, P. Thangarasu, J.A. Arenas-Alatorre, I.A.
Reyes-Dominguez, M. de la Luz Corea, Crystal phase induced band gap energy enhancing

the photo-catalytic properties of Zn–Fe 2 O 4/Au NPs: experimental and theoretical
studies, Catalysis Science & Technology, 9 (2019) 3066-3080.
[28] 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.
[29] 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.
[30] Z. Li, M. He, Y. Wen, X. Zhang, M. Hu, R. Li, J. Liu, J. Chu, Z. Ma, X. Xing, Highly
Monodisperse Cu–Sn Alloy Nanoplates for Efficient Nitrophenol Reduction Reaction via
Promotion Effect of Tin, Inorganic Chemistry, (2020).
[31] Z. Wei, Y. Li, L. Dou, M. Ahmad, H. Zhang, Cu3–x Ni x Al-Layered Double Hydroxide-
Reduced Graphene Oxide Nanosheet Array for the Reduction of 4-Nitrophenol, ACS
Applied Nano Materials, 2 (2019) 2383-2396.
[32] M. Govindasamy, S. Kogularasu, S.-M. Chen, Y.-H. Cheng, M. Akilarasan, V. Mani,
Highly sensitive and selective detection of phenolic compound in river and drinking water
samples using one–pot synthesized 3d–cobalt oxide polyhedrons, Journal of The
Electrochemical Society, 164 (2017) B463.
[33] R. Karthik, M. Govindasamy, S.-M. Chen, Y.-H. Cheng, P. Muthukrishnan, S.
Padmavathy, A. Elangovan, Biosynthesis of silver nanoparticles by using Camellia
japonica leaf extract for the electrocatalytic reduction of nitrobenzene and photocatalytic

degradation of Eosin-Y, Journal of Photochemistry and Photobiology B: Biology, 170
(2017) 164-172.
[34] J. Zeyer, P.C. Kearney, Degradation of o-nitrophenol and m-nitrophenol by a
Pseudomonas putida, Journal of Agricultural and Food Chemistry, 32 (1984) 238-242.
[35] Y. Xu, X. Shi, R. Hua, R. Zhang, Y. Yao, B. Zhao, T. Liu, J. Zheng, G. Lu, Remarkably
catalytic activity in reduction of 4-nitrophenol and methylene blue by Fe3O4@ COF
supported noble metal nanoparticles, Applied Catalysis B: Environmental, 260 (2020)
118142.
[36] N.K.R. Bogireddy, P. Sahare, U. Pal, S.F.O. Méndez, L.M. Gomez, V. Agarwal, Platinum
nanoparticle-assembled porous biogenic silica 3D hybrid structures with outstanding 4-
nitrophenol degradation performance, Chemical Engineering Journal, 388 (2020) 124237.
[37] A.H. Mady, M.L. Baynosa, D. Tuma, J.-J. Shim, Facile microwave-assisted green
synthesis of Ag-ZnFe2O4@ rGO nanocomposites for efficient removal of organic dyes
under UV-and visible-light irradiation, Applied Catalysis B: Environmental, 203 (2017)
416-427.
[38] B. Palanivel, T. Maiyalagan, V. Jayarman, C. Ayyappan, M. Alagiri, Rational design of
ZnFe2O4/g-C3N4 nanocomposite for enhanced photo-Fenton reaction and supercapacitor
performance, Applied Surface Science, 498 (2019) 143807.
[39] T.-W. Chen, U. Rajaji, S.-M. Chen, M.M. Al Mogren, M. Hochlaf, S.D.A. Al 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, 57 (2019) 116-124.

[40] W. Liu, Y. Zhou, J. Bao, J. Wang, Y. Zhang, X. Sheng, Y. Xue, C. Guo, X. Chen, Co-
CoO/ZnFe2O4 encapsulated in carbon nanowires derived from MOFs as electrocatalysts
for hydrogen evolution, Journal of colloid and interface science, 561 (2020) 620-628.
[41] J. Li, F. Wei, C. Dong, W. Mu, X. Han, A Z-scheme ZnFe2O4/RGO/In2O3 hierarchical
photocatalyst for efficient CO2 reduction enhancement, Journal of Materials Chemistry A,
(2020).
[42] L. Zhang, R. Long, Y. Zhang, D. Duan, Y. Xiong, Y. Zhang, Y. Bi, Direct Observation for
Dynamic Bond Evolution in Single‐Atom Pt/C3N4 Catalysts, Angewandte Chemie
International Edition, (2020).
[43] Q. Jiang, M. Liu, C. Shao, X. Li, H. Liu, X. Li, Y. Liu, Nitrogen doping
polyvinylpyrrolidone-based carbon nanofibers via pyrolysis of g-C3N4 with tunable
chemical states and capacitive energy storage, Electrochimica Acta, 330 (2020) 135212.
[44] G. Chang, Y. Luo, W. Lu, X. Qin, A.M. Asiri, A.O. Al-Youbi, X. Sun, Ag nanoparticles
decorated polyaniline nanofibers: synthesis, characterization, and applications toward
catalytic reduction of 4-nitrophenol and electrochemical detection of H 2 O 2 and glucose,
Catalysis Science & Technology, 2 (2012) 800-806.
[45] Y. Wei, L.-T. Kong, R. Yang, L. Wang, J.-H. Liu, X.-J. Huang, Single-walled carbon
nanotube/pyrenecyclodextrin nanohybrids for ultrahighly sensitive and selective detection
of p-nitrophenol, Langmuir, 27 (2011) 10295-10301.
[46] 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.

[47] L. Chu, L. Han, X. Zhang, Electrochemical simultaneous determination of nitrophenol
isomers at nano-gold modified glassy carbon electrode, Journal of Applied
Electrochemistry, 41 (2011) 687-694.
[48] J. Li, D. Kuang, Y. Feng, F. Zhang, Z. Xu, M. Liu, A graphene oxide-based
electrochemical sensor for sensitive determination of 4-nitrophenol, Journal of hazardous
materials, 201 (2012) 250-259.
[49] W. Huang, C. Yang, S. Zhang, Simultaneous determination of 2-nitrophenol and 4-
nitrophenol based on the multi-wall carbon nanotubes Nafion-modified electrode,
Analytical and bioanalytical chemistry, 375 (2003) 703-707.
[50] A. Arvinte, M. Mahosenaho, M. Pinteala, A.-M. Sesay, V. Virtanen, Electrochemical
oxidation of p-nitrophenol using graphene-modified electrodes, and a comparison to the
performance of MWNT-based electrodes, Microchimica Acta, 174 (2011) 337-343.
[51] Y. Tang, R. Huang, C. Liu, S. Yang, Z. Lu, S. Luo, Electrochemical detection of 4-
nitrophenol based on a glassy carbon electrode modified with a reduced graphene oxide/Au
nanoparticle composite, Analytical Methods, 5 (2013) 5508-5514.
[52] C.A. de Lima, P.S. da Silva, A. Spinelli, Chitosan-stabilized silver nanoparticles for
voltammetric detection of nitrocompounds, Sensors and Actuators B: Chemical, 196
(2014) 39-45.
[53] J. Xu, L. Zhang, R. Shi, Y. Zhu, Chemical exfoliation of graphitic carbon nitride for
efficient heterogeneous photocatalysis, Journal of Materials Chemistry A, 1 (2013) 14766-
14772.

[54] G. Rounaghi, H. Azizi-toupkanloo, Voltammetric determination of 4-nitrophenol using a
modified carbon paste electrode based on a new synthetic crown ether/silver nanoparticles,
Materials Science and Engineering: C, 32 (2012) 172-177.
[55] H. Yin, Y. Zhou, S. Ai, X. Liu, L. Zhu, L. Lu, Electrochemical oxidative determination of
4-nitrophenol based on a glassy carbon electrode modified with a hydroxyapatite
nanopowder, Microchimica Acta, 169 (2010) 87-92.
Research Highlights
 ZnFe2O4 nanoparticles covered with graphic carbon nitride sheets were synthesized
through a green based sonochemical method.
 The electro-catalytic activity of the proposed hybrid electro-catalyst was investigated.
 The hybrid electro-catalyst has express nanomolar limit of detection in phosphate buffer
(pH 7.0).
 The hybrid electro-catalyst showed a superior electrochemical performance (wide linear
range and high sensitivity).
 Such a unique electro-catalyst was successfully applied real sample analysis in water
samples.
CRediT authorship contribution statement
Sathishkumar Chinnapaiyan: Data processing, Methodology, Formal analysis, Writing -
original draft. Tse-Wei Chen: Methodology, Formal analysis, Revision work. Shen-Ming

Chen: Project administration, Resources, Supervision. Zeid Abdullah Alothmanc, Mohammad
Ajmal Ali: Administration, Resources, Supervision, Funding acquisition. Saikh Mohammad
Wabaidur: Resources, Methodology, Fahad Al-Hemaid: Visualization, Methodology, Shih-Yi
Lee: Formal analysis, Supervision, Funding acquisition, Wen-Han Chang: Visualization,
Methodology.
國立台北科技大學
DEPARTMENT OF CHEMICAL ENGINEERING AND BIOTECHNOLOGY
NATIONAL TAIPEI UNIVERSITY OF TECHNOLOGY
No. 1, Section 3, Chung-Hsiao East Road
Taipei - 106, Taiwan, Republic of China
Declaration of interests
☒ The authors declare that they have no known competing financial interests or personal
relationships that could have appeared to influence the work reported in this paper.
☐ The authors declare the following financial interests/personal relationships which may be
considered as potential competing interests:
Yours,
Sathishkumar Chinnapaiyan and other authors

National Taipei University of Technology
Taiwan-106.