These results convey that the NiO nanoparticles modi fied electrode can act as a novel non-enzymatic sensor in trace level quanti fication of nitrite.. 3.9.[r]
Trang 1Original Article
Photocatalytic, nitrite sensing and antibacterial studies of facile
bio-synthesized nickel oxide nanoparticles
C.R Rajith Kumara, Virupaxappa S Betageria, G Nagarajub, G.H Pujarc, B.P Sumad,
M.S Lathaa,*
a Research Centre, Department of Chemistry, G M Institute of Technology, Davangere, Karnataka, 577006, India
b Energy Materials Research Laboratory, Department of Chemistry, SIT, Tumakuru, Karnataka, 572103, India
c Research Centre, Department of Physics, G M Institute of Technology, Davangere, Karnataka, 577006, India
d Department of Chemistry, Bangalore University, Central College Campus, Bengaluru, 560001, India
a r t i c l e i n f o
Article history:
Received 15 October 2019
Received in revised form
5 February 2020
Accepted 11 February 2020
Available online xxx
Keywords:
NiO nanoparticles
Calotropis gigantea
Dye degradation
Antibacterial activity
Nitrite sensing
a b s t r a c t
In the present work, Nickel oxide nanoparticles (NiO NPs) were synthesized using leaves extract of
C gigantea through a solution combustion method The NiO NPs were characterized through analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) The XRD results revealed rhombohedral structured crystallites with average size of 31 nm SEM and TEM images indicate that the nanoparticles are agglomerated with an asymmetrical shape The optical energy bandgap of 3.45 eV was estimated using UV-diffused reflectance spectroscopy (UV-DRS) The synthesized NiO NPs have shown superior photodegradation for methylene blue (MB) dye Further, the antibacterial activity of the pre-pared nanoparticles was tested against E.coli and S.aureus bacterial strains In addition, nanoparticles were utilized for electroanalytical applicability as a novel non-enzymatic sensor in the trace level quantification of nitrite The proposed nitrite sensor showed wide linearity in the range 8e1700mM and good stability with a lower detection limit of 1.2mM
© 2020 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
1 Introduction
Nanoscience and nanotechnology have acquired an excellent
impetus in the rapidly growing technological era by covering the
basic understanding of physicochemical and biological properties
in atomic/sub-atomic levels with promising applications in various
fields [1] In the last few years, various researchers investigated on
transition metal oxide nanoparticles due to their increasing
importance and potential applications [2] Among all, NiO an
interesting p-type, wide direct bandgap semiconductor
(3.4e4.0 eV), has caught more attention owing to its key
applica-tions Indeed, nano-sized NiO materials have gained great interest
with respect to bulk NiO because of their size quantization and
large surface-area ratio [3] Due to their unique and remarkable
properties NiO NPs gained significant importance in various fields,
as battery cathodes/anodes [4], catalysis [5], solar cells [6], mate-rials for sensors [7], electrochemical super capacitors [8] Various plants have been increasingly employed in the synthesis of nano-particles due to their ample advantages in elimination of elaborate processes of maintaining cell cultures, cost-effectiveness and easy scale up for large-scale synthesis During the bioproduction of NPs, plant extracts act as both reducing and stabilizing agents [9] Kumar
et al [10], and Vidya et al [11], have reported about the synthesis of
Ag NPs, and ZnO NPs using leaf extract of Calotropis gigantea In the present study, NiO NPs have been synthesized using leaves extracts
of C gigantea plant The C gigantea, also called as Arka, Madara, etc., belongs to the family of Apocynaceae and is available throughout India, especially in the dry and vast land Various phytochemical constituents are present in different parts of the Calotropis plant, mainly in the leaves, which acts as a reducing and stabilizing agents during the synthesis of NPs
Highly toxic dyes play a major role in polluting water These, are frequently being used in the industries like textile, food, cosmetics, paper, plastics, etc., [12] The natural degradation of such dyes is very difficult due to their complex structure However, recently,
* Corresponding author GM Institute of Technology Davangere, Karnataka,
577006, India.
E-mail address: lathamschem97@gmail.com (M.S Latha).
Peer review under responsibility of Vietnam National University, Hanoi.
Contents lists available atScienceDirect Journal of Science: Advanced Materials and Devices
j o u r n a l h o m e p a g e : w w w e l s e v i e r c o m / l o c a t e / j s a m d
https://doi.org/10.1016/j.jsamd.2020.02.002
2468-2179/© 2020 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ ).
Trang 2various semiconductor photocatalysts NiO, Cu2O, FeO, etc., have
been developed to degrade the organic pollutants [13,14] In the
present study, the synthesized NiO NPs have been used to study the
photocatalytic degradation of methylene blue dye Various
nano-structure materials have shown good antibacterial activity against
human pathogens [15] Earlier reports have demonstrated the
possibility of utilization of metal oxide NPs, in particular, NiO NPs in
biomedicines due to their unique therapeutic and biological
prop-erties such as adsorbing and metal ion releasing ability, cytotoxic
effects and surface-area ratio [16] Hence, the antibacterial activity
of NiO NPs has been demonstrated in the present study
In the past decades, the highly sensitive detection of‘nitrite’ has
caught increasing interest because of its harmful effect on both
human health and global environment Further, ground water
pollution is rapidly increasing by‘nitrates’ due to the anthropogenic
activities [17] The World Health Organization (WHO) recommends,
the maximum limit of‘nitrite’ should be 3 mg/L in drinking water
[18], hence, it is an important task of chemists to monitor the
existing levels/limits of nitrite in water and environment Generally,
the analysis of nitrites can be quantified by using various
tech-niques such as chromatography,
spectrophotometry/spectro-fluorimetry, electroluminescent and capillary electrophoresis
techniques However, some of the above quantitative techniques
lack sensitivity and, high detection limits and do require extensive
instrumentation In contrast, electrochemical methods give better
precision quantification over all these methods in terms of
sensi-tivity/selectivity [19] In a quantitative analysis, the thorough
exploitation of CMEs within thefield of electrochemistry and
sur-face manipulation with selective indicator moieties is desirable to
achieve the tailored properties Such CMEs have found to be very
sensitive, easy to fabricate and target specific in electrochemical
applications [20] Here, the synthesized NiO NPs have been used as
a modifier molecule in the fabrication of electrode The modifier
electrode has been explored for its electroanalytical applicability as
a novel non-enzymatic sensor in trace level quantification of nitrite
2 Experimental section
2.1 Materials
All the chemicals (analytical grade) were purchased from
SDeFine Chemicals Pvt Ltd and Hiemedia and used without any
further purification
2.2 Instrumentation and experimental methods
The Crystalline nature and phase purity was identified with the
aid of the X-ray diffractometer (Rigaku Smart Lab) The morphology
and elemental composition of the material was examined using
SEM and EDAX (Hitachi S3400n), respectively The HR-TEM with
SAED (Jeol/JEM 2100) was used to measure shape and size of the
nanoparticles, respectively The FT-IR spectrometer (Bruker
alpha-P) was used to examine the functional groups Absorption spectra
were recorded with the UVeVisible spectrophotometer (Agilent
technology cary-60 spectrophotometer) The diffuse reflectance
spectrum was measured using the Lab India UV 3092, UV-VIS
spectrophotometer Electrochemical measurements were
ach-ieved using the CH instrument
2.3 Synthesis of NiO NPs
Freshly collected leaves of C gigantea were washed, dried and
grinded well The Soxhlet extractor with water as solvent was used
for the extraction for 5 h and the obtained extract was dried using a
rotary evaporator The combustion synthesis method was used to
synthesize NiO NPs using Nickel nitrate hexahydrate (Ni (NO3)26H2O) as an oxidizer and C gigantea leaves extract as a fuel
In this process, 2 gm of the extract dissolved in 100 mL of double distilled water was, constantly stirred for 10 min to get a homog-enous solution Ni (NO3)26H2O of 0.5 M was dissolved in 10 mL of
C gigantea extract and was placed in a preheated muffle furnace (400± 10C) A smouldering reaction takes place and the entire
process was completed within 10 min The obtained NiO NPs were subjected for calcinations at 500C for 3 h to eliminate the impu-rities Until further use, the obtained product was stored in an airtight container
2.4 Photo catalytic studies The photocatalytic studies of NiO NPs were assessed by the degradation of cationic methylene blue (MB) dye in aqueous media using a 250 W UV-light irradiation source For the photocatalytic experiments, a visible annular photoreactor was used, which con-sists of cylindrical tubes with transparent interior to employ com-plete radiation In this process, 50 mg of NiO NPs as a photocatalyst was added to quartz tubes of 100 mL capacity, which contains
100 mL MB solution of concentration 5 ppm The solution was continuously air bubbled for complete mixing of the MB dye and the photocatalyst Then, 2 mL was taken out from the above solu-tion, thefirst time after 15 min and then at regular intervals of
30 min The percentage of degradation of the cationic MB dye has been calculated using the BeereLambert law as follows [21]:
% of degradation¼Ci Cf
where, Ciand Cfare the initial andfinal concentration of the dye solution, respectively
2.5 Antibacterial studies The antibacterial activity of NiO NPs was screened against Gram positive bacteria NCIM-5022 and Gram negative
bacteriaNCIM-5051 through the Agar well diffusion method [22] The bacteri-cidal activity of NiO NPs was tested in Nutrient Agar (NA) media, the
NA plates were prepared using 28 gm of NA media Then, it was dissolved in 1000 mL of double distilled water and subjected to pasteurization at 121C with pressure of 15 lbs during 15e20 min
NA plates with 100ml of 24 h mature broth culture of each indi-vidual bacterial strains were prepared and swabbed using a sterile L-shaped glass rod In each petri - plate 6 mm wells were made using a sterile cork bore The NiO NPs were dispersed in sterile double distilled water and loaded onto the well The zone of inhi-bition (ZOI) was measured after the incubation of NA plates for 24 h
at 37C [23,24]
2.6 Fabrication of the electrode for electrochemical sensing Prior to fabrication, the glassy carbon electrode was uniformly polished using an alumina slurry on polishing pads to get a mirror like shiny surface To remove physically adhered impurities on the surface of the electrode, it was washed and ultrasonicated with double distilled water and ethanol respectively for 15 min Modi fi-cation of the surface of the bare glassy carbon electrode was carried out by drop coating 10mL of a NiO NPs dispersed solution (1 mg/mL) The modified electrode was dried at room temperature and used as it
is in further experiments The electrocatalytic behaviour of the NiO modified glassy carbon electrode was evaluated by using the CH Instrument with a three electrode configuration comprising of the NiO particles modified glassy carbon electrode as the working
Trang 3electrode, a platinum disc electrode as a counter electrode and
saturated Ag/AgCl electrode as a reference electrode [25]
3 Results and discussion
3.1 Structural and morphological analysis
The diffractogram of green synthesized NiO NPs is depicted in
Fig 1 (a)The XRD peaks coincide with the rhombohedral structure
and match well with the standard value of JCPDS (No 22e1189),
with lattice parameters (a¼ 2.954, c ¼ 7.236) and Space group R-3m
166 From the XRD pattern, it was confirmed that NiO NPs exhibited
a crystalline nature with no impurity peaks The crystallite size of NiO NPs was estimated using the Debye-Scherer's formula [32]:
D¼0:9l
where, ‘D’ is the crystallite size of synthesized NPs, ‘l’ is the wavelength of X-ray radiation (1.54 Å),‘b’ is the full width at half maximum (FWHM) of the diffraction peak and ‘q’ is Bragg's
Fig 1 (a) XRD pattern (b) EDAX spectrum (c, d) SEM images of synthesized NiO NPs.
Fig 2 (a) TEM, (b) HR-TEM images, (c) Interplanar spacing (d) SAED pattern of synthesized NiO NPs.
Trang 4diffraction angle The average crystallite size of NiO NPs was found
to be 31 nm
InfigFig 1 (b)EDAX report confirms the elemental composition
of Ni and O The SEM micrographs (Fig 1(c and d) show the
agglomeration with irregularly shaped nanoparticles The TEM
micrograph (Fig 2 (a)) confirms that sizes of crystallites are in the
range of about 10e30 nm which is in good agreement with the
estimated value of XRD the analysis.Fig 2(b and c) represent the
HR-TEM micrographs that show particles in hexagonal and
rhom-bohedral shape with interplanar spacing of 0.21 nm The SAED
pattern depicted inFig 2(d) indicates the presence of (111) (200)
and (220) planes of the synthesized rhombohedral NiO NPs
3.2 Fourier transform infrared spectroscopy analysis
The FT-IR spectrum of NiO NPs is shown inFig 3 The spectrum
is scanned in the range 400e4000 cm1 to analyse the various
functional groups The absorption band that appeared at
3410 cm1corresponds to (OeH) stretching of water and at
1632 cm1 to (HeOeH) bending vibrations The band at
1114 cm1is due to (CeO) bonds of carbon dioxide adsorbed on the NPs surface The bands corresponding to stretching and bending vibrations of (CeH) were observed at 2912 and 1381 cm1, respectively In addition, the significant absorption band at
430 cm1is attributed to metaleoxygen (NieO) stretching vibra-tions [37].Thus, the expected structure and functional groups are confirmed by the above results
3.3 Diffuse reflectance spectroscopic (DRS) analysis Fig 4 (a)shows the DRS spectrum of green synthesized NiO NPs
A blue shifted strong absorption peak is observed at 305 nm DRS Spectral data can be used to estimate the optical energy bandgap of biosynthesised NiO NPs as shown inFig 4 (b) The optical energy bandgap was determined using the KubelkaeMunk equation [22]:
Fig 3 FT-IR spectrum of synthesized NiO NPs.
Fig 4 (a) Diffuse reflectance spectrum (DRS) (b) Optical energy band gap (Eg) of synthesized NiO NPs.
Fig 5 Time dependent absorbance spectrum of synthesized NiO NPs against Methy-lene blue dye.
Trang 5FðRÞ ¼ð1 RÞ2
where, R is the reflection coefficient of the sample From eq.(3),
plot of F(R)2 vs the photon energy (eV) gives an optical energy
bandgap (Eg) of 3.45 eV Thus, nanoscale NiO exhibits directly a
wide bandgap semiconductor nature
3.4 Photocatalytic studies
The photocatalytic behavior of green synthesized NiO NPs is
assessed through the photo-degradation of the MB dye with the aid
of visible annular type photoreactor under UV light irradiation The
actual trail starts when the light is irradiated and, the photon of
energy is consumed by the semiconducting NiO in which the band
gap is higher Electrons and hole pairs are generated in the
con-duction and valence bands If the charge carriers are not put
together again, then the migration of free electrons on the surface
leads to the oxygen reduction and formation of peroxides and
su-peroxides The newly generated holes can oxidizes water and forms
OH free radicals Such radicals are unstable and highly reactive in
nature, which eventually leads to the organic dye degradation The
photocatalytic action on dyes is enhanced by factors like particle
size, morphology, composition, size distribution, surface area, band
gap, etc The steady decrease in the absorption peak intensity at
663 nm by the time exposed to UV light indicates the dye
degra-dation as shown in Fig 5 The degradation efficiency has been
calculated using eq (1) The calculated efficiency is found to be 97.76% at 180 min against MB dye [21] The degradation mechanism
in dye solution is stated in the following equations(4e11) Com-parable results of the degradation efficiency of MB dye with other metal oxide nanoparticles are tabulated inTable 1
NiOþ hv / NiO (e
3.5 Antibacterial studies The antibacterial study of the synthesized NiO NPs was tested against the human pathogenic bacteria's Staphylococcus aureus and Escherichia coli, employing the Agar well diffusion method Generally, the antibacterial activity depends upon the reactive ox-ygen species (ROS), surface area, particle size, etc NiO NPs produce ROS (hydroxyl, superoxide radical, singlet oxygen, and
alpha-Table 1
Comparison of results with published data: photocatalytic activity (MB dye) with
different metal oxide NPs.
Sl.
No
Photocatalyst Synthesis method average
crystal size (nm)
% of dye degradation
references
1 ZnO NPs Sol gel 30 81 [ 32 ]
2 Co-precipitation 23 90 [ 33 ]
3 Solution combustion 20 81 [ 25 ]
4 Ag 2 O NPs Solution combustion 11 84 [ 34 ]
5 MgO NPs Microwave assisted 14 88 [ 35 ]
Hydrothermal 20 92
6 NiO NPs Green Synthesis 20 97 [ 36 ]
7 precipitation 2e3 97 [ 37 ]
8 Solution combustion 31 98 Present
work Bold signifies the current work details/data compared to published data.
Fig 6 Antibacterial activity of NiO NPs against E.coli and S.aureus bacterial strains (S) Standard antibiotic (C) control (a) 500mg/mL (b) 1000mg/mL.
Table 2 Antibacterial activity of synthesized NiO NPs.
Treatment Bacterial strains Sample Concentration Escherichia coli
(mean ± SE)
Staphylococcus aureus (mean ± SE) Ciprofloxacin 10mg/mL 9.26 ± 0.28 14.13 ± 0.67 NiO NPs 500mg/mL 2.95 ± 0.48 4.63 ± 0.41
1000mg/mL 6.14 ± 0.37 7.86 ± 0.52 Values are the mean ± SE of inhibition zone in mm.
Trang 6oxygen) through the Fenton reaction, which leads to lipid
peroxi-dation, DNA damage and protein oxidation which can eliminate the
bacteria The zone of inhibition formed by the NiO NPs of known
concentrations (500 and 1000mg/mL) with reference to the positive
control (Ciprofloxacin) is shown inFig 6and corresponding data
are tabulated inTable 2 The antibacterial activity of NiO NPs shows
a significant inhibition to both bacterial strains compared to
stan-dard antibiotic Ciprofloxacin [25,26]
3.6 Electrochemical investigation of NiO nanoparticles
The initial electrochemical characterization of the NiO
nano-particles modified glassy carbon electrode surface was carried out
by using the most powerful electrochemical techniques such as
cyclic voltammetry (CV) The redox activity of the NiO
nano-particles modified electrode was studied in the presence of a
standard redox standard potassium ferricyanide solution From the voltammogram inFig 7, it is observed that theDE value of 136 mV for NiO NPs modified electrode (peak b) shows a better redox ac-tivity with increased current density than the bare glassy carbon electrode withDE value of 263 mV (peak a) The decrease in peak potentials has increased effect on conductivity This increased ac-tivity might be attributed to the high surface area provided by the nanoparticles in comparison to the bare glassy carbon electrode [27e30]
The NiO NPs modified electrode was utilized to investigate its electrocatalytic property in the electro oxidation of nitrite The voltammograms at modified interface were recorded in the pres-ence of a nitrite in acetate buffer of pH 4 at the scan rate of 50 mV/
s From Fig 8, it is clear that the NiO nanoparticles modified electrode in the absence of nitrite did not show any redox signa-ture (peak c) suggesting that the modified electrode is inactive in absence of nitrite under the potential window studied However,
in the presence of nitrite the modified electrode showed an enhanced current response responsible for the electro oxidation of nitrite with potential at 0.93 V (peak a) in comparison to the unmodified electrode at 1.03 V (peak b) The observed results illustrate the electrocatalytic behaviour of the modified electrode towards the electro oxidation process Hence, the NiO NPs modi-fied electrode can be used in the electrochemical quantification of nitrite at trace level
As presentedFig.S1 (a) (in ESI), with increasing scan rate from 10
to 300 mV/s the anodic peaks were shifting towards more positive potentials with increase in peak current response with R2¼ 0.98 showing that the process of nitrite oxidation at NiO NPs modified electrode is a diffusion controlled process
3.7 Optimization of experimental parameters Owing to the excellent analytical sensitivity and resolved re-sponses of the differential pulse voltammetry (DPV) technique over cyclic voltammetry, the experimental parameters were optimized The factors which affect the analytical responses such as pH, deposition potential, deposition time and the concentration were varied and their effect on the current responses were studied The optimized parameters are as follows-pH:4, deposition
Fig 7 Overlaid Cyclic voltammograms at (a) bare (b) NiO NPs modified electrode in
presence of a potassium ferricyanide solution and 0.1 M KCl as supporting electrolyte.
Scan rate: 50 mV/s.
Fig 8 Overlaid Cyclic voltammograms at a) bare, b) NiO NPs modified electrode in
presence and c) absence of nitrite in acetate buffer and 0.1 M KCl.
Fig 9 Overlaid differential pulse voltammograms at NiO NPs modified electrode with increasing nitrite concentration in an acetate buffer under optimized conditions Insetecalibration plot of the peak current versus concentration.
Trang 7potential:0.4 V and deposition time:15 s All the graphs are
depic-ted inFig.S1 (b-d) (in ESI)
3.8 Calibration plot and linearity
The determination of nitrite has been done using differential
pulse voltammetry (DPV) due to its high current sensitivity and
better resolution compared to cyclic voltammetry Hence, under
the optimized experimental conditions, the performance of the
NiO NPs modified electrode on increasing nitrite concentration
has been studied as shown in Fig 9 The anodic peak currents
linearly increase with the successive addition of nitrite in the
concentration range 8e1700mM with linear regression co-efficient
of 0.998 The detection limit (3s) was found to be 1.2mM These
results convey that the NiO nanoparticles modified electrode can
act as a novel non-enzymatic sensor in trace level quantification of
nitrite
3.9 Stability of the modified electrode
The stability of the modified electrode was studied by
contin-uously recording the responses at the modified electrode up to 10
cycles as depicted inFig.S5 and S6 (ESI) The modified electrode
showed significant analytical responses responsible for the electro
oxidation of nitrite even after 10 cycles However, the peak current
density decreased which might be due to an oxide layer formation
on the electrode surface [31] This reveals that the modified
elec-trode is very stable and can be used in the continuous monitoring of
nitrite The modified electrode showed excellent analytical
per-formance in comparison to other reported nitrite sensors and is
given inTable 3
4 Conclusion
In this study, NiO NPs have been synthesised through a
so-lution combustion method using C gigantea leaves extract as a
fuel NiO NPs and were characterised using X-RD, SEM with
EDAX, HR-TEM with SAED and FT-IR spectroscopy The
syn-thesised NiO NPs were utilized to study their diversified
appli-cations in dye degradation, anti-bacterial activity and in
electrochemical sensing The X-RD pattern confirms the
rhom-bohedral structure of NiO NPs with a particle size in the range
10e30 nm The EDAX spectrum confirms the presence of Ni and
O as major elements in its elemental composition The NiO NPs
exhibited very good photocatalytic activity in the degradation of
methylene blue dye The anti bacterial activity studies revealed
that the nanoparticles have good ability to inhibit the growth of
E.coli and S.aureus pathogens The electrochemical investigation
of the NiO NPs modified electrode depicts an excellent electro
catalytic behaviour in the quantification of nitrite at trace level in
comparison to the bare electrode The modified electrode showed
wide linearity in the concentration range 8e1700 mM with a
detection limit of 1.2 mM, which allows the exploration of NiO NPs as a novel non-enzymatic nitrite sensor for biological applications
Declaration of competing interest 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
Acknowledgments
Dr G Nagaraju thanks the DST-Nano mission (SR/NM/NS-1262/ 2013) Govt of India, New Delhi for providing characterization techniques and also the VGST, Govt of Karnataka (CISEE-VGST/GRD-531/2016e17) for UV-DRS studies Rajith Kumar C R thanks the Department of Biotechnology, GM Institute of Technology, Davan-gere and Siddaganga Institute of Technology, Tumakuru for providing lab facility
Appendix A Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jsamd.2020.02.002
References
[1] V.K Prashant, Photophysical, photochemical and photocatalytic aspects of metal nanoparticles, J Phys Chem B 106 (2002) 7729e7744
[2] K.C Patil, S.T Aruna, S Ekambaram, Combustion synthesis, Curr Opin Solid State Mater Sci 2 (1997) 158e165
[3] L Brus, Capped nanometer silicon electronic materials, Adv Mater 5 (1993) 286e288
[4] F Zheng, S Xu, Y Zhang, Facile fabrication of hierarchically porous NiO mi-crospheres as anode materials for lithium ion batteries, J Mater Sci Mater Electron 27 (2016) 3576e3582
[5] M Hassanpour, H Safardoust-Hojaghan, M Salavati-Niasari, J Mater Sci Mater Electron (2017), https://doi.org/10.1007/s10854-017-6860-3 [6] X Xu, Z Liu, Z Zuo, M Zhang, Z Zhao, Y Shen, H Zhou, Q Chen, Y Yang,
M Wang, Hole selective NiO contact for efficient perovskite solar cells with carbon electrode, Nano Lett 15 (2015) 2402e2408
[7] D Li, Y Li, F Li, J Zhang, X Zhu, S Wen, S Ruan, Humidity sensing properties
of MoO3-NiO nanocomposite materials, Ceram Int 41 (2015) 4348e4353 [8] J Cheng, B Zhao, W Zhang, F Shi, G Zheng, D Zhang, J Yang, High-perfor-mance super capacitor applications of NiO-Nanoparticle-Decorated milli me-ter-long vertically aligned carbon nanotube Arrays via an effective supercritical CO2-assisted method, Adv Funct Mater 25 (2015) 7381e7391 [9] A.M El Badawy, R.G Silva, B Morris, K.G Scheckel, M.T Suidan, T MTolaymat, Surface charge-dependent toxicity of silver nanoparticles, Environ Sci Tech-nol 45 (2010) 283e287
[10] V Kumar, S Yadav, Plant-mediated synthesis of silver and gold nanoparticles and their applications, J Chem Technol Biotechnol 84 (2009) 151 [11] C Vidya, S Hiremath, M.N Chandraprabha, M.A.L Antonyraj, I.V Gopal,
A Jain, K Bansal, Green synthesis of ZnO nanoparticles by Calotropis gigantea, Int J Curr Eng Technol 1 (2013) 118
[12] B.A van Driel, P.J Kooyman, K.J van den Berg, A Schmidt-Ott, J Dik, A quick assessment of the photocatalytic activity of TiO2 pigments - from lab to conservation studio, Micro J126 (2016) 162e171
Table 3
Comparison of reported values with other modified electrodes.
Modifier Technique Linearity range (mM) Limit of detection (mM) Reference
SPCE/anodized/CuAgNP Hydrodynamic chronoamperometry 20e370 11.1 [ 39 ]
poly (4-aminobenzoic acid/o-toluidine) (4-AB/OT)/CPE Amperometry 6e600 3.5 [ 40 ]
Bold signifies the current work details/data compared to published data.
Trang 8[13] S Min, F Wang, Z Jin, J Xu, Cu 2 O nanoparticles decorated BiVO4 as an
effective visible-light-driven p-n heterojunction photocatalyst for methylene
blue degradation, SuperlatticesMicrostruct 74 (2014) 294e307
[14] X Wan, M Yuan, Shao-long Tie, S Lan, Effects of catalyst characters on the
photocatalytic activity and process of NiO nanoparticles in the degradation of
methylene blue, Appl Surf Sci 277 (2013) 40e46
[15] A Azam, A.S Ahmed, M Oves, Antimicrobial activity of metal oxide
nano-particles against Gram positive Gram negative bacteria: a comparative study,
Int J Nanomed 7 (2012) 6003e6009
[16] Q.A Pankhurst, N TThanh, S.K Jones, J Dobson, Progress in applications of
magnetic nanoparticles in biomedicine, J Phys Appl Phys 42 (2009) 224001
[17] J Sa, J.A Anderson, FTIR study of aqueous nitrate reduction over Pd/TiO2,
Appl Catal B Environ 77 (2008) 409e417
[18] WHO (World Health Organization), Guide Lines for Drinking-Water Quality
vol 1, World Health Organization, Geneva, 2004
[19] M.J Moorcroft, J Davis, R.G Compton, Detection and determination of nitrate
and nitrite: a review, Talanta 54 (2001) 785e803
[20] K Kalcher, Chemically modified carbon paste electrodes in voltammetric
analysis, Electroanalysis 2 (1990) 419e433
[21] Udayabhanu G Nagaraju, H Nagabhushana, R.B Basavaraj, G.K Raghu,
D Suresh, H.R Naika, S.C Sharma, Green nonchemical route for the synthesis
of NiO superstructures, evaluation of its applications toward photocatalysis,
photoluminescence, and biosensing, Cryst Growth Des 16 (2016)
6828e6840
[22] M.M Naik, H.S.B Naik, G Nagaraju, M Vinuth, K Vinu, S.K Rashmi, Effect of
aluminium doping on structural, optical, photocatalytic and antibacterial
ac-tivity on nickel ferrite nanoparticles by solegel auto-combustion method,
J Mater Sci Mater Electron 29 (2018) 20395e20414
[23] K Lingaraju, H.R Naika, H Nagabhushana, G Nagaraju, Euphorbia
hetero-phylla (L.) mediated fabrication of Zno NPs: characterization and evaluation of
antibacterial and anticancer properties, Biocatal Agric Biotechnol 18 (2019)
100894
[24] K Karthik, S Dhanuskodi, C Gobinath, S Prabukumar, S Sivaramakrishnan,
Dielectric and antibacterial studies of microwave assisted calcium hydroxide
nanoparticles, J Mater Sci Mater Electron 28 (2017) 16509e16518
[25] N.S Pavithra, K Lingaraju, G.K Raghu, G Nagaraju, Citrus maxima (Pomelo)
juice mediated eco-friendly synthesis of NiO nanoparticles: applications to
photocatalytic, electrochemical sensor and antibacterial activities,
Spec-trochim Acta Mol Biomol Spectrosc 185 (2017) 11e19
[26] S.B Patil, T.N Ravishankar, K Lingaraju, G.K Raghu, G Nagaraju, Multiple
applications of combustion derived nickel oxide nanoparticles, J Mater Sci.
Mater Electron 29 (2018) 277e287
[27] C.M Welch, R.G Compton, The use of nanoparticles in electroanalysis: a
re-view, Anal Bioanal Chem 384 (2006) 601e619
[28] F Pergola, G Raspi, R Guidelli, Voltammetric behavior of nitrite ion on
platinum in neutral and weakly acidic media, Anal Chem 44 (1972)
745e755
[29] B Piela, P.K Wrona, Oxidation of nitrites on solid electrodes I Determination
of the reaction mechanism on the pure electrode surface, J Electrochem Soc.
149 (2002) E55eE63 [30] S.A Prashanth, M Pandurangappa, Amino-calixarene-modified graphitic carbon as a novel electrochemical interface for simultaneous measurement of lead and cadmium ions at picomolar level, J Solid State Electrochem 20 (2016) 3349e3358
[31] B.P Suma, S.A Prashanth, M Pandurangappa, Silver nanoparticles-chitosan composite embedded graphite screen-printed electrodes as a novel electro-chemical platform in the measurement of trace level nitrite: application to milk powder samples, Curr Anal Chem 15 (2019) 56e65
[32] A Balcha, O.P Yadav, T Dey, Photocatalytic degradation of methylene blue dye by zinc oxide nanoparticles obtained from precipitation and sol-gel methods, Environ Sci Pollut Res 23 (2016) 25485e25493
[33] I Kazeminezhad, A Sadollahkhani, Influence of pH on the photocatalytic activity
of ZnO nanoparticles, J Mater Sci Mater Electron 27 (2016) 4206e4215 [34] S.P Vinay, G Nagaraju, C.P Chandrappa, N Chandrasekhar, Novel Gomutra (cow urine) mediated synthesis of silver oxide nanoparticles and their enhanced photocatalytic, photoluminescence and antibacterial studies, J Sci.: Adv Mater Devices 4 (2019) 392e399
[35] K Karthik, M Shashank, V Revathi, T Tatarchuk, Facile microwave-assisted green synthesis of NiO nanoparticles from Andrographis paniculata leaf extract and evaluation of their photocatalytic and anticancer activities, Mol Cryst Liq Cryst 673 (2018) 70e80
[36] M.I Din, A.G Nabi, A Rani, A Aihetasham, M Mukhtar, Single step green synthesis of stable nickel and nickel oxide nanoparticles from Calotropis gigantea: catalytic and antimicrobial potentials, Environ Nanotechnol Monit Manag 9 (2018) 29e36
[37] K Maniammal, G Madhu, V Biju, Nanostructured mesoporous NiO as an efficient photocatalyst for degradation of methylene blue: structure, proper-ties and performance, Nanostruct NanoObjects 16 (2018) 266e275 [38] D Manoj, R Saravanan, J Santhanalakshmi, S Agarwal, V.K Gupta,
R Boukherroub, Towards green synthesis of monodisperse Cu nanoparticles:
an efficient and high sensitive electrochemical nitrite sensor, Sensor Actuator.
B Chem 266 (2018) 873e882 [39] N.C Lo, I.W Sun, P.Y Chen, CuAg nanoparticles formed in situ on electro-chemically pre-anodized screen-printed carbon electrodes for the detection of nitrate and nitrite anions, J Chin Chem Soc 65 (2018) 982e988
[40] B Norouzi, M Rajabi, Fabrication of poly (4-aminobenzoic acid/o-toluidine) modified carbon paste electrode and its electrocatalytic property to the oxidation of nitrite, J Anal Chem 72 (2017) 897e903
[41] Y Han, R Zhang, C Dong, F Cheng, Y Guo, Sensitive electrochemical sensor for nitrite ions based on rose-like AuNPs/MoS2/graphene composite, Biosens Bioelectron 142 (2019) 111529