Effect of pyridinium based ionic liquid on the sensing property of Ni0 nanoparticle for the colorimetric detection of hydrogen peroxide

Article abstract of DOI:10.1016/j.molstruc.2020.128620

In this work, we presented a new colorimetric technique for the easy and quick detection of hydrogen peroxide. Two types of ionic liquids namely imidazolium and pyridinium containing cations with an acetate anion were evaluated in this study. Ni nanoparticle is synthesized using the wet chemical method, which is further characterized using various analytical techniques. Ni nanoparticles coated with pyridinium based ionic liquid showed robust peroxidase-like activity, which resulted in better dispersion of nickel nanoparticle and is able to quickly catalyze the oxidation reaction of substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H₂O₂), leading to the generation of a blue-colored solution. On the basis of color development, colorimetric sensing of [Pyr]Ac- Ni⁰ was achieved with a detection limit (LOD) of 120 μM/L within a linear range of 400–4000 μM. The proposed method is significantly selective for [Pyr]Ac- Ni⁰and can be conveniently and affordably applied to the detection of hydrogen peroxide without any complicated instrumentation.

Full text of DOI:10.1016/j.molstruc.2020.128620

Journal Pre-proof
0
Effect of pyridinium based ionic liquid on the sensing property of Ni nanoparticle for
the colorimetric detection of hydrogen peroxide
Faiza Zarif, Sajid Rauf, Shazia Khurshid, Nawshad Muhammad, Akhtar Hayat, Abdur
Rahim, Noor Samad Shah, Chang Ping Yang
PII:
S0022-2860(20)30945-5
DOI:
https://doi.org/10.1016/j.molstruc.2020.128620
MOLSTR 128620
Reference:
To appear in: Journal of Molecular Structure
Received Date: 22 April 2020
Revised Date: 29 May 2020
Accepted Date: 4 June 2020
Please cite this article as: F. Zarif, S. Rauf, S. Khurshid, N. Muhammad, A. Hayat, A. Rahim, N.S.
0
Shah, C.P. Yang, Effect of pyridinium based ionic liquid on the sensing property of Ni nanoparticle
for the colorimetric detection of hydrogen peroxide, Journal of Molecular Structure (2020), doi: https://
doi.org/10.1016/j.molstruc.2020.128620.
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.

Credit Author Statement
Conceptualization; Nawshad Muhammad, Akhtar Hayat Data curation; Faiza Zarif, Sajid
Rauf Formal analysis; Abdur Rahim, Noor Samad Shah Funding acquisition; Shazia
Khurshid, Chang Ping Yang Investigation; Methodology; Project administration;
Supervision; Nawshad Muhammad, Shazia Khurshid Validation; Nawshad Muhammad,
Akhtar Hayat, original draft; Writing ; Faiza Zarif, Sajid Rauf - review & editing. Shazia
Khurshid, Nawshad Muhammad, Akhtar Hayat, Abdur Rahim, Noor Samad Shah, Chang Ping
Yang

0
1
2
Effect of pyridinium based ionic liquid on the sensing property of Ni
nanoparticle for the colorimetric detection of hydrogen peroxide
1
2
1
3**
3
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
Faiza Zarif , Sajid Rauf , Shazia Khurshid , Nawshad Muhammad , Akhtar Hayat ,
3
4
2*
Abdur Rahim , Noor Samad Shah , Chang Ping Yang
Department of Chemistry, Government College University, Katchery road, Lahore, 54000,
1
Pakistan.
2
Hubei Collaborative Innovation Centre for Advanced Materials, Faculty of Physics and
Electronic Science, Hubei University, Wuhan, Hubei 430062, P.R. China.
3
Interdisciplinary Research Centre in Biomedical Materials (IRCBM), COMSATS University
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
Islamabad, Lahore Campus, 54000, Pakistan.
4
Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus,
61100, Pakistan
*Corresponding authors
E-mail addresses:
**Dr.Nawshad Muhammad nawshadmuhammad@cuilahore.edu.pk
*Prof. Dr. Chang Ping Yang cpyang@hubu.edu.cn
Abstract
In this work, we presented a new colorimetric technique for the easy and quick detection of
hydrogen peroxide. Two types of ionic liquids namely imidazolium and pyridinium containing
cations with an acetate anion were evaluated in this study. Ni nanoparticle is synthesized using
the wet chemical method, which is further characterized using various analytical techniques. Ni
nanoparticles coated with pyridinium based ionic liquid showed robust peroxidase-like activity,
which resulted in better dispersion of nickel nanoparticle and is able to quickly catalyze the
oxidation reaction of substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of hydrogen
peroxide (H O ), leading to the generation of a blue-colored solution. On the basis of color
2
2
0
development, colorimetric sensing of [Pyr]Ac- Ni was achieved with a detection limit (LOD) of
120 μM/L within a linear range of 400-4000 μM. The proposed method is significantly selective
0
for [Pyr]Ac- Ni and can be conveniently and affordably applied to the detection of hydrogen
peroxide without any complicated instrumentation.
Keywords. Pyridinium ionic liquid; Nickel nanoparticle; Sensing property; Enzymatic
chromogenic substrate; H O decomposition
2
2
1

3
4
1. Introduction
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
Natural enzymes serve as a biological catalyst to degrade H O in catalyzing a wide variety of
2
2
biochemical reactions in a cascade manner with high specificity and selectivity [1]. Hydrogen
peroxide is a major by-product of numerous enzymatic reactions catalyzed by a large number of
oxidase enzyme in the biological system. Abnormal production of H O is an indication of
2
2
oxidative stress, inflammation, respiratory disorders, aging, cancer, diabetes and other chronic
diseases etc [2-5]. Therefore, H O is one of the most important and commonly used analyte
2
2
attracting immense attention from scientists. Much effort has been devoted to design the novel
H O sensing platforms based on the enhancement of their analysis performances. Recently,
2
2
colorimetric biosensing has attracted significant attention with its great potential because of
simple instrumentation, high sensitivity, ease of operation, quick response and low-cost [6, 7].
The widespread application of native enzyme, horseradish peroxidase (HRP) used for the
catalytic decomposition of peroxides, is restricted by its intrinsic drawbacks such as easily
denaturation under ultra-pH conditions, low operational stability, extreme temperatures and
tedious purification techniques. Besides, some of their applications are also limited by their high
cost, expensive stabilizer, rigorous storage conditions, difficulties in recovery and recycling [8-
10]. For many years, the design and construction of nanomaterials based nanozyme has received
immense attention due to their unique advantages such as low-cost, high stability, long term
storage, easy preparation, great resistance to harsh environmental conditions, good tunability in
catalytic activities compared to the natural enzymes [11-13].
5
5
5
5
5
5
6
4
5
6
7
8
9
0
In the context of engineered nanomaterials, it has been shown that metal nanoparticle facilitates
the non-specific adsorption of matrix components due to the presence of reactive group on the
surface that may result in the decreased or enhanced catalytic activity [14, 15]. Unfortunately,
the practical application of some nanomaterials is hampered due to its some of the inherent
shortcomings (e.g., heterogeneous distribution, agglomeration, instability and storage difficulty).
To overcome these issues, most of the metal particles usually require grafting by using some
capping agents in order to modify their surface states thereby enhancing catalytic activity.
6
6
6
6
1
2
3
4
A recent study demonstrates the success of using a stabilizing agent to prevent nanoparticle
aggregation and remained high activity. Ionic liquids are promising materials in many fields of
chemistry. They can be synthesized by various combination of cations and anions with a melting
point below 100
°C having a wide range of distinct properties such as negligible vapor pressure,
2

6
6
5
6
high thermal stability, greater ionic conductivity, catalytic stability and stronger ability to
dissolve all kinds of metal precursors [16, 17].
6
6
6
7
7
7
7
7
7
7
7
7
8
9
0
1
2
3
4
5
6
7
Nickel nanoparticles have attracted significant attention due to its excellent catalytic activity in
oxidation reactions[18, 19]. Due to high surface area of the nanoparticles, they are extremely
reactive, thus undergo aggregation without appropriate protection or passivation of their surfaces
[20, 21]. Our work reports for the first time hereby, the use of nickel nanoparticles dispersed in
ionic liquid (NiNPs-IL) as peroxidase mimetics for the sensitive colorimetric determination of
hydrogen peroxide. The aim of this study was to construct a new biosensor with enhanced
biomimetic properties like good dispersibility, high thermal stability, best catalytic response, and
rapid separation in order to investigate the interaction with ionic liquids to find new possibilities.
Compared with imidazole-based IL, pyrdinium based IL dispersed nickel nanoparticle integrated
many advantages such as well dispersibility, good stability, mixed for a long time and high
catalytic activity.
7
7
8
9
2. Experimental Section
2.1. Reagents and Chemicals:
8
8
8
8
8
8
8
8
8
0
1
2
3
4
5
6
7
8
Nickel (II) chloride (NiCl ·6H O), sodium borohydride (NaBH ), 100% pure Glacial Acetic acid
2
2
4
CH COOH and pyridine were bought from Sigma-Aldrich Chemical Company (St. Louis, USA.
3
https://www.sigmaaldrich.com/). 1-methylimidazole C H N (99.2%) was provided by ACROS
4
6
2
(http://www.acros.com/). Hydrogen peroxide (35% of H O ,) was obtained from Merck kGaA
2
2
(https://www.merckgroup.com/). Phosphate buffer saline (PBS) was provided by BDH chemicals
(https://www.alfa.com/en/). 2 mL disposable cuvettes were supplied by Kartell. All chemicals and
reagents employed were used in this work as received without further treatment. Deionized water is
®
preferred to use produced by ELGA PURELAB Ultra water deionizer throughout the
experimental work to prepare a fresh solution.
8
9
2.2. Instrumentation:
9
9
9
9
9
0
1
2
3
4
UV-Vis spectra were collected on a double beam UV-Vis spectrophotometer (HITACHI, U-2900).
The XRD patterns of nickel nanoparticle were collected in an X-ray diffraction PANalytical
XPERT-PRO™ provided with Cu-Kα radiation (λ = 1.5418
Å) by scanning angles of 2θ=20°-80°.
Fourier transforms infrared (FT-IR) spectra of nickel nanoparticle were recorded over the mid-IR
-
1
range of 600-4000 cm using Thermo Nicolet 6700, USA FT-IR spectrometer. Morphology
3

0
9
9
9
9
9
5
6
7
8
9
observations of Ni nanoparticle were carried out using the Scanning electron microscope (SEM,
TESCAN, Vega3 LMU) at an accelerated voltage of 10 kV taking images at different
magnifications. The microstructure and morphology were reinforced at different sizes are studied
by Transmission Electron Microscopy (Tecnai G2 F30 S-TWIN 300 kV / FEG Transmission
Electron Microscopy). The chemical characterization and electronic state was investigated using X-
1
1
1
1
00 ray photoemission spectroscopy (XPS, VGS ESCALAB 210) utilizing monochromatic Mg Kα as
01 an X-ray source at constant pass energy mode. The working pressure utilized in the analysis
−
10
02 chamber was typically 5E
Torr. The binding energy scale was calibrated at 285.0 eV by
03 measuring the C1s peak and the accuracy of the measurement was approximately ±0.1 eV.
0
1
04 2.3. Synthesis of Ni nanoparticle
1
1
1
1
1
05 NiNPs were synthesized using a chemical reduction method. In a typical method, sodium
06 borohydride solution (NaBH , 0.79 M) was poured into an aqueous solution of Nickel (II)
4
07 chloride (NiCl ·6H O) dropwise with continuous magnetic stirring. NaBH acts as a reducing
2
2
4
2
+
0
08 agent which reduced the Ni and water to Ni and H via the reaction mechanism as follow
2
2
+
–
0
09
10
Ni + 2BH + 6H O → Ni + 2B(OH ) + 7H
4 2 3 2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
The reaction process was continued with stirring till the complete use of total volume of
11 NaBH solution till the black colloidal solution of NiNPs was obtained, thereby suggesting the
4
12 presenceof Ni(II) species.The NiNPs collected by centrifugation were washed continously with
13 ethanol in order to remove any unreacted reactants . Subsequently, the final product was dried
o
o
14 overnight at 90 C ,calcined in the programmable furnace at 400 C with a heating ramp rate of
o
15 5 C/min for characterization.
16
17 2.4. Preparation of protic ionic liquids
18An equimolar mixture of 1-methylimidazole and acetic acid was mixed in a two-necked flask
19under cooling conditions. The reaction mixture was left for stirring at room temperature for 12 h
20to obtain 1-methyl-imidazolium acetate [Mim]Ac as shown in scheme 1. The obtained product
o
21was subjected to the rotary evaporator at 70 C under low pressure in order to remove any
1
22leftover moisture and unreacted reactant. The structure of [Mim]Ac was characterized using H
1
23NMR spectroscopy (Bruker, 400 MHz, DMSO- d6) with the following the H NMR chemical
24shifts δ =7.60 (s, 1H, C2-H), 7.12 (s, 1H, C4-H), 6.90 (s, 1H, C5-H), 4.35 (s, 1H, N2-H), 3.65 (s,
1
253H, N3-CH3), 1.92 (s, 3H, CH3COO). The total peak integral in H NMR spectrum was found to
26correspond for [Mim]Ac. No impurity peak was detected.
4

1
27
O
:
H
-
N
+
1
2 h
O
O
N
H
Room Temp
+
H C
3
N
O
CH3
H C
N
3
CH3
1
1
28
29
1
1
1
1
1
1
1
30
31
32
Scheme 1: Synthesis of [Mim]Ac
33Synthesis and purification of the pyridinium based ionic liquid (scheme 2) were analogous to the
1
34above procedure; H NMR spectroscopy (Bruker, 500 MHz, DMSO-d6); δ = 1.2(3H, s), 6.64(2H,
35m), 7.12 (1H, t), 7.05 (1H, t), 7.73 (2H, d)
36
O
-
1
2 h
O
O
H
Room Temp
+
H C
3
+
O
CH3
N
N
.
.
H
1
1
37
38
Scheme 2: Synthesis of [Pyr]Ac
0
1
39 2.5. Fabrication of Ni @IL
0
0
1
1
1
1
1
40 The coating of Ni nanoparticles was performed in a below-mentioned way: Briefly, 6 mg Ni
41 nanoparticle was mixed in 1 mL [Mim]Ac followed by grinding mechanically for 30 min using
0
42 pestle and mortal in order to ensure well-dispersed nanoparticle named [Mim]Ac-Ni . A similar
43 procedure for coating will be followed using pyridinium acetate-based ionic liquid and named as
0
44 [Pyr]Ac-Ni .
1
45 2.6. Peroxidase analysis
0
1
1
1
1
46 The intrinsic peroxidase-like activity of both prepared ionic liquid (IL) coated Ni nanoparticle was
47 assessed by catalyzing the oxidation of chromogenic substrate TMB using H O . The protocol was
2
2
48 performed by taking 40 µL of coated catalyst in 560µL of PBS in the presence of 100 µL of Ionic
49 liquid, TMB (18 mM), and H O (20 mM). Subsequently, the mixed solutions were then incubated
2
2
5

1
1
50 for 10 min to observe the color change at an absorbance value of 652 nm. The intense color having
51 an absorption maximum at a wavelength of 652 nm implies higher peroxidase-like activity.
1
1
52 3. Results and Discussion
0
53 3.1.Characterization of Ni nanoparticle
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
54The vibrational spectra of synthesized Ni nanoparticles are presented in Fig.1. The broadband
-1
-1
55observed at 3360 cm corresponds to adsorbed water molecules [22]. A small peak at 2360 cm
56corresponds to the presence of atmospheric CO in the air [23]. In addition, asymmetric
2
-1
57stretching mode of vibrations v3(BO ) at 1159 cm could be assigned to B-O bond in BO3
3
-1
58group. The peak at 1005 cm refers to symmetrical stretching vibration of B-O bond in BO
4
59group [24]. Moreover, the XRD analysis of black powders prepared through the chemical route
0
60confirmed the formation of Ni nanoparticles when the reduction of metal salt (nickel chloride)
o
o
o
61was conducted with NaBH . The sharp diffraction pattern at a 2θ value of 35.2 , 44.5 and 52.36
4
62corresponds to the miller indices (111), (200) and (220) respectively, indicating the face-centered
63cubical structure of Ni(0). The pattern is in accordance with the Joint Committee on Powder
64Diffraction Standards (JCPDS 04-0850) [25, 26]. No impurity peaks were observed, which
65further indicates that phase pure metal nickel was prepared under the present experimental
o
66conditions. The average crystallite size was determined for the most intense peak at 2θ= 44.5
67using the Debye Scherer equation was found to be 11.3 nm.
68
d = K *λ / β*cosθ
69Where K is Scherrer constant (K=0.94), λ is the wavelength of X-ray source (CuKα =1.54184Ǻ),
70β represents the true half peak width expressed in radian, and θ is the diffraction angle of the
71centroid of the peak in degrees. The morphology of NiNP was analyzed by Scanning Electron
72microscopy (SEM) as shown in Fig. 3 which illustrated the formation of spherical agglomerates
73[27]. Moreover, the transmission electron microscopy has been employed to study the particle
74size and microstructure at different sizes shown in Fig 1 (d-f). The synthesized Ni NPs are
75distributed homogeneously and are interacted with one another at every resolution. There is an
76interface formed among Ni NPs, which very easily helps in the transport of electron during the
77colorimetric mechanism of TMB oxidation.
78
6

1
1
79
80
Fig. 1. Fourier transform infrared (FTIR) spectroscopy analysis, XRD pattern of Ni(0)
nanoparticle SEM micrograph (a-c); TEM microstructure images at a different scale of as-
prepared Ni(0) nanoparticle (d-f).
1
1
1
1
1
1
1
1
1
1
1
1
1
81
82
83
84
85
86
87
88
89
90
91
92
93
The XPS has verified the complete spectra of Ni including some contumacious carbon and
oxygen shown in Fig 2 (a). The spectra of Ni 2p1/2 and Ni 2p3/2 core levels and its satellite
peaks are depicted in Fig. 2 (b) for the sample of Ni NPs after Shirley background removal.
The Ni 2p3/2 and Ni 2p1/2 peaks appear at an approximate value of 855.9 eV and 874.6 eV,
respectively and the corresponding satellite peaks are observed at 861.9 and 881.3 eV,
respectively. The observed differences between both Ni 2p XPS spectra are in Ni metal and
some part of the NiO binding energy region, as indicated by the arrows in Fig. 2 (b). In
addition, the presence of oxygen 1s in Fig 2 (c) spectra tell us that there is purely high
oxidant oxygen available in Ni NPs while for the contumacious amount of carbon presence is
due to environment of sintering as well the carbon has made the bond with –OH and –O
presented in Fig 2(d).
7

1
1
94
95
Fig. 2. Complete XPS spectrum of Ni (a); Ni spectra (b); Oxygen 1s spectra (c); and carbon
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
96
97
1s spectra (d).
98 3.2.The intrinsic peroxidase-like activity of IL-NiNPs
99 The peroxidase-like activity of IL-NiNPs was tested by accelerating the catalytic oxidation
00 reaction of TMB using H O and monitoring the absorption spectra for a colorimetric reaction.
2
2
01 The catalytic activity of the prepared nanoparticles was measured in the TMB- H O reaction
2
2
02 system. To identify the role of ionic liquid (IL) for catalytic reaction, the interaction of IL with
03 nanoparticle leads to the stabilization of nanoparticle thereby enhancing the thermal stability of
04 enzymatic product without losing its catalytic activity [8, 28].For instance, in order to prepare
05 high-efficiency catalysts according to the characteristics of different reaction systems using ionic
06 structure designability has become the latest research hotspot [29-31]. Significant improvement
07 in the activities suggest that ionic liquid plays a major role in catalysis and their positive effect is
08 possibly connected with their greater solvation power, good dispersion agent, π-π stacking
09 interaction, electrostatic attraction, weak interaction with substrate and product, involvement of
10 cationic part of IL containing acidic hydrogen thereby facilitating the decomposition of H O to
2
2
11 generate •OH in the oxidation of peroxidase substrate TMB [12, 17, 32-34].
8

2
2
2
2
2
2
2
2
2
2
2
12 During our investigations, in the work, we have noted that nanoparticles stabilized in pyridinium
13 based acidic ionic liquid showed excellent peroxidase-like activity as compared to the
14 imidazolium-based ionic liquid. On the basis of combination of distinct properties stated above,
15 ILs could have been widely employed as a best dispersion agent for nanoparticles, which
0
16 facilitates the reduction of Ni to prevent it from the undesirable agglomeration as shown in
17 Fig. 3. In this work, the dispersion of NiNPs provides a theoretical basis for the research of
18 enhanced catalytic performance in different IL medium. Depending upon the intrinsic makeup of
19 ionic liquid employed in this work, it was observed that Ni nanoparticles remain dispersed in
20 [Pyr]Ac for a prolonged period of time as compared to [Mim]Ac, suggesting a significant
21 possibility of enhancing the catalytic activity of nickel nanoparticles. The dispersing results of
0
22 Ni in [Pyr]Ac and [Mim]Ac is exhibited in Fig.3 (A and B).
2
2
23
0
24 Fig.3. The photograph of dispersion stability of Ni in [Pyr]Ac (A) and [Mim]Ac(B).
2
2
25
0
26 It could be seen that Ni in [Mim]Ac shows less dispersion stability, therefore, nickel
0
2
2
2
2
2
2
2
2
2
2
27 nanoparticles were settled down in [Mim]Ac after 30 min. However the dispersion of Ni in
28 [Pyr]Ac remained quite stable for a prolonged period of time. This may be due to the increased
0
29 polarity between Ni and [Pyr]Ac that formed a stable solution.
0
30 As shown in Fig. 4 (A), the system containing Ni without the presence of ionic liquid shows
31 negligible color change in solution, while addition of [Mim]Ac to the catalyst still showed no
32 effect on the sensing property and the absorbance is almost zero at a wavelength of 652 nm,
33 indicating that chromogenic substrate TMB was hardly oxidized by hydrogen peroxide. The
34 intense color change was observed in the case of addition of [Pyr]Ac in the system which
35 verifies the selectivity of [Pyr]Ac for the sensing application. Furthermore, Fig. 4 (B) shows the
36 effect of different constituents on the sensing property of [Pyr]Ac. It was observed that the color
9

2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
37 of reaction mixture changed from colorless solution to blue-colored solution in the presence of
38 [Pyr]Ac without the catalyst. Note that, an obvious deep blue color change visually noted for
0
39 [Pyr]Ac- Ni in the presence of TMB-H O system indicates the rapid oxidation reaction of
2
2
40 TMB as shown in Fig.4B (b). The typical absorbance at a wavelength of 652 nm demonstrates
.
+
41 the formation of a deep blue-colored one-electron oxidized product, TMB . The change in color
42 development and absorption maxima at 652 nm implies that both of the catalyst [Pyr]Ac and
0
43 [Pyr]Ac- Ni had higher enzymatic peroxidase activities. Moreover, pyridinium based IL
44 solutions without TMB or H O exhibited negligible absorption over the wavelength range of
2
2
0
45 550-750 nm, signifying that both [Pyr]Ac and [Pyr]Ac- Ni indeed possess peroxidase-like
46 activity. More specifically, as we already know that the stronger affinity of nanoparticle towards
47 TMB and H O is beneficial in improving the catalytic response of the catalyst. When [Pyr]Ac
2
2
0
48 were coated on the surface of Ni , hydrogen bonding between the [Pyr]Ac and chromogenic
49 substrate TMB could possibly drive the movement of TMB. Similarly, the loose stack of
0
50 [Pyr]Ac around Ni may offer rational pathways for the significant movement of H O .
2
2
0
51 Obviously, [Pyr]Ac- Ni was the most active catalyst to generate •OH via H O decomposition
2
2
52 and its corresponding solution changes to the deep blue color through TMB oxidation.
53
(
c)
(b)
1
.0
1.0
0.8
0.6
0.4
0.2
0.0
A
B
54
(
a) (b) (c) (d)
55
0
.8
(a)
(b)
(c)
56
0
.6
57
58
(a)
0
.4
59
6
0.2
0
(b)
(c)
(d)
(
a)
61
0
.0
5
50
600
650
700
750
62550
600
650
700
750
Wavelength(nm)
Wavelength(nm)
63
0
64 Fig.4.A. Effect of ionic liquid on the sensing property of Ni nanoparticle. Ni + H O + TMB
2
2
0
0
65 (a) [Mim]Ac – Ni + H O + TMB (b) [Pyr]Ac- Ni + H O + TMB (c) B. Effect of different
2
2
2
2
66 constituents on the sensing property of Ni nanoparticle UV-Vis absorption spectra (from 550 to
0
67 750 nm) of different reaction systems: [Pyr]Ac + H O + TMB (a); [Pyr]Ac- Ni + H O + TMB
2
2
2
2
0
0
68 (b); [Pyr]Ac- Ni + H O (c); [Pyr]Ac- Ni + TMB (d). The inset was corresponding to the
2
2
69 observed color change of varying experimental systems.
70
1
0

2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
71 ILs containing carbon backbone are synthetically-accessible and chemist can easily tune it to
72 modify the surface of nanoparticles in order to improve the catalytic performance [35]. The
73 stronger interaction was noticed while using most electrophilic cation with the metal precursor
74 thereby decreasing the particle nucleation and growth process. Considering the structure of
75 pyridinium based IL compared to imidazolium-based IL, pyridine is a basic aromatic
76 heterocyclic organic compound with one methine group (=CH−) replaced by nitrogen while
77 imidazole is a planar 5-membered ring. It can be postulated that the change in the deepest color
78 change of nickel nanoparticle observed in case of pyridine based IL was due to the high
79 aromaticity in the ring structure pyridinium cation and carboxylate anion involving extensive
80 delocalization of electron, thereby, creating an electron rich conducive environment that may
81 ease in the reaction imparting intense color due to charge-transfer complex between the [Pyr]Ac
0
82 and Ni resulting from the one-electron substrate oxidation. Therefore, these results confirm the
0
83 significant peroxidase-like activities of [Pyr]Ac-Ni making it much sensitive, selective and
84 highly efficient colorimetric sensor for visual detection of H O .
2
2
85
86 Optimization of sensing conditions
87 To achieve the best sensing response, various experimental parameters were optimized including
88 pH, temperature, catalyst dosage, the volume of [Pyr]Ac, reaction time, TMB concentration,
89 H O concentration of the reaction system. The result of the present study showed that the strong
2
2
90 absorbance at 652 nm as depicted in Fig. 5, may be ascribed to ox-TMB, which has a significant
91 effect on the catalytic activity of the reaction system. The pH of the solution is a key factor
92 affecting the catalytic behaviour of the sensing system. Considering the fact, enzymatic activity
0
93 declines dramatically after exposure to extreme pH. In contrast, [Pyr]Ac- Ni showed the
94 highest catalytic activity over a broad range of pH (3.0-12.0), which is a very meaningful signal
95 to diverse its application as enzyme mimics nearly around physiological pH values. As observed
96 from Fig.5(a), the highest oxidation peak was observed at pH 7.4, which is consistent with
97 previously reported nanozymes [12]. Besides, the reaction activity enhanced continuously as the
o
o
98 temperature ranged from 10 C to 50 C as presented in Fig.5(b). At higher temperature, H O
2
2
99 would be readily decomposed into oxygen and water, resulting in the decreased OH radicals,
0
00 thereby limiting the catalytic activity of [Pyr]Ac- Ni . However, considering the ease of
o
01 experimentation work for the bioassay, we selected 25 C as an incubation temperature.
02 The amount of catalyst was optimized using a stock concentration of 6 mg/ml in µl range for
03 subsequent experiments. The best colorimetric response was observed when the optimum
04 amount of 40 µlcatalyst was used as presented in Fig.5 (c). It was seen that increasing the
1
1

3
3
3
3
3
3
3
3
3
3
3
3
3
05 concentration of catalyst helps in accelerating the conversion of TMB into oxy-TMB. Further
06 increasing the concentration caused a steep decrease in absorbance which may occur due to the
07 agglomeration of catalyst at high concentration, leading to the obstruction in the adsorption of
08 TMB and H O over its surface. Therefore, better activity was observed at 40 µlof catalyst,
2
2
09 which may become inactive beyond its limit. The effect of varying pyridine based IL on nickel
0
10 nanoparticle was investigated. It was noted that the peroxidase-like activity of Ni was
11 extensively enhanced by increasing the volume of [Pyr]Ac as depicted in Fig.5 (d). Therefore,
12 based on the best response and observing a noticeable color change, 100 µl[Pyr]Ac was selected
13 for the reaction system. A study focusing on the effect of different incubation times was also
14 investigated on sensor response. It is noteworthy that the curve increased linearly initially with
0
15 the increase of reaction time, whereas after 10 minutes, the catalytic activity of [Pyr]Ac- Ni
16 enhanced with time slowly as shown in Fig.5 (e).
17
3
3
18
0
19 Fig.5. Influences of peroxidase-like catalytic activity of [Pyr]Ac- Ni against pH (a),
3
3
3
3
3
3
20 temperature (b), Volume of Catalyst (c), Volume of [Pyr]Ac (d), Time (e). The maximum point
21 in each graph was set as 100%.
22 The effects of TMB and H O on absorbance were investigated as illustrated in Fig.6 (a& b). In
2
2
23 addition, the concentration of substrate TMB is a key factor in determining the color level of the
24 reaction system to ensure the formation of stable blue charge-transfer complex. It was found that
25 absorbance increased rapidly by increasing the TMB concentration. But when the concentration
1
2

3
3
3
3
3
3
3
3
3
3
3
26 of substrate TMB reached 18 mM, the growth rate becomes slow and the reaction mixture
27 appeared precipitate when TMB concentration was higher than 18 mM. Therefore, 18 mM was
28 chosen as a suitable TMB concentration in order to produce a noticeable color change without
29 producing excessive absorbance at 652 nm. Similarly, when the H O concentration approached
2
2
30 20 mM, the catalytic activity reached its maximum. Such a higher concentration of H O2
2
0
31 indicates that [Pyr]Ac- Ni possess more catalytic stability in comparison to natural enzyme
0
32 [36]. As the catalytic activity of [Pyr]Ac- Ni is H O concentration-dependent, therefore the
2
2
33 system discussed above could be effectively used for the fast detection of hydrogen peroxide.
34 Based on the results discussed hereby, the following reaction parameters were found to provide
o
35 the best results: buffer pH 7.4, reaction temperature (25 C), 10 min incubation time, 40µl
36 catalyst, 100 µl [Pyr]Ac, 18 mM TMB and 20 mM H O .
2
2
3
3
37
0
38 Fig.6. Influences of the peroxidase-like catalytic activity of [Pyr]Ac- Ni against TMB
39 concentration (a) H O concentration (b). The maximal point in each curve was set as 100%
3
3
3
3
3
3
3
3
3
3
3
3
2
2
40
0
413.4. Robustness and reusability of peroxidise activity of [Pyr]Ac- Ni
0
42As inorganic nanomaterials, the stability of [Pyr]Ac- Ni over a broad range of pH values and
43temperature ranges is crucial to expand its application. In general, the natural enzyme activity is
44easy to lose significantly after incubation at low pH or high pH and high temperature[37]. In
0
45contrast [Pyr]Ac- Ni showed stable and significant catalytic activity after incubation over a
46broad range of pH (3-12) and following temperatures (10-50°C). However, in view of its
47reproducibility, the catalyst was examined for five consecutive cycles. After each cycle, the
48reaction mixture was continuously centrifuged to collect the catalyst, washed with de-ionized
49water and subsequently subjected to further reaction. As shown in fig. 7, there was not much
50significant decrease in catalytic activity even after consecutive five cycles which shows good
1
3

3
3
51stability of the catalyst further expanding its application towards clinical diagnostics and
52environmental analysis.
3
3
53
0
54
Fig.7.Reusability analysis of [Pyr]Ac-Ni for the detection of H O
2
2
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
55 3.5. Steady-State Kinetic analysis
0
56 The catalytic mechanism of [Pyr]Ac-Ni was further studied based on enzyme kinetics theory
57 using the Michaelis–Menten equation by changing the suitable concentration of substrate TMB,
58 keeping the concentration of H O constant and vice versa. Therefore, the Michaelis–Menten
2
2
59 constant (K ) and maximal reaction velocity (Vmax) were obtained from the Lineweaver–Burk
m
60 plot in this system from the obtained experimental results. In our work, our material showed
61 higher k value with TMB and H O than that for the natural enzyme (HRP), suggesting the
m
2
2
62 lesser binding affinity of catalyst for TMB and H O . Therefore, in accordance to literature
2
2
63 study, higher concentration of H O is required to attain the maximal activity for the catalyst, if
2
2
64 the K value is high. It can be deduced, that in a catalytic process, TMB molecule adsorbs on
m
65 the catalyst surface by donating lone-pair of electrons from the amino group to its surface,
0
66 increasing the electron density around [Pyr]Ac-Ni . This would facilitate the electron transfer
67 process from the surface of catalyst to H O , resulting in the reduction of H O to H O and
2
2
2
2
2
68 increasing the oxidation reaction rate of TMB using H O Nevertheless, V value of [Pyr]Ac-
2
2.
max
0
0
69 Ni with H O and TMB is much higher than that for the natural enzyme, making [Pyr]Ac-Ni a
2
2
70 good candidate for rapid H O detection.
2
2
71
72
73
74
75
1
4

0
3
76 Table 1. Comparison of K and V of [Pyr]Ac-Ni with a natural enzyme (HRP)
m max
-8
-1
K [mM]
m
V [10 MS ]
m
Catalyst
Pyr]Ac-Ni
HRP
TMB
0.54
H O
TMB
7.3
H O
Ref
This work
[38]
2
2
2
2
0
[
0.34
5.1
0.275
0.214
1.24
2.46
3
3
3
3
3
3
77
78 3.6. Colorimetric Detection of H O2
2
79 Based on the above-mentioned optimized conditions, an effective and rapid colorimetric strategy
80 was designed for the fast visual detection of H O based on the peroxidase-like property of
2
2
0
81 [Pyr]Ac-Ni nanoparticle as shown in scheme 3.
82
3
3
83
84 Scheme 3. Schematic Illustration of the Possible Mechanism of TMB oxidation in the presence
0
3
3
3
3
3
3
3
3
85
of [Pyr]Ac-Ni for the colorimetric sensing of H O
2
2
86 As illustrated in Fig.8 (a), the maximal absorbance was observed at 652 nm when the
87 concentration of H O was varied from 400-4000 μM. The marked color change was noted
2
2
88 easily detectable by the naked eye (Fig.8(a)inset) and their corresponding absorbance relates to
89 the concentration of H O , which indicates that the developed visual method is feasible. Fig.8(b)
2
2
90 shows the calibration plot of H O within the linear range from 400-4000 μM and the value for
2
2
2
91 limit of detection is calculated to be 120 μM with an R value of 0.98. Upon the addition of
0
92 higher concentration of H O , Ni nanoparticles tend to become more and more stable. This
2
2
1
5

3
3
3
3
3
3
93 method thus enables the visual detection of H O with an LOD value of of 120 μM over the
2 2
94 wide and dynamic linear range of 400-4000 μM.Compared with reported literature, the
0
95 colorimetric strategy based on the peroxidase-like property of [Pyr]Ac-Ni nanoparticleis
96 comparable to the other methods in terms of analytical performance (Table. 2). It can be seen
0
97 that [Pyr]Ac-Ni offered lower LOD and a wide linear range compared to reported literature to
98 give a proof of concept that our designed assay can work at higher as well low concentrations.
3
4
99
00 Fig.8. Dependence of the absorbance at a wavelength of 652 nm using a varying concentration
4
4
4
4
4
01 of H O (a) Linear calibration plot (b). The inset shows the corresponding photographs of
2
2
02 different reaction mixtures.
03
04 Table 2. Comparison of different catalysts for H O detection in terms of linear range and limit
2
2
05 of detection (LOD)
Biosensing
Principle
Linear range LOD (μM)
(μM)
Ref
materials
Ni-MOF
colorimetric
colorimetric
Electrochemical
method
0.06-160
20-100
1-1000
0.008
8
[39]
[40]
[41]
NiO NPs
CuNi-NGr/GCE
10
NP-PtNi
Electrochemical
method
10-180
1.0
[42]
NanoporousPtNi/C
Amperometry
100-1000
50-9650
10-500
31.5
1
[43]
[44]
[45]
Cu NPs@3DGr/NiF Amperometry
NiFe LDH Colorimetric
4.4
1
6

NiO-SPE
Electrochemical
method
11-2400
3.22
[46]
NiSnanocubes
colorimetric
colorimetric
4-40
1.7-2
120
[47]
0
[
Pyr]Ac-Ni
400-4000
This work
4
4
4
4
4
4
4
4
4
4
4
4
06
07
08 3.7. Interference study
09 Selectivity is a key feature to evaluate the catalytic response of a newly developed method
10 having diverse biomedical applications towards clinic diagnostics. To further assess the
11 specificity of the proposed system, the sensing system was explored with potential-interference
12 substances such asascorbic acid, PBS, dopamine, urea, uric acid and glucose. As illustrated in
13 Fig.9 the concentration of interfering analytes is 10-fold excess of glucose and none of them
14 induces any detectable signal with respect to the glucose analyte. All of the experiments were
15 carried out in the presence of PBS. The addition of hydrogen peroxide led to the formation of
16 the blue color solution clearly seen by the naked eye for glucose analyte. Thus, this analytical
17 platform has much ability to detect hydrogen peroxide significantly.
4
4
18
19 Fig.9. Interfering study and absorbance responses of glucose over potential interfering analytes
4
4
4
4
4
4
20 (ascorbic acid, phosphate buffer, dopamine, urea, and uric acid). The concentration of glucose
-6
−1
-6
21 used was 20 × 10 mole L and the concentration of other interfering analyte was 40 × 10
−
1
22 mole L . The inset represents the color intensity response of different reaction mixtures.
23
24
25
1
7

4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
26 4. Conclusion
0
27 In summary, we provided the first report that the [Pyr]Ac-Ni serves as an effective peroxidase
28 mimic which could effectively catalyze the oxidation reaction of peroxidase substrate TMB
29 using H O to produce the blue-colored product. It was confirmed that the coating of pyridinium
2
2
30 based IL could really contribute to improve the catalytic response of NiNp which was verified
31 by the rapid oxidation of substrate TMB by H O . In other words, pyridinium based IL could
2
2
32 efficiently overcome the aggregation of nickel nanoparticle to a greater extent; this was a
33 significant factor for the enhancement in the catalytic performance of nickel nanoparticle. Based
0
34 on the superior catalytic activity of [Pyr]Ac-Ni , a new colorimetric sensor with high selectivity
35 and efficiency has been established with a low limit of detection value of 120 μM/L for H O2
2
36 detection. On the basis of all of these findings discussed above, we designed a simple, rapid,
37 inexpensive, highly sensitive and selective method for the development of highly stable
38 biomimetic catalyst which may offer a strategy for the visual colorimetric sensing of H O in
2
2
39 medical diagnostics.
40
41 Acknowledgment
42 This study is financially supported by Higher Education Commission (HEC), Pakistan NRPU
43 grant 7657 research project and Department of Chemistry, Government College University,
44 Lahore, 54000, Pakistan. The authors acknowledge the National Natural Science Foundation of
45 China (NSFC, Grant Nos. 11674086) for analysis of X-ray photoemission spectroscopy (XPS)
46 and Transmission Electron Microscopy (TEM).
47
48 Conflict of interest
4
4
49 There is no conflict of interest of all co-authors.
50
4
4
51 References
52
4
4
4
4
4
4
4
4
4
4
53
54
55
56
57
58
59
60
61
62
[1] N. Wang, J. Sun, L. Chen, H. Fan, S. Ai, A Cu2 (OH) 3Cl-CeO2 nanocomposite
with peroxidase-like activity, and its application to the determination of hydrogen
peroxide, glucose and cholesterol, Microchimica Acta 182(9-10) (2015) 1733-1738.
[2] B. Halliwell, M.V. Clement, L.H. Long, Hydrogen peroxide in the human body,
FEBS letters 486(1) (2000) 10-13.
[3] M.J. Sullivan-Gunn, P.A. Lewandowski, Elevated hydrogen peroxide and
decreased catalase and glutathione peroxidase protection are associated with aging
sarcopenia, BMC geriatrics 13(1) (2013) 104.
[4] J.E. Klaunig, Oxidative Stress and Cancer, Current pharmaceutical design 24(40)
(2018) 4771-4778.
1
8

4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
5
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
00
01
02
03
04
05
06
07
08
09
10
[5] M.A. Yorek, The role of oxidative stress in diabetic vascular and neural disease,
Free radical research 37(5) (2003) 471-480.
[6] N. Sui, S. Li, Y. Wang, Q. Zhang, S. Liu, Q. Bai, H. Xiao, M. Liu, L. Wang, W.Y.
William, Etched PtCu nanowires as
a
peroxidase mimic for colorimetric
determination of hydrogen peroxide, Microchimica Acta 186(3) (2019) 186.
[7] N. Wang, J. Duan, W. Shi, X. Zhai, F. Guan, L. Yang, B. Hou, A 3-dimensional
C/CeO 2 hollow nanostructure framework as a peroxidase mimetic, and its
application to the colorimetric determination of hydrogen peroxide, Microchimica
Acta 185(9) (2018) 417.
[8] Y. Lin, J. Ren, X. Qu, Catalytically active nanomaterials: a promising candidate
for artificial enzymes, Accounts of chemical research 47(4) (2014) 1097-1105.
[9] J. Xie, X. Zhang, H. Wang, H. Zheng, Y. Huang, Analytical and environmental
applications of nanoparticles as enzyme mimetics, TrAC Trends in Analytical
Chemistry 39 (2012) 114-129.
[10] S. Singh, Nanomaterials exhibiting enzyme-like properties (Nanozymes):
Current advances and future perspectives, Frontiers in chemistry 7 (2019) 46.
[11] T.G. Choleva, V.A. Gatselou, G.Z. Tsogas, D.L. Giokas, Intrinsic peroxidase-
like activity of rhodium nanoparticles, and their application to the colorimetric
determination of hydrogen peroxide and glucose, Microchimica Acta 185(1) (2018)
22.
[12] F. Zarif, S. Rauf, M.Z. Qureshi, N.S. Shah, A. Hayat, N. Muhammad, A. Rahim,
M.H. Nawaz, M. Nasir, Ionic liquid coated iron nanoparticles are promising
peroxidase mimics for optical determination of H 2 O 2, Microchimica Acta 185(6)
(2018) 302.
[13] J. Wu, X. Wang, Q. Wang, Z. Lou, S. Li, Y. Zhu, L. Qin, H. Wei, Nanomaterials
with enzyme-like characteristics (nanozymes): next-generation artificial enzymes
(II), Chemical Society Reviews 48(4) (2019) 1004-1076.
[14] M. Nasir, M.H. Nawaz, U. Latif, M. Yaqub, A. Hayat, A. Rahim, An overview on
enzyme-mimicking nanomaterials for use in electrochemical and optical assays,
Microchimica Acta 184(2) (2017) 323-342.
[15] S. Rauf, M. Hayat Nawaz, M. Badea, J. Marty, A. Hayat, Nano-engineered
biomimetic optical sensors for glucose monitoring in diabetes, Sensors 16(11) (2016)
1931.
[16] R. Hayes, G.G. Warr, R. Atkin, Structure and nanostructure in ionic liquids,
Chemical reviews 115(13) (2015) 6357-6426.
[17] J.P. Hallett, T. Welton, Room-temperature ionic liquids: solvents for synthesis
and catalysis. 2, Chemical reviews 111(5) (2011) 3508-3576.
[18] Y.G. Morozov, O. Belousova, M. Kuznetsov, Preparation of nickel nanoparticles
for catalytic applications, Inorganic Materials 47(1) (2011) 36-40.
[19] P. Song, D. Wen, Z. Guo, T. Korakianitis, Oxidation investigation of nickel
nanoparticles, Physical Chemistry Chemical Physics 10(33) (2008) 5057-5065.
[20] G. Zhu, Y. Liu, S. Sweeney, S. Chen, Functionalization and Grafting of
Nanoparticle Surfaces, (2018).
[21] K. Raj, B. Viswanathan, Synthesis of nickel nanoparticles with fcc and hcp
crystal structures, (2011).
[22] A. Kumar, P. Kumar, C. Joshi, M. Manchanda, R. Boukherroub, S. Jain, Nickel
decorated on phosphorous-doped carbon nitride as an efficient photocatalyst for
reduction of nitrobenzenes, Nanomaterials 6(4) (2016) 59.
1
9

5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
[23] A.S. Bhatt, D.K. Bhat, M.S. Santosh, C.-w. Tai, Chitosan/NiO nanocomposites: a
potential new dielectric material, Journal of materials Chemistry 21(35) (2011)
13490-13497.
[24] I. Markova-Deneva, Infrared spectroscopy investigation of metallic
nanoparticles based on copper, cobalt, and nickel synthesized through borohydride
reduction method, Journal of the University of Chemical Technology and Metallurgy
45(4) (2010) 351-378.
[25] Z.G. Wu, M. Munoz, O. Montero, The synthesis of nickel nanoparticles by
hydrazine reduction, Advanced Powder Technology 21(2) (2010) 165-168.
[26] A. Pandey, R. Manivannan, Chemical reduction technique for the synthesis of
nickel nanoparticles, Int J Eng Res Appl 5(4) (2015) 96-100.
[27] P. Khanna, P.V. More, J.P. Jawalkar, B. Bharate, Effect of reducing agent on the
synthesis of nickel nanoparticles, Materials Letters 63(16) (2009) 1384-1386.
[28] Y. Lin, A. Zhao, Y. Tao, J. Ren, X. Qu, Ionic liquid as an efficient modulator on
artificial enzyme system: toward the realization of high-temperature catalytic
reactions, Journal of the American Chemical Society 135(11) (2013) 4207-4210.
[29] D.U. Lee, J.Y. Jeong, J.W. Han, G.-C. Kwon, P. Attri, I.T. Kim, Effect of Ionic
Liquids on the Physical Properties of the Newly Synthesized Conducting Polymer,
International Journal of Polymer Science 2018 (2018).
[30] J. Fraga-Dubreuil, K. Bourahla, M. Rahmouni, J.P. Bazureau, J. Hamelin,
Catalysed esterifications in room temperature ionic liquids with acidic counteranion
as recyclable reaction media, Catalysis Communications 3(5) (2002) 185-190.
[31] B. Yang, Synthesis and Characterization of Brønsted Acidic Ionic Liquids,
AASRI International Conference on Industrial Electronics and Applications (IEA
2015), Atlantis Press, 2015.
[32] S.S. Mondal, D. Marquardt, C. Janiak, H.-J. Holdt, Use of a 4, 5-
dicyanoimidazolate anion based ionic liquid for the synthesis of iron and silver
nanoparticles, Dalton Transactions 45(13) (2016) 5476-5483.
[33] V.V. Singh, A.K. Nigam, A. Batra, M. Boopathi, B. Singh, R. Vijayaraghavan,
Applications of ionic liquids in electrochemical sensors and biosensors, International
Journal of Electrochemistry 2012 (2012).
[34] D. Van Dao, T.T. Nguyen, H.-Y. Song, J.-K. Yang, T.-W. Kim, Y.-T. Yu, I.-H.
Lee, Ionic liquid-assisted preparation of Ag-CeO2 nanocomposites and their
improved photocatalytic activity, Materials & Design 159 (2018) 186-194.
[35] B. Zhang, N. Yan, Towards rational design of nanoparticle catalysis in ionic
liquids, Catalysts 3(2) (2013) 543-562.
[36] L. Lin, X. Song, Y. Chen, M. Rong, T. Zhao, Y. Wang, Y. Jiang, X. Chen, Intrinsic
peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and
their application in the colorimetric detection of H2O2 and glucose, Analytica chimica
acta 869 (2015) 89-95.
[37] R. Li, M. Zhen, M. Guan, D. Chen, G. Zhang, J. Ge, P. Gong, C. Wang, C. Shu, A
novel glucose colorimetric sensor based on intrinsic peroxidase-like activity of
C60-carboxyfullerenes, Biosensors and Bioelectronics 47 (2013) 502-507.
[38] F. Qiao, L. Chen, X. Li, L. Li, S. Ai, Peroxidase-like activity of manganese
selenide nanoparticles and its analytical application for visual detection of hydrogen
peroxide and glucose, Sensors and Actuators B: Chemical 193 (2014) 255-262.
2
0

5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
[39] J. Chen, Y. Shu, H. Li, Q. Xu, X. Hu, Nickel metal-organic framework 2D
nanosheets with enhanced peroxidase nanozyme activity for colorimetric detection
of H2O2, Talanta 189 (2018) 254-261.
[40] Q. Liu, Y. Yang, H. Li, R. Zhu, Q. Shao, S. Yang, J. Xu, NiO nanoparticles
modified with 5, 10, 15, 20-tetrakis (4-carboxyl pheyl)-porphyrin: Promising
peroxidase mimetics for H2O2 and glucose detection, Biosensors and Bioelectronics
64 (2015) 147-153.
[41] L. Shabnam, S.N. Faisal, A.K. Roy, A.I. Minett, V.G. Gomes, Nonenzymatic
multispecies sensor based on Cu-Ni nanoparticle dispersion on doped graphene,
Electrochimica Acta 224 (2017) 295-305.
[42] C. Xu, J. Wang, J. Zhou, Nanoporous PtNi alloy as an electrochemical sensor for
ethanol and H2O2, Sensors and Actuators B: Chemical 182 (2013) 408-415.
[43] M. Janyasupab, C.-W. Liu, Y. Zhang, K.-W. Wang, C.-C. Liu, Bimetallic Pt–M
(M= Cu, Ni, Pd, and Rh) nanoporous for H2O2 based amperometric biosensors,
Sensors and Actuators B: Chemical 179 (2013) 209-214.
[44] L. Zhu, X. Guo, Y. Liu, Z. Chen, W. Zhang, K. Yin, L. Li, Y. Zhang, Z. Wang, L.
Sun, High-performance Cu nanoparticles/three-dimensional graphene/Ni foam
hybrid for catalytic and sensing applications, Nanotechnology 29(14) (2018) 145703.
[45] T. Zhan, J. Kang, X. Li, L. Pan, G. Li, W. Hou, NiFe layered double hydroxide
nanosheets as an efficiently mimic enzyme for colorimetric determination of glucose
and H2O2, Sensors and Actuators B: Chemical 255 (2018) 2635-2642.
[46] P. Salazar, V. Rico, A.R. González-Elipe, Non-enzymatic hydrogen peroxide
detection at NiO nanoporous thin film-electrodes prepared by physical vapor
deposition at oblique angles, Electrochimica Acta 235 (2017) 534-542.
[47] H. Liu, H. Ma, H. Xu, J. Wen, Z. Huang, Y. Qiu, K. Fan, D. Li, C. Gu, Hollow and
porous nickel sulfide nanocubes prepared from a metal-organic framework as an
efficient enzyme mimic for colorimetric detection of hydrogen peroxide, Analytical
and bioanalytical chemistry 411(1) (2019) 129-137.
5
5
85
86
2
1

Highlights
‹
‹
‹
Effect of ionic liquid types on sensing of Ni nanoparticle
Pyridinium based ionic liquid showed robust peroxidase-like activity
The sensing system generates a blue colored solution

Conflict of interest
The manuscript is submitting to your esteemed journal solely with the mutual understanding of
all co-authors. There is no conflict of interest of all co-authors.
Regards
Dr Nawshad Muhammad