Preparation and characterization of a novel poly-geminal dicationic ionic liquid (PGDIL)

Article abstract of DOI:10.1016/j.molliq.2019.111896

1,4-bis(3-(m-aminobenzyl)imidazole-1-yl)butane bis(hexafluorinephosphate), a novel geminal dicationic ionic liquid (GDIL) containing anilino groups has been synthesized to prepare a novel poly-geminal dicationic ionic liquid film by electro-polymerization. The morphology and structure of the PGDIL film were analyzed by SEM and FTIR, and a possible polymerization mechanism of GDIL on an Au electrode surface was determined to be 3D instantaneous nucleation. The existence of polyaniline-like units in the PGDIL chain was confirmed by FTIR, indicating that the anilino groups of GDIL were electro-polymerized on the surface of the Au electrode using the chronoamperometry method. The electrochemical performance of the PGDIL film in phenol was studied by cyclic voltammetry, and it was determined that the PGDIL film electrode promoted enhanced phenol electrocatalysis compared to the untreated Au electrode. This work extends the application range of poly ionic liquids and associates ionic liquids with conductive polymers. Where further studies on other physical and chemical properties of polymers will be necessary.

Full text of DOI:10.1016/j.molliq.2019.111896

Journal Pre-proof
Preparation and characterization of a novel poly-geminal dicationic ionic liquid
(PGDIL)
Yanni Guo, Deliang He, Aomei Xie, Wei Qu, Yining Tang, Jun Shang, Rilong Zhu
PII:
S0167-7322(19)33552-4
DOI:
https://doi.org/10.1016/j.molliq.2019.111896
MOLLIQ 111896
Reference:
To appear in: Journal of Molecular Liquids
Received Date: 25 June 2019
Revised Date: 14 September 2019
Accepted Date: 9 October 2019
Please cite this article as: Y. Guo, D. He, A. Xie, W. Qu, Y. Tang, J. Shang, R. Zhu, Preparation and
characterization of a novel poly-geminal dicationic ionic liquid (PGDIL), Journal of Molecular Liquids
(2019), doi: https://doi.org/10.1016/j.molliq.2019.111896.
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Preparation and characterization of a novel poly-geminal dicationic
ionic liquid (PGDIL)
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Yanni Guo · Deliang He · Aomei Xie ·Wei Qu · Yining Tang · Jun Shang · Rilong Zhu
(1. College of Chemistry and Chemical Engineering, Hunan University, 410082 Changsha, China)
(2. College of Marxism, Jishou University, 416000 Jishou, China)
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Abstract: 1,4-bis(3-(m-aminobenzyl)imidazol-1-yl)butane bis(hexafluorinephosphate), a novel geminal
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dicationic ionic liquid (GDIL) containing anilino groups has been synthesized to prepare a novel poly-geminal
dicationic ionic liquid film by electro-polymerization. The morphology and structure of the PGDIL film were
analyzed by SEM and FTIR, and a possible polymerization mechanism of GDIL on an Au electrode surface was
determined to be 3D instantaneous nucleation. The existence of polyaniline-like units in the PGDIL chain was
confirmed by FTIR, indicating that the anilino groups of GDIL were electro-polymerized on the surface of the Au
electrode using the chronoamperometry method. The electrochemical performance of the PGDIL film in phenol
was studied by cyclic voltammetry, and it was determined that the PGDIL film electrode promoted enhanced
phenol electrocatalysis compared to the untreated Au electrode. This work extends the application range of poly
ionic liquids and associates ionic liquids with conductive polymers. Where further studies on other physical and
chemical properties of polymers will be necessary.
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Keywords Geminal dicationic ionic liquid; Poly-ionic liquid; Electro-polymerization; Polyaniline
:
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ꢀ Deliang He, Rilong Zhu
delianghe@163.com, zrlden@hnu.edu.cn
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1. Introduction
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Poly ionic liquids (PILs), unlike conventional polymers, is a polymer that contains at least one ion center in a
polymer chain and a repeating unit similar to a common ionic liquid structure. They are a kind of functional
polymer materials which combine the properties of polymers and ionic liquids [1] and can be used as catalysts for
catalytic reactions by introducing the groups with catalytic activity into their molecular structures. Salamone and
coworkers first reported the polymerization of several vinylimidazolium-based PILs in 1973 [2]. In general, there
are two main routes to prepare PILs. The first one is the direct radical polymerization of IL monomers, which is
the most convenient and commonly employed approach. Green et al. [3] prepared a series of alkyl-substituted
vinylimidazolium PILs using a free-radical polymerization method and further investigated the impact of the alkyl
chain length on the thermal stability and ionic conductivity of PILs. Based on this method, Sun et al. [4] prepared
a porous quaternary phosphonium-based PIL that showed a hierarchical structure and excellent amphiphilicity.
The second route is the post-polymerization modification of polymer with IL monomers. Post-polymerization is
usually finished in the presence of reactive chemical groups, such as amino groups and sulfhydryl groups. Han et
al. [5] reported a PIL-modified hybrid monolithic column, which was designed and synthesized using
polymerizable ionic liquids with catalytic active groups as the monomer. PILs with multiple monomer link
polymer structure are prepared by the polymerization of polymerizable groups or unsaturated groups such as C=C
in the monomer [6, 7]. However, most of the studies involving ionic liquids deal with the unique physicochemical
and solvation properties of monocationic ionic liquids (MILs). Multifunctional ionic liquids such as dicationic
ionic liquids (DILs) and tricationic ionic liquids, which can extend the horizon of applications of ionic liquids,
have not yet been studied to a high degree.
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DILs, a new type of ILs are considered as combination of three structural moieties: (1) cationic head groups;
(2) a linkage chain; and (3) the counter anions [8]. Compared to the traditional monocationic ionic liquids [9-14],
DILs can be classified as homoanionic dicationic ionic liquids and heteroanionic dicationic ionic liquids. These
DILs can further be categorized as symmetrical and asymmetrical DILs for both homoanionic and heteroanionic
DILs. Homoanionic dicationic ionic liquids are typical DILs, which consist of a dication and two identical anions.
Symmetrical or geminal dicationic ILs (GDILs) can be synthesized joining two same cation, such as imidazolium
or pyrrolidinium, which may contain cyclic or aliphatic chain via either a rigid or a flexible spacer. A common
spacer is an alkyl chain [15, 16]. Armstrong and co-workers [14] studied structure and properties relationship by
synthesizing 39 imidazolium-based and pyrrolidinium-based dicationic ILs. The head groups were linked with an
alkyl chain (from 3 to 12 carbons long), and hence, reacted with four different traditional anions. The thermal
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stability of these ILs in the range of -4 to >400°C, which were found to be greater than those of most traditional
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monocationic ILs. GDILs have the more unique physical and chemical properties and solvation characteristics and
can be used as separation material [17], surfactants [18] and catalyst candidates [19,20], while still have not yet
been studied heavily to the best of our knowledge [21, 22]. The same is true of poly-GDILs (PGDILs).
The application of PILs modified electrodes in electrocatalysis of organic pollutants has attracted extensive
interest and attention recently [23]. Jian Hu [24] reported
a
cross-linker-based PIL
(poly(1,4-butanediyl-3,3ʹ-bis-l-vinylimidazolium dibromide)) for the sensitive detection of 4-nonylphenol. It not
only has the designability of ionic liquids (ILs) but also realizes the solidification of ILs, improves the utilization
ratio of ILs, and solves the difficulty of inconvenient storage of ILs as liquid. At the same time, its specific surface
area and reaction sites are enlarged because of the structure of polymer, which enhance the electrocatalytic effect
of phenols on the electrode [25, 26].
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The most common approach toward the formation of PILs is direct free radical polymerization of the
unsaturated C=C in IL monomers. Polyaniline (PANI) is one of the most attractive materials among a variety of
conducting polymers due to its unique electrical properties, environmental stability, and easy fabrication process,
which is the result of the polymerization of aniline monomer. This material has been widely selected as electrode
active materials due to its good electrical conductivity and flexible functionality [24]. In this work, with the
introduction
of
anilino
groups
into
the
GDIL
structure,
a
novel
GDIL
(1,4-bis(3-(m-aminobenzyl)imidazol-1-yl)butane bis(hexafluorinephosphate)) is synthesized to prepare a novel
PGDIL with polyaniline-like structure. It is expected that the PGDIL film have the advantages of both polyaniline
and ionic liquids.
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2. Experimental
2.1 Main reagents and instrumentation
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m-nitrobenzyl chloride; imidazole; acetonitrile; ethyl acetate; 1,4-dibromobutane; zinc powder; ammonium
hexafluorophosphate; alumina (1.0ꢀm, 0.3 ꢀm, 0.05 ꢀm); metallographic sandpaper; sodium dihydrogen
phosphate; acetic acid; sodium acetate trihydrate; citric acid; sodium chloride; sodium carbonate; sodium
bicarbonate; boric acid; sodium tetraborate; potassium chloride; potassium ferrocyanide; potassium ferricyanide;
phenol. The experimental reagents are analytical pure and the water used in the experiment is double distilled
water.
Heat-collecting type constant temperature magnetic heating stirrer (CJJ 78-1); Rotary evaporator (R.1002);
Field emission scanning electron microscope (JSM-6700F); Ultrasonic cleaner (SK 5200HP); Infrared
Spectrophotometer (TJ270-30A); NMR spectrometer (INOVA-400); Automatic double distilled water distillation
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apparatus (Shanghai Asia-Pacific Glass instrument Company); Electrochemical workstation (IVIUMSTAT,
IVIUM Technologies BV); Electrochemical research experiment using classical three-electrode system: working
electrode is Au electrode; The reference electrode is Ag/AgCl electrode (self-made and the auxiliary electrode is
platinum wire electrode).
2.2 Synthesis of 1,4-bis(3-(m-aminobenzyl)imidazol-1-yl)butane bis(hexafluorinephosphate)
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([C (m-ABIM) ][PF ] )
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All experiments were performed under a nitrogen atmosphere, and the experimental reagents were analytical
pure, and the water used in the experiment was double distilled water. The synthesis of [C (m-ABIM) ][PF ]
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6 2
(GDIL) is shown in Scheme 1.
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Imidazole (0.2 mol, 13.616 g) and KOH (13.44 g) were dissolved in 50 mL acetonitrile in a three-mouth
flask, and a mixture of m-nitrobenzyl (0.2 mol, 34.316 g) and acetonitrile (50 mL) was added in drops. The
reaction mixture was refluxed and stirred for 24 h at 55 ºC. After that, 100 mL of water was added and separated
the liquid into a brown oily substance. 1-(3-nitrobenzyl) imidazole was obtained by ethyl acetate extraction and
rotary evaporation with a yield was of 67 %.
0.2 mol 1-(3-nitrobenzyl) imidazole was dissolved in 100 mL acetonitrile, and 0.1mol 1,4-dibromobutane
was added dropwise. The reflux reaction was carried out at 65 ºC with stirring for 24 h. After the reaction, the
solvent was dried and the solid was washed with ethyl acetate several times. It was dried to produce a yellowish
solid powder, 1,4-bis(3-(3-nitrobenzyl)imidazol-1-yl)butane bromide ([C (m-NBIM) ][Br] ) at a yield of 57 %.
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0.1 mol [C (m-NBIM) ][Br] and 0.4 mol Zn powder were added to a three-mouth flask with 80 v%
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acetonitrile aqueous solution as the solvent. 0.1 mL 33% FeCl aqueous solution was added as the catalyst and
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then refluxed with stirring at 70 ºC for 4 h. After the reaction was completed, the reaction liquid was filtered. After
separating solvent and removing impurities from the filtrate and drying under vacuum at 40 ºC,
1,4-bis(3-(3-aminobenzyl)imidazol-1-yl)butane bromide was obtained as a yellowish solid powder (yield 30%).
An aqueous solution of ammonium hexafluorinephosphate was gradually added to the aqueous solution of
[C (m-ABIM) ][Br] (the molar ratio of NH PF and [C (m-ABIM) ][Br] was 2:1). After stirring for 5 h at 60 ºC,
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the mixture was filtered to obtain a solid and via washing and vacuum drying [C (m-ABIM) ][PF ] was obtained
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6 2
1
as a yellowish solid (yield 72%). H NMR (DMSO, 400 MHz, ppm): δ 9.45(s, 4H); 8.39(s, 2H); 8.28(d, 4H);
7.55-8.15(m, 8H); 5.55(s, 4H); 4.23(t, 4H); 2.08(m, 4H).
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Scheme 1 The synthesis of [C (m-ABIM) ][PF ] (GDIL)
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6 2
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Density functional theory (DFT) simulation was performed using the Gaussian 09 software package. The
calculation was carried out using the DFT method with Becke’s three-parameter hybrid exchange functionals and
the Lee-Yang-Parr correlation functional (B3LYP) employing the 6-31G (d, p) basis set for all atoms [27, 28]. The
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possible 3D molecular structure model is shown in the Fig. 1. The structure of [C (m-ABIM) ] consists of
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zigzag bands of molecule[29].
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Fig. 1 The optimized structures of the [C (m-ABIM) ] at the B3LYP/6-31G (d, p) level.
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2.23 Preparation of poly-[C (m-ABIM) ][PF ] (PGDIL)
4 2 6 2
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An electrochemical tri-electrode system was introduced for electrochemical polymerization, in which Au,
Platinum wire, and Ag/AgCl electrode were used as the working electrode, counter electrode, and reference
electrode, respectively. The treated Au working electrode was placed in acetonitrile solution containing 0.01
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mol/L [C (m-ABIM) ][PF ] and 0.1 mol/L sodium perchlorate (supporting electrolyte), and the
4 2 6 2
poly-[C (m-ABIM) ][PF ] (PGDIL) film was prepared on the surface of Au electrode by means of
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6 2
chronoamperometric polymerization at constant potential of 1.2 V for 1800 s. The prepared PGDIL film was
rinsed repeatedly with double distilled water, then dried under 50 ºC in the vacuum drying chamber. All
electrochemical experiments were performed at ambient room temperature under a nitrogen atmosphere, and the
water used in the experiment was double distilled water.
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Fig. 2 Current vs. time transient during the potentiostatic electropolymerization of GDIL at potential of 1.2 V. Inset:
comparison of the experiment curve with theoretical curves from the Scharifker–Hills model
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Chronoamperometry is an important diagnostic technique for the initial stage of electrocrystallization [30].
Fig. 2 shows a current transient (CTT) recorded during the polymerization of GDIL monomer at 1.2V. The
electropolymerization process should be hardly affected by other reactions. The CTT can be divided into three
regions. In the first region (t< 2 s), the decrease in oxidation current is related to charging of the double layer due
to the specific adsorption of GDIL on the Au electrode. The second region corresponds to the increase in the
oxidation current up to a maximum, which is typical of nucleation and growth processes. The third region
corresponds to the decrease in the oxidation current, which is typical of a diffusion controlled process. An analysis
of the CTT was performed by fitting the experimental data to a dimensionless theoretical curve for crystal
nucleation and diffusion controlled growth in three dimensions (3D), as proposed by Scharifker and Hills [31].
The instantaneous and progressive theoretical transients are given by Eqs. (1) and Eqs. (2), respectively:
i 2
1.9542
=
=
{1 − exp[ −1.2564( t / t )]} 2
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m
(1)
(2)
2
m
t / tm
i
i 2
1.2254
2
2
{1 − exp[ −2.3367 (t / t ) ]}
m
2
m
t / tm
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In the equation, im and tm represent the maximum current density and its corresponding time, respectively.
The experiment data are fitted as shown in the inset of Fig. 2 Inset. The experimental curve conforms to the
theoretical curve of the instantaneous nucleation model. Therefore, it can be concluded that instantaneous
nucleation predominated at the oxidant peak potential for the electropolymerization of GDIL.
2.4 Electrochemical properties of PGDIL film
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The electrochemical properties of PGDIL film modified electrode were investigated by electrochemical
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impedance spectroscopy [32]. The prepared PGDIL/Au electrode was placed in 5.0×10 mol/L Fe(CN)
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solution with 0.1 mol/L KCl as the electrolyte for cyclic voltammetry(CV) test and AC impedance test
respectively, Platinum wire was used as the counter electrode, and an Ag/AgCl electrode (self-made) was used as
the reference electrode. The CV scanning rate was 0.05 V/s and the scanning range was -0.2~0.6 V. The
electrochemical impedance frequency ranges from 100000 to 0.01 Hz, and the sine wave signal amplitude is 5
mV.
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The Au electrode and PGDIL/Au film modified electrode were used as working electrodes, and stirred and
enriched for 3 min at open circuit potential, respectively, and cyclic voltammetry tests were carried out at a
scanning rate of 0.5 V/s in the range of 0~1 V potential. The electrochemical behaviors of the Au electrode and
PGDIL/Au electrode in NaH PO –C H O (pH=5) buffer solution containing 0.15 mmol/L phenol were studied.
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After each test, the phenol adsorbed on the surface of the electrode can be removed for continuous test by cyclic
voltammetry scanning in a blank base solution at a scanning rate of 0.1 V/s for 10 cycles. All electrolytes were
deoxygenated w ith nitrogen before testing in order to avoid the interference of oxygen in the solution to the test.
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3. Results and discussions
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Fig. 3(A) is a photo map of the PGDIL powder scanning electron microscope. As shown in the picture, the
PGDIL powder is composed of homogeneous, stacked, spherical particles, which is similar in shape to most
conductive polymers. The PGDIL membrane is loose and porous, which is beneficial to the adsorption of
contaminants in the film.
In order to gain further insight into the structure of the PGDIL and GDIL, the IR spectrum of the polymer
−
1
powder was collected, as shown in Fig. 3(B). In the FTIR spectra of PGDIL, the bands at 3158 cm and 3106
−
1
cm , which are attributed to the C–H ring stretching vibration of the aromatic rings (imidazolium and benzene)
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1
[33], are clearly visible, and then shift to low-frequency regions, vibrating 3057 and 2999 cm , respectively.
Since more hydrogen bonds(C–H···F) were formed after polymerization, the C–H bond length increased, the bond
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-1
force constant decreased, and the absorption wavenumber shifted red [34]. 3556 cm and 3452 cm signified the
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stretching vibration band of N–H (primary amines), the shoulder band at 3324 cm as the N–H frequency
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doubling peak of the bending vibration, while 3462 cm was the stretching vibration band of N–H (secondary
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amines), and the shoulder band 3324 cm depicted the N–H frequency doubling peak of bending vibration [35].
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Fig. 3 (A) SEM diagram of PGDIL. (B) The IR spectra of GDIL and PGDIL. (C) Schematic diagram of PGDIL
molecular structure (Hydrogen atoms not shown for clarity)
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Comparing the red curve (GDIL) with the black curve (PGDIL), the peak at 1312 cm may be attributed to
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the C–N stretching vibration band of ph–NH , and the peaks in the range of 1700 cm to 1400 cm belong to the
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N–H deformation vibration (1609 cm ) and the stretching vibration band of C=C and C–C in aromatic rings,
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imidazole ring deformation at 924 cm , P–F stretching vibration and N–H (primary amines) out-of-plane bending
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-1
vibration at 830 cm (broad peak) [36], C–(CH ) –C skeletal vibration at 739 cm , C–H (1,3-di substituted
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-1
benzene ring) out-of-plane bending vibration at 682 cm are observed respectively in the infrared spectra of the
-1
GDIL monomer [37]. While in the infrared spectra of PGDIL, the peak at 1329 cm belongs to the C–N stretching
-1
vibration of the benzene-quinone ring variant, the peak at 1250 cm is assigned to the conjugate C=N stretching
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+
+
vibration in the quinone ring structure, and 1108 cm belongs to the N=Q=N, Q=N H=B and B–N H–B
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stretching vibration [38], an imidazole ring deformation at 920 cm , P–F stretching vibration at 835 cm (sharp
peak), which means the –NH groups participate in the polymerization reaction and convert into –NH– or –N=,
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-1
the C–(CH ) –C skeletal vibration at 744 cm , C–H (1,3,5-tri substituted benzene ring) out-of-plane bending
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2
-1
vibration at 652 cm are observed, respectively [37]. However, the infrared spectra of PGDIL is quite different to
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-1
that of GDIL in the range of 1700 cm to 1400 cm due to the benzenoid diimine and quinoid diamin structures
formed by polymerization of anilino groups of GDIL which is similar to that of polyaniline (as shown in Fig. 3(C))
[39].
Combined with the infrared spectra above, it can be determined that the polymer formed by the successful
polymerization of aniline groups of GDIL monomer has a benzenoid diimine and quinoid diamin structure, similar
to that of polyaniline, and it is a partially oxidized and reduced structure. In addition, the synthesis process of
PGDIL is shown in Scheme 2.
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Scheme 2 The synthesis process of PGDIL.
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Fig. 4(A) is a cyclic voltammetry curve of bare Au and PGDIL/Au electrode in 5.0×10 mol/L Fe(CN)
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solution. The ability of the film to block electrons can be determined by the reversibility of redox peaks and the
peak current, which is to detect the change in properties before and after electrode modification. As the diagram
3-/4-
shows, Fe (CN)6
probes on the Au and PGDIL/Au electrode surface all have obvious redox peaks, but there are
great differences in the peak types. There is a pair of obviously reversible redox peaks on the bare Au electrode,
while on the PGDIL/Au modified electrode, the reduction peak current and the anodic peak current are obviously
reduced, the peak-peak potential difference increases, and the degree of irreversibility decreases, which indicates
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3
that the polymer film modified on the electrode provides the Fe (CN)6
probe molecule to encounter greater
obstacle, but the apparent presence of redox peaks also indicates that the modified polymer film is relatively loose
and has better conductive properties.
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3-/4-
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Fig. 4 (A) The cyclic voltammetry curves of PGDIL/Au and Au in the presence of 5.0 mmol L Fe(CN)
with 0.1
with 0.1
6
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1
-1
3-/4-
mol L KCl as electrolyte. (B) The EIS plots of PGDIL/Au and Au in the presence of 5.0 mmol L Fe(CN)
6
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1
mol L KCl as electrolyte. Inset is the Randle's equivalent circuit
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Fig. 4(B) shows the AC impedance spectra of the Au and PGDIL/Au at potential of 0.3 V. It can be seen
from the graph that both the bare gold electrode and the polymer modified electrode have a semicircle at high
frequency and a straight line at low frequency region, which illustrates that the reaction processes of the Au and
PGDIL/Au electrode are controlled by electrochemical reaction and diffusion. The real parts of the impedance
diagrams are the same, indicating that the solution ohm resistances are the same during all electrode reactions,
namely the electrolytes. The semicircle diameter of the high frequency region of the modified electrode is larger
than that of the bare gold electrode, which indicates that the charge transfer resistance of the electrolyte ions in the
film modified gold electrode is greater than that of the bare gold electrode. The circular diameter of the modified
electrode in high frequency region is larger than that of the bare gold electrode, which indicates that the charge
transfer resistance of the electrolyte ions in the film modified gold electrode is greater than that of the bare gold
electrode. This is because the modified film is less conductive than the gold electrode and obstructs the electrons
in reaching the electrode through the membrane layer. In the process of dynamic control at the low frequency
region, the relative velocity of reaction in kinetic process of the modified electrode is higher than that of the bare
gold electrode because the frequency of each modified electrode is greater than that of the bare gold electrode.
The slope of the straight line in the low frequency region of the bare gold electrode is larger than that of each
modified electrode, indicating that the diffusion resistance of the modified gold electrode is larger than that of the
bare Au electrode. The illustration is an equivalent circuit model based on the electrochemical impedance data
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fitting of the modified electrode, where R represents the solution resistance, and R represents the charge-transfer
s ct
resistance, which to some extent, reflects the polymer film on the surface of the electrode. With a larger R value,
ct
the electronic transmission must overcome a larger barrier (denser and thicker film layer), which, in turn, leads to
a more difficult reaction. C represents a double-layer capacitance and W represents the Warbury impedance.
dl
Fig. 5(A) shows the cyclic voltammetry curves of the PGDIL/Au and Au electrodes in buffer solution. It can
be seen from the diagram that the two electrodes have no peak current response on the cyclic voltammetry
measured in the phenol-free buffer, and the curve current is close to 0 ꢀA, which indicates that the buffer solution
can be used as the supporting electrolyte for the electrocatalytic reaction. When the concentration of phenol in the
buffer is 0.015 mol/L, there is almost no oxidation peak on the bare gold electrode, and the electrochemical
response is very weak, while there is a oxidation peak at 0.7 V on the PGDIL/Au electrode, its oxidation peak
type is obvious, and the electrochemical reaction of phenol on the electrode is completely irreversible. The PGDIL
membrane has stronger adsorption capacity and higher enrichment efficiency to allow the phenol concentration on
the electrode surface to increase, and thus the oxidation peak current will increase.
1
1
1
1
14
1
1
1
1
5
6
7
8
Fig. 5 (A) Cyclic voltammograms of PGDIL/Au and bare Au electrode with and without 0.015 mol/L phenol (Scan rate
is 0.5 V/s). (B) CVs of 15mmol/L phenol with various scan rates (0.1~0.9 V·s ). Inset: corresponding relationships
between the anodic peak currents and scan rates
-1
To further study the mass transfer characteristics of phenol on the PGDIL/Au composite membrane modified
1
2
2
2
9
0
1
2
electrode, the cyclic voltammetry curves of the composite membrane modified electrode in 0.015mol/L phenol
solution were measured when the scan rate was in the range of 0.1~0.9 V/s, as shown in Fig. 5(B). It can be seen
from the diagram that with the increase of the scan rate, the oxidation peak current increases and the oxidation
peak potential shifts positively, which indicates that the oxidation of phenol on the PGDIL/Au electrode is
11

1
2
3
4
5
kinetically-controlled. Furthermore, using the oxidation peak current ( p
i
) as the vertical coordinate and the scan
are in
rate ( ) as the transverse coordinate, the p curve was obtained (Fig. 5(B) Inset). It was shown that Ip and υ
υ
i
~
υ
good linear relationship, which shows the reaction is controlled by the adsorption process. The linear equation is
2
Ip=1.352+8.497*
υ
, r =0.9981.
According to the laviron equation [40] for the irreversible reaction process controlled by adsorption,
ꢃꢄ
ꢃꢄꢇꢈ
ꢃꢄ
6
7
ꢀꢁ
=
Eꢂ-ꢅn ln ꢅ + ꢅn ln
υ,
ꢉ=1-
α
, the number of electrons involved in the reaction can be obtained from the
ꢆ
nꢆ
ꢆ
RT
slope of the relation between Ep and ln
υ, that is,
=0.0437, where α is the transfer coefficient. For the
ꢊ1-αꢋnF
8
9
0
1
2
3
4
5
6
7
8
9
irreversible adsorption control process of 0.5, it is known that T = 298.15 K, R = 8.314, F = 96500 C/mol, and the
number of electrons involved in the reaction is = 1.175, close to 1. In other words, when the scanning rate is 0.5
n
1
1
1
1
1
1
1
1
1
1
V/s, the electrocatalytic oxidation of phenol on PGDIL film modified electrode is controlled by single electron
transfer.
Based on the above results, as shown in Fig. 6, it was speculated that the electrocatalytic mechanism of
phenol is that phenol is adsorbed on PGDIL film modified electrode first, and with the rise of electrode potential,
phenol adsorbed on the PGDIL film modified electrode is electrochemically activated and loses electrons to form
active intermediates with positive centers. This process is the control step, and then the proton is quickly lost to
form a large number of phenoxy radicals. It is an initial oxidation step, the continued electrochemical oxidation of
the phenoxy radicals would first result in the formation of hydroquinone (or catechol) and then to benzoquinone.
The further reactions of the quinones are slow reactions with the main products being organic acids (maleic,
formic, oxalic acid), and finally mineralized to carbon dioxide and water [41, 42].
2
2
0
1
Fig. 6 Electrocatalytic mechanism of phenol
1
2

1
4. Conclusion
2
3
4
5
6
7
8
9
0
1
2
3
A novel ionic liquid 1,4-bis(3-(m-aminobenzyl)imidazol-1-yl)butane bis(hexafluorinephosphate), containing
anilino groups, was synthesized and characterized. The FTIR and NMR results showed that the synthesized
product was consistent with the target ionic liquid. Furthermore, using the above ionic liquid as a monomer, a
novel PGDIL film was successfully prepared via a chronoamperometry method. The SEM result revealed that the
morphology of the PGDIL was loose and porous composed of homogeneous, spherical, and stacked particles,
which was beneficial to the adsorption of contaminants on the film. The existence of polyaniline-like units in the
PGDIL chain was confirmed by FTIR, indicating that the anilino groups of GDIL was electro-polymerized on the
surface of the Au electrode by the chronoamperometry method. The electrochemical performance of PGDIL film
was studied, and it is found that the PGDIL flim modified electrode showed improved effects on phenol
electrocatalysis compared than that of the Au electrode. It can be expected to be used in electrochemical catalytic
reaction of other organic compounds. It extends the range of poly ionic liquids and associates ionic liquids with
conductive polymers again, but the related chemical and electrochemical properties need to be studied further.
1
1
1
1
14
5. References
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
[1] Z. Zhou, D.L. He, R.H. Yang, Y.N. Guo, J.F. Zhong, G.X. Li, Electropolymerization of benzotriazolein room
temperature
ionic
liquid
[bmim]PF6,
J.
Appl.
Electrochem.
38
(2008)
1757-1761.
http://doi.org/10.1007/s10800-008-9627-y.
[2] J.C. Salamone, S.C. Israel, P. Taylor, B. Snider, Synthesis and homopolymerization studies of
vinylimidazolium salts, Polymer 14 (1973) 639-644. http://doi.org/10.1016/0032-3861(73)90039-6.
[3] M.D. Green, D. Salas-de la Cruz, Y.S. Ye, J.M. Layman, Y.A. Elabd, K.I. Winey, T.E. Long, Alkyl-substituted
n-vinylimidazolium polymerized ionic liquids: thermal properties and ionic conductivities, Macromol. Chem.
Phys. 212 (2011) 2522-2528. https://doi.org/10.1002/macp.201100389.
[4] Q. Sun, S.Q. Ma, Z.F. Dai, X.J. Meng, F.S. Xiao, A hierarchical porous ionic organic polymer as a new
platform for heterogeneous phase transfer catalysis, J. Mater. Chem. A 3 (2015) 23871-23875.
https://doi.org/10.1039/C5TA07267K.
[5] H.F. Han, Q. Wang, X. Liu, S.X. Jiang, Polymeric ionic liquid modified organicsilica hybrid monolithic
column
for
capillary
electrochromatography,
J.
Chromatogr.
A
1246
(2012)
9-14.
https://doi.org/10.1016/j.chroma.2011.12.029.
[6] Q. Zhang, S.Y. Wu, L. Zhang, J. Lu, F. Verproot, Y. Liu, Z.Q. Xing, J.H. Li, X.M. Song, Fabrication of
polymeric ionic liquid/graphene nanocomposite for glucose oxidase immobilization and direct
electrochemistry, Biosens. Bioelectron. 26 (2011) 2632-2637. https://doi.org/10.1016/j.bios.2010.11.024.
[7] J.Y. Yuan, S. Wunder, F. Warmuth, Y. Lu, Spherical polymer brushes with vinylimidazolium-type poly(ionic
liquid)
chains
as
support
for
metallic
nanoparticles,
Polymer.
53
(2012)
43-49.
https://doi.org/10.1016/j.polymer.2011.11.031.
1
3

1
2
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
4
5
6
7
8
[8] R.A. Patil, M. Talebi, L.M. Sidisky, D.W. Armstrong, Examination of selectivities of thermally stable geminal
dicationic ionic liquids by structural modification, Chromatographia 80 (2017) 1563-1574.
http://doi.org/10.1007/s10337-017-3372-5.
[9] D.L. He, Y.N. Guo, Z. Zhou, S.B. Xia, X. Xie, R.H. Yang, Electropolymerization of ionic liquid substituted
polyphenylene as supercapacitors materials, Electrochem. Commun. 11 (2009) 1671-1674.
https://doi.org/10.1016/j.elecom.2009.06.024.
[10]Z. Zhou, D.L. He, Y.N. Guo, Z.D. Cui, L.P. Zeng, G.X. Li, R.H. Yang, Photo-induced polymerization in ionic
liquid medium: Preparation of polyaniline nanoparticles, Polym. Bull. 62 (2009) 573-580.
http://doi.org/10.1007/s00289-009-0038-y.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
[11]L. Guglielmero, A. Mezzetta, L. Guazzelli, C.S. Pomelli, F. D’Andrea, C. Chiappe, Systematic synthesis and
properties evaluation of dicationic ionic liquids, and a glance into a potential new field, Front. Chem. 6 (2018)
612-619. https://doi.org/10.3389/fchem.2018.00612.
[12]A. Ehsani, E. Kowsari, F.B. Ajdari, R. Safari, H.M. Shiri, Influence of newly synthesized geminal dicationic
ionic liquid on electrochemical and pseudocapacitance performance of conductive polymer electroactive film,
J. Colloid Interf. Sci. 505 (2017) 1158-1164. https://doi.org/10.1016/j.jcis.2017.07.001.
[13]M. Moosavi, F. Khashei, E. Sedghamiz, Molecular dynamics simulation of geminal dicationic ionic liquids
[C (Mim) ][NTf ] - structural and dynamical properties, Phys. Chem. Chem. Phys. 20 (2017) 435-448.
n
2
2 2
https://doi.org/10.1039/c7cp05681h.
[14]J.L. Anderson, R.F. Ding, A. Ellern, D.W. Armstrong, Structure and properties of high stability geminal
dicationic ionic liquids, J. Am. Chem. Soc. 127 (2005) 593-604. https://doi.org/10.1021/ja046521u.
[15]Asiah Nusaibah Masri, Abdul Mutalib MI and Jean-Marc Leveque, A review on dicationic ionic liquids:
classification
https://doi.org/10.4172/2169-0316.1000197.
[16]H. Zhang, J. Liu, M. Li, B. Yang, Functional groups in geminal imidazolium ionic compounds and their
influence on thermo-physical properties, J. M. Liq. 269 (2018) 738-745.
https://doi.org/10.1016/j.molliq.2018.08.037.
and
application,
Ind.
Eng.
Manage.
5
(2016)
197-204.
[17]N. Shahkaramipour, M. Adibi, A.A. Seifkordi, Y. Fazli, Separation of CO /CH through alumina-supported
2
4
geminal
ionic
liquid
membranes,
J.
Membrane
Sci.
455
(2014)
229-235.
https://doi.org/10.1016/j.memsci.2013.12.039.
[18]Y.S. Ding, M. Zha, J. Zhang, S.S. Wang, Synthesis, characterization and properties of geminal imidazolium
ionic liquids, Colloids and Surfaces A: Physicochem. Eng. Aspects 298 (2007) 201-205.
https://doi.org/10.1016/j.colsurfa.2006.10.063.
[19]A. Chinnappan, H. Kim, Environmentally benign catalyst: Synthesis, characterization, and properties of
pyridinium dicationic molten salts (ionic liquids) and use of application in esterification, Chem. Eng. J. 187
(2012) 283-288. https://doi.org/10.1016/j.cej.2012.01.101.
[20]J. Cheng, C. Xiang, Y. Zou, H. Chu, S. Qiu, H. Zhang, L. Sun, F. Xu, Highly active nanoporous Co-B-TiO2
framework
for
hydrolysis
of
NaBH4,
Ceramics
International
41
(2015)
899-905.
https://doi.org/10.1016/j.ceramint.2014.09.007.
1
4

1
2
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
4
5
6
7
8
9
0
[21]C. Zafer, K. Ocakoglu, C. Ozsoy, S. Icli, Dicationic bis-imidazolium molten salts for efficient dye sensitized
solar cells: synthesis and photovoltaic properties, Electrochim. Acta 54 (2009) 5709-5714.
https://doi.org/10.1016/j.electacta.2009.05.016.
[22]X.J. Li, D.W. Bruce, J.M. Shreeve, Dicationic imidazolium-based ionic liquids and ionic liquid crystals with
variously
positioned
fluoro
substituents,
J.
Mater.
Chem.
19
(2009)
8232-8238.
https://doi.org/10.1039/B912873E.
[23]X. Wang, H. Wei, X. Liu, W. Du, X. Zhao, X. Wan, Novel three-dimensional polyaniline nanothorns vertically
grown on buckypaper as high-performance supercapacitor electrode, Nanotechnology 30 (2019)
325401-325409. https://doi.org/10.1088/1361-6528/ab156d.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
[24]J. Hu, H. Dai, Y. Zeng, Y. Yang, H. Wang, X. Zhu, L. Li, G. Zhou, R. Chen, L. Guo, A cross-linker-based
poly(ionic liquid) for sensitive electrochemical detection of 4-nonylphenol. Nanomaterials 9 (2019) 513-524.
https://doi.org/10.3390/nano9040513.
[25]M. Watanabe, S. Yamada, N. Ogata, Ionic conductivity of polymer electrolytes containing room temperature
molten salts based on pyridinium halide and aluminium chloride, Electrochim. Acta 40 (l995) 2285-2288.
https://doi.org/10.1016/0013-4686(95)00179-I.
[26]A. Noda, M. Watanabe, Highly conductive polymer electrolytes prepared by in situ polymerization of vinyl
monomers in room temperature molten salts, Electrochim. Acta 45 (2000) 1265-1270.
https://doi.org/10.1016/S0013-4686(99)00330-8.
[27]A.D. Becke, Density-functional thermochemistry. III. The role of exact exchange, J. Chem. Phys. 98 (1993)
5648–5652. https://doi.org/10.1063/1.464913.
[28] C. Lee, W. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy formula into a functional
of the electron density, Phys. Rev. B 37 (1988) 785-789. https://doi.org/10.1103/PhysRevB.37.785.
[29]S. Yeganegi, A. Soltanabadi, D. Farmanzadeh, Molecular dynamic simulation of dicationic ionic liquids:
effects of anions and alkyl chain length on liquid structure and diffusion, J. Phys. Chem. B 116 (2012)
11517-11526. https://doi.org/10.1021/jp3059933.
[30]Yu.A. Ivanova, D.K. Ivanou, E.A. Streltsov, Electrodeposition of Te onto monocrystalline n- and p-Si(1 0 0)
wafers, Electrochim. Acta 52 (2007) 5213-5218. https://doi.org/10.1016/j.electacta.2007.02.032.
[31]G. Gunawardena, G. Hills, I. Montenegro, B. Scharifker, Electrochemical nucleation: Part I. General
considerations, Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 138 (1982) 225-239.
https://doi.org/10.1016/0022-0728(82)85080-8.
[32]E. Laviron, Adsorption, autoinhibition and autocatalysis in polaro-graphy and in linear potential sweep
voltammetry, Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 52 (1974) 355-393.
https://doi.org/10.1016/S0022-0728(74)80448-1.
[33]Shanghai Institute of Organic Chemistry of CAS, Chemistry Database[DB/OL]: Infrared spectrum database.
http://www.organchem.csdb.cn/scdb/irs/irs_pro_query.asp, 2019 (accessed 14 January 2019).
[34]Lingzhi Meng, Shuling Gong, Yongbing He, Infrared and Raman spectrum, in: Lingzhi Meng, Shuling Gong,
nd
Yongbing He (Eds.), Organic spectral analysis, 2 , Wuhan University Press, Wuhan, 2003, pp. 207-212.
[35]Y.N. Guo, D.L. He, S.B. Xia, X. Xie, X. Gao, Q. Zhang, Preparation of a novel nanocomposite of polyaniline
core decorated with anatase-TiO nanoparticles in ionic liquid/water microemulsion, Journal of Nanomaterials
2
2012 (2012) Article ID 202794, 7 pages. http://dx.doi.org/10.1155/2012/202794.
1
5

1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
[36]D.O. Ponkratov, E.I. Lozinskaya, P.S. Vlasov, P.H. Aubert, C. Plesse, F. Vidal, Y.S. Vygodskii, A.S. Shaplov,
Synthesis of novel families of conductive cationic poly(ionic liquid)s and their application in all-polymer
flexible
pseudo-supercapacitors,
Electrochimi.
Acta
281
(2018)
777-788.
https://doi.org/10.1016/j.electacta.2018.05.191.
[37]Lingzhi Meng, Shuling Gong, Yongbing He, Infrared and Raman spectrum, in: Lingzhi Meng, Shuling Gong,
nd
Yongbing He (Eds.), Organic spectral analysis, 2 , Wuhan University Press, Wuhan, 2003, pp. 230-232.
[38]X.Y. Mei, Z. Yue, Q. Ma, H. Dunya, B.K. Mandal, Synthesis and electrochemical properties of new dicationic
ionic liquids, J. Mol. Liq. 272 (2018) 1001-1018. https://doi.org/10.1016/j.molliq.2018.10.085.
[39]N.A. Abdul-Manaf, W.Y.W. Yusoff, S.Z.N. Demon, N.A. Shaari, A. Shamshuddin, N.S Mohamed, Anodic and
cathodic deposition of polyaniline films: a comparison between the two methods, Mater. Res. Express 6 (2019)
096453. https://doi.org/10.1088/2053-1591/ab0259.
1
1
1
1
1
1
1
1
1
[40]E. Laviron, General Expression of the Linear Potential Sweep Voltammogram in the Case of Diffusionless
Electrochemical Systems, Journal of Electroanalytical Chemistry and Interfacial Electrochemistry 101 (1979)
19-28. https://doi.org/10.1016/S0022-0728(79)80075-3.
[41]T.A. Enache, A.M. Oliveira-Brett, Phenol and para-substituted phenols electrochemical oxidation pathways, J.
Electroanal. Chem. 655 (2011) 9-16. https://doi.org/10.1016/j.jelechem.2011.02.022.
5
+
[42]D.L. He, S. Mho, Electrocatalytic reactions of phenolic compounds at ferric ion co-doped SnO :Sb
2
electrodes, J. E. C. 568 (2004) 19–27. https://doi.org/10.1016/j.jelechem.2003.12.030.
1
6

Highlights
ꢀ
Anilino groups was introduced into ionic liquid structure to prepare
poly-ionic liquid
ꢀ
ꢀ
The ploy-ionic liquid containing polyaniline-like units
The modified electrode suggested to give a high sensitivity in detection
phenol

Conflict of interest statement
We declare that we do not have any commercial or associative interest that
represents a conflict of interest in connection with the work submitted.
Signed by all authors as follows:
Guo Yanni: gyn0303@hnu.edu.cn
Deliang He: delianghe@163.com
Aomei Xie:1179769510@qq.com
Wei Qu: qw779470790@163.com
Tang Yining: yiningt@163.com
Shang Jun: JZSH79@163.com
Rilong Zhu: zrlden@hnu.edu.cn