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Title: Electrochemical detection of rutin on nitrogen-dopedgraphene modified carbon ionic liquid electrode
Author: Wei Sun Lifeng Dong Yongxi Lu Ying Deng JianhuaYu Xiaohuan Sun Qianqian Zhu
PII: S0925-4005(14)00356-6DOI: http://dx.doi.org/doi:10.1016/j.snb.2014.03.080Reference: SNB 16731
To appear in: Sensors and Actuators B
Received date: 15-10-2013Revised date: 12-3-2014Accepted date: 20-3-2014
Please cite this article as: W. Sun, L. Dong, Y. Lu, Y. Deng, J. Yu, X.Sun, Q. Zhu, Electrochemical detection of rutin on nitrogen-doped graphenemodified carbon ionic liquid electrode, Sensors and Actuators B: Chemical (2014),http://dx.doi.org/10.1016/j.snb.2014.03.080
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Electrochemical detection of rutin on nitrogen-doped graphene
modified carbon ionic liquid electrode Wei Sun1*, Lifeng Dong2, 3*, Yongxi Lu2, Ying Deng2, Jianhua Yu2, Xiaohuan Sun2, Qianqian Zhu2
1.College of Chemistry and Chemical Engineering, Hainan Normal University, Haikou
571158, P. R. China;
2.College of Materials Science and Engineering, Qingdao University of Science and
Technology, Qingdao 266042, P. R. China;
3.Department of Physics, Astronomy, and Materials Science, Missouri State University,
Springfield, MO 65897, USA
*Corresponding Authors: W. Sun Tel: +86-898-31381637, E-mail: [email protected]
and L. F. Dong. +86-532-84022869, E-mail: [email protected]
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Abstract: In this paper nitrogen-doped graphene (NG) was synthesized and applied to
modify an ionic liquid 1-hexylpyridinium hexafluorophosphate based carbon ionic liquid
electrode (CILE). The fabricated NG/CILE exhibited excellent electrochemical
performances. Electrochemical behaviors of rutin on NG/CILE were carefully investigated
with a pair of well-defined redox peaks appeared, which was attributed to the presence of
NG with electrocatalytic activity. Electrochemical parameters of rutin on NG/CILE were
calculated with the values of charge transfer coefficient (α), electron transfer number (n)
and electrode reaction standard rate constant (ks) as 0.57, 1.76 and 1.24 s-1, respectively.
Under the optimal conditions rutin could be detected in the concentration range from
7.0×10-10 to 1.0×10-5 mol/L with the detection limit as 0.23 nmol/L (3σ) by differential
pulse voltammetry. The proposed method was further applied to the determination of rutin
tablet samples with satisfactory results.
Keywords: nitrogen-doped graphene, rutin, carbon ionic liquid electrode, electrochemistry.
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1. Introduction
Graphene (GR) is a two-dimensional layer of carbon atoms with extended
honeycomb network, which is the basic building block of other carbon materials such as
fullerene, carbon nanotubes (CNT) and graphite [1]. Due to its unique structure, GR has
exhibited many excellent mechanical, thermal and electrical properties. So the applications
of GR and its related composite have been the research focuses in recent years. Because of
the excellent electrochemical properties of GR, it has been used in the fields of
electrochemistry and electrochemical sensors. Shao et al. reviewed the GR based
electrochemical sensors and biosensors [2]. Brownson et al. reported the electrochemistry
of GR from fundamental concepts through to prominent applications [3]. Chen et al. also
reviewed the electrochemistry of GR-based materials [4].
Chemical doping is a feasible method to tailor the properties of materials. By doping
a foreign atom into the molecular structure of host materials, specific characteristics could
be found. Due to the similar atomic size to that of carbon, nitrogen (N) and boron atoms
are the commonly used candidates for the doping of carbon nanomaterials. The chemical
doping in carbon can also enrich the free charge-carrier densities, and enhance the
electrical and/or thermal conductivities [5]. Tang et al. investigated the electrocatalytic
activity of N-doped CNT cups [6]. Gong et al. reported that N-doped CNT arrays
demonstrated high elctrocatalytic activity for the oxygen reduction reactions [7].
Carrero-Sanchez et al. investigated the biocompatibility and toxicological effects of
N-doped CNT [8]. Jia et al. also investigated the bioelectrochemistry and enzymatic
activity of glucose oxidase with a bamboo-shaped N-doped CNT [9]. In recent years
N-doped GR (NG) had also been studied due to its specific properties. Guo et al. reviewed
the recent progresses of GR doping and the various potential applications [10]. Wang et al.
also reviewed the recent progress of synthesis, characterization and its potential
applications in NG [11]. When nitrogen is doped into the GR, there are three commonly
present bonding configurations present, that are pyridinc N, pyrrolic N and graphitic N,
which can impart some specific properties as compared with the pristine GR [12]. NG can
be used in different fields of electrochemistry such as fuel cell, lithium ion batteries,
field-effect transistor, supercapacitors and electrochemical sensors. Wang et al. studied the
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application of NG in electrochemical biosensing [13]. Shao et al. applied NG for the
electrochemical energy devices and biosensors [14]. Sheng et al. fabricated a NG based
electrochemical sensor for the simultaneous determination of ascorbic acid, dopamine and
uric acid [15]. Lin et al. also prepared NG as a metal-free catalyst for the oxygen reduction
reaction [16]. Sun et al. also applied NG with high nitrogen level for superior capacitive
energy storage [17]. Therefore NG has great potential applications in the field of
electrochemistry and electrochemical sensors.
Rutin is a flavonoid compound with many functions such as anti-inflammatory,
anti-bacteria, anti-tumor and anti-oxidant [18-20], which can act as a scavenger of various
oxidizing species. Different analytical methods, such as capillary electrophoresis, HPLC,
spectrophotometry, flow injection analysis and electrochemical methods, have been
devised to detect rutin in various samples [21-23]. Due to the electroactivity of rutin,
electrochemical techniques have been used for the rutin detection with the advantages
such as higher sensitivity, wider linear range and less expensive instruments. By using
different kinds of modifier on the electrode, chemically modified electrodes have been
devised and used for the investigation on the electrochemistry of rutin. Yang et al. reported
selective determination of rutin by using gold nanoparticles/ethylenediamine/CNT
modified glassy carbon electrode (GCE) [24]. Wang et al. investigated the electrochemical
behaviors of rutin on ionic liquid (IL)/multi-walled CNT modified carbon paste electrode
(CPE), and further applied to the determination of rutin in tablets and urine samples
without the influence of coexisting substances [25]. Duan et al. applied a carbon-coated
nickel nanoparticles modified GCE (C-Ni/GCE) for the investigation on the
electrochemical properties of rutin and its interaction with bovine serum albumin via
voltammetry [26]. Our group also applied different kinds of chemically modified
electrodes such as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) modified
carbon ceramic electrodes (CCE) [27], single-walled CNT modified carbon ionic liquid
electrode (CILE) [28], or GR-MnO2 nanocomposite modified CILE for the
electrochemical detection of rutin [29]. By using different kinds of nanomaterials as the
modifiers, rutin can be detected with satisfactory results due to its electroactivity. As
compared with GR-MnO2 nanocomposite used for electrode modification, NG is another
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kind of functionalized GR with specific properties.
In this paper a NG modified CILE was fabricated and further used for sensitive
electrochemical detection of rutin. By using IL as the modifier in the traditional CPE,
CILE has exhibited many advantages including higher sensitivity, wider electrochemical
windows and excellent anti-fouling ability, which is resulted from the incorporation of
high ionic conductive IL [30-32]. Also a layer of IL film is present on the surface of CPE,
which can provide an active interface for the electrochemical reaction and further
modification. Shiddiky et al. reviewed the recent applications of CILE in the field of
electrochemical sensors, which could act as working electrode with excellent
performances [33]. Different kinds of modified CILE had been fabricated and used for the
electrochemical applications. Li et al. investigated the electrocatalytic properties of
hemoglobin on a mesoporous molecular sieve MCM-41 modified CILE [34]. Hu et al.
applied a gold nanoparticle and GR modified CILE for the electrochemical detection of
hydroquinone [35]. By using the NG synthesized with solvothermal method, NG modified
electrode was prepared with direct casting on the surface of CILE, which exhibited
excellent electrochemical performance. Rutin was further detected by NG/CILE with
improved sensitivity and wider linear range, and rutin tablet samples were also detected
with satisfactory results.
2. Experimental
2.1. Instruments and chemicals
All the voltammetric measurements including cyclic voltammetry (CV), differential
pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) were
executed on a CHI 750B electrochemical workstation (Shanghai CH Instrument, China). A
conventional three-electrode system was used with a NG/CILE as working electrode, a
platinum wire as auxiliary electrode and a saturated calomel electrode (SCE) as reference
electrode. Transmission electron microscopy (TEM) image was acquired by a JEM-2100
transmission electron microscopy (TEM, JEOL, Japan) at 200 kV acceleration potential.
Graphite powder (particle size 30 μm, Shanghai Colloid Chem. Co., China),
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1-hexylpyridinium hexafluorophosphate (HPPF6, Lanzhou Greenchem. ILS. LICP. CAS.,
China) and rutin (Sinopharm Chem. Reagent Ltd. Co., China) were used as received.
Rutin tablet samples (20 mg/tablet) were produced by Shanxi Yunpeng Pharmaceutical Co.
Ltd. (B080302) and Shanghai Zhaohui Pharmaceutical Co. Ltd. (090904), respectively.
2.2. Solvothermal synthesis of NG
Nitrogen-doped graphene was synthesized using a solvothermal method [36,37].
Briefly, lithium nitride (Li3N, 1.0 g) and tetrachloromethane (CCl4, 2.0 mL) were used as
nitrogen source/catalyst and carbon source, respectively. The reaction was conducted at
200 °C for 20 h. When the autoclave cooled down to room temperature after the reaction,
the product was transferred to a beaker (250 mL), and washed subsequently by 18 wt.%
HCl aqueous solution, de-ionized water, acetone, and de-ionized water, until the pH value
of the solution reached to 7. Then, the product was dried at 100 °C for 12 h to get the NG.
2.3. Fabrication of the modified electrode
Based on the reported procedure [38], CILE was fabricated with the following
procedure. 3.0 g of graphite powder and 1.0 g of HPPF6 were mixed in a mortar, ground
carefully and heated at 80 °C to get a homogeneous paste. A portion of the resulting paste
was filled into one end of a glass tube (Ф=4.2 mm) with a copper wire inserted at the other
end to act as the electrical contact. The surface of CILE was polished to a mirror-like
interface on a weighing paper just before use.
The modifier was prepared by dispersing 1.0 mg of NG into 1.0 mL of absolute
ethanol with ultrasonication for 2 h. Then 7.0 μL of 1.0 mg/mL NG solution was pipetted
onto the newly prepared CILE surface and dried at the room temperature to get the
modified electrode (NG/CILE).
2.4. Electrochemical procedure
CV and DPV were carried out in a three-electrode cell containing 0.1 mol/L PBS.
The sample solutions were prepared as follows. Two pieces of rutin tablets were carefully
ground in the agar, transferred to a 10 mL calibrated tube and diluted to the scale with
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ethanol. Then 100 μL sample solution was taken and diluted with pH 2.5 PBS in a 10 mL
calibrated tube and cyclic voltammogram was recorded in the potential range from 0.10 to
0.80 V. Differential pulse voltammograms were recorded in the potential range of 0.2 to
0.8 V with the instrumental parameters selected as: increment potential, 0.004 V; pulse
amplitude, 0.05 V; pulse width, 0.05 s; sample width, 0.017 s; pulse period, 0.2 s; quiet
time, 2 s.
3. Results and discussion
3.1. Characteristics of NG
NG was synthesized by a solvothermal method reported in our previous work [36],
and the typical TEM image was shown in Fig.1. The result demonstrated that NG sheets
were heavily folded with a dimension of circa 20 to 100 nm due to high surface energy.
The content and bonding status of nitrogen had been analyzed by X-ray diffraction (XPS)
with the amount of nitrogen dopant was determined to be 10.5%. Also three types of
bonding configurations of nitrogen atoms, that were pyridinic, pyrrolic, and quaternary
nitrogen existed within carbon structures. More information about the synthesis of NG by
this solvothermal process could be found in our recent reports and the detailed
explanations about the formation mechanism were discussed [36, 37].
Please, insert Fig. 1 here
3.2. Electrochemical behaviors of rutin
Electrochemical behaviors of rutin on different electrodes were investigated with the
cyclic voltammograms shown in Fig.2. No electrochemical responses appeared in buffer
solution (curve a) for NG/CILE, indicated that NG/CILE was stable in the selected
condition. As for 5.0×10-5 mol/L rutin solution, a pair of well-defined redox peaks
appeared on CILE (curve b) and NG/CILE (curve c), indicating that the electrochemical
reaction of rutin had took place. The electrochemical mechanism of rutin on the electrode
had been reported widely with a two-proton two-electron process [27]. On CILE (curve b)
the redox peak potentials were recorded as 0.547 V (Epa) and 0.453 V (Epc) with the
redox peak currents as 25.8 μA (Ipa) and 24.6 μA (Ipc). While on NG/CILE (curve c) the
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values of Epa and Epc were got as 0.551 V and 0.432 V, with the increase of Ipa and Ipc to
98.5 μA and 95.3 μA, respectively. The redox peak currents on NG/CILE was about 3.8
times higher than that of CILE (curve b), which could be attributed to the presence of NG
on the electrode surface. Due to the presence of different nitrogen functional groups
incorporated into GR, NG has proved to exhibit high electrocatalytic ability with big
surface area. Nitrogen doping also change the density of electronic state around the Fermi
level of GR. So the electrochemical response was enhanced on NG/CILE, which could be
a platform for sensitive rutin determination.
Please, insert Fig. 2 here
3.2. Influence of pH
The influence of pH on the cyclic voltammetric responses of 5.0×10-5 mol/L rutin
was investigated in the pH range from 1.5 to 6.0 with the voltammograms shown in
Fig.3A. It can be seen that a pair of well-defined redox peak appeared with the change of
the electrochemical responses at different pH value. The relationships between the formal
peak potential (E0') and the oxidation peak current (Ipa) with pH were further plotted. It
can be seen that the redox peak potentials shifted to the negative direction with the
increase of buffer pH, indicating that protons took part in the electrode reaction. The
relationship between E0' and pH was calculated as E0'(V) = -0.061 pH+0.64 (γ=0.995). The
slope value of -0.061 V/pH was close to theoretical value of -0.059 V/pH, indicating that
the ratio of electron and proton taking part in the electrode reaction was 1:1. The
maximum value of Ipa appeared at the pH value of 2.5 and then decreased gradually with
the further increase of buffer pH (Fig. 3B), indicating the participating of proton in the
electrode reaction. At the acidic buffer solution, more protons can be provided, which is
benefit for the electrochemical reaction of rutin. Therefore, pH 2.5 was selected as the
optimal pH for detection in the following experiments.
Please, insert Figure 3 here
3.3. Influence of scan rate
The influence of scan rate on the electrochemical response of 5.0×10-5 mol/L rutin on
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NG/CILE was recorded with the results shown in Fig. 4. The redox peak currents
increased gradually with the increase of scan rate in the range from 50 to 400 mV/s along
with the shift of the redox peak potentials (Fig. 4A), indicating a quasi-reversible process.
A good linear relationship between the redox peak current (Ip) and the square root of scan
rate (υ1/2) were plotted (Fig. 4B) with the linear regression equations as Ipa(μA)= −542.34
υ1/2(V/s)+62.84 (γ=0.998) and Ipc(μA)=562.82υ1/2(V/s) −77.53 (γ=0.999), which indicated
a diffusional controlled electrode process. The redox peak potential and lnυ also exhibited
a good linear relationship (Fig. 4C) with the linear regression equations as Epa(V)=
0.036lnυ−0.35 (γ=0.998) and Epc(V)=−0.028lnυ−0.62 (γ=0.993). According to the
Laviron’s equation [39], the values of charge transfer coefficient (α), electron transfer
number (n) and electrode reaction standard rate constant (ks) were calculated as 0.57, 1.76
and 1.24 s-1, respectively. So there are two electrons involved in the electrode reaction,
which was in agreement with the reference [27].
Please, insert Fig. 4 here
3.4. Chronocoulometric curve
Due to the diffusional controlled electrochemical reaction of rutin on NG/CILE, the
chronocoulometric response of rutin on NG/CILE was investigated to calculate the
diffusional coefficient (D). Fig. 5 showed the chronocoulometric curve of NG/CILE in the
buffer solution (curve a) and rutin solution (curve b). A good linear relationship between Q
and t1/2 was further plotted with the result shown in the inset of Fig. 5. The linear
regression equation was got as Q (μC) =199.85t1/2-43.5 (γ=0.999). According to Anson's
equation: Q=2nFAD1/2ct1/2/π1/2+Qdl+nFΓ, the D value of rutin was calculated as 1.72×10-5
cm2/s, which was close to the previous reported value of 2.0×10-5 cm2/s at a single-walled
CNT modified gold electrode [40]. So the electrochemical reaction was fast on NG/CILE
due to the presence of high conductive NG on the electrode surface, and the
electrochemical reaction was controlled by the diffusion process of rutin from solution to
the electrode surface.
Please, insert Fig. 5 here
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3.5. Analytical application
Because DPV has higher sensitivity and selectivity than CV, it is adopted for the
quantitative determination of rutin with the typical voltammograms shown in Fig. 6.
Under the optimal conditions the peak currents increased linearly with rutin concentrations
in the range from 7.0×10-10 to 5.0×10-8 mol/L and 7.0×10-8 to 1.0×10-5 mol/L (as shown in
Fig.6) with the linear regression equations as Ipa(μA)=6.17+424.98C (μmol/L) (γ=0.993)
and Ipa(μA)=36.44+12.07C (μmol/L) (γ=0.995), respectively. The detection limit was
calculated as 0.23 nmol/L (3σ), which was lower than some former reported values [27-29,
40]. The modified electrode exhibited good reproducibility and the relative standard
deviation (RSD) of 11 successive detections for 5.0×10-5 mol/L rutin was got as 2.0%. 5
modified electrodes were fabricated independently, which gave a satisfactory RSD value
of 2.4% for the detection of 5.0×10-5 mol/L rutin solution, indicating the good
repeatability of the electrode fabrication.
Please, insert Fig. 6 here
3.6. Sample analysis
The proposed method was further applied to determinate the rutin content in tablet
samples. A 100 μL samples solution was diluted with pH 2.5 PBS in a 10 mL calibrated
tube for the detection with the proposed procedures. The results were shown in Table 1
and the recovery was calculated by the standard addition method to evaluate the accuracy
of the method. It can be seen that the results were satisfactory with the recovery in the
range of 99.8±0.19~101.3±0.32%, showing that the proposed electrode could be
efficiently applied to detection of rutin in commercial pharmaceutical samples.
Please, insert Table 1 here
4. Conclusion
By using NG as the modifier and CILE as the substrate electrode, NG/CILE was
fabricated and further used for the sensitive detection of rutin. NG is a functionalized GR
with nitrogen atom doped in the GR, which exhibits the electrocatalytic ability with the
remain of some properties of GR, such as large surface area and high conductivity. Rutin
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can be electrochemically detected on NG/CILE in the concentration range from 7.0×10-10
to 1.0×10-5 mol/L with the detection limit of 0.23 nmol/L (3σ). The comparison of the
analytical parameters of this method with other reported values for rutin determination
was summarized in Table 2. It can be seen that a broader linear range and a lower
detection limit for rutin detection could be achieved on NG/CILE. So the NG modified
CILE can be used as a sensitive platform for the electrochemical detection of rutin.
Table 2
Acknowledgements
This work was supported by the National Natural Science Foundation of China
(51172113, 21365010), the Shandong Natural Science Foundation for Distinguished
Young Scholars (JQ201118), the Taishan Scholar Overseas Distinguished Professorship
program from Shandong Province Government, PR China, and the Qingdao Municipal
Science and Technology Commission (12-1-4-136-hz).
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References
[1] A.K. Geim, A.K., Novoselov, K.S., The rise of graphene, Nat. Mater. 6 (2007)
183-191.
[2] Y.Y. Shao, J. Wang, H. Wu, J. Liu, I.A. Aksay, Y.H. Lin, Graphene based
electrochemical sensors and biosensors: a review, Electroanalysis 22 (2010) 1027-1036.
[3] D.A.C. Brownson, D.K. Kampouris, C.E. Banks, Graphene electrochemistry:
fundamental concepts through to prominent applications, Chem. Soc. Rev. 41 (2012)
6944-6976.
[4] D. Chen, L.H. Tang, J.H. Li, Graphene-based materials in electrochemistry. Chem. Soc.
Rev. 39 (2010) 3157-3180.
[5] Y.C. Ma, A.S. Foster, A.V. Krasheninnikov, R.M. Nieminen, Nitrogen in graphite and
carbon nanotubes: magnetism and mobility, Phys. Rev. B 72 (2005) 205416-205421.
[6] Y. F. Tang, L. A. Brett, R. K. Douglas, S. Alexander, Electrocatalytic activity of
nitrogen-doped carbon nanotube cups. J. Am. Chem. Soc. 131 (2009) 13200-13201.
[7] K. P. Gong, F. Du, Z. H. Xia, M. Durstock, L. M. Dai, Nitrogen-doped carbon
nanotube arrays with high electrocatalytic activity for oxygen reduction, Science 323
(2009) 760-764.
[8] J.C. Carrero-Sánchez, A.L. Elías, R. Mancilla, G. Arrellín, H. Terrones, J.P. Laclette, M.
Terrones, Biocompatibility and toxicological studies of carbon nanotubes doped with
nitrogen, Nano. Lett. 6 (2006) 1609-1616.
[9] N.Q. Jia, L. Liu, Q. Zhou, L.J. Wang, M.M. Yan, Z.Y. Jiang, Bioelectrochemistry and
enzymatic activity of glucose oxidase immobilized onto the bamboo-shaped
CNx nanotubes, Electrochim. Acta 51 (2005) 611-618.
[10] B.D. Guo, L. Fang, B.H. Zhang, J.R. Gong, Graphene doping: a review, Insciences J.
1 (2011) 80-89.
[11] H.B. Wang, T. Maiyalagan, X. Wang, Review on recent progress in nitrogen-doped
graphene: synthesis, characterization, and its potential applications, ACS Catal. 2 (2012)
781-794.
[12] P.H. Matter, L. Zhang, U.S. Ozkan, The role of nanostructure in nitrogen-containing
carbon catalysts for the oxygen reduction reaction, J. Catal. 239 (2006) 83-96.
Page 13 of 26
Accep
ted
Man
uscr
ipt
13
[13] Y. Wang, Y.Y. Shao, D.W. Matson, J.H. Li, Y.H. Lin, Nitrogen-doped graphene and its
application in electrochemical biosensing, ACS Nano. 4 (2010) 1790-1798.
[14] Y.Y. Shao, S. Zhang, M.H. Engelhard, G.S. Li, G.C. Shao, Y. Wang, J. Liu, I.A. Aksay,
Y.H. Lin, Nitrogen-doped graphene and its electrochemical applications, J. Mater. Chem.
20 (2010) 7491-7496.
[15] Z.H. Sheng, X.Q. Zheng, J.Y. Xu, W.J. Bao, F.B. Wang, X.H. Xia, Electrochemical
sensor based on nitrogen doped graphene: simultaneous determination of ascorbic acid,
dopamine and uric acid, Biosens. Bioelectron. 34 (2012) 125-131.
[16] Z.Y. Lin, M. Song, Y. Ding, Y. Liu, M.L. Liu, C.P. Wang, Facile preparation of
nitrogen-doped graphene as a metal-free catalyst for oxygen reduction reaction, Phys.
Chem. Chem. Phys. 14 (2012) 3381-3387.
[17] L. Sun, L. Wang, C.G. Tian, T.X. Tan, Y. Xie, K.Y. Shi, M.T. Li, H.G. Fu,
Nitrogen-doped graphene with high nitrogen level via a one-step hydrothermal reaction of
graphene oxide with urea for superior capacitive energy storage, RSC Adv. 2 (2012)
4498-4506.
[18] R.M. Gené, C. Cartañá, T. Adzet, E. Marín, T. Parella, S. Cañigueral,
Anti-inflammatory and analgesic activity of baccharis trimera: identification of its active
constituents, Planta Med. 62 (1996) 232-235.
[19] S.Y. Park, S.H. Bok, S.M. Jeon, Y.B. Park, S.J. Lee, T.S. Jeong, Effect of rutin and
tannic acid supplements on cholesterol metabolism in rats. Nutr. Res. 22 (2002) 283-295.
[20] R. Guo, P. Wei, Studies on the antioxidant effect of rutin in the microenvironment of
cationic micelles, Microchim. Acta 161 (2008) 233-239.
[21] H. Wu, M. Chen, Y. Fan, F. Elsebaei, Y. Zhu, Determination of rutin and quercetin in
Chinese herbal medicine by ionic liquid-based pressurized liquid extraction-liquid
chromatography-chemiluminescence detection, Talanta 88 (2012) 222-229.
[22] Z. Legnerová, D. Šatíský, P. Solich, Using on-line solid phase extraction for
simultaneous determination of ascorbic acid and rutin trihydrate by sequential injection
analysis, Anal. Chim. Acta 497 (2003) 165-174.
[23] H. Xu, Y. Li, H.W. Tang, C.M. Liu, Q.S. Wu, Determination of rutin with UV-Vis
Page 14 of 26
Accep
ted
Man
uscr
ipt
14
spectrophotometric and laser-induced fluorimetric detections using a non-scanning
spectrometer, Anal. Lett. 43 (2010) 893-904.
[24] S.L. Yang, L.B. Qu, G. Li, R. Yang, C.C. Liu, Gold nanoparticles/ethylenediamine/
carbon nanotube modified glassy carbon electrode as the voltammetric sensor for selective
determination of rutin in the presence of ascorbic acid, J. Electroanal. Chem. 645 (2010)
115-122.
[25] X.L. Wang, C.C. Cheng, R.R. Dong, J.C. Hao, Sensitive voltammetric determination
of rutin at a carbon nanotubes–ionic liquid composite electrode, J. Solid State Electrochem.
16 (2012) 2815-2821.
[26] L.S. Duan, L.J. Yang, H.Y. Xiong, X.H. Zhang, S.F. Wang, Studies on the
electrochemistry of rutin and its interaction with bovine serum albumin using a glassy
carbon electrode modified with carbon-coated nickel nanoparticles, Microchim. Acta 180
(2013) 355-361.
[27] T.R. Zhan, X.Y. Sun, X.Z. Wang, W.G. Hou, W. Sun, Application of ionic liquid
modified carbon ceramic electrode for the sensitive voltammetric detection of rutin,
Talanta 82 (2010) 1853-1857.
[28] Z.H. Zhu, X.Y. Sun, X.M. Zhuang, Y. Zeng, X.T. Huang, W. Sun, Single-walled
carbon nanotubes modified carbon ionic liquid electrode for sensitive electro-chemical
detection of rutin, Thin Solid Films 519 (2010) 928-933.
[29] W. Sun, X.Z. Wang, H.H. Zhu, X.H. Sun, F. Shi, G.N. Li, Z.F. Sun, Graphene-MnO2
nanocomposite modified carbon ionic liquid electrode for the sensitive electrochemical
detection of rutin, Sens. Actuators B Chem. 178 (2013) 443-449.
[30] H.T. Liu, P. He, Z.Y. Li, C.Y. Sun, L.H. Shi, Y. Liu, G.Y. Zhu, J.H. Li, An ionic
liquid-type carbon paste electrode and its polyoxometalate-modified properties,
Electrochem. Commun. 7 (2005) 1357-1363.
[31] N. Maleki, A. Safavi, F. Sedaghati, F. Tajabadi, Efficient electrocatalysis of L-cysteine
oxidation at carbon ionic liquid electrode, Anal. Biochem. 369 (2007) 149-153.
[32] M. Musameh, J. Wang, Sensitive and stable amperometric measurements at ionic
liquid–carbon paste microelectrodes, Anal. Chim. Acta 606 (2008) 45-49.
Page 15 of 26
Accep
ted
Man
uscr
ipt
15
[33] M.J.A. Shiddiky, A.A.J. Torriero, Application of ionic liquids in electrochemical
sensing systems, Biosens. Bioelectron. 26 (2011) 1775-1787.
[34] Y. Li, X. Zenga, X. Liua, X. Liub, W. Weia, S. Luoa, Direct electrochemistry and
electrocatalytic properties of hemoglobin immobilized on a carbon ionic liquid electrode
modified with mesoporous molecular sieve MCM-41, Colloids Surf. B Biointerfaces 79
(2010) 241-245.
[35] S. Hu, Y.H. Wang, X.Z. Wang, L. Xu, J. Xiang, W. Sun, Electrochemical detection of
hydroquinone with a gold nanoparticle and graphene modified carbon ionic liquid
electrode, Sens. Actutaors B Chem.168 (2012) 27-33.
[36] Q.Q. Zhu, J.H. Yu, W.S. Zhang, H.Z. Dong, L.F. Dong, Solvothermal synthesis of
boron-doped graphene and nitrogen-doped graphene and their electrical properties, J.
Renewable Sustainable Energy 5 (2013) 021408.
[37] L.L. Xu, J.H. Yu, Q.Q. Zhu, X.X. Wang, L.F. Dong, Graphene and N-doped
graphene coated with SnO2 nanoparticles as supercapacitor electrodes, ECS Transactions
53(2013) 1-8.
[38] W. Sun, P. Qin, R.J. Zhao, K. Jiao, Direct electrochemistry and electrocatalys is of
hemoglobin on gold nanoparticle decorated carbon ionic liquid electrode, Talanta 80(2010)
2177-2181.
[39] E. Laviron, General expression of the linear potential sweep voltammogram in the
case of diffusionless electrochemical systems, J. Electroanal. Chem. 101 (1979) 19-28.
[40] B. Z. Zeng, S.H. Wei, F. Xiao, F.Q. Zhao, Voltammetric behavior and determination
of rutin at a single-walled carbon nanotubes modified gold electrode, Sens. Actuators B
Chem. 115 (2006) 240-246.
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Biographies
Wei Sun is a professor in College of Chemistry and Chemical Engineering, Hainan
Normal University. He received his PhD in analytical chemistry from Ocean University of
China in 2002. His current interests are bioelectroanalysis and biosensors.
Lifeng Dong is a professor in College of Materials Science and Engineering, Qingdao
University of Science and Technology. His current interests are material chemistry.
Yongxi Lu is a master candidate in Qingdao University of Science and Technology. She
majors in chemical modified electrode.
Ying Deng is a master candidate in Qingdao University of Science and Technology. She
majors in graphene modified electrode.
Jianhua Yu is a lecturer in College of Materials Science and Engineering, Qingdao
University of Science and Technology. She majors in material chemistry.
Xiaohuan Sun is a master candidate in Qingdao University of Science and Technology.
She majors in nanomaterials modified electrode.
Qianqian Zhu is a master candidate in Qingdao University of Science and Technology.
She majors in nanomaterials.
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Figure Captions:
Fig.1 TEM image of the synthesized NG sheets.
Fig.2 Cyclic voltammograms of (a) NG/CILE in the buffer solution, (b) CILE and (c)
NG/CILE in pH 2.5 PBS containing 5.0×10-5 mol/L rutin. Scan rate: 100 mV/s.
Fig.3 (A) Cyclic voltammograms of 5.0×10-5 mol/L rutin on NG/CILE with different pH
PBS (from a to g are 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, respectively), scan rate: 100 mV/s; (B)
The relationship between the oxidation peak current (Ipa) and pH; (C) The relationship
between the formal peak potential (E0') and pH.
Fig.4 (A) Cyclic voltammograms of 5.0×10-5 mol/L rutin on NG/CILE with different scan
rate (υ) in pH 2.5 PBS (from a to n are 30, 50, 70, 90, 120, 160, 200, 240, 280, 320, 360,
400, 450, 500 mV/s, respectively); (B) Linear relationship of cathodic and anodic peak
current (Ip) versus υ1/2; (C) Linear relationship between the redox peak potentials (Ep) and
lnυ.
Fig.5 Chronocoulometric curves of NG/CILE in (a) pH 2.5 PBS, (b) pH 2.5 PBS
containing 5.0×10-5 mol/L rutin. Insert is the linear relationship of Q and t1/2.
Fig.6 (A) Differential pulse voltammograms of rutin on NG/CILE at the lower
concentration range from a to h as 0.0007, 0.001, 0.003, 0.005, 0.07, 0.01, 0.03, 0.05
μmol/L and (B) the relationship of the cathodic peak current with the rutin concentration at
lower range; (C) Differential pulse voltammograms of rutin on NG/CILE at the high
concentration range from a to j as 0.07, 0.1, 0.3, 0.5, 0.7, 1.0, 3.0, 5.0, 7.0, 10.0 μmol/L
and (D) the relationship of the cathodic peak current with the rutin concentration at higher
range.
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Table captions:
Table 1 Determination results of rutin in compound tablet samples (n=6)
Table 2 Comparison of the analytical parameters for rutin detection by different methods
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Fig.1
20 nm
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Fig.2
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Fig.3
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Fig.4
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Fig.5
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Fig.6
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Table 1
Sample Specified
(μmol/L)
Detected
(μmol/L)
Added
(μmol/L)
Total
(μmol/L)
RSD
(%)
Recovery
(%)
B080302 60.2 59.8 30.0 89.6 1.12 99.8±0.19
090904 60.2 60.9 30.0 92.1 2.03 101.3±0.32
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Table 2
Methods Linear range
(μmol/L)
LOD
(μmol/L) Samples Refs
HPLC-Chemiluminescence detection 0.16-8.19 0.018 Chinese herbal medicine [21]
Sequential injection analysis 3.28-32.80 2.46 pharmaceutical formulation [22]
UV-Vis spectrophotometry 4.09-36.85 0.12 pharmaceutical formulation [23]
Gold nanoparticle/ethylenediamine/CNT/GCE 0.48~0.96 0.032 tablet [24]
IL/multi-walled CNT/CPE 0.03~1.5 0.01 tablets and urine [25]
C-Ni/GCE 0.002~1.7 0.0006 / [26]
EMIMBF4 modified CCE 0.3~100.0 0.09 tablets [27]
Single-walled CNT/CILE 0.1~800.0 0.07 tablets [28]
GR-MnO2/CILE 0.01~500.0 0.0027 tables [29]
Single-walled CNT/Au electrode 0.02~5.0 0.01 drug and flos sophorae buds [40]
NG/CILE 0.0007~10.0 0.00023 tablets This work
