A novel ionic liquid functionalized graphene oxide supported gold nanoparticle composite film for sensitive electrochemical detection of dopamine

Article abstract of DOI:10.1039/c6ra25627a

A simple and sensitive electrochemical sensor for detection of dopamine has been developed based on ionic liquid functionalized graphene oxide supported gold nanoparticles (GO-IL-AuNPs) coated onto a glassy carbon electrode. The prepared graphene oxide, ionic liquid functionalized graphene oxide and GO-IL-AuNPs were characterized in detail by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The electrochemical properties of the hybrid nanomaterials were evaluated through cyclic voltammetry and electrochemical impedance spectroscopy. Meanwhile, the activities of hybrid nanomaterials toward the oxidation of dopamine were analyzed via cyclic voltammetry and differential pulse voltammetry. The resulting sensor showed excellent electrocatalytic activity towards dopamine. Under the optimum conditions, differential pulse voltammetry was employed to detect ultra-trace amounts of dopamine, for which a wide linear range of 7 nM to 5 μM and a limit of detection 2.3 nM (S/N = 3) were obtained. The proposed sensor exhibited excellent accuracy and precision and the relative standard deviation (RSD) was less than 5%. The highly sensitive sensor was successfully used for accurate determination of the content of dopamine in practical samples.

Full text of DOI:10.1039/c6ra25627a

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A novel ionic liquid functionalized graphene oxide
supported gold nanoparticle composite film for
sensitive electrochemical detection of dopamine
Cite this: RSC Adv., 2017, 7, 2315
Jianbo Li, Yanhui Wang, Yuanling Sun, Chaofan Ding, Yanna Lin, Weiyan Sun
and Chuannan Luo*
A simple and sensitive electrochemical sensor for detection of dopamine has been developed based on
ionic liquid functionalized graphene oxide supported gold nanoparticles (GO-IL-AuNPs) coated onto
a glassy carbon electrode. The prepared graphene oxide, ionic liquid functionalized graphene oxide and
GO-IL-AuNPs were characterized in detail by scanning electron microscopy, X-ray diffraction and
Fourier transform infrared spectroscopy. The electrochemical properties of the hybrid nanomaterials
were evaluated through cyclic voltammetry and electrochemical impedance spectroscopy. Meanwhile,
the activities of hybrid nanomaterials toward the oxidation of dopamine were analyzed via cyclic
voltammetry and differential pulse voltammetry. The resulting sensor showed excellent electrocatalytic
activity towards dopamine. Under the optimum conditions, differential pulse voltammetry was employed
to detect ultra-trace amounts of dopamine, for which a wide linear range of 7 nM to 5 mM and a limit of
detection 2.3 nM (S/N ¼ 3) were obtained. The proposed sensor exhibited excellent accuracy and
precision and the relative standard deviation (RSD) was less than 5%. The highly sensitive sensor was
successfully used for accurate determination of the content of dopamine in practical samples.
Received 21st October 2016
Accepted 14th December 2016
DOI: 10.1039/c6ra25627a
www.rsc.org/advances
lower cost of the electrochemical instrument combined with
fast detection, simplicity, facile operation and impressive cost-
1
. Introduction
Dopamine (DA) is a catecholamine neurotransmitter secreted effectiveness. With the development of novel functional mate-
by the brain that plays a critical role in maintaining the func- rials, chemically modied electrodes are now widely used for
tional activities of many organs, such as the heart, brain and the detection of dopamine in order to achieve lower detection
1–3
15,16
kidney.
Dopamine can directly affect human emotions, limits and improve analytical sensitivity and selectivity.
learning and memory ability. Meanwhile, as a very important
Graphene oxide (GO) as a single-atom-thick and two-
neurotransmitter, it mainly exists in the body uid and brain dimensional carbon material has attracted remarkable
cells. Research indicates that abnormal levels of dopamine are interest in electrochemical analysis since it was rst success-
1
7–19
linked to some ailments, such as Alzheimer's disease, depres- fully manufactured in 2004.
Graphene oxide is widely used
sion, Parkinson's disease, hyperactivity disorder and schizo- in the sensing eld for its excellent properties, such as huge
4–7
phrenia. Hence, the rapid and accurate measurement of the surface area, unique structures and good chemical stability.
content of DA is a signicant research area in clinical practice. GO is a layered exible material with a wealth of functional
So far, many analytical approaches have been developed for groups, such as hydroxyl (OH), epoxy (C–O–C), and carboxyl
detection of DA, including high performance liquid chroma- (COOH) groups, on both the edges and basal planes. It can be
8
9
10
tography, uorescence, chemiluminescence,
mass-spec- easily functionalized to form GO-based materials. Guo et al.
and surface plasmon reported a high performance dopamine electrochemical
11
12,13
trometry, capillary-electrophoresis,
14
resonance. However, the above-mentioned analytical methods sensor based on graphene oxide and Ag hybrid matrix elec-
are costly and time consuming, require complicated pretreat- trodeposition L-lysine lms, which was used to sensitively
2
0
ment, consume large quantities of chemical agents and produce determine DA in the presence of ascorbic acid. Ghoreishi
environmental pollution. Compared with the above methods, et al. fabricated a graphene oxide nano-sheet modied carbon
electrochemical techniques for detecting DA have attracted paste electrode for the determination of dopamine in the
2
1
considerable attention because of the major advantage of the presence of tyrosine. Thirumalraj et al. report the prepara-
tion of highly stable fullerene C60 decorated graphene oxide
nanocomposite and its sensitive electrochemical detection of
dopamine in rat brain and pharmaceutical samples. GO-
based materials modied electrodes are used for detection of
Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong (University
2
2
of Jinan), School of Chemistry and Chemical Engineering, University of Jinan, Jinan
50022, China. E-mail: chm_y518@163.com; Tel: +86 531 89736065
2
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DA because of three major reasons: biocompatibility, rapid
electron transfer and low cost.
2
. Experimental
2.1. Reagents and apparatus
Ionic liquids (IL) are composed of large organic cations, such
as pyridinium, phosphonium or imidazolium, and a relatively Dopamine, epinephrine, serotonin, ascorbic acid, uric acid,
ꢀ
ꢀ
small anion, such Cl , Br , or larger complexes like tetra- chloroauric acid and 1-butyl-3-methyl imidazole hydrobromide
uoroborate or hexauorophosphate. Ionic liquids have some were purchased from Aladdin Industrial Corporation
unique properties, such as high electric conductivity, low vola- (Shanghai, China). Graphite powder, H SO , HNO , KCl,

2
4
3
tility and low toxicity. IL as a promising material have attracted KMnO and ethanol were purchased from Sinopharm Group
4
great interest in the last few years. They have been widely used Chemical Reagent Co. without further purication. The 0.1 M
as electrode modiers for constructed sensors, because of their phosphate buffer solution (PBS) was prepared from Na HPO4
2
viscosity, high conductivity and fairly wide electrochemical and NaH PO . Chemicals used in the experiment were of
2
4
23–24
window.
The excellent electrochemical conductivity of ILs analytical grade and all solutions were prepared with doubly
could lead to more sensitive electrochemical responses, espe- distilled deionized water. Dopamine hydrochloride injection
cially for the detection of trace components. Furthermore, ILs samples were purchased from the local hospital. The urine
can be uniformly dispersed in graphene oxide owing to their samples were collected from volunteers, and they were
good solvation properties.
informed and agreed to follow the experiment.
In recent years, GO-based materials graed onto noble
All electrochemical measurements were performed on a CHI
metal nanoparticles have attracted considerable interest 660D electrochemistry workstation (Beijing Huake Putian
owing to their exible structure, excellent catalytic capabilities Technology Co., Ltd. China). The classical three-electrode
2
5
and excellent electron transport properties. Recently, gold system was adopted. An Ag/AgCl (saturated KCl) electrode and
nanoparticles have been considered as an attractive candidate a platinum electrode were used as the reference and counter
because of their huge specic surface area, excellent biocom- electrodes, respectively. A bare or modied glassy carbon elec-
patibility, good chemical stability and outstanding conduc- trode (GCE) was used as the working electrode. Nanophase
tivity and catalytic properties. The unique two-dimensional materials were characterized by scanning electron microscopy
crystal structure of GO acts as the substrate support for gold (S-2500, Hitachi High-tech International Trading Co., Ltd,
nanoparticles, which was attributed to the high electro- Shanghai, China), X-ray diffraction (XRD, Focus D8 Bruker AXS
catalytic activities and extraordinary electronic transport Co. Ltd., Germany) and Fourier transform infrared spectroscopy
properties. Meanwhile, composite materials prepared by gold (FTIR, Nicolet NEXUS-470, Thermo Nicolet, USA). Electro-
nanoparticles dotted on graphene oxide as an enhanced chemical impedance spectroscopy (EIS) was performed on
sensing material have unparalleled electrochemical a CHI 604D Electrochemical Workstation (Shanghai CH
performance.
Instruments Inc., China). All the electrochemical experiments
Herein, nanocomposites composed of gold nanoparticles were carried out at room temperature.
anchored to ionic liquid functionalized graphene oxide were
achieved by a simple one pot reaction. Ionic liquid as a linker
attached gold nanoparticles and graphene oxide through elec-
trostatic forces. Combining the advantageous features of gold
nanoparticles and ionic liquid functionalized graphene oxide,
the nanocomposites could incur synergy on electrochemical
properties and thus improve the sensitivity of the nano-
materials. The prepared nanomaterials-modied glassy carbon
electrode exhibited remarkable electrochemical catalytic activ-
ities towards dopamine. With a huge specic surface area and
a large quantity of oxygen groups, GO shows good adsorption of
dopamine. These oxidized areas on the GO plane break the
long-range conjugated network and p-electron cloud, leading to
a degradation of carrier mobility and conductivity. Ionic liquid
functionalized graphene oxide could effectively prevent the
agglomeration of graphene oxide, and the conductivity of the
electrode could be enhanced and AuNPs have excellent load
effects. The introduction of AuNPs brings not only electro-
chemical activity but also a certain biocompatibility. Mean-
while, AuNPs can effectively catalyze the electrochemical
reaction of dopamine on the electrode surface. The electro-
chemical performance of the as-prepared sensor toward the
2
.2. Synthesis of GO-IL-AuNPs
The graphene oxide was synthesized from graphite power
according to the modied Hummers' method.
dispersed in ultrapure water to get a stock solution of 1.0 mg
mL . 10 mg of 1-butyl-3-methyl imidazole hydrobromide was
mixed with 10 mL of the GO dispersion. A GO-IL hybrid solution
was obtained.
2
6,27
The GO was
ꢀ1
The gold nanoparticles were prepared using the method of
28
sodium citrate reduction of chloroauric acid. 3.65 mL of
chloroauric acid solution (0.01 M) was diluted into 150 mL and
heated to micro-boiling. Then, 3.0 mL of sodium citrate was
quickly added whilst heating and stirring. When the solution
turned wine red, heating was stopped but stirring was
continued until the solution was cooled to room temperature.
ꢁ
The gold nanoparticles were stored in a refrigerator at 4 C. 10
mL of gold nanoparticles was added into 20 mL of GO-IL hybrid
solution, and ultrasonic treatment for 30 min produced the GO-
IL-AuNPs composite.
2.3. Preparation of the modied electrodes
oxidation of dopamine was explored in detail. The results Prior to the modication, the glassy carbon electrode (GCE) was
indicated that the proposed sensor could achieve simple and polished with 0.3 and 0.05 mm alumina slurries sequentially.
efficient detection of dopamine.
Subsequently, the electrode was washed thoroughly with
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Scheme 1 Schematic illustration of the electrochemical sensors for
the determination of DA.
Fig. 1 The SEM images of (a) GO, (b) GO-IL, (c) AuNPs, (d) GO-IL-
AuNPs.
ultrapure water and dried at room temperature. 5 mL of the as-
prepared GO-IL-AuNPs composite suspension was modied to
the surface of the polished GCE and the GO-IL-AuNPs nanolms
modied GCE (GO-IL-AuNPs/GCE) was thus obtained. The
schematic illustration is shown in Scheme 1. As a control, GO
modied GCE (GO/GCE) and GO-IL modied GCE (GO-IL/GCE)
were also prepared.
exhibit typical 1-butyl-3-methyl imidazole hydrobromide
absorption features of N–H stretching vibration (3120 cm ),
symmetric methylene stretching vibrations (2870 cm
ꢀ
1
ꢀ
1
and
ꢀ
1
ꢀ1
2960 cm ), C–N stretching vibration (1630 cm ), imidazole
ꢀ
1
ring skeletal vibration (1570 cm ), imidazole ring deformation
ꢀ
1
(
1060 cm ), and C–H out-of plane bending vibration (835
ꢀ
1
ꢀ1
ꢀ1 32,33
3. Results and discussion
cm , 735 cm and 620 cm ).
The results indicate that GO
has been combined with the ionic liquid.
3.1. Characterization of the nanocomposites
The surface topography of (a) GO, (b) GO-IL, (c) AuNPs and (d)
GO-IL-AuNPs nanocomposites was investigated by SEM
3.2. Electrochemical studies
measurement, and the SEM images are shown in Fig. 1. It is Electrochemical impedance spectroscopy (EIS) is a powerful
clear from Fig. 1a that the prepared graphene oxide displayed and effective method to monitor the interfacial properties of
a typical crumpled and wrinkled lamellar structure. Fig. 1b different modied electrodes. In the electrochemical imped-
presents an SEM image of GO-IL, which indicates that the ance spectra, the semicircle part at high frequencies refers to
surfaces of the GO sheets were uniformly coated with IL. Fig. 1c the electron transfer controlled process and the linear part at
shows the SEM image of AuNPs, which show a particle diameter low frequencies represents the diffusion controlled process.
in the range of 12–18 nm. The representative SEM image of GO- The semicircle diameter of the Nyquist plots is equal to the
IL-AuNPs is also shown in Fig. 1d, clearly illustrating that the electron transfer resistance (Ret), which controls the electron
uniform particle size gold nanoparticles are evenly decorated on transfer kinetics of the redox reaction at the electrode
3
4,35
the surface of the GO-IL, which suggests that GO-IL-AuNPs have surface.
been successfully synthesized. calculated through the semicircle diameter. The electro-
The XRD patterns of (a) GO, (b) GO-IL, (c) GO-IL-AuNPs are chemical impedance of the bare GCE, GO/GCE, GO-IL/GCE and
The electron transfer resistance can be directly
3
ꢀ/4ꢀ
given in Fig. 2A. It is obvious that graphene oxide displays GO-IL-AuNPs/GCE was determined in 0.2 mM [Fe(CN)
a strong spectral peak at 10.3 corresponding to the (0 0 2) solution containing 0.1 M KCl over the impedance frequency
6
]
ꢁ
29
5
diffraction crystalline plane. The XRD patterns of GO-IL are range from 1.0 ꢂ 10 to 0.1 Hz. The Nyquist spectra are shown
ꢁ
shown in Fig. 2Ab, and many diffraction peaks between 20 and in Fig. 3A. It was easy to get the Ret of the bare GCE, GO/GCE,
ꢁ
30
3
0 were attributed to the ionic liquid crystal structure and GO-IL/GCE and GO-IL-AuNPs/GCE, which were about 278 U,
proven successful synthesis of GO-IL. The XRD pattern of the 1032 U, 117 U and 37 U, respectively. At the same time, the R of
et
GO-IL-AuNPs composite shows the major diffraction peaks of 2q these electrodes were in the following order: GCE > GO/GCE >
ꢁ
ꢁ
ꢁ
at 38.4 , 44.2 and 65.3 , which corresponded to the (1 1 1), (2 GO-IL/GCE > GO-IL-AuNPs/GCE. This indicates that the resis-
0) and (2 2 0) planes of AuNPs and proved that AuNPs were tance of electron transfer is effectively reduced owing to the
successfully loaded on the surface of GO-IL. introduction of IL and gold nanoparticles with excellent elec-
0
To further investigate the formation of GO and GO-IL, FT-IR tron transfer properties. The GO-IL-AuNPs/GCE has good
spectra were obtained. The FT-IR spectrum of GO is shown in electro-catalytic performance for oxidation of DA.
Fig. 2Ba; the characteristic absorption bands at about 3400,
The electrochemical behaviors of DA at different modied
720, 1640, 1400 and 1100 cm correspond to the stretching electrodes were investigated using cyclic voltammetry. Fig. 3B
vibrations of hydroxyl groups, carboxyl groups, alkene, carbon shows the CVs of the bare (a), GO (b), GO-IL (c) and GO-IL-
ꢀ
1
1
31
skeleton and epoxy, respectively. The spectrums of GO-IL AuNPs (d) modied electrodes in 0.1 M PBS (pH 7.0)
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Fig. 2 (A) The XRD patterns of (a) GO, (b) GO-IL and (c) GO-IL-AuNPs. (B) The FT-IR spectra of (a) GO and (b) GO-IL.
ꢀ
1
containing 1 mM DA at a scan rate of 100 mV s . As can be seen may have better adsorption capacity for dopamine. Further-
from Fig. 3Ba, the bare GCE shows an obvious electrochemical more, the gold nanoparticles have better catalytic performance
oxidation peak for DA. Compared with the bare electrode, the for dopamine.
DA electrochemical response signal intensity at the different
modied electrodes was increased, which indicated that the
3.3. Optimization of the experimental conditions
modied materials have excellent electrical conductivity and
electro-catalytic activity for DA oxidation. It is worth noting that
a signicant enhancement response signal was observed at the
GO-IL-AuNPs/GCE (Fig. 3Bd), proving that the GO-IL-AuNPs
nanocomposite has excellent electrical conductivity and
electro-catalytic properties for oxidation of DA. Furthermore,
the CVs responses of DA at the different electrodes were inves-
tigated in the presence of ascorbic acid. As shown in Fig. 3C, the
CVs response of the bare GCE and GO modied GCE are only
observed as one peak for the oxidation of AA and DA in PBS
solution with 1 mM DA and 40 mM AA, indicating that the peak
potential for AA and DA is indistinguishable. However, two well-
dened oxidation peaks, corresponding to the oxidation of AA
and DA, respectively, are clearly observed in the CV responses of
the GO-IL and GO-IL-AuNPs modied GCEs, which provides the
possibility of the detection of DA in the presence of ascorbic
acid. The ionic liquid has a stronger electrical conductivity so
3
.3.1. Inuence of the amount of GO-IL-AuNPs nano-
composite suspension. The effect of the loading amount of GO-
IL-AuNPs on the electrode surface on the sensing properties was
investigated. The relationship between the peak currents of DA
and the amount of GO-IL-AuNPs on the GCE is shown in Fig. 4A.
The response current value of 1 mM DA gradually increased with
ꢀ
1
the increase of the amount of GO-IL-AuNPs (1 mg mL
)
modied to the electrode surface from 3 to 6 mL. Nevertheless,
a further increase in the volume of modication conversely
caused a decrease in the response current of DA. Consequently,
6
mL of GO-IL-AuNPs suspension was thought to be the optimal
amount for the modied electrode.
.3.2. Effect of solution pH. The effect of pH on the elec-
3
trochemical response of 1 mM DA was investigated over the pH
range from 4.5 to 7.5 and the results are shown in Fig. 4B. It is
obvious that the peak current of DA increases continuously with
3 6
Fig. 3 Electrochemical impedance spectroscopy recorded in 0.2 mM K [Fe(CN) ] solution (A). Cyclic voltammograms showing the response of
different modified electrodes to 1 mM DA (B); 1 mM DA and 40 mM AA (C) in 0.1 M PBS. (a) GCE, (b) GO/GCE, (c) GO-IL/GCE, and (d) GO-IL-AuNPs/
GCE.
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Fig. 4 (A) Effect of the volume of GO-IL-AuNPs. (B) Effect of pH value. (C) Effect of accumulation time. (D) CVs of GO-IL-AuNPs/GCE in 0.1 M
ꢀ1
PBS (pH 5.5) with 10 mM DA at different scan rates (0.02, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18, and 0.2 V s ). Inset: the linear relationship between peak
current and scan rate.
the increasing of the pH from 4.5 to 5.5, and then gradually a typical adsorption controlled process rather than a diffusion
decreases on further increasing of the pH. Therefore, pH of 5.5 controlled process.
was considered to be the optimal pH for the subsequent elec-
trochemical experiments.
3.4. Analytical characteristics
3.3.3. Effect of accumulation time. There is no doubt that
the accumulation time will affect the sensitivity of the proposed Under the optimal experimental conditions, the proposed
sensor. The accumulation time can increase the amount of DA sensor was employed for detecting various concentrations of DA
on the surface of the modied electrodes and thus improve the
electrochemical response signal. Fig. 4C shows the relationship
between the response current and the accumulation time. The
response current gradually increased with the accumulation
time increasing from 10 to 70 s. When the accumulation time
exceeded 70 s, the peak current leveled off. Taking into account
the sensitivity and efficiency of the sensor, 70 s was selected as
the optimum accumulation time for the determination of DA.
3.3.4. Effect of scan rate. The effect of different scan rates
on the electrochemical behavior of 10 mM DA at the GO-IL-
AuNPs/GCE was investigated with cyclic voltammetry. The cor-
responding cyclic voltammograms are shown in Fig. 4D. It can
be seen that the oxidation peak current increased gradually with
the increase of scan rate. The linear relationship between the
oxidation peak current and scan rate was obtained in the range
ꢀ1
p
of 0.02–0.2 V s and the linear regression equation was I (mA)
ꢀ
1
¼
7.93005 + 101.3351n (V$s ), R ¼ 0.9994. It indicated that the Fig. 5 Differential pulse voltammograms of different concentrations
of DA at GO-IL-AuNPs/GCE (pH ¼ 5.5). Inset: linear calibration curve in
the range 7 nM to 5 mM DA.
oxidation process of DA at the GO-IL-AuNPs/GCE surface was
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Table 1 Comparison of the performances of some sensors for the Table 2 Determination of DA in actual samples (n ¼ 6)
detection of DA
Added
(mM)
Found
(mM)
RSD
(%)
Recovery
(%)
Linear
Detection
Sample
Urine
Modied electrodes Method range (nM) limit (nM) References
0
—
—
—
Pt/graphene/GCE
SWCNTs/GCE
NCQDs/GCE
GNR/GCE
PtNPs-MWCNT/GCE DPV
AuNPs@MIES/GE
GO-IL-AuNPs/GCE
DPV
DPV
DPV
SWV
30–8130
10–200
10–1000
10–100
60–2030
20–540
7–5000
30
15
10
5.5
50
36
37
38
39
40
41
0.5
1.0
1.5
0
1.0
1.5
2.0
0.51
0.98
1.52
1.02
2.02
2.57
3.00
3.7
3.2
3.6
2.1
2.3
2.2
2.5
102
98
101
—
100
102
99
Injection
DPV
DPV
7.8
2.3
This work
in 0.1 M PBS by more sensitive differential pulse voltammetry. 3.5. Detection of dopamine in real samples
The electrochemical response of DA may follow the two proton
In order to verify the reliability of the proposed sensor, the GO-
IL-AuNPs/GCE was used for the analysis of DA in urine and
dopamine hydrochloride injection samples by differential pulse
cyclic voltammetry. The standard addition method was
employed to analyze the content of DA in these actual samples.
The results of the analysis are summarized in Table 2. As can be
seen from the results in Table 2, the proposed sensor has good
accuracy of detection with recoveries in the range from 98% to
transfer process through the ECE mechanism on the modied
electrode. DA oxidation at the surface of the modied electrode
was enhanced by diffusion and adsorption through graphene
oxide and the ionic liquid, to make contact with the electrode
surface easy and facilitate the electron transfer. The electro-
catalytic performance of the GO-IL-AuNPs/GCE for DA is shown
in Fig. 5. The inset of Fig. 5 displays the linear relationship
between response current and the DA concentration in the
102% and a relative standard deviation below 4%. The above
range of 7 nM to 5 mM. The linearity regression equation was I
p
sample analysis results indicate that the proposed sensor is very
feasible and sensitive enough to detect trace dopamine in real
samples. The sample was characterized by high performance
liquid chromatography aer 50 cycles. As a result, dopamine
was not detected, which indicates that the DA had reacted
completely aer 50 cycling tests.
(
mA) ¼ 0.0111c (nM) + 2.4126 (R ¼ 0.9994). The detection limit of
DA was calculated to be 2.3 nM (S/N ¼ 3). The above results
indicate that the reported GO-IL-AuNPs/GCE has excellent
electro-catalytic ability for DA oxidation. As a comparison, the
analysis performance of other dopamine sensors is listed in
Table 1. It can be seen that the proposed sensor demonstrated
better performance compared to other sensors.
To ensure the repeatability of the proposed sensor, repeated 4. Conclusions
experiments were operated in PBS containing 1 mM DA with the
In this work, a novel platform of an electrochemical sensor
same modied electrode. The results of ten measurements
showed a relative standard deviation (RSD) of 2.8%. Addition-
ally, the reproducibility of the sensor was estimated by using six
sensors prepared in the same way for determination of the same
DA solution. The relative standard deviation (RSD) was 3.1%.
The storage stability of the proposed sensor was also evaluated.
When the sensor was stored in the environment for two weeks,
the response current was not signicantly weakened and
remained at 96.5% of its initial current response, and 92.2% of
the initial current response remained aer four weeks. These
results indicated that the proposed sensor had good repeat-
ability, reproducibility and stability.
based on 1-butyl-3-methylimidazolium cationic groups func-
tionalized graphene oxide lm loaded gold nanoparticles was
constructed. The ionic liquid has good biocompatibility and
strong electron transfer performance. The loading of gold
nanoparticles signicantly enhanced the catalytic performance
of the complexes. The electrochemical properties were evalu-
ated toward the electro-oxidation of dopamine. The interference
experiments showed that some common interferents, such as
uric acid, epinephrine, and ascorbic acid, caused no interfer-
ence in the determination of dopamine. Moreover, the
proposed sensor has good stability, excellent selectivity and
good electrocatalytic activity. Under the optimal conditions,
a stable linear relationship was observed between the response
current and the concentration of DA in the range from 7 nM to 5
mM with a limit of detection 2.3 nM. The as-prepared sensor was
employed to analyze real samples and achieved satisfactory
results.
In order to evaluate the potential of interference during DA
detection, possible interfering compounds such as AA, glucose,
uric acid (UA), epinephrine (EP) and serotonin (5-HT) were
used. It was found that 40-fold concentrations of AA, uric acid,
and epinephrine and 100-fold concentrations of glucose and
serotonin (5-HT) had no obvious inuence on the response
current of 1 mM DA with deviations below ꢃ5%. Besides, some
2
+
3+
ꢀ
2
00-fold concentration of excess ions such as Mg , Al , Cl ,
Acknowledgements
2
ꢀ
ꢀ
SO4 and NO3 had no inuence on the DA response signal.
These results demonstrate that GO-IL-AuNPs/GCE has good This work was supported by the Shandong Provincial Natural
selectivity towards DA.
Science Foundation of China (No. ZR2012BM020) and the
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Scientic and technological development Plan Item of Jinan 12 S. R. Wallenborg, L. Nyholm and C. E. Lunte, End-Column
City in China (No. 201202088).
Amperometric Detection in Capillary Electrophoresis:
Inuence of Separation-Related Parameters on the
Observed Half-Wave Potential for Dopamine and Catechol,
Anal. Chem., 1999, 71, 544–549.
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Sensitive detection of endocrine disrupters using ionic
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