Carbon-doped h-BN for the enhanced electrochemical determination of dopamine

Article abstract of DOI:10.1016/j.electacta.2020.137682

Since dopamine (DA) is one of the central neurotransmitters and plays an important role in the human metabolism, its accurate detection is crucial for the diagnosis of DA-linked diseases. Herein, we demonstrated a novel electrochemical sensor for DA detection based on carbon-doped hexagonal boron nitrogen (C-hBN). C-hBN was prepared via a thermal polymerization process using melamine borate as a precursor. The successful C-doping was evidenced by fourier transform infrared (FTIR), photoluminescent (PL) and x-ray photoelectron spectroscopy (XPS). The carbon-doping can increase reactive sites and facilitate electrons transfer in h-BN, which was confirmed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The C-hBN modified glassy carbon electrode (C-hBN/GCE) exhibited the enhanced electrocatalytic activity toward DA redox, whose CV peak current is 2.8 and 4.3 times higher than those of pure h-BN modified and bare GCEs, respectively. Based on CV method, the C-hBN/GCE presented a low detection limit of 5.8 nM (S/N = 3) and a sensitivity of 2037 μA?mM?cm^?2. The linear response ranges were over the DA concentrations of 0.01–40 μM and 40–300 μM, respectively. In addition, the sensor was applied to detect DA in real samples including human serum and urine, and satisfactory results were achieved. The results suggested that the defect-engineered h-BN holds great potential for the development of electroanalytical devices with high-performance.

Full text of DOI:10.1016/j.electacta.2020.137682

Electrochimica Acta 369 (2021) 137682
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Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Carbon-doped h-BN for the enhanced electrochemical determination
of dopamine
Huiying Ouyanga,b, Weifeng Lia,∗, Yumei Longa,b,∗
a College of Chemistry, Chemical engineering and Materials Science, Soochow University, Suzhou 215123, P R China
b The Key Lab of Health Chemistry and Molecular Diagnosis of Suzhou, Suzhou 215123,P R China
a r t i c l e i n f o
a b s t r a c t
Article history:
Since dopamine (DA) is one of the central neurotransmitters and plays an important role in the hu-
man metabolism, its accurate detection is crucial for the diagnosis of DA-linked diseases. Herein, we
demonstrated a novel electrochemical sensor for DA detection based on carbon-doped hexagonal boron
nitrogen (C-hBN). C-hBN was prepared via a thermal polymerization process using melamine borate as a
precursor. The successful C-doping was evidenced by fourier transform infrared (FTIR), photoluminescent
(PL) and x-ray photoelectron spectroscopy (XPS). The carbon-doping can increase reactive sites and fa-
cilitate electrons transfer in h-BN, which was confirmed by cyclic voltammetry (CV) and electrochemical
impedance spectroscopy (EIS). The C-hBN modified glassy carbon electrode (C-hBN/GCE) exhibited the en-
hanced electrocatalytic activity toward DA redox, whose CV peak current is 2.8 and 4.3 times higher than
those of pure h-BN modified and bare GCEs, respectively. Based on CV method, the C-hBN/GCE presented
a low detection limit of 5.8 nM (S/N = 3) and a sensitivity of 2037 μA•mM•cm−2. The linear response
ranges were over the DA concentrations of 0.01–40 μM and 40–300 μM, respectively. In addition, the
sensor was applied to detect DA in real samples including human serum and urine, and satisfactory re-
sults were achieved. The results suggested that the defect-engineered h-BN holds great potential for the
development of electroanalytical devices with high-performance.
Received 9 October 2020
Revised 16 December 2020
Accepted 23 December 2020
Available online 28 December 2020
Keywords:
Boron nitrogen
Carbon-doping
Dopamine
Electrochemical sensor
© 2020 Elsevier Ltd. All rights reserved.
1. Introduction
trode fouling and interference from some coexistent molecules, in-
cluding uric acid (UA) and ascorbic acid (AC) [9]. Hence, substantial
Dopamine
(DA),
chemically
known
as
3,4-
efforts have been dedicated to developing new chemical sensors, in
which the sensing materials can effectively interact with DA and
produces the enhanced electrochemical signal [1, 10]. However, it
remains a challenge to obtain suitable sensing materials for elec-
trochemically modified electrode.
dihydroxyphenethylamine, is an important monoamine neuro-
transmitter and widely distributed in the human body [1, 2]. As a
crucial chemical messenger, DA makes a key contribution to the
communication among neurons in the central nervous system,
thus regulating the neuronal activities such as emotions and
cognitions [3]. Nevertheless, abnormal concentration of DA will
induce parkinson’s disease and mental disorder [4-6]. In order to
exert normal neurological functions, the basal concentration of DA
in physiological fluids is about 0.01–1 μM [5]. Hence, the accurate
detection and in-situ monitoring of DA levels in the extracellular
fluids has a pivotal role for clinical diagnoses and physiological
functions.
Hexagonal boron nitride (h-BN) is a two-dimension (2D) ma-
terial and has aroused increasing research interest. In contrast to
graphite, h-BN shows ionic features and strong interaction due
to the different electronegativity between N and B. Such a struc-
ture endows h-BN with many fascinating properties, and makes it
very promising for applications in optoelectronic, energy conver-
sion, water treatment and electrochemical sensor [11–14]. How-
ever, the pristine h-BN has a wide bandgap (~ 5.9 eV) and shows
poor electron transfer ability, which seriously limited its direct ap-
plication for electrochemical sensing [14]. It is noteworthy that the
performances of h-BN are strongly dependent on its microstruc-
ture, such as morphology and defects [15–17]. Recently, intensive
attention has been paid on the microstructure modification to im-
prove the sensing property of h-BN [18–22].
Since DA is highly electroactive, electrochemical strategy could
be potential for its determination [7, 8]. However, the determina-
tion of DA at a bare electrode is limited by its low sensitivity, elec-
∗
Corresponding authors.
E-mail addresses: liweifeng@suda.edu.cn (W. Li), Yumeilong@suda.edu.cn (Y.
Long).
https://doi.org/10.1016/j.electacta.2020.137682
0013-4686/© 2020 Elsevier Ltd. All rights reserved.

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
Generally, defect states existed in the forbidden zone can act
as traps or recombination centers for charge carriers, consequently
influencing the electronic conductivity and chemical reactivity of a
semiconductor. These characteristics play key roles in the electro-
chemical process. Hetero-atom doping is the most popular method
to artificially create defects in the crystals and further improve the
sensing properties of the modified electrodes [23–25]. Both the
theoretical calculations and experimental results suggested that
carbon-doping can reduce the bandgap of h-BN and accordingly
modify their physicochemical performances [26–29]. Considering
the electrocatalytic activity of the h-BN towards DA [30, 31], it is
expected that carbon-doped h-BN is the more promising electrode
material for electrochemical sensor.
Electrochemical measurements, including CV and EIS were con-
ducted on a CHI 660D workstation (Chenhua Instruments Co.,
Shanghai, China). A three-electrode setup was adopted for all the
measurements, which is composed of a GCE (working electrode),
a Pt wire (counter electrode) and a saturated calomel electrode
(SCE, reference electrode). DA determination was monitored by CV
method in phosphate buffer solution. The scanning potential range
was from −0.2 to 0.6 V. EIS was collected using [Fe(CN)6]3-/4−
(1 mM) as prober in KCl solution (0.1 M).
2.4. Fabrication of C-hBN/GCE
Before modification, a GCE (5 mm in diameter) was pretreated
using alumina slurry (50 nm) to obtain a mirror surface. Then, the
electrode was ultrasonically rinsed with water and ethanol, and
dried with nitrogen. 2.0 mg of C-hBN powder was dispersed into
2 mL deionized water under ultrasonic irradiation to form a ho-
mogeneous suspension. After that, 10 μL of C-hBN suspension was
pipetted onto the surface of the cleaned GCE and dried naturally
at room temperature. The modified electrode was named as C-
hBN/GCE. In the same way, h-BN/GCE was also constructed.
In this work, a novel electrochemical sensor was developed for
DA detection based on C-hBN. The doping of carbon in h-BN was
characterized by FTIR, PL and XPS. C-hBN was employed to modify
GCE without need of any binders and its electrochemical detec-
tion of DA was systematically investigated. The carbon-doping will
create reactive sites and facilitate electron transfer, which can en-
hance the electrocatalytic activity of h-BN towards DA. Finally, the
method was applied for DA detection in biological samples.
3. Results and discussion
2. Experimental
3.1. Characterization of samples
2.1. Chemicals
Fig. 1a shows XRD patterns of samples. There are four diffrac-
tion peaks in the XRD patterns for both the samples. The peaks
at 26.1°, 42.1°, 54.0° and 76.5° are indexed to (002), (100), (004)
and (110) crystal facets, respectively for hexagonal boron nitrogen
(JCPDS No. 34–0421) [33]. No additional peak can be discerned,
suggesting the high purity of the product. Compared with pure h-
BN, all the diffraction peaks of the C-hBN become weak and broad,
indicating the low crystallinity caused by carbon-doping. Fig. 1b
presents the FTIR spectra of the samples. The formation of BN was
evidenced by the appearance of absorption bands at 1384 cm−1
and 798 cm−1, which correspond to the stretching vibration of B-
N and bending vibration of B-N-B, respectively [34]. Two IR signals
Melamine (C3H6N6), boric acid, pure h-BN nanoparticles was
bought from Aladdin. Polyethylene glycol (PEG, Kw
=
2000),
sodium dihydrogen phosphate, disodium phosphate, potassium
ferrocyanide/ferricyanide and potassium chloride were purchased
from Sinopharm Chemical Reagent Shanghai Co., Ltd. DA, uric acid
(UA), ascorbic acid (AA) and human serum were obtained from
Sangon Biotech Co. Ltd. (Shanghai, China). All the chemicals were
analytical grade and all solutions were prepared using double dis-
tilled water.
2.2. Synthesis of carbon-doped h-BN
at 3431 and 3265 cm−1 are ascribed to O H and N H stretching
vibrations [35]. Different from pure h-BN, several additional ab-
sorption peaks appeared in the range of 1050–1200 cm−1 for the
–
–
Carbon-doped h-BN was synthesized using melamine borate as
precursor modified from the previous literature [32], in which PEG
was employed as carbon source. Typically, 3 g of melamine and
1 g of H3BO3 were dissolved into 200 mL hot water (85 °C) to get a
clear solution. The solution was further stirred for 1 h and then 1 g
of PEG was added. After the water was removed by rotary evap-
oration, the white solid powder was collected, dried, and ground
to obtain a precursor. The precursor was pressed into plate and
heated at 1050 °C for 3 h in nitrogen atmosphere. The obtained
powder was washed with HNO3 (0.2 M) in hot water and dried
at 80 °C overnight. The resulting yellow sample was named as C-
hBN. As comparison, pure h-BN nanoparticles were bought from
Aladdin.
–
C-hBN. These peaks are related to C-B and C N bonds [36, 37], re-
vealing the successful doping of carbon atoms into h-BN.
Fig. 1c and d present TEM images of pure and carbon-doped h-
BN. Pure h-BN shows typical layer structure with lateral dimension
of 30–200 nm (Fig. 1c). These nano-sheets have smooth surface.
For C-hBN, the sample is composed of sub-micrometer blocks with
flat surface and they are composed of many small flakes (Fig. 1d).
The chemical compositions and states of C-hBN were exam-
ined with XPS technique. As shown in Fig. S1a, the survey spec-
trum shows four XPS peaks at 190.9, 284.6, 398.2 and 532.8 eV,
which are corresponded to B 1 s, C 1 s, N 1 s and O 1 s, respec-
tively. The O 1 s signal should be originated from the absorbed
water. The high-resolution XPS spectrum (HR-XPS) of B 1 s can be
resolved into three sub-peaks (Fig. S1b). These peaks centered at
189.8, 190.5 and 191.9 eV are related to B-C, B-N and B-O bonds
[38-40], respectively. For C 1 s (Fig. S1c), it’s HR-XPS peak was fit-
ted by four sub-peaks with band energies of 283.8, 284.8, 286.2,
2.3. Instruments
The samples were structurally characterized by X-ray diffrac-
tion technique (XRD, PANalytical, X-Pert-Pro-MPD, Cu-K
radia-
α1
tion) and their morphologies were observed by transmission elec-
tron microscopy (TEM, FEI Tecnai G20). FTIR spectra were recorded
on a Nicolet 550 spectrometer and PL properties were measured
using a Hitachi F-4500 fluorescence spectrometer. The chemical
compositions of sample were examined by XPS method (Axis Ul-
tra HAS spectrometer). The zeta potential was acquired using Nano
Particle Analyzer (HORIBA, Japan) at room temperature. The mea-
surements were performed at pH of 6.0 after 5 min equilibration
time.
–
–
–
and 288.7 eV, and they are assigned to the C-B, C C, C N, and C O
bonds, respectively [38, 41]. The HR-XPS analysis of N 1 s is shown
in Fig. S1d, two sub-peaks at 397.9 eV and 398.7 eV are attributed
–
to N-B and N C bonds [38]. The XPS results further confirmed the
successful introduction of carbon into h-BN, which is consistent
with the FTIR results.
Fig. S2 shows the PL spectra of pure and carbon-doped h-
BN. No distinct emission is observed in the pure h-BN excited by
2

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
Fig. 1. (a) XRD and (b) FTIR of h-BN and C-hBN; (c) TEM imagines of h-BN and (d) C-hBN.
they are the concentration of [Fe(CN)6]3−/4−, diffusion coefficient
220 nm. On the contrary, C-hBN exhibits complex luminescence
phenomenon. A broad emission band can be clearly found extend-
ing from 260 to 400 nm and it was composed of several emission
peaks. This emission band should be attributed to carbon-related
point defects, such as the occupation of carbon atom into nitrogen
−
(6.5 × 10−6 cm2ꢀs
1) and the number of electrons participat-
ing in the reaction (n = 1). Fig. S4 displays the CVs of electrodes
at different scan rate. The redox peak currents of the three elec-
trodes enhance with increasing scan rate (Fig. S4a, c, e). Moreover,
Ip shows good linear relationship to υ1/2 (Fig. S4b, d, f). Accord-
ingly, the EASAs were estimated to be 0.21, 0.17 and 0.26 cm2 for
GCE, h-BN/GCE and C-hBN/GCE, respectively. The high EASA of C-
hBN/GCE can provide more active sites and consequently enhance
electrochemical performance.
ꢀ
sub-crystal site (CN ) [42-44]. Especially, carbon is relatively easy
to occupy nitrogen site due to the low formation energy [45]. Thus,
ꢀ
CN should be the dominant point defect in the present system.
Fig. S3 shows the zeta potential analyses on h-BN and C-hBN
suspensions (pH=6). The pristine h-BN in the aqueous medium
shows positive zeta potential value of 15.3 mV (Fig. S3a). On the
other hand, the carbon-doping leads to negative zeta potential
value of −29.4 mV (Fig. S3b). The carbon-doping modified the sur-
face atomic microstructure and altered the surface charge char-
Fig. 2b demonstrates Nyquist plots of the electrodes and they
were described by the Randel equivalent circuit (inset). In the
equivalent circuit, Rct, RS, ZW and Qdl are electron transfer resis-
tance, uncompensated solution resistance, Warburg impedance and
double layer capacitance, respectively. The Rct is derived from the
semicircle diameter. By impedance fitting analysis, the Rct values of
bare GCE, h-BN/GCE and C-hBN/GCE are 1875, 3281 and 509 ꢀ, re-
spectively. Thus, the heterogeneous electron transfer rate constant
(ket) was obtained based on following equation [47]:
acteristics of h-BN, which is consistent with the abovementioned
ꢀ
point defect of CN
.
3.2. Electrochemical characterization
Fig. 2a displays CVs for bare GCE, h-BN/GCE and C-hBN/GCE us-
ing [Fe(CN)6]3−/4− (1 mM) as probe in 0.1 M KCl solution. All the
electrodes present a couple of well-defined redox peaks. The peak
current increases in the order of h-BN/GCE < GCE < C-hBN/GCE.
The largest peak current was acquired at C-hBN/GCE. The lowest
electrochemical current of h-BN/GCE should be ascribed to the in-
sulativity of h-BN. Thus, C-hBN/GCE can provide high electrochem-
ically active surface area (EASA), which is calculated by Randles-
Sevcik equation [46]:
RT
n2F2ARctC
ket
=
(2)
In the above formula, R, T and F are constants with usual physi-
cal meaning, n, A and C are the number of electrons transferred per
molecule, electrode area and concentration of redox couple. Thus,
the ket values are calculated to be 0.724 × 10−3, 0.414 × 0
and
−
3
2.71 × 10−3 cmꢀs
for bare GCE, h-BN/GCE and C-hBN/GCE, re-
−
1
spectively. The lowest ket value of h-BN/GCE is attributed to the in-
sulativity of h-BN, which hiders the electron transfer. On the other
hand, C-hBN/GCE exhibits the largest ket value, suggesting that C-
hBN can facilitate electron transfer between electrode and solution.
Ip = 2.69 × 105 · n3/2 · A · D1/2 · C · v1/2
(1)
In the equation, Ip,
A and υ refer to peak current, EASA
and scan rate, respectively. C, D and n are constants here and
3

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
Fig. 2. (a) CVs and (b) Nyquist plots of various electrodes in 0.1 M KCl solution containing 1.0 mM of [Fe(CN)6]3−/4−. The CV was measured with scan rate of 100 mVs−1
;
(a) The EIS was tested in the frequency from 1 Hz to 1 MHz and inset is the Randel equivalent circuit. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
Fig. 3. (a) CVs of bare GCE, h-BN/GCE and C-hBN/GCE in 0.2 M PB solution (pH = 6.0) containing 100 μM of DA; (b) CVs of C-hBN/GCE in the absence/presence of 100 μM
DA in PB solution (pH = 6.0). The scan rate is 100 mVs−1
.
The carbon-doping tunes the electronic structure and reduces the
bandgap of h-BN [48], promoting electrochemical reaction
3.4. Influence of scan rate and pH value
Fig. 4a shows the influence of scan rate (20–200 mVs−1) on
CV response of DA (100 μM) over C-hBN/GCE in PB solution
(pH = 6.0). As the scan rate increases, both the oxidation current
(Ipa) and reduction current (Ipc) simultaneously raise. Fig. 4b illus-
trates that the redox peak current (Ip) has good linear-relationship
with the square root of the scan rate (ʋ1/2). The linear fitting equa-
tions are defined as Ipa = −1.861 ʋ1/2 - 2.274 (R = 0.995) and
Ipc = 1.857 ʋ1/2 + 1.881 (R = 0.972), respectively. Thus, the redox of
DA at C-hBN/GCE is diffusion-controlled. Besides, the positive shift
for oxidation peak potential (Epa) and negative shift of reduction
peak potential (Epc) are observed with increasing scanning rate.
As shown in Fig. 4c, the calibration plots between redox peak po-
tential of DA (Ep) and lnʋ have good linear relationship, revealing
quasi-reversible electrochemical process [50]. Based on the Laviron
equations [51], electron transfer coefficient (α) and the number of
transferred electrons (n) can be obtained.
3.3. Electrochemical behaviors of DA over C-hBN/GCE
Fig. 3 illustrates the electrochemical response of various work-
ing electrodes towards DA. The CV measurements were conducted
in 0.2 M phosphate buffer (PB) solution (pH = 6.0) with a scan rate
−
of 100 mV•s
1. As shown in Fig. 3a, there is a pair of weak re-
dox peak for the bare GCE. After h-BN-modifying, the redox peaks
slightly enhanced. Interestedly, the peak current significantly im-
proved at C-hBN/GCE, whose current value is 4.3 higher than that
of the bare GCE.
Fig. 3b gives the CVs of C-hBN/GCE in the presence and ab-
sence of DA. No electrochemical signal can be found without DA.
On the contrary, a pair of well-defined redox peak is observed
when 100 μM DA was added. Therefore, C-hBN/GCE has a good
electro-catalytic effect in the redox reaction of DA and can be em-
ployed for DA detection. The superior electrochemical properties
of C-hBN/GCE should be attributed to its high EASA and the fast
electron transfer rate, which is induced by the carbon-doping. Un-
der the condition of pH = 6, DA should be existed in the form
RT
Epa = E0
+
ln υ
(3)
(1 − α)nF
RT
ln υ
αnF
Epc = E0
−
(4)
ꢀ
of cationic DA+ considering its pKb of 8.87 [49]. Meanwhile, CN
in h-BN will create a negative charge center. Hence, the forma-
Where E0 refers to the formal potential. R, T and F are con-
stants with their traditional meanings. Hence, the α and n were
calculated to be 0.62 and 2.25, respectively, indicating that a two-
electron transferred process occurred during the electrochemical
redox of DA.
ꢀ
tion of CN can interact with DA+ through Coulomb force. In this
way, more active sites were provided for DA to participate in elec-
ꢀ
trochemical reaction over the modified electrode. In addition, CN
can tailor the electronic structure through constructing defect en-
ergy levels in the bandgap of h-BN and thus facilitate charge trans-
fer, which will improve the reaction kinetics due to their desirable
electro-catalytic activity.
The effect of electrolyte pH on DA detection (100 μM) was
shown in Fig. 5a. Among seven PB buffers (pH = 3.0, 4.0, 5.0, 6.0,
7.0, 8.0 and 9.0), the best electrochemical response is achieved in
4

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
Fig. 4. (a) CVs of the C-hBN/GCE at different scan rates from 20 to 200 mV/s in 0.2 M PB solution (pH=6) containing 100 μM DA; (b) plots of redox peak current (Ip) vs. the
square root of scan rate (ʋ1/2); (c) plots of redox peak potential vs. lnʋ. (For interpretation of the references to color in this figure legend, the reader is referred to the web
version of this article.)
Fig. 5. (a) CVs of C-hBN/GCE at different solution pH values. (b) Plots of oxidation peak potential vs pH (Conditions: 100 μM of DA, 0.2
M PB solution, scan rate:
−
100 mV
s
1).
•
were given in Fig. S5. The regression equations are Ipa = 0.0539
C + 0.0628 (R2 = 0.993, 1–100 μM) for bare GCE and Ipa = 0.0714
C + 0.102 (R2 = 0.998, 0.5–250 μM) for h-BN/GCE, respectively.
Their sensitivities are 0.0539 and 0.0714 μA•μM−1 for bare GCE
and h-BN/GCE, respectively. Obviously, the C-hBN/GCE exhibits bet-
ter analytical performances than those of the bare and h-BN mod-
ified GCEs in the detection DA.
Fig. 6. Mechanism for the electrochemical reaction of DA on the C-hBN/GCE.
pH = 6.0. Therefore, the pH = 6.0 was selected for following ex-
periments. In addition, the redox peak potential shifts negatively
with increasing pH value (Fig. 5b). The result is consistent with
Nernst equation of Ep (V) = −0.0592 m/n pH + b [52]. Two lin-
ear regression equations were acquired in the plots of peak poten-
tial (Ep) as function of pH. Their slopes are 0.062 and 0.054 V/pH,
respectively. It is concluded that the redox process of DA at C-
hBN/GCE involves equal number of proton and electron. Accord-
ingly, the electrochemical reaction mechanism of DA at C-hBN/CGE
is illustrated by Fig. 6.
Table S1 summarizes analytical properties of several modified
electrodes in the electrochemical detection of DA. The C-hBN/GCE
demonstrates some advantages, such as wide linear concentration
range and low detection limit. This is due to the following fac-
tors: 1) The carbon doping can increase electrochemically active
area and provide more reaction sites for DA; 2) The replacement
of nitrogen by carbon will introduce negatively charged center in
the h-BN, which can electrostatically interact with the protonated
DA and improve the electrochemical reaction; 3) the extrinsic de-
ꢀ
fect of CN will modify the electronic structure of h-BN and thus
facilitate electron transfer, resulting in the enhanced electrochemi-
3.5. Sensing performances of C-hBN/GCE towards DA
cal activity towards DA.
The sensing performances of C-hBN/GCE towards DA were
investigated under the optimized conditions using CV method.
Fig. 7a shows CVs measured at different concentrations of DA (in-
set is the magnification at low concentrations). The redox peak
gradually enhances as the DA concentration increases from 0.01
to 300 μM. For simplicity, the anode peak current (Ipa) was em-
ployed to determine DA. By linear fitting (Fig. 7b), the regression
equations are Ipa = 0.397 C + 0.337 (R2 = 0.997) in the concentra-
tion range of 0.01–40 μM and Ipa = 0.180 C + 10.264 (R2 = 0.995)
in the concentration range of 40–300 μM, respectively. The sensi-
tivities of the sensor are 0.379 and 0.18 μA•μM−1 for 0.01–40 μM
and 40–300 μM, respectively. The detection limit is estimated to
be 5.8 nM by 3σ/S, in which σ is the standard deviation of the
background current and S is the slope of the calibration curve. As
a comparison, the bare and h-BN modified GCEs were also em-
ployed to detect DA under the same conditions and the results
3.6. Selectivity, stability and real sample detection
The selectivity of C-hBN/GCE was studied by detecting 100 μM
of DA coexisting with various interfering compounds (ICs) through
CV measurements under the same conditions. The investigated ICs
include 100-fold concentration of K+, Ca2+, Na+, Mg2+, glucose,
H2O2, 10-fold concentration of serine, alanine, threonine, glycine,
histidine, phenylalanine, tyrosine, phenol and the same concentra-
tion of AA, UA. As shown in Fig. 8, the relative errors on the cur-
rent signal of DA induced by ICs are less than 5%, which con-
firmed the good selectivity of C-hBN/GCE towards DA.
Five C-hBN/GCEs fabricated in the same way were employed to
determine DA (100 μM) under the same conditions and the rela-
tive standard deviation (RSD) of the peak current was 3.14%, sug-
gesting the favorable reproducibility of the method. Besides, the CV
response of DA (100 μM) at the same C-hBN/GCE was measured
5

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
Fig. 7. (a) CVs of C-hBN/GCE for various DA concentrations (0.01–300 μM) in 0.2 M PB solution (pH = 6.0) with scan rate of 100 mVs−1. Inset displays CVs at low DA
concentrations. (b) Calibration plots between oxidation peak current and DA concentration.
ues are 95.5%~104.8% and the RSD values are less than 5%. There-
fore, the proposed method is reliable in the detection of DA in real
samples.
Conclusions
In this work, a novel DA sensor was developed by modifying
GCE with C-hBN without any linker. C-hBN/GCE exhibited the en-
hanced electrocatalytic activity towards DA compared with those
ꢀ
of h-BN/GCE and bare GCE. It should be the fact that CN de-
fects can provide more active sites for DA and facilitate electrons
transfer. The developed sensor possessed excellent analytical per-
formances in the detection of DA, such as low detection limit of
5.8 nM, wide linear concentration range of 0.01–40 μM and 40–
300 μM, high sensitivity of 2037 μAꢀmM−1ꢀcm−2 and favorable se-
Fig. 8. The effect of different interfering species on the CV responses of DA at
lectivity. In the real sample analysis, C-hBN/GCE showed the de-
C-hBN/GCE. The measurements were performed in 0.2 M PB solution containing
sired recovery rate with low RSD (< 5%), confirming its potential
for practical application. It is believed that engineering defects in
the electrode materials will offer an innovative way for fabricating
electrochemical sensor with high-performance.
100 μM DA coexisting with 10 mM of (a) K+, (b) Ca2+, (c) Na+, (d) Mg2+, (e) glu-
cose, (f) H2O2, 1 mM of (g) serine, (h) alanine, (i) threonine, (j) glycine, (k) histidine,
(l) phenylalanine, (m) tyrosine, (n) phenol and 100 μM of (o) AA and (p) UA.
Table 1
DA assay in human serum and urine samples using C-hBN/GCE (n = 3).
Declaration of Competing Interest
Sample
Added (μM)
Founded (μM)a
Recovery (%)
RSD (%)
serum
0
NDb
–
–
The authors declare that they have no known competing finan-
cial interests or personal relationships that could have appeared to
influence the work reported in this paper.
60
80
100
0
62.87
79.49
102.57
ND
104.8
99.4
102.6
–
2.29
2.46
3.27
–
urine
30
60
90
28.64
60.92
89.67
95.5
101.5
99.6
3.59
2.93
3.51
Credit authorship contribution statement
Huiying Ouyang: Conceptualization, Data curation, Methodol-
ogy, Investigation, Writing - original draft. Weifeng Li: Formal
analysis, Data curation, Methodology, Writing - review & editing.
Yumei Long: Supervision, Validation, Data curation, Methodology,
Writing - review & editing, Funding acquisition.
a
Average of three replicate measurements;.
Not detected.
b
repeatedly. After 10 consecutive measurements, the current change
is not obvious and the RSD was calculated as 2.92%, indicating the
good operation stability of the modified electrode. Additionally, the
current response of the electrode retained 92.1% of its initial value
after four weeks storage.
Acknowledgments
This work is supported by the National Natural Science Foun-
dation of China (21005053), the Priority Academic Program Devel-
opment of Jiangsu Higher Education Institutions and the Project of
Scientific and Technologic Infrastructure of Suzhou (SZS201708).
The validity of the C-hBN/GCE for real sample assay was ex-
plored by detecting DA in human serum and urine. Human serum
was obtained from Sangon Biotech Co. Ltd. (Shanghai, China) and
used without further treatment. The urine sample was centrifuged
at 8000 rpm for 10 min. Then both the serum and urine samples
were diluted 100 times with 0.2 M PB solution (pH = 6.0). The
standard addition method was used for the determination DA and
each sample was measured three times in parallel. Table 1 lists the
recovery results in the human serum and urine. The recovery val-
Supplementary materials
Supplementary material associated with this article can be
found, in the online version, at doi:10.1016/j.electacta.2020.137682.
6

H. Ouyang, W. Li and Y. Long
Electrochimica Acta 369 (2021) 137682
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7