Enhanced Electrocatalytic Activity of Thiophene-Substituted Asymmetric Porphyrin Film for Electrochemical Determination of Dopamine

Article abstract of DOI:10.1134/S0036024420130087

Abstract: Thiophene substituted porphyrin derivative was synthesized and investigated. The porphyrin derivative was characterized via MALDI-MS, ¹H NMR, FT-IR, and cyclic voltammetry methods. The poly-porpyrin (PPor) film was electrochemically d

Full text of DOI:10.1134/S0036024420130087

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2020, Vol. 94, No. 13, pp. 2836–2843. © Pleiades Publishing, Ltd., 2020.
COLLOID CHEMISTRY
AND ELECTROCHEMISTRY
Enhanced Electrocatalytic Activity of Thiophene-Substituted
Asymmetric Porphyrin Film for Electrochemical
Determination of Dopamine
a,
b
Sadik Cogal * and Aysegul Oksuz
a
Burdur Mehmet Akif Ersoy University, Faculty of Engineering and Architecture,
Department of Polymer Engineering, Burdur, 15030 Turkey
b
Suleyman Demirel University, Faculty of Arts and Science, Department of Chemistry, Isparta, 32260 Turkey
e-mail: sadik_cogal@yahoo.com
Received December 31, 2019; revised February 12, 2020; accepted March 11, 2020
*
Abstract—Thiophene substituted porphyrin derivative was synthesized and investigated. The porphyrin deriv-
1
ative was characterized via MALDI-MS, H NMR, FT-IR, and cyclic voltammetry methods. The poly-
porpyrin (PPor) film was electrochemically deposited on a glassy carbon electrode (GCE) via cyclic voltam-
metry in phosphate buffer solution (PBS). The electrocatalytic activity of the polymeric porphyrin film-mod-
ified electrode (GCE-PPor) was investigated towards dopamine through differential pulse voltammetry
(
DPV) method. The electrochemical results revealed that GCE-PPor exhibited a better catalytic activity
towards dopamine in PBS when compared to an unpolymerized porphyrin-modified electrode. The PPor-
–1
–2
modified electrode shows a sensitivity of 5.82 μA μM cm and low detection limit of 0.42 μM with high
selectivity in the presence of ascorbic acid (AA) and uric acid (UA) as interferents. The enhancement of the
electrocatalytic activity can be explained by the enhanced π-conjugation after polymerization.
Keywords: porphyrin, thiophene, polymer, electrocatalytic, dopamine
DOI: 10.1134/S0036024420130087
INTRODUCTION
Among various materials, porphyrins and their
metal derivatives are very suitable materials for elec-
tron transfer based applications due to their large aro-
matic conjugated π-system and unique electrochemi-
cal behavior [3–6]. The properties of these molecules
can be readily tuned by adding various substituents to
beta-/meso-positions at the porphyrin core [7]. Due
to their excellent properties and diverse range of deriv-
Dopamine is one of the important catecholamine
neurotransmitters present in human organism and has
a crucial role in functioning of central nervous and
endocrine systems. Therefore, abnormal level of this
compound results in several diseases including Par-
kinson’s syndrome, dementia, schizophrenia [1, 2].
–8
The DA concentration is normally between 10 and atives, porphyrins have been used in dye-sensitized
–6
10
M in biological systems. Hence, its accurate and solar cells (DSSCs) [8], catalysis [9], sensors [10], and
selective determination is of great significance for ana- photodynamic therapy [11], etc. So far, many kinds of
lytical applications and early diagnosis. Compared materials were used as substituents to synthesize por-
with traditional methods, electrochemical sensors phyrin derivatives with new functionalities. Among
have been proposed for DA determination due to their them, thiophene moieties have found significant
extraordinary characteristics such as high sensitivity, attention due to their distinctive features [12]. Thio-
high selectivity, reproducibility, cost-effectiveness, phene substituents not only extend the conjugation of
portability and fast response. However, DA coexists the porphyrin core but also play an important role as
mostly in the body fluids with other important sub- an electroactive group to prepare polymers of the cor-
stances such as ascorbic acid (AA) and uric acid (UA) responding porphyrin derivatives [13]. For example,
as a purine metabolite. Since these two compounds Bhyrappa and Bhavana [14] reported that the electro-
have similar oxidation potentials to DA, their interfer- chemical properties of the meso-tetrathienyl porphy-
ence influences on DA determination must be taken rins better than that of containing aryl groups at meso
into consideration to increase sensor selectivity. positions. Electroactive polymer coated electrodes are
Therefore, numerous materials have been applied in of special interest because of their potential applica-
electrochemical sensors for DA detection without any tions. Poly-porphyrin coated electrodes have been
potential interferents.
widely applied in various electrochemical applications.
2836

ENHANCED ELECTROCATALYTIC ACTIVITY
2837
Br
CHO
CHO
TFA
0.18 M HCl
N
H
S
Br
CH2Cl2
BF3 · OEt2
DDQ
N
HN
N
+
+
CHO
Br
rt.
S
NH
NH HN
1)
NH HN
(2)
B(OH)2
(
S
MeOOC
Pd(PPh3)4
Na2CO3
DME
S
(Por-1)
80°C
N
HN
COOMe
NH
N
(Por-2)
S
Fig. 1. Synthesis of Por-1 and Por-2.
For example, 2-thienyl substituted poly-porphyrin were
In this study, meso-substitued porphyrin derivative
synthesized and used to electrochemically detect differ- containing thiophene moiety was synthesized and
electrochemically polymerized to prepare electroac-
tive film on GCE surface. The electrocatalytic behav-
ior and selectivity of the modified-GCE electrode was
investigated towards dopamine in the presence of its
major interferences of AA and UA. The reproducibil-
ity of the sensor was also investigated.
ent explosives including 2,4-DNT, TNT, Tetryl, RDX,
and nitromethane [15]. Chen et al. [16] reported iron
tetra(o-aminophenyl)porphyrin (FeTAPP)
films
obtained via electrochemical polymerization and
investigated their electrocatalytic behaviors for reduc-
tion of hydrogen peroxide, molecular oxygen and
chloroacetic acids. Kuzmin et al. [17] reported a new
superoxide-assisted
electrochemical
deposition
EXPERIMENTAL
Materials
Pyrrole, 4-bromobenzaldehyde, 2-thienylcarboxyal-
method to prepare poly-porphyrin electrocatalytic
films, which were tested for oxygen electro-reduction
in alkaline condition. Furthermore, porphyrins have
been recently used as catalysts for the development of
modified electrodes for oxidation of dopamine [18,
dehyde,
4-methoxycarbonylphenylboronic
acid,
tetrakis(triphenylphosphine)palladium(0) [Pd(PPh ) ],
3
4
boron trifluoride-diethyl ether (BF · OEt ), trifluo-
roacetic acid (TFA), sodium carbonate (Na CO ),
3
2
1
9]. However, these porphyrin derivatives have been
2
3
generally immobilized in different inorganic materials
due to the aggregation behaviors or self-decomposi-
tion reactions [20–22]. Therefore, it is of interest to
2
1
,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ),
,2-dimethoxyethane (DME), hexane, and dichloro-
methane (DCM) were purchased from Sigma-
modify electrode surfaces with porphyrin derivatives, Aldrich. All of these materials were used as received.
demonstrating enhanced catalytic activities. Silica Gel 60 (0.04–0.063) was obtained from Merck.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 94 No. 13 2020

2838
SADIK COGAL, AYSEGUL OKSUZ
S
Drying
at rt.
N
HN
N
1
mg/mL
1
0 μL
COOMe
NH
Por-2 in
DCM
S
Por
GCE
GCE-Por
Electropolymerization
from −2.0 to + 2.0 V
cycle
HO
HO
NH
2
2e−
O
O
−
NH
2
5
+ 2H+
S
N HN
COOMe
NH N
Detection of
dopamine
PPor
S
GCE-PPor
n
Scheme 1. Electrode modification with porphyrin.
5
-(4-Bromophenyl)dipyrromethane (1) was synthe- (0.1 mmol, 10.6 mg), and Pd(PPh ) (0.01 mmol,
3 4
sized using a procedure reported by Lindsey et al. [23].
1
1.56 mg) was dissolved in 5 mL of DME and refluxed
5
-Mesityldipyrromethane (2) was synthesized as
at 80°C for 22 h under argon atmosphere. After cool-
ing down to room temperature, DME was removed
using rotary evaporator. The residue was dissolved in
DCM and washed three times with distilled water and
the organic phase was extracted. The DCM was
removed completely from the reaction mixture using
rotary evaporator and the purification of the obtained
powder was carried out through silica gel column
using 1 : 1 DCM : hexane as an eluent. Yield: 35%. 1H
described in a method reported by Rohand et al. [24].
Synthesis of 5-(4'-Bromophenyl)-15-(Mesityl)-10,20-
Bis(2-Thienyl)porphyrin (Por-1)
First of all, 100 mL of dichloromethane was added
in a 250 mL round bottom flask and then purged with
nitrogen for 10 min. 5-(4-Bromophenyl)dipyrometh-
ane (1) (1 mmol, 301.18 mg), 5-mesityldipyrrometh-
ane (2) (264.0 mg), and 2-thiophenecarboxyaldehyde
NMR (CDCl , 400 MHz): δ (ppm) = 9.11–9.063 (d,
3
(
2 mmol, 190.8 mg) were added. After the solution was 2H, pyrrolic-H), 8.89 (d, 4H, pyrrolic-H), 8.71 (d,
degassed, boron trifluoride-diethyl ether (BF ⋅ OEt ) 2H, pyrrolic-H), 8.26–8.32 (d, 2H, Ar-H), 8.01–8.04
3
2
(
0.2 mmol, 23.2 μL) was added and stirred for 60 min (m, 2H, Ar–H), 8 (d, 2H, Ar–H), 7.92 (3H, thienyl-
at room temperature in dark (protecting the reaction H), 7.5 (3H, thienyl-H), 7.29 (4H, mesityl Ar–H),
from the light). Then, DDQ (2 mmol, 0.452 g) was
added and final solution was stirred for additional
4
.01 (s, 3H, COOMe), 2.63 (s, 3H, mesityl-H), and
1
.85 (s, 6H, mesityl-H). MALDI TOF MS: calcd. for
6
0 min at room temperature in open atmosphere. The
+
C H N O S ([M+H] ) 803.00; found 804.54.
51
38
4
2
2
solvent was removed completely from the reaction
mixture using rotary evaporator. Finally, the purifica-
tion was carried by column chromatography using a
Electrochemical Experiments
silica gel and 1 : 3 DCM : hexane as an eluent. Yield:
1
1
1%. H NMR (CDCl , 400 MHz): δ (ppm) = 9.00–
3
An Ivium CompactStat potentiostat/galvonastat
9
.04 (d, 2H, pyrrolic-H), 8.80 (d, 4H, pyrrolic-H),
.69–8.71 (d, 2H, pyrrolic-H), 8.05–8.09 (m, 2H,
was used for electrochemical experiments. Glassy car-
bon electrode (GCE) disc was used as working elec-
trode in three-electrode system, while platinum (Pt)
wire and silver/silver chloride (Ag/AgCl) were used as
counter and reference electrodes, respectively. The
disperse solution of porphyrin was obtained by soni-
cating 1.0 mg Por 2 in 1 mL of DCM. Then, 10 μL of
porphyrin dispersion was dropped on the GCE surface
8
Ar-H), 7.88–7.92 (3H, thienyl-H), 7.83–7.85 (d, 2H,
Ar-H), 7.5 (3H, thienyl-H), 7.26–7.28 (d, 2H, mesityl
Ar–H), 2.63 (s, 3H, mesityl-H), and 1.84 (s, 6H, mesi-
tyl-H). MALDI TOF MS: calcd. for C H BrN S
43
31
4 2
+
([M + H] ) 747.77; found 748.64.
Synthesis of 5-(4'-Methoxycarbonyl-1,1'-Biphenyl)-15- and the electrode was left at ambient atmosphere to be
(
Mesityl)-10,20-Bis(2-Thienyl)porphyrin (Por-2)
dried. Prior to any coating, the surface of GCE was
Por-2 was synthesized thorough palladium-cata- cleaned thoroughly with alumina powder of 0.05 μm.
lyzed Suzuki-coupling reaction as shown in Fig. 1. Schematic illustration of fabrication process of the
Por-1 (0.1 mmol, 4-methoxycarbonylphenylboronic modified GCE electrode with poly-porphyrin was
acid (0.11 mmol, 19.8 mg), 74.775 mg), Na CO
shown in Scheme 1.
2
3
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ENHANCED ELECTROCATALYTIC ACTIVITY
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Por-2
Por-1
500
3
3000
2500
2000
1500
1000
500
−
1
Wavenumber (cm )
Fig. 2. FT-IR spectra of porphyrin derivatives.
Characterization
FTIR
Figure 2 represents the FTIR spectra of the por-
Fourier-transform infrared (FTIR) spectroscopic
analyses were taken in KBr pellet on a Perkin Elmer phyrin derivatives. The spectra of Por-2 showed a
Spectrum BX FTIR spectrometer. The NMR strong and intense absorption peaks at around 1722
–1
(
400 MHz) spectra of the obtained compounds were and 1276 cm due to the carbonyl (C=O) and ester
measured using a Bruker Ultrashield Plus Biospin (C–O–C) bonds. The presence of these absorption
spectrometer. MALDI-TOF mass spectra were peaks confirms the formation of Por-2 derivative. The
recorded on Bruker Microflex LT spectrometer. The bands at around 1610, 1557, 1471, 1400, 1177, and
–1
electrochemical measurements were performed at 977 cm in two spectrums are due to the ring stretch-
room temperature on IVIUMSTAT potentiostat.
ing modes of the porphyrin derivatives. In addition,
both compounds displayed a vibrational peak at
–1
3
313 cm , which is due to the stretching of pyrrolic
RESULTS AND DISCUSSION
N–H bonds.
Synthesis
Electrochemical Polymerization
The polymerization of porphyrin (Por-2) on GCE
The synthetic steps of Por-2 compound are repre-
sented in Fig. 1. Firstly, 5-(4-bromophenyl)dipyrro-
methane (1) and 5-mesityldipyromethane (2) were surface was carried out using cyclic voltammetry (CV)
synthesized as described in the literature. Por-1 com- method. Figure 3 shows CV curves recorded during
pound was synthesized by using Lindsey method cata- the electropolymerization of Por-2 on GCE. The
lyzed with BF ⋅ OEt followed by oxidation step using 5-positions on the thienyl substituents are electroac-
3
2
DDQ in dichloromethane. The condensation of tive and therefore, offer the possibility of the corre-
dipyrromethanes and pyrrole resulted in Por-1 deriva- sponding porphyrin molecule to be polymerizable to
tive. Three different main products were formed at the form electropolymer film (Scheme 1). As seen from
end of this reaction, so that Por-1 was separated by sil- Fig. 3, new oxidation and reduction peaks are
ica gel-column chromatography as described above. observed and their currents increase regularly with
Then, the Por-2 was synthesized via palladium-cata- increasing the scanning cycles, indicating the forma-
lyzed Suzuki-Miyaura cross-coupling reaction by tion of poly-porphyrin conducting layer on the GCE
introducing 4-methoxycarbonylphenyl group at the surface. The anodic peak located at +0.4 V can be
Por-1 meso position.
attributed to the oxidation of the porphyrin ring [25],
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 94 No. 13 2020

2840
SADIK COGAL, AYSEGUL OKSUZ
5
00
00
00
00
while the anodic peak at +1.2 V indicating the oxida-
tion of the 2-thienyl groups at the meso positions [15].
4
3
2
Electrochemical Characterization
Oxidation of
Oxidation of thienyl group
porphyrin ring
Electrochemical behaviors of bare GCE, GCE-
Por, and GCE-PPor were investigated in 5.0 mM of
3
–/4–
[
Fe(CN) ]
solution prepared in 0.1 M KCl.
6
100
Figure 4a shows cyclic voltammograms of different
electrodes for applied potential from –0.3 to –0.5 V at
0
–1
scan rate of 50 mV s . It was observed that the anodic
peak current (52.6 μA) and cathodic peak current
ꢀ100
(
0.15 μA) of GCE-PPor are distinct and higher than
ꢀ
2
ꢀ1
0
1
2
that of unmodified GCE and Por coated electrode
(GCE-Por). This result indicates the faster electron
transfer on the GCE-PPor electrode, which may be
explained by π-enhanced conjugation.
Potential vs. Ag/AgCl (V)
Fig. 3. CVs of GCE-Por for applied potential from –2.0 to
2.0 V at a scan rate of 50 mV s–1 for 5 cycles in 0.1 PBS
+
(
pH 7.4).
The electrocatalytic behaviors of GCE-PPor elec-
trode in the presence of DA were investigated by using
CV measurements. For comparison, the CV measure-
ments were taken in the same conditions for bare GCE
and GCE-Por electrodes. The CVs of DA at different
7
5
(
a)
c
5
0
5
0
a
–1
electrodes were recorded at a scan rate of 50 mV s for
the potential range from –0.2 to 0.5 V, which are pre-
sented in Fig. 4b. These CVs clearly show that the dif-
ferent electrodes exhibit oxidation/reduction couples,
which are due to specific electrochemical response of
DA molecule. The anodic oxidation peak potentials of
DA obtained at the bare GCE, GCE-Por, and GCE-
PPor are 0.21, 0.174, and 0.168 V, respectively. It was
calculated that the anodic peak current of DA at the
GCE-PPor (22.7 μA) was 1.6 and 9.4 times bigger
than that at the bare GCE (13.8 μA) and GCE-Por
(2.4 μA), respectively. Compared with the GCE-Por,
GCE-PPor electrode exhibited significantly enhanced
catalytic activity towards DA. This improvement could
be explained by the highly conjugated structure of por-
phyrin after electropolymerization. The polymer film
of porphyrin has higher electron mobility than the
unpolymerized form, resulting in higher response cur-
rent of DA.
2
b
−25
−50
−
75
−
0.4
−0.2
0
0.2
0.4
0.6
Potential vs. Ag/AgCl (V)
2
5
c
(
b)
2
0
1
5
a
b
1
0
The effects of scan rate on the electron transfer
behavior of GCE-PPor were investigated through
cyclic voltammetry. Figure 5a shows the CVs of GCE-
PPor in 0.1 M PBS with constant concentration
5
0
5
(
0.5 mM) of DA at varied scan rates from 25 to
−
–1
4
00 mV s . The CVs under same conditions showed
that oxidation and reduction peak potentials of DA are
−10
reproducible. Furthermore, the anodic (I ) and
pa
−
0.2 −0.1
0
0.1
0.2
0.3
0.4
0.5
cathodic peak current (I ) values were plotted vs. scan
Potential vs. Ag/AgCl (V)
pc
rate, which give linear plots with the following equa-
–1
tions: I (μA) = 0.1754х (V s ) + 5.7726 for anodic
pa
Fig. 4. (a) CVs of (a) bare GCE, (b) GCE-Por, and (c)
GCE-PPor were taken in 5.0 mM [Fe(CN)6]
–1
3–/4–
scan and I (μA) = –0.1339ν (V s ) + 1 0.4928 for
pc
solu-
2
–1
cathodic scan with a correlation coefficients (R ) of
tion in 0.1 M KCl at the scan rate of 50 mV s . (b) CVs of
DA (0.5 mM) at the bare GCE (a), GCE-Por (b), and
GCE-PPor (c) performed 0.1 M PBS (pH 7.4) at a scan
0.9986 and 0.9994, respectively (Fig. 5b). This result
suggests a quasi-reversible electron transfer took place
on the poly-porphyrin modified electrode.
rate of 50 mV s–1 for the potential range of –0.3 to 0.5 V.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A
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ENHANCED ELECTROCATALYTIC ACTIVITY
(a)
2841
1
00
14
1
4
00 mV s−
(
a)
8
0
0
0
0
0
1
9.2 μM
12
6
4
2
5 mV s−1
10
8
2
6
1.0 μM
−20
−40
−60
−80
4
2
Without addititon
0
−0.1
0
0.1
0.2
0.3
0.4
0.5
−
0.2 −0.1
0
0.1 0.2 0.3 0.4 0.5
Potential vs. Ag/AgCl (V)
Potential vs. Ag/AgCl (V)
8
6
4
2
0
(b)
8
6
4
2
0
(b)
0
0
0
0
y = 0.1754x + 5.7726
2
R = 0.9986
Anodic
Cathodic
−20
−40
−60
y = −0.1339x + 0.4928
2
R = 0.9994
0
5
10
DA (μM)
15
20
0
50 100 150 200 250 300 350 400 450
C
−1
Scan rate (mV s )
Fig. 6. (a) DPV’s of GCE-PPor in 0.1 M PBS (pH 7.4)
with different DA concentrations (1.0–19.2 μM) at a scan
Fig. 5. (a) The CVs of GCE-PPor at varied scan rates in 0.1
M PBS (pH 7.4) containing 0.5 mM dopamine. (b) Plots
of anodic and cathodic peak currents versus scan rates.
–1
rate of 10 mV s . (b) Calibration curve obtained from
DPVs.
Dopamine Detection with Differential Pulse
Voltammetry
centration of dopamine, respectively. Sensitivity of
the PPor-based sensor was estimated to be
–1
–2
5
.82 μA μM cm by using the slope value of the
The analytical studies show that DPV method is
more sensitive than that of the CV and has been widely
selected for electrochemical determination of very low
amounts of analytes [26]. Thus, the electrochemical
detection of DA on the GCE-PPor electrode was per-
formed through DPV measurements by applying a
regression equation (determined from linear part of
the calibration curve). On the other hand, the limit of
detection was found as 0.42 μM (S/N = 3) for dopa-
mine. These analytical parameters obtained from the
developed sensor were compared to previously
reported works, as given in Table 1.
–1
potential of –0.2–0.5 V at a scan rate of 10 mV s .
DPVs recorded for different DA concentrations were
presented in Fig. 6a. The oxidation peak current of DA
tends to increase with increasing the DA concentra-
tion in buffer solution. The measured peak currents
from DPVs were plotted against corresponding DA
concentration to obtain the calibration curve for
GCE-PPor electrode. It is clearly seen that the peak
currents change linearly with the DA concentration
between 1.0 and 19.2 μM (linear range), obtaining a
Selectivity and Reproducibility
The selectivity is an important factor for the sensors
and therefore it should be explored through interfer-
ences. It is well know that, UA and AA are found in the
biological systems with DA and the concentrations of
these two interferences are higher than that of DA.
Therefore, DPV measurements of 10 μM dopamine
on GCE-PPor were performed at higher concentra-
regression equation of i (μA) = 0.4112C (μM) +
p
DA
2
0
.1394 with good correlation coefficient (R ) of 0.998, tions of AA and UA (Figs. 7a and 7b). It is obviously
in which the i and C refer to peak current and con- observed that the UA (10–98 μM) and AA (50–
p
DA
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 94 No. 13 2020

2
842
Table 1. Comparison of analytical parameters of some dopamine sensors-based on porphyrin materials
Sensor
Sensitivity, μA μM–1 cm–2 Detection limit, μM Linear range, μM
SADIK COGAL, AYSEGUL OKSUZ
References
GCE-PPor
5.82
—
0.665
—
0.42
0.58
3 × 10
3.5 × 10–
0.1
0.8 × 10
9.45 × 10–
0.01
1.0–19.2
2–200
This work
[18]
RGO/Cu-TECP/GCE
RGO/Zn-TPP/GCE
ERGO-P/GCE
–
3
0.04–238
0.1–500
0.4–10.3
0.0024–3.6
1–70
[19]
[20]
[21]
[22]
[27]
[28]
2
–1
TCPP-Sa/CPE
0.41 (given as μA μM )
–3
Na (CuTCPP)/graphene/GCE
—
—
—
4
3
Porphyrin-RGO/GCE
TCPP/CCG/GCE
0.01–70
GCE, glassy carbon electrode; graphene oxide; RGO, reduced graphene oxide; ERGO, electrochemically reduced graphene oxide; Cu-
TECP, tetrakis-(ethoxycarbonyl) porphyrin copper(II); Na (CuTCPP), copper(II)-tetra(4-carboxyphenyl)porphyrin tetrasodium salt;
4
TCCP, meso-tetra(4-carboxy phenyl); Sa, clay; CPE, carbon paste electrode; Zn-TPP, zinc-tetraphenylporphyrin; P, 5,15-pentafluo-
rophenyl-10,20-p-aminophenylporphyrin; TCCP, meso-tetra(4-carboxyphenyl)porphyrin; CCG, chemically reduced graphene mea-
sured but calculated from the material balance.
9
10 μM) as interfering species did not affect the DA
The reproducibility of the poly-porphyrin based
current response of the GCE-PPor electrode, demon- sensor was investigated by preparing five fresh elec-
strating high selectivity towards DA.
trodes, which were tested in 10 μM dopamine by using
DPV. These measurements exhibited a relative stan-
dard deviation (RSD) of 0.19%, demonstrating
acceptable reproducibility.
1
4
(
a)
12
CONCLUSIONS
910 ꢁM
Asymmetric thiophene porphyrin derivative was
synthesized by using condensation reaction followed
with Pd-catalyzed Suzuki-Coupling. The porphyrin
derivative was electrochemically polymerized on GCE
and the electrocatalytic activity of the formed polymer
porphyrin was investigated towards oxidation of dopa-
mine. It was found that poly-porphyrin modified
GCE (after cycling between –2.0 to +2.0 V for 5 cycles
in 0.1 M PBS) exhibited better electrocatalytic activity
with high sensitivity (5.82 μA μM cm ) and low
detection limit for dopamine. The poly-porphyrin
modified electrode also exhibited good selectivity in
the presence of ascorbic acid and uric acid as interfer-
ence compounds as well as sufficient reproducibility.
1
0
AA
5
DA
8
6
4
2
0
0 ꢁM
–1
–2
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0.1
0
0.1
0.2
0.3
0.4
0.5
Potential vs. Ag/AgCl (V)
14
(
b)
12
FUNDING
1
0
8
6
4
2
0
DA
This work was supported by the Burdur Mehmet Akif
Ersoy University Coordinatorship of Scientific Research
Project with the project no. 0369-NAP-16.
9
8 ꢁM
UA
1
0 ꢁM
CONFLICT OF INTEREST
The authors declare that they have no conflict of interest.
ꢀ0.1
0
0.1
0.2
0.3
0.4
0.5
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