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Application of Planar Electrode Modified with Ferrocene to Glucose Biosensor
Yi-Sheng Wang(汪乙生), Chung-Min Lien(連崇閔), Hau Lin(林浩)
Department of Chemical and Materials Engineering, Southern Taiwan University
ABSTRACT
RESULTS AND DISCUSSION
. A study was conducted to use the ferrocene to modify the screen printed planar
electrode which was used as the working electrode to detect the responding current of
reduction of hydrogen peroxide and then the concentration of hydrogen peroxide could
be obtained from the responding current and consequently, the concentration of the
glucose could be obtained. The results showed that the responding current for the carbon
paste electrode modified with the ferrocene was elevated significantly. The optimum
weight ratio for ferrocene : graphite carbon powders was 3 : 7 . At 30℃ , -0.2V operating
potential, and in 0.05 M PBS buffer solution( pH = 7.4 ), when the screen printed planar
electrode was modified with the ferrocene [ferrocene : graphite carbon powders = 3 : 7
( weight ratio )] , the detection limit was 0.01 mM H2O2 , the linear range was 0.01～0.4
mM H2O2, R2=0.994, and the sensitivity was 238.27 μA/cm2ּmM H2O2 . For the glucose
screen printed planar sensor, the detection limit was 0.06 mM C6H12O6 ; the linear range
was 0.06 ~ 2.5 mM C6H12O6 ; R2 = 0.997 and the sensitivity was 5.12 μA/cm2 ．
mMC6H12O6 .
INTRODUCTION
In recent years, diabetes has become one of the top ten causes of death for the people
in Taiwan. Therefore, developing a rapid, convenient, and economical glucose biosensor
for detecting the glucose is an important research subject. The glucose and oxygen can be
catalyzed by the glucose oxidase and the glucose is oxidized to gluconic acid and the
oxygen is reduced to hydrogen peroxide. Because the ferrocene (Fe(C5H5)2) possesses the
excellent conductivity and catalytic characteristic, it can be used to elevate the responding
current for detection of reduction of hydrogen peroxide. A study was conducted to use the
ferrocene to modify the carbon paste electrode and screen printed planar electrode which
were used as the working electrodes to detect the responding current of reduction of
hydrogen peroxide in the phosphate buffer solution(PBS) and then the concentration of
hydrogen peroxide could be obtained from the responding current and consequently, the
concentration of the glucose could be determined.
(A)
(A)
(B)
(C)
(D)
(B)
Fig. 2 TB graphs of the carbon paste
electrodes with different ratios of ferrence to
graphite carbon powders; the ferrence to
graphite carbon powders were 〔(A) 3:7 (B)
2:8 (C) 1:9 (D) 0:10 (unmodified carbon paste
electrode ) 〕; the operating potential = –0.2 V;
in 0.1 M KCl of 5 mL 0.05 M PBS buffer
solution (pH =7.4); stirring rate =500 rpm;
after deoxygenating by purging nitrogen gas
for 20 minutes,10 μL of 50mM H2O2 is
injected per 100 seconds
Fig 1. CV graphs for (A) carbon paste
electrode modified with ferrocene (B)
unmodified carbon paste electrode; after
deoxygenating by purging nitrogen gas for 20
minutes; in 0.1 M KCl of 5 mL 0.05 M PBS
buffer solution (pH =7.4) the range of
scanning potential: -0.8～+0.8 V, scanning
rate = 50 mV/s
EXPERIMENTAL
Chemicals and Reagents
Ferrocene(Fe(C5H5)2); Hydrogen Peroxide (H2O2); D(+)-Glucose
Monohydrate(C6H12O6); Glucose Oxidase(EC 1.1.3.4, Type X-S: From Aspergillus Niger,
50000 units/mg); Graphite Carbon Powder; Carbon Paste; Cyclohexanone(C6H10O); Nafion;
Potassium Dihydrogenphosphate (KH2PO4); Potassium Chloride (KCl).
Equipment
Electrochemical Analyzer (BAS 100W) was used to measure the activity of electrode by
Cyclic Voltammetry ( CV ) and Time Base ( TB ) mode ; pH meter (Metrohm 731); Carbon
Paste Electrode and Screen Printed Planar Electrode were used as the working electrodes,
Coiled Platinum Wire was used as the counter electrode and Ag / AgCl was used as the
reference electrode.
Fig.4 The TB graph of screen printed planar
electrodes for detection of the linear range of H2O2
(ferrocene : graphite carbon powders = 3 : 7)
Fig. 3 The TB graph of screen printed
planar electrodes for detection of the
detection limit of H2O2 (ferrocene :
graphite carbon powders = 3 : 7)
Procedure
Take one section of 7 cm electric wire with 0.05 cm inside diameter. After depriving
the coating 0.5 cm length from both ends, the nake-ended wire was washed, dried and
ready for use. Then the ferrocene powders, graphite carbon powders and carbon paste
were mixed with the appropriate ratio. After the mixing was complete, the mixture was
evenly coated on the nake-ended electric wire and dried in the oven and then we obtained
the carbon paste electrode. The surface area of the carbon paste electrode was 0.0805 cm2 .
0.5 cm
0.05 cm
7 cm
Fig. 5 The TB graph of screen printed planar
electrode for detection of the detection limit
of glucose (ferrocene : graphite carbon
powders = 3 : 7)
Different weights of
ferrocene
Fig. 6 The TB graph of screen printed
planar electrode for detection of the
linear range of glucose (ferrocene :
graphite carbon powders = 3 : 7)
CONCLUSIONS
Different weights of carbon
powders
Coated on
the nakeended
electric
wire
Mixing with equal
weight of carbon
paste
The above mentioned mixture with the appropriate ratio was evenly coated on the front
side of screen plate and then the PE paper was placed under the screen plate and the
plastic plate was used to print the mixture on the PE paper evenly. The electrode was
dried in the oven. After the electrode was dried, the 2μL glucose oxidase solution was put
onto the electrode and the electrode was dried at room temperature. Then 5μL of 1%
Nafion solution was dropped onto the electrode evenly and after the electrode was dried
at room temperature, we obtained the screen printed planar glucose electrode.
1
the 2μL glucose
oxidase solution
was put onto the
electrode and the
electrode was
dried
2
5μL of 1% Nafion
solution was
dropped onto the
electrode evenly
The results showed that the responding current for the carbon paste electrode modified with
the ferrocene was elevated significantly. The optimum weight ratio for ferrocene : graphite
carbon powders was 3 : 7 . At 30℃ , -0.2V operating potential, stirring rate = 500 rpm and in
0.05 M PBS buffer solution( pH = 7.4 ), when the screen printed planar electrode ( the surface
area of the screen printed planar electrode was 0.2827 cm2 )was modified with the ferrocene
[ferrocene : graphite carbon powders = 3 : 7 ( weight ratio )] , the detection limit was 0.01 mM
H2O2 , the linear range was 0.01～0.4 mM H2O2, R2=0.994, and the sensitivity was 238.27
μA/cm2ּmM H2O2 . For the glucose screen printed planar sensor, the detection limit was 0.06
mM C6H12O6 ; the linear range was 0.06 ~ 2.5 mM C6H12O6 ; R2 = 0.997 and the sensitivity
was 5.12 μA/cm2 mM C6H12O6 .
REFERENCES
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Actuators B, 76,193 (2001).
3.M. A. Kim and W.-Y. Lee, “Amperometric Phenol Biosensor Based on Sol-Gel
Silicate/Nafion Composite Film,” Analytica Chimica Acta, 479, 143 (2003).
4. Y.-M. Uang and T.-C. Chou , “Fabrication of Glucose Oxidase/Polypyrrole
Biosensor by Galvanostatic Method in Various pH Aqueous Solutions,” Biosensors
and Bioelectronics, 19, 141 (2003).