Sivasankar et al.
Electrochemically Exfoliated Graphene for Nanosensor Applications
Table III. Determination of L-phenylalanine in blood plasma sample.
4. CONCLUSIONS
In this study, we have demonstrated the successful syn-
thesis of graphene by electrochemical exfoliation using
potassium sulfate as an intercalating agent. The electro-
chemically exfoliated graphene was well characterized
using various physicochemical techniques. The fabricated
EEG/GCE has been subjected to simultaneous determi-
nation of vanillin and L-phenylalanine and it showed
an overwhelming response. Owing to large surface area
and subtle electronic properties, the EEG/GCE enhances
the oxidation signals and sensitivity towards of vanillin
and L-phenylalanine. The EEG/GCE shows higher sen-
sitivity, linearity and lower limit of detection. The
fabricated electrode was able to detect vanillin and
L-phenylalanine in real samples with detection limit of
0ꢃ8×10−6 Mol L−1 and 2×10−6 Mol L−1 and satisfactory
recoveries of 103.15% and 99.25%. These studies clearly
indicate that such solution processable graphene sheets
by exfoliation of graphite at low temperature offers the
possibility of construction of high quality graphene elec-
trodes. Such low cost fabrication of conductive graphene
sheets will go a long way in the area of electronic
devices.
Concentration of
L-phenylalanine (ꢂM)
Blood sample Added (ꢂM) Found (ꢂM)a Recovery(%) Average (%)
1
2
100
100
98.6
99.9
98.6
99.9
99.25
Note: aAverage of five replicate measurements ( standard deviation).
in the range of 2.6 ꢂM–17.8 ꢂM and 6.6 ꢂM–29.4 ꢂM
with (R2 = 0ꢃ9973) and (R2 = 0.9918) for L-phenylalanine
and vanillin respectively. The limit of detection was esti-
mated as 0.02 ꢂM and 0.01 ꢂM (S/N = 3). A com-
parison of EEG with other similarly modified electrodes
are given in Tables I and II for L-phenylalanine and
vanillin.
Nyquist plots were constructed using bare GCE and
EEG shown in Figures 6(C) and (D) respectively. From
the EIS of bare and modified graphite electrode Ret was
calculated and they found to be 5213ꢄ and 1.8ꢄ respec-
tively. This results clearly shows that EEG is an excellent
conductive martial which transfers electron quickly at the
surface.
References and Notes
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3.5. Analytical Application
Using the fabricated EEG electrode a real time sample,
human plasma, was tested its L-phenylalanine content
100 ꢂL of L-phenylalanine was added to diluted blood
IP: 5.62.159.18 On: Thu, 23 May 2019 19:42:36
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tion conditions. The % recovery was estimated and given
in Table III. This results indicate that L-phenylalanine can
be detected with a very good recovery rate about 98.6 to
99.9% with detection limit of 0ꢃ8 ×10−6 Mol L−1
.
Similarly to find out the vanillin content in a real time
sample, biscuits two different brands were obtained the
local market, dissolved in DD water, stirred for 10 min-
utes, filtered and diluted. To the diluted sample a spike
standard solution of vanillin was added and quantified with
the fabricated EEG electrode. The obtained results are
given Table IV. Here also the EEG exhibited very good
recovery rate above 103.5–102.8% with detection limit
of 2 ×10−6 Mol L−1
.
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Table IV. Determination of vanillin in biscuit samples.
Concentration of
vanillin (ꢂM)
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F. Miao, and C. N. Lau, Nano Lett. 8, 902 (2008).
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Added
Sample (ꢂM)
Found
(ꢂM)a
Biscuits
sample Recovery (%) Average (%)
1
2
100 103.5 0.15 3.5 0.15
100 102.8 0.12 2.8 0.12
103.5
102.8
103.5
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Note: aAverage of five replicate measurements ( standard deviation).
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