The Effect Of Carbon Dots On Conductive Ink As A Vitamin C Electrochemical Sensor
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Date
2021-06-01
Authors
Lee, Mun Yi
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The demand for portable and disposable electrochemical sensors using
conductive ink is increasing due to its flexibility and conductivity. With the recent
discovery of carbon dots and its conductivity improvement, it can be modified as an
additives in the conductive ink to see its effect as an electrochemical sensor towards
vitamin C. In this study, an easy and inexpensive fabrication of unsupported sensor
strips using carbon black (CB) as filler and alternate different binder such as polyvinyl
alcohol (PVA) and polymethyl methacrylate (PMMA) was fabricated. The conductive
ink prepared was casted on non-woven cloth using membrane casting tool and allowed
to cured. It was then cut into standard sizes for characterization as well for cyclic
voltammetry (CV) for vitamin C detection. The optimum of the conductive ink was 6:4
(m:m) CB: PVA, with higher molecular weight (MW) and hydrolysis degree (DH) of
PVA. Crosslinking of PVA was not needed as it will decrease the conductivity of the
ink. The lowest resistivity obtained for CB/PVA and CB/PMMA sensor strips were
0.357 ± 0.03 Ω·cm and 2.735 ± 0.2 Ω·cm which show CB/PVA conductive ink has more
potential than CB/PMMA conductive ink and even commercial ink. The blending of
carbon dots (CDs) was able to decrease the resistivity at optimum amount. However,
CB/PVA sensor strip was not able to produce any oxidation and reduction peak in CV
showing its non-responsiveness towards detection of vitamin C while CB/PMMA
sensor strip was able to measure the vitamin C presence with limit of detection (LOD)
of 0.622 mM and linear range of 5 – 15 mM. CDs was coated on CB/PVA and
CB/PMMA sensor strips surface but only adhere to CB/PMMA which may due to
porous structure of CB/PMMA sensor strip while detaching of CDs observed for
CB/PVA. The CDs coated on the surface was able to decrease the resistance up to 36%
for both sensor strips and increase the background current of CB/PMMA CV response
showing improved conductivity. However, the peak current response decreased due to
repulsion reaction of same negative charge of vitamin C and the carboxyl groups on
CDs surface. Therefore, the CDs modification was deduced only suitable for detecting
positive charge analyte. The proposed sensor strips exhibited great stability with a 10-
cycles CV run in neutral, acidic but decent performance in alkaline condition.