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Abstract
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Graphene, a new class of 2D carbon nanomaterials with one atom thickness, has attracted
considerable attention in recent years [1]. Graphene based electrodes could be modified with
other nanomaterials or biological molecules to further improve their electrochemical
performances [2]. Recently, determination of insulin with various electrodes has been
reported in literature. As insulin is a predictor of diabetes, insulinoma and trauma [3], its
detection has a lot of importance in clinical diagnostics.
In this study, the surface of carbon ceramic electrode (CCE) was graphenized using direct
voltage in sulfuric acid. Afterward, the graphenized CCE (GCCE) was floated in 0.01 M
NiNO3 solution and the potential was cycled between -1.5 to 1.0 V with a scan rate of 25 mV
s-1. During 65 cycles, nickel nanoparticles were electrodeposited on the surface of GCCE
(Ni/GCCE). Then, the modified electrode was activated by cyclic voltammetry in optimized
conditions and finally the NiO/GCCE was prepared. The morphology and structure of the
NiO/GCCE was characterized by SEM, AFM and EDS techniques. By using cyclic
voltammetry technique, various experimental parameters influencing the electrochemical
behavior of the NiO/GCCE were optimized. The electrocatalytic activity of the NiO/GCCE
toward the electro-oxidation of insulin was studied in details. The NiO/GCCE showed high
sensitivity for insulin detection in low concentrations with the detection limit of 0.63 nM,
dynamic range of 1 to 200 nM and sensitivity of 3883.19 μA μM-1 cm-2
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