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Abstract
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In this study, electron transfer performance and direct electrochemistry of hemoglobin immobilized
on graphene quantum dots-chitosan nanocomposite (Hb-GQDs-Chit) for biosensing purposes
was investigated. Transmission electron microscopy, UV-Vis, photoluminescence, scanning electron
microscopy, X-ray diffraction, electrochemical impedance spectroscopy and cyclic voltammetry
techniques were used for characterizing of the prepared biosensor. Electron transfer coefficient ()
of the Hb-GQDs-Chit was calculated to be 0.56, indicating good activity and fast heterogeneous
electron transfer rate between the Hb and electrode surface. The biosensor exhibited good linear
response to hydrogen peroxide over the concentration range 1.5–195 M with a detection limit of
068 M and sensitivity of 053 A M−1 cm−2. Due to the unique electron transfer ability and
high surface-to-volume ratio of GQDs, and also good biocompatibility of chitosan, the fabricated
biosensor shows good stability, short response time and high sensitivity. The prepared biosensor
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