Year

2019

Degree Name

Doctor of Philosophy

Department

School of Chemistry

Abstract

Electrochemical detection of vital biomolecules using nano-carbon materials has attracted great attention to effectively carry-out electrochemical sensing of important neurotransmitters in the brain. Multi-walled carbon nanotubes (MWNTs) and graphene (G) have been employed as promising nano-carbon materials according to physical, electrical, optical, and thermal properties along with remarkable electrochemical performance. Modified MWNTs and G, on the same hand, exhibited greater electrocatalytic activity and improved redox signals of the targeted analytes. For this reason, the primary goal of this study is to fabricate simple, low cost, biocompatible, and modified MWNTs sensor appropriate for dopamine (DA) neurotransmitter detection. To obtain improved sensitivity and selectivity of DA compared to conventional electrodes, our MWNTs electrode was fabricated by a direct draw of MWNTs fibers from MWNTs forest converted into yarn/probe style by twisting then modified with nafion. The second goal was based on applying reduced graphene oxide (RGO) as graphene derivative along with poly (ethylenedioxythiophene): poly (styrenesulfonate) PEDOT:PSS to prepare RGO/PEDOT:PSS dispersion modified with nafion. RGO/PEDOT:PSS-nafion composite drop-casted onto gold mylar sheets to prepare films at specific dimensions. The deposited films were divided into strips in order to be tested for serotonin (5-HT) neurotransmitter detection. The electrocatalytic activity of both electrodes was investigated via electrochemical analytical methods including cyclic voltammetry (CV) and differential pulse Vvoltammetry (DPV) towards mentioned neurotransmitters in the presence of common interferences. The voltammetric studies included different parameters such as modifying with concentric or diluted nafion, number of nafion layer coated the electrode, varied dip-coating times in nafion, and different films thickness which were all investigated.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.