Functionalized carbon nanotubes as the platforms in the dopamine and ascorbic acid biosensors

The main goal of this study was to design and develop novel carbon nanotube (CNT) based platforms as biosensors for simultaneous voltammetric detecting dopamine (DA) and ascorbic acid (AA). The use of such novel nanostructured electrode platforms will enable the development of affinity-based biosensors for disease diagnostics and therapy monitoring. Such bio-sensing systems will perform sensitively and selectively for detection of the neurotransmitters/neurochemicals by utilizing certain CNT material structure and introducing various functional groups, thus enhance response to the specific bioanalytes. The electrical devices are extremely useful for delivering the diagnostic information in a fast and simple way. A highly sensitive and selective dopamine sensor was fabricated with a unique 3D CNTs nanoweb electrode. The as-synthesised CNT nanoweb was modified by oxygen plasma to graft functional groups in order to increase selective and electroactive sites at the CNT sidewalls. This electrode was characterized physically and electrochemically using HRSEM, Raman, FT-IR and cyclic voltammetry (CV), respectively. Our investigations indicated that the O2-plasma treated CNT nanoweb electrode could serve as a highly sensitive biosensor for the selective sensing of dopamine (1 μM to 20 μM) in the presence of ascorbic acid (1000 μM). Polymer adsorbed multiwalled CNTs (MWCNTs), such as Nafion/MWCNTs and poly (diallyldimethylammonium chloride)/MWCNTs (PDDA/MWCNTs), were prepared to selectively sensing DA and AA, respectively. Compared with the as synthesized CNT nanoweb, the composite materials showed enhanced sensitivity towards oxidation of DA and AA. The the MWCNTs composites were characterized using thermogravimetric analysis (TGA), zeta potential, HRSEM, Raman and CV. In addition, differential pulse voltammetry (DPV) was conducted to determine DA (0.1 μM to 10 μM) and/or AA (10 μM to 200 μM) in the DA and AA mixture solution.