Studies On The Application Of Carbon Nanotubes Modified Electrodes In Sensors

In this dissertation, efforts have been devoted to the fabrication of electrochemical sensor based on the carbon nanotubes compsite modified electrodes. The dissertation consists of two main parts: one is sol-gel derived carbon nanotubes ceramic composite electrodes for electrochemical sensing and the other is the anodic stripping voltammetric determination of lead in tap water at a Carbon nanotubes/Nafion Composite film Electrode.(1) Rigid and surface renewable carbon nanotubes ceramic composite electrodes (NCE) were fabricated by dispersion of mutilwall carbon nanotubes (MWNT) in sol-gel solution. The electrochemical behavior of such electrodes has been compared with carbon (graphite) ceramic composite electrodes (CCE) and evaluated with respected to the electrochemistry of some biological molecules, such as ascorbic acid (AA), uric acid (UA), acetaminophenol (AP),β-nicotinamide adenine dinucleotide (NADH), epinephrine (EP), dopamine (DA), cysteine, and hydrogen peroxide with cyclic voltammetry. In all cases, NCE provide better reversibility with substantial decreased overpotential, better defined peak shape, and higher sensitivity compared with CCE. In addition, carbon nanotubes and graphite ceramic electrodes were employed as H2O2 and NADH probes. The obtained experimental results further demonstrated remarkable electrochemical advantages of NCE compared with CCE for sensoring applications.(2) Mercury-free sensors for lead (Pb2+) determination based on glassy carbon electrode modified with Nafion and multi-wall carbon nanoturbs (MWNTs/Nafion) had been developed. The analysis of Pb2+ using anodic stripping voltammetry (ASV) includes two steps. Pb2+ ions are firstly accumulation on electrode surface in a Pb2+ solution (9ml) during a preconcentration step at the potential of–1.2V, followed by a measurement step the voltammogram was record by applying a positive-going differential pulse voltammetry potential scan. The scan from–1.0V and was terminated at 0.0V. Linear calibration curve was found in the range of 0.50 to at most 80 nM Pb2+ after 5 min of preconcentration. The detection limit was calculated from 3S/N to be 0.10nM of Pb2+. Reproducibility (RSD%) was found to be 2.77% for a single sensor (five measurements) and 2.15% for five sensors. The sensitivity of determining lead is 0.6188μA/nM. Compared with a nafion and multi-wall film coated GCE greatly improves the sensitivity. The high sensitivity, selectivity, and stability of this MWNTs/Nafion film coated electrode demonstrated its practical application for a simple, rapid and economical determination of trace levels of Pb2+ in tap water samples.