Studies On The Application Of Carbon Nanotubes Composite Film Modified Electrodes In Biosensors

In this dissertation, efforts have been devoted to the fabrication of electrochemical sensor and biosensor based on the carbon nanotubes compsite film modified electrodes. The dissertation consists of two main parts: one is the study of the amperometric glucose biosensors based on integration of glucose oxidase onto Prussian blue/carbon nanotubes nanocomposite electrodes and the other is the electrochemical electrocatalytic oxidation of NADH with meldola's blue functionalized carbon nanotubes electrodes.(1) Nano-sized Prussian blue (PB) particles were synthesized with a chemical reduction method and then the PB nanoparticles were assembled on the surface of multiwall carbon nanotubes modified glassy carbon electrode (PB/MWNT/GCE). The results showed that the PB/MWNT nanocomposite exhibits a remarkably improved catalytic activity towards the reduction of hydrogen peroxide. Glucose oxidase (GOD) was immobilized on the PB/MWNT platform by an electrochemically polymerized o-phenylenediamine (OPD) film to construct an amperometric glucose biosensor. The biosensor exhibited a wide linear response up to 8 mM with a low detection limit of 12.7μM (S/N=3). The selectivity and stability of the biosensor were also investigated.(2) Meldola's blue (MB) functionalized carbon nanotubes (CNT) nanocomposite film (MB/CNT) electrode was prepared by non-covalent adsorbing MB on the surface of a carbon nanotubes modified glassy carbon electrode (CNT/GCE). Electrochemical behaviors of the resulting electrode were investigated thoroughly with cyclic voltammetry in the potential range of -0.6 to 0.2 V, and two well-defined redox couples were clearly visualized. We also studied the electron transfer kinetics of MB loaded on CNT (MB/CNT) in comparison with that of MB on conventional graphite powder (MB/GP). The heterogeneous electron-transfer rate constant (ks) of MB/CNT was calculated to be about three times larger than that of MB/GP. Based on the results, a new NADH sensor was successfully established using the MB/CNT/GCE. Under a lower operation potential of -0.1 V, NADH could be detected linearly up to a concentration of 500μM with an extremely lower detection limit of 0.048μM estimated at a signal to noise ratio of 3. Sensitivity, selectivity, reproducibility and stability of the NADH sensor were also investigated and the main analytical data were also compared with those obtained with the MB/GP/GCE.