Studies On The Application Of Founctional Carbon Nanotubes Modified Electrodes In Electrochemical Sensors

In this paper, great efforts have been devoted to the fabrication of electrochemical sensors based on the functionalized carbon nanotubes modified electrodes. This paper has three parts: the diazotization was further studied for grafting carbon nanotubes which use dopamine and Nile blue A as the mediator to prepare the NADH sensor; the electrochemical electrocatalytic reduction of H₂O₂ with meldola's blue functionalized carbon nanotubes(CNT) electrodes.(1) The dopamine molecules were covalent to the surface of CNT through electrochemical reduction 4-nitrophenyl diazonium salt. The diazonium cations were synthesized in the electrochemical cell by the reaction of the corresponding 4-nitroaniline with NaNO2 in HCl/H2O solution. Then the nitrophenyl group was electrochemically reduced to aminophenyl groups. According to ring-opening reaction of succinic anhydride, the electrode was successfully modifled by the carboxyl group. Dopamine could be firmly covalented on the surface of carbon nanotubes by carbodiimide reaction. Cyclic voltammetry and electrochemical impedance spectroscopy were used to identify the property of the electrodes. The modified electrodes exhibited a wide linear range up to 400μM with a lower detection limit of 3.02μM as well as a high sensitivity of 6.80μA/mM (S/N=3) for NADH. Selectivity and reproducibility of the NADH sensor were also investigated.(2) A novel amperometric NADH sensor was presented based on a Nile blue A (NB), through the diazotization, ring-opening reaction of succinic anhydride, carbodiimide reaction. Cyclic voltammograms of the redox composite showed two redox couples (about -0.1 V and -0.35 V). The new redox couple has a more positive formal potential which can catalytic oxidation of NADH and the usual redox couple displays hardly electrocatalytic NADH. The electrode showed excellent electrocataltyic activity towards NADH in the presence of other interferences (ascorbic acid, acetaminophen, dopamine and uric acid) at -0.1 V. The NADH sensor shows remarkable analytical characteristics for NADH, better reproducibility as well as reasonable selectivity.(3) Meldola's blue (MB) functionalized CNT (MB/CNT) electrode was prepared by non-covalent adsorbing MB on the surface of carbon nanotubes modified glassy carbon electrode (MB/CNT/GCE). Two well-defined redox couples were visualized. MB/CNT/GCE can effectively oxidation of H₂O₂. Compared with the MB/GCE, the MB/OMC/GCE displayed the highest catalytic oxidation current with the same H₂O₂ concentration. The electrode had a linear range up to 3.5 mM with a lower detection limit of 336μM as well as a high sensitivity of 587μA/mM (S/N=3) for H₂O₂.