Investigation on electrochemical properties of carbon nanotubes

The electrochemical behavior of carboxyl-modified carbon nanotube (CNT) films was investigated. The structure of the modified CNT was characterized by scanning electron microscopy, Raman spectroscopy and infrared spectroscopy. Experimental results showed that the physical structure of CNTs was not changed, but the ends of CNT were opened, and oxidized into carboxylate groups, which might react with other reagents. Cyclic voltammetry of Fe2+ was conducted in 0.2 M HClO4, A stable, quasi-reversible voltammetric response is seen for Fe3+/(2+) at the carboxyl-modified CNT electrode, and the anodic and the cathodic peak potentials were 1.120 and 0.145 V vs. saturated calomel electrode at a scan rate of 0.15 V s(-1), respectively. Both anodic and cathodic peak currents depended linearly on the square root of the scan rate over the range of 0.025-0.2 V s(-1), which suggested that the process of the electrode reactions was diffusion-controlled. There were significant differences in voltammetry between the non-modified CNT surface and the carboxyl-modified CNT surface for Fe2+. The low level and stable detection of hydrazine was performed in a phosphate buffer pH 6.6. The peak current increased linearly with the hydrazine concentration from 0.01 to 1 mM and the concentration limit of quantitation was 0.01 mM. The results obtained are discussed in detail. (C) 2003 Elsevier Science B.V. All rights reserved.