H^sub 2^O^sub 2^ Detection at Carbon Nanotubes and Nitrogen-Doped Carbon Nanotubes: Oxidation, Reduction, or Disproportionation?

The electrochemical behavior of hydrogen peroxide (H...O...) at carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) was investigated over a wide potential window. At CNTs, H...O... will be oxidized or reduced at large overpotentials, with a large potential region between these two processes where electrochemical activity is negligible. At N-CNTs, the overpotential for both H...O... oxidation and reduction is significantly reduced; however, the reduction current from H...O..., especially at low overpotentials, is attributed to increased oxygen reduction rather than the direct reduction of H...O..., due to a fast chemical disproportionation of H...O... at the N-CNT surface. Additionally, N-CNTs do not display separation between observable oxidation and reduction currents from H...O... Overall, the analytical sensitivity of N-CNTs to H...O..., either by oxidation or reduction, is considerably higher than CNTs, and obtained at significantly lower overpotentials. N-CNTs display an anodic sensitivity and limit of detection of 830 mA M... cm... and 0.5 ...M at 0.05 V, and a cathodic sensitivity and limit of detection of 270 mA M... cm... and 10 ...M at -0.25 V (V vs Hg/Hg...SO...). N-CNTs are also a superior platform for the creation of bioelectrodes from the spontaneous adsorption of enzyme, compared to CNTs. Glucose oxidase (GOx) was allowed to adsorb onto N-CNTs, producing a bioelectrode with a sensitivity and limit of detection to glucose of 80 mA M... cm... and 7 ...M after only 30 s of adsorption time from a 81.3 ...M GOx solution. (ProQuest: ... denotes formulae/symbols omitted.)