title: H2O2 Detection at Carbon Nanotubes and Nitrogen-Doped Carbon Nanotubes: Oxidation, Reduction, or Disproportionation?
abstract: The electrochemical behavior of hydrogen peroxide (H2O2) at carbon nanotubes (CNTs) and nitrogen-doped carbon nanotubes (N-CNTs) was investigated over a wide potential window. At CNTs, H2O2 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 H2O2 oxidation and reduction is significantly reduced; however, the reduction current from H2O2, especially at low overpotentials, is attributed to increased oxygen reduction rather than the direct reduction of H2O2, due to a fast chemical disproportionation of H2O2 at the N-CNT surface. Additionally, N-CNTs do not display separation between observable oxidation and reduction currents from H2O2. Overall, the analytical sensitivity of N-CNTs to H2O2, 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(-1) cm(-2) and 0.5 μM at 0.05 V, and a cathodic sensitivity and limit of detection of 270 mA M(-1) cm(-2) and 10 μM at -0.25 V (V vs Hg/Hg2SO4). 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(-1) cm(-2) and 7 μM after only 30 s of adsorption time from a 81.3 μM GOx solution.
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, Texas 78712-1224, United States.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Goran
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, Texas 78712-1224, United States.
authors.forename: Ethan N H
authors.initials: EN
authors.lastname: Phan
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, Texas 78712-1224, United States.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Favela
authors.affiliation: Department of Chemistry, Center for Nano- and Molecular Science and Technology, The University of Texas at Austin, 105 E. 24th St. Stop A5300, Austin, Texas 78712-1224, United States.
authors.forename: Keith J
authors.initials: KJ
authors.lastname: Stevenson
mesh_terms: D055664:Electrochemical Techniques; D004566:Electrodes; D006861:Hydrogen Peroxide / Q000032:analysis*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D037742:Nanotubes, Carbon; D006861:Hydrogen Peroxide; D009584:Nitrogen