Recoverable Solution Reaction of HiPco Carbon Nanotubes with Hydrogen Peroxide

Abstract

There is increasing interest in developing single-walled carbon nanotubes (SWNTs)-based optical biosensors\nfor remote or in vitro and in vivo sensing because the near-IR optical properties of SWNTs are very sensitive\nto surrounding environmental changes. Many enzyme-catalyzed reactions yield hydrogen peroxide (H₂O₂) as\na product. To our knowledge, there is no report on the interaction of H₂O₂ with SWNTs from the optical\nsensing point of view. Here, we study the reaction of H₂O₂ with an aqueous suspension of water-soluble (ws)\nHiPco SWNTs encased in the surfactant sodium dodecyl sulfate (SDS). The SWNTs are optically sensitive\nto hydrogen peroxide in pH 6.0 buffer solutions through suppression of the near-IR absorption band intensity.\nInterestingly, the suppressed spectral intensity of the nanotubes recovers by increasing the pH, by decomposing\nthe H₂O₂ into H₂O and O₂ with the enzyme catalase, and by dialytically removing H₂O₂. Preliminary studies\non the mechanisms suggest that H₂O₂ withdraws electrons from the SWNT valence band by charge transfer,\nwhich suppresses the nanotube spectral intensity. The findings suggest possible enzyme-assisted molecular\nrecognition applications by selective optical detection of biological species whose enzyme-catalyzed products\ninclude hydrogen peroxide.