Web Release Date: October 30,
Redox Reaction of DNA-Encased HiPco Carbon Nanotubes with Hydrogen Peroxide: A Near Infrared Optical Sensitivity and Kinetics Study
and
Department of Chemistry, University of Arkansas, 2801 South University Avenue, Little Rock, Arkansas 72204, and Chemistry Division, Naval Research Laboratory, Washington, D.C. 20375
Received: July 27, 2007
In Final Form: September 4, 2007
Abstract:
The near-infrared optical properties of single-walled carbon nanotubes (SWNTs) have attracted particular attention for nanobiosensors based on their redox chemistry. In this work, we studied the redox reaction of single-stranded DNA (ssDNA)-encased HiPco nanotubes with hydrogen peroxide. The absorption intensity of the near-infrared interband transitions of semiconducting nanotubes decays exponentially with reaction time. The rate constant increases linearly with the H2O2 concentration, consistent with pseudo first-order kinetics. The spectral changes are reversible by tuning the pH, and the sensitivity is enhanced at lower pH in the pH range of 6-8. The reaction rate depends on the buffer, which follows the order MES > Tris > phosphate > TE. The detection limit for H2O2 is determined by three different methods based on the concentration-dependent rate constant, spectral intensity change, and signal-to-noise ratio. Our current work provides new insights into the solution chemistry of the ssDNA-SWNT hybrids for optical biosensing.
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