Singling out the Electrochemistry of Individual Single-Walled Carbon Nanotubes in Solution

Article · July 2008with82 Reads
DOI: 10.1021/ja710625p · Source: PubMed
Abstract
Bandgap fluorescence spectroscopy of aqueous, micelle-like suspensions of SWNTs has given access to the electronic energies of individual semiconducting SWNTs, while substantially lower is the success achieved in the determination of the redox properties of SWNTs as individual entities. Here we report an extensive voltammetric and vis-NIR spectroelectrochemical investigation of true solutions of unfunctionalized SWNTs and determine the standard electrochemical potentials of reduction and oxidation as a function of the tube diameter of a large number of semiconducting SWNTs. We also establish the Fermi energy and the exciton binding energy for individual tubes in solution. The linear correlation found between the potentials and the optical transition energies is quantified in two simple equations that allow one to calculate the redox potentials of SWNTs that are insufficiently abundant or absent in the samples.
  • ... CNT electrodes do not typically show well-defined redox peaks, but continuous cathodic current originating from a mixture of variable CNTs in the film. A detailed spectroelectrochemical study of a range of single-walled carbon nanotubes (SWCNTs) in solution showed how the redox potentials of individual nanotubes depend on their diameter and chirality [123]. The overall electrochemical activity consists of highly active defect-rich areas, including edges, oxides, and the comparably inert basal plane [120]. ...
  • ... First, the fact that the assembly of two species results in energy transfer rather than charge transfer is usually assessed by investigating the relative position of the energy levels of the bare species. This can be done in the present case since the measurement of the redox potentials of both H 2 TPP and SWNTs have been published by several teams [38, 39, 40, 41, 42]. The energy level scheme is depicted inFig. ...
  • ... By using this technique, SWCNTs were solubilized and their electrochemical properties studied. The CV experimental results were checked for consistency with the electronic spectra as a function of the potential and the exciton binding energy [143,144] of the nanotubes and the average reduction and oxidation potentials for the CNTs were confidently established (see Fig. 17) [136]. ...
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