Spectroscopic Determination of the Electrochemical Potentials of n-Type Doped Carbon Nanotubes

Understanding the doping mechanism that involves substantial charge transfer between carbon nanotubes and chemical adsorbent is of critical importance for both basic scientific knowledge and nanodevice applications. Nevertheless, it is difficult to estimate the modification of electronic structures of the doped carbon nanotubes. Here we report measurements of electrochemical potentials of n-doped single-walled carbon nanotubes (SWCNTs) by using photoluminescence (PL) measurement. The change of the measured PL intensity before and after n-type doping was used to extract the electrochemical potential using the Nernst equation. The measured electrochemical potentials of SWCNTs approached the theoretical reduction potential of SWCNTs as the mole concentration of the dopant increased. The doping effect was also confirmed by the change of absorption spectroscopy. The quenching of the PL and absorption intensity was strongly correlated to the standard reduction potential of the dopant and its concentration. This investigation could be a cornerstone for SWCNTs-based electronic device applications such as solar cells, light-emitting diodes, and nanogenerators.