Bandgap Selective Chemical Doping of Semiconducting Hipco Single-walled Carbon Nanotubes

Bandgap modulation of single-walled carbon nanotubes (SWCNTs) can be achieved by encapsulation of metallofullerenes, covalent functionalization or changing the tube aggregation states. Another attractive idea is to dope SWCNTs by adding electron donors or acceptors since it allows us to control their electronic states without generating defects in the SWCNT bonding structures. Reversible doping in SWCNTs has been reported by utilizing either chemical dopants [1] or electrochemical methods [2]. A more recent paper reported a diameter selective charge transfer in a dopant-intercalated SWCNT system [3]. By adding a pH-sensitive dopant, ferricyanide, in an aqueous solution of SDS micelleembedded individual SWCNTs, we show that we can reversibly control the electron Fermi level of isolated semiconducting SWCNTs and subsequently change their bandgap absorption.