In-situ Vis/NIR spectroelectrochemistry of single-walled carbon nanotubes enriched with (6,5) tubes

An in-situ optical Vis/NIR spectroelectrochemistry study was performed on single-walled carbon nanotubes (CoMoCat) enriched with (6,5) tubes via density-gradient ultracentrifugation. Thin semitransparent solid films were prepared from the solution of sorted nanotubes by vacuum filtration and purification with water. Despite the appearance of some bundling of the nanotubes during this procedure, peaks corresponding to optical transitions of tubes with distinct chiralities may be observed in the spectra. The effects of electrochemical redox doping on the electronic state of the nanotubes were investigated in an electrode potential window between -2 and +1.7 V vs. Ag-pseudoreference electrode. The bleaching of ΔE₁₁^S and ΔE₂₂^S optical transitions is traced for particular tubes, which allows a partial quantification of changes in the electronic density of states (DOS) caused by their filling with electrons or holes.