Photoluminescence Properties of Single-Walled Carbon Nanotubes Influenced by the Tether Length of Reagents with Two Reactive Sites

The functionalization of single-walled carbon nanotubes (SWNTs) is an effective method for controlling a local band gap, resulting in photoluminescence (PL) in the near-infrared region. Herein, SWNTs were functionalized using a series of bromoalkanes and dibromoalkanes to evaluate the effects of their length on the nanotube PL properties. When bromoalkanes (CnH2n+1Br) or dibromoalkanes (CnH2nBr2) with tether lengths of six or more were utilized for six different semiconducting SWNTs, the obtained SWNT adducts exhibited two new PL peaks, whereas dibromoalkanes with tether lengths of 3-5 (CnH2nBr2: n=3-5) produced single peaks. Combined with theoretical calculations, the results suggested that the tether length of reagents changes the formation mechanism of functionalized adducts, that is, CnH2nBr2 (n=3-5) tends to result in kinetic products.