The local strain at the addition is cited as another factor controlling the emission wavelength of functionalized SWNTs.

Introducing the quantum defects into single-walled carbon nanotubes (SWNTs) enhances their photoluminescence (PL) with red-shifted peaks; however, the precise control of the chemical modification and PL wavelength remains difficult. In this work, the stepwise chemical functionalization of SWNTs was shown to be useful for controlling site-specific functionalization and PL, experimentally and theoretically. Dialkylated and hydroalkylated SWNTs were selectively synthesized using alkyllithium reagents, bromoalkane, and trifluoroacetic acid. The n Bu-SWNT- n Bu and n Bu-SWNT-H adducts of the (6,4), (6,5), (8,3), and (7,5) SWNTs that were separated using gel chromatography showed dominant E11 ** PL and E11* PL, respectively. The systematic assignments of the PL were performed based on the thermodynamic stability and transition energy of 1,2- and 1,4-adducts of SWNTs using density functional theory (DFT) and time-dependent DFT calculations. It was shown that the steric hindrance of the added group and the R value, that is, mod(n – m, 3) in an (n,m) chiral nanotube, are key factors that control the addition site and the magnitude of the local band gap.

Single-walled carbon nanotubes (SWNTs) were functionalized by reacting them with sodium naphthalenide and dendrons to control their photoemission in the near-IR region.

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.

The helicity sorting and optical resolution of single-walled carbon nanotube (SWNT) derivatives were investigated to elucidate their fundamental properties and to fully understand their application scope. Herein, the helicity sorting and optical resolution of functionalized SWNTs (SWNTs-xylyl), which were prepared by reductive alkylation using 1,2-bis­(bromomethyl)­benzene, were achieved for the first time via gel chromatography using an agarose gel as the stationary phase. By applying a stepwise elution, three surfactant types (6,4) SWNTs-xylyl, (11,–5) SWNTs-xylyl, and (6,5) SWNTs-xylyl were successfully separated and characterized. The circular dichroism spectra of (11,–5) SWNTs-xylyl and (6,5) SWNTs-xylyl were mirror images of each other along the abscissa, confirming the successful enantiomeric separation of these functionalized SWNTs. Both of the SWNTs-xylyl enantiomers showed red-shifted near-infrared (NIR) photoluminescence (PL) peaks, which were assigned to quantum defects formed by the chemical modification process. The intensity of the red-shifted PL peak of SWNTs-xylyl significantly increased after the separation. Compared to the sample before the separation, the purified (6,5) SWNTs-xylyl exhibited a considerable red-shifted PL with reduced concentration quenching effects. Owing to these properties, the helicity sorting and optical resolution of functionalized SWNTs may have practical applications as efficient NIR optical materials.