Controlling Near-Infrared Photoluminescence Properties of Single-Walled Carbon Nanotubes by Substituent Effect in Stepwise Chemical Functionalization

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 nBu-SWNT-nBu and nBu-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.

Automated summary

The stepwise chemical functionalization of single-walled carbon nanotubes (SWNTs) was employed to selectively control site-specific functionalization and photoluminescence (PL). The addition site and the magnitude of the local band gap were found to be controlled by the steric hindrance of the added group and the R value in an (n,m) chiral nanotube.