Photodetachment of aryl moieties from covalently functionalized single-walled carbon nanotubes by UV laser irradiation

Abstract

Photodetachment of aryl moieties from covalently functionalized SWNTs was studied by temperature-dependent and UV Raman spectroscopic tools. The sidewall functionalized SWNTs were prepared via diazonium reactions from 4-bromoaniline and isoamyl nitrite. I–V conductivity measurements were performed for the functionalized SWNTs, after purification from pristine SWNTs using their different solubility. Temperature dependent Raman data appeared to be in line with thermal gravimetric (TGA) data exhibiting removal of aryl moieties above 590 °C. Raman spectra of the functionalized SWNTs were examined using ultraviolet excitation at 244 nm (5.08 eV) and 325 nm (4.82 eV) as well as visible irradiation at 633 nm (1.96 eV). Our experimental results indicated that the disorder-induced D mode should change significantly, whereas the tangential G modes do not become different under UV irradiation. The D mode for the functionalized SWNTs was found weakly at ∼1410 cm⁻¹ at a low power of UV irradiation, whereas it was observed strongly at ∼1310 cm⁻¹ upon 633 nm irradiation. The attached aryl moieties appeared to be removed by UV irradiation as indicated from almost identical spectra with those of pristine SWNTs.