Low excitation of Raman D-band in [2+1] cycloaddition functionalized single-walled carbon nanotubes

The D band to G band intensity ratio in the Raman spectroscopy has been widely used to identify the degree of covalent functionalizations of single-walled carbon nanotubes (SWCNTs). The Raman D band at ∼1350 cm−1 is extremely sensitive to the sidewall sp3 scattering centers created by covalent functionalizations. However, we report here that [2 + 1] cycloaddition functionalization does not efficiently excite the Raman D band even up to ∼ 3% of the functionalization as manifested by X-ray photoelectron spectroscopy (XPS). In-depth Raman spectra and XPS spectra analysis suggest that such low excitation of the Raman D band originates from the weakened electron scattering in [2 + 1] cycloaddition functionalized SWCNTs due to their unique sidewall bonding configurations. Our results reveal the origin of the low excitation of the Raman D band in [2 + 1] cycloaddition functionalized SWCNTs, and provide a precise and in-depth understanding of [2 + 1] cycloaddition functionalized SWCNTs.