Raman Spectral Evolution in Individual Metallic Single-Walled Carbon Nanotubes upon Covalent Sidewall Functionalization

Changes in the Raman spectra of individual metallic single-walled carbon nantoubes (SWNTs) upon sidewall covalent bond formation have been studied. In light of the Fermi level shift dependent G-band line shape and D-band intensity in metallic tubes, the validity of commonly used D to G intensity ratio as an assessment tool for covalent bond formation is first examined. The evolution of G-band and disorder Raman spectral features upon covalent reaction with 4-bromobenzene diazonium tetrafluoroborate is then presented. The initial degree of disorder has a strong influence on the covalent sidewall functionalization. Implications on developing electronically selective covalent chemistries and assessing their selectivity in separating metallic and semiconducting SWNTs are discussed.