Acid-dependent oxidation mechanisms on single-walled carbon nanotubes analyzed by photoinduced force microscopy

This study employs photo-induced force microscopy (PiFM) and Raman spectroscopy to investigate how oxidative treatments (HNO₃vs HNO₃/H₂SO₄) influence functional group distribution and morphology of carbon nanotubes. Raman spectral analysis revealed distinct oxidation mechanisms introducing functional groups and structural defects between the two acid treatments. Comparison of PiFM mapping images of C-O-C (at 1100 cm^-1) and C=O containing groups (at 1730 cm^-1) between the two treatments further highlighted these differences: mixed acid oxidation induced localized carbonyl formation and tube shortening, while HNO₃treatment resulted in longitudinal functionalization that preserves tube length.