Application of principal component analysis to discriminate the Raman spectra of functionalized multiwalled carbon nanotubes

Raman spectra of starting (pristine) and functionalized multiwalled carbon nanotubes (MWNTs) were analyzed by principal component analysis (PCA) because the original Raman spectra showed very little differences between them. The nanotubes were functionalized with amines: dodecylamine (MWNT1), nonylamine (MWNT2), phenylamine (MWNT3) and octadecylamine (MWNT4), and with dithiols: 1,4‐butane dithiol (MWNT5), 1,6‐hexane dithiol (MWNT6) and 1,8‐octane dithiol (MWNT7). The D and G band intensity ratios (∼1338 and ∼1575 cm −1 ) of the functionalized MWNTs spectra were compared with those of the starting material. For the studied systems, PCA allowed the differentiation between starting and functionalized MWNTs. The present study demonstrated the potential of the application of PCA to the study of functionalized nanotubes by Raman spectroscopy.