Spectroelectrochemical properties of the single walled carbon nanotubes functionalized with polydiphenylamine doped with heteropolyanions

A combined chemical–electrochemical method was used for covalent functionalization of single-walled carbon nanotube (SWNT) with polydiphenylamine (PDPA) doped with heteropolyanions of H3PMo12O40·xH2O. The functionalization process induces in Raman spectra of SWNTs the following changes: (i) an increase in relative intensity of the D band, accompanied a gradual up-shift of the G band in the case of the semiconducting tubes and a decrease in the relative intensity of band peaked at 1540 cm−1 is remarked in the case of the metallic tubes; (ii) in the anti-Stokes Raman spectrum an increase in the relative intensity of Raman line of metallic tubes peaked at −1560 cm−1 is remarked when the cycles number increases. The additional down-shift of the FTIR bands belonging to H3PMo12O40 heteropolyanions (at 881, 943 and 1055 cm−1) and PDPA (at 688, 736 and 1016 cm−1) originates in hindrance steric effects induced the covalent functionalization of SWNTs with polymer molecules. Using Raman scattering and FTIR spectroscopy we demonstrate that chemical polymerization of diphenylamine in the presence of H3PMo12O40·xH2O and SWNTs results in a composite of the type blend based on PDPA in un-doped state and SWNTs doped with H3PMo12O40 heteropolyanions. - Graphical abstract: Stokes and anti-Stokes Raman spectra of the SWNTs before (a) and after electrochemical functionalization with PDPA doped with heteropolyanions by 5 (b) and 25 (c) voltammeter cycles. Highlights: ► A chemical–electrochemical method is used to functionalization of SWNTs. ► Functionalization of wall-side of tube is evidenced by anti-Stokes Raman studies. ► FTIR spectra proves insertion of heteropolyanions in polydiphenylamine matrix. ► FTIR spectra of polymer functionalized SWNTs reveal hindrance steric effects.