Influence of Single-Walled Carbon Nanotubes Enriched in Semiconducting and Metallic Tubes on the Vibrational and Photoluminescence Properties of Poly(para-phenylenevinylene)

Abstract

A new synthesis method based on the electrochemical reduction of α,α,α′,α′-tetrabromo-p-xylene in the presence of single-walled carbon nanotubes (SWNTs) is used to obtain composites of carbon nanotubes (CNTs) functionalized with poly­(para-phenylenevinylene) (PPV). To separate the effects of metallic and semiconducting CNTs on their interaction with PPV, the experiments are carried out with SWNTs enriched in semiconducting (S, 99%) and metallic (M, 98%) tubes. Significant changes in the relative intensity and shift of the radial breathing vibrational mode are reported in the Raman spectra of the as-prepared SWNTs samples, i.e., as mixtures of metallic (33%) and semiconducting (66%) entities and SWNTs enriched in M tubes (98%) that result from the electrofunctionalization with PPV. This different behavior originates in the noncovalent and covalent functionalization of SWNTs enriched in M and S SWNTs tubes with PPV, respectively. A gradual decrease in the absorption of the infrared (IR) bands of PPV situated in the spectral range of 750–1000 cm–1 as a result of the increase of the polymer weight on the blank Au support is reported. The electrofunctionalization of the as-prepared SWNTs induces position changes of the PPV IR absorption bands. In the presence of S-enriched SWNTs, a significant increase in the absorbance of the two IR bands peaked at 1452 and 1471 cm–1, which are assigned to the vibrational modes of the phenyl ring stretching and the quinoid structure of the PPV, respectively, is reported. This results from the covalent bonding of the PPV macromolecular chains onto the surface of the SWNTs enriched in S tubes. Our results also demonstrate that the photoluminescence quenching effect reported for the PPV/SWNTs composites is due to the metallic nanotubes.

Infrared dichroism studies and anisotropic photoluminescence properties of poly(para-phenylene vinylene) functionalized reduced graphene oxide

“…1 corresponds to the 30th CV of the PPV lm, electrochemical synthesized onto Au electrode, when four cathodic peaks at À0.16 V, À0.5 V, À1.05 V, and À1.78 V versus Ag/AgCl were observed. As shown in previously paper, 5 during the cathodic scanning of the potential from +2 to À2 V versus Ag/AgCl, the four cathodic peaks are also observed in the rst 5 CVs, when the formation of a TBPX diradical was induced.…”

“…A consequence of the high chemical reactivity of TBPX diradicals toward themselves is the spontaneous dimerization reaction that leads to the formation of a dimer with the chemical formula of Br 2 HC-C 6 H 4 -CH]CH-C 6 H 4 -CHBr 2 . 5 As numbers of CVs increase, successive reduction reactions of the dimer enable the growth of PPV MCs. 5 Fig.…”

“…5 As numbers of CVs increase, successive reduction reactions of the dimer enable the growth of PPV MCs. 5 Fig. 1 highlights an up-shi of the last cathodic peak from À1.78 V to À1.7 V, À1.67 V, À1.66 V, À1.65 V, and À1.64 V, as gradually increasing of the RGO weight percentage concentration from 0 wt% to 0.01 wt%, 0.025 wt%, 0.05 wt%, 0.1 wt%, and 0.5 wt%, respectively.…”

“…The preceding variations indicate that the reaction mechanism of the electrochemical synthesized PPV is changed in the presence of RGO when the formation of the RGO sheets covalently functionalized with the PPV oligomers in un-doped state is induced and occurs similar to how the composites based on PPV in un-doped state and SWCNTs highly separated in metallic and semiconducting tubes. 5 During the anodic scanning of the potential from À2 to +2 V versus Ag/AgCl, when the working electrode was immersed in the solution of 0.02 M TBPX and 0.1 M TBAB in DMF : H 2 O, the development of a broad oxidation maximum $+1.32 V versus Ag/AgCl is observed in the case of the 30th CV of PPV. The presence of RGO in the synthesis solution induces, during the anodic scanning, only an increase of the current densities in the potential range (+0.5; +2) V versus Ag/ AgCl.…”

“…3 A partial and total conversion, respectively, of the PPV precursor solution occurs as the conversion temperature is increased from 100 C to 300 C. 3 Another method used to obtain PPV lms in un-doped state was the electrochemical reduction of TBPX at potentials smaller than À1.3 V. 4,5 For the particular case of the composites based on PPV and singlewalled carbon nanotubes (SWCNTs), it was demonstrated that the chemical and E methods led to a non-covalent and a covalent functionalization, respectively, of SWCNTs with PPV in undoped state. 5,6 To date, the transformation of the PPV lms from un-doped state to a doped one was carried out either by chemical oxidation reactions in the presence of FeCl 3 , I 2 , or H 2 SO 4 compounds 7 or by electro-oxidation of the un-doped PPV lms. 8 In the case of the electropolymerization of the monomers by cyclic voltammetry, depending on the potential at which cyclic voltammograms (CVs) were stopped, conjugated polymers (CPs) in un-doped or doped state 9 were synthesized.…”