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Absorption and photoluminescence ͑PL͒ studies have been carried out on pristine standard poly͑paraphenylene vinylene͒ PPV and a series of PPV-single-walled carbon nanotubes ͑SWNT͒ composite films. Drastic changes in the PL and absorption spectra are observed with the increase of the SWNT fraction. A model is presented which is able to explain quantitatively the modification of absorption spectra, and particularly the new features in PL spectra as a function of SWNT percentages in the films. We provide evidence for strong electronic interaction between SWNT and the PPV polymer precursor precluding the complete thermal conversion of the polymer matrix.

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Surface-enhanced Raman scattering (SERS) has proved to be an effective technique for studying the structural properties of conducting polymer thin films. The enhancement process has a twofold origin, electromagnetic and chemical. The electromagnetic enhancement, which is the dominant mechanism in SERS generation, consists in the excitation of localized and delocalized surface plasmons (SPs) in the metallic support of the thin film. The Raman emission of the adsorbed molecules on the metal surface (the most efficient being Ag, Au and Cu) is due to the intense evanescent electromagnetic field located at the interface between the metal and the surrounding medium. The second enhancing mechanism for SERS is of chemical origin, involving the formation of new chemical bonds between the molecules and the metal surface, with the polarizability thus becoming considerably higher than that of the free molecules. This mechanism is as a rule accompanied by a metal-molecule or molecule-metal charge transfer, which partly accounts for the success of the SERS studies on conducting polymers. Unfortunately, these studies have revealed that the chemical effects at the polymer-metal interface varied substantially depending on the various types of polymer and metallic support. In this context, polyaniline containing two different entities (a reduced and an oxidized state) in its repeating units exhibits specific alterations in its SERS spectra depending on the type of metallic support. This paper presents new results concerning the structure of emeraldine-base and emeraldine-salt polyaniline thin films deposited on rough Ag and Au supports. The effect on the SERS spectra of the polymer-metal and polymer-ambient interface chemical reactions is also described. The presence of an interface compound depending on the oxidizing properties of the metallic support has a strong influence on the SERS spectra, no matter how the PAN films were deposited on the support (whether by solvent evaporation or by an electrochemical process, i.e. cyclic voltammetry). When an emeraldine base is doped with HSO 4 − ions, it turns into an emeraldine salt, which exhibits a disordered state in its macromolecular chain, leading to a modified profile of the ∼1162 cm −1 Raman line which is associated with the C-H bond of the quinoid ring. The Lorentzian profile is altered by the addition of a Gaussian profile component. For a rough Ag support, the SERS spectra show that the transformation of emeraldine base films into emeraldine salt films is a reversible process.

Prototypal photoluminescent nanofibres of poly-(p-phenylene-vinylene) (PPV) were prepared by the wetting template method in polycarbonate nanoporous membranes with an easy all-in solution polymer precursor route. Both nanowires and nanotubes were obtained by varying the dilution of the polymer precursor in methanol prior to thermal conversion. PPV nanotubes exhibit unique features, such as blue-shifted emission at 2.80 eV, higher quantum yield, and longer fluorescence lifetime with respect to PPV films. These effects are attributed to the cancellation of interchain interactions that are consistent with nanoscale tubular structures formed from weakly interacting and short polymer chain segments. The synthesis of these objects opens up perspectives for tunable photoluminescence properties in the blue spectral range and for biochemical applications.