Photoabsorption and desorption studies on poly-3-hexylthiophene/multi-walled carbon nanotube composite films

Abstract

Photon stimulated ion desorption (PSID) and Near-edge X-ray absorption fine structure (NEXAFS) studies have been performed on poly-3-hexylthiophene and nanocomposites thin films made of poly-3-hexylthiophene/multi-walled carbon nanotubes (MWNT) filled with iron/iron-oxide. The experiments were performed at the Brazilian Synchrotron Light Source (LNLS) operating in a single-bunch mode following sulphur K-shell photoexcitation and using time-of-flight mass spectrometry for ion analysis. Both PSID mass spectra show great similarity and exhibit desorption of the polymer fragments only. This result seems to be in accordance with previous morphological studies on these materials, which suggested that the nanotubes are highly dispersed and involved by the polymer. Although similar, the spectra present shifts in the direction of greater time-of-flights in the case of the poly-3-hexylthiophene/multi-walled carbon nanotube composite. This behavior may be related to the donation of electronic charge between the polymer matrix and the carbon nanotubes. In both cases, S + desorption seems to be suppressed, which may be due to the hexyl side-chains. Relative desorption ion yield curves have been determined as a function of the photon energy, which reproduced the photoabsorption spectrum. These results are discussed in terms of the indirect XESD (X-ray induced electron stimulated desorption) process.