Photothermal Spectroscopy of Polyaniline Films

In this work, we obtained photoacoustic spectra (PAS) of undoped and doped poly(o-methoxyaniline) (POMA). The fittings for the PAS spectra are obtained from equation for the photoacoustic signal. For these curves, the thermal parameters obtained from the Photopyroelectric Spectroscopy (PPES) were used. [1] Two Gaussian curves, which fit well the UV-Vis absorption spectrum of undoped POMA, plus a third Gaussian centered at 820 nm, which fit well the UV-Vis absorption spectrum of doped POMA, were used for these fittings. The PAS signal was used to obtain the optical characteristics of the POMA films, like the optical absorption coefficient β and the optical gap between the valence and the molecular exciton band of the undoped POMA. The values of β in the maximum of the absorption bands agree very well with the intensities of the Gaussian curves used for the PPES fittings. The optical gap obtained here agrees with the value of the literature obtained from the UV-Vis optical absorption.