In-Situ Spectroscopy of Redox Reaction in PPY

In-situ Raman spectra of PPy are obtained with excitations of 514.5 and 1060nm. Strong Raman scattering observed with a deep reduction at 514.5nm excitation coincides with the degree of transparency of PPy of which color turns into pale yellow from dark on the reduction. The Raman scattering intensity of PPy with the deep reduction is 10 folds stronger than that of fresh PPy. The intensity enhancement of the Raman spectra with 1064nm excitation is insignificant but the spectra reveal much more information than those with 514.5nm excitation. Conjugation length generally shortens at the early stage of reduction but recovers on prolonged reduction with 1064nm excitation. Reduced PPy is easily oxidized after cutting-off the applied potential and the Raman spectrum of reduced PPy left in the system for 30min is almost the same as that of fresh PPy.