Overall expanded uncertainty estimation in polaron concentration of p-toluene sulfonic acid doped polyaniline by EPR spectroscopy

Abstract

Conjugated polymers like polyaniline (PANI) are peculiar in terms that a minor change in doping level leads to only a slight change in polaron concentration but orders of magnitude change in electrical conductivity. Therefore, precise and accurate determination of polaronic concentration is essential to predict the exact doping status which is not a straight forward task. Herein, we report use of Electron Paramagnetic Resonance (EPR) spectroscopy technique for the quantitative estimation of polaron concentration in p-toluene sulfonic acid (PTSA) doped PANI (PANI-PTSA) samples with evaluation of overall uncertainty in the results calculated as per GUM guidelines. EPR spectra of the samples and reference were recorded under identical temperature and relative humidity conditions and all kind of uncertainty sources i.e. Type A and Type B were identified and quantified. In particular, the random effects viz. sample preparation, instrument stability, reference material, calibration of balance, operator etc. are categorized under above uncertainty sources. DPPH standard used in these measurements has spin concentration 1.5271810¹⁸ ± 0.07542162410¹⁸ spins/g at 95% confidence level.