QCM based mercury vapor sensor modified with polypyrrole supported palladium

Polypyrrole (PPy) nanofibers loaded with either palladium (II) acetate (PPy/Pd(O2CCH3)2) or palladium (II) nitrate (PPy/Pd(NO3)2) were characterized by TEM, SEM, EDX, Raman and FTIR techniques prior to their use as sensing materials for QCM based mercury vapor sensors. The QCM based sensor loaded with PPy/Pd(O2CCH3)2 nanofibers was observed to perform better over that of the PPy/Pd(NO3)2 loaded QCM and is postulated to be due to the lack of Pd salt reduction in the PPy/Pd(O2CCH3)2 matrix. The developed sensor was observed to operate with a response precision of ±5% over a 16 h testing period, and can withstand the presence of different levels of humidity at an operating temperature of 28 °C. Furthermore, the PPy/Pd(O2CCH3)2 based sensor was found to have a response time (t90) of ∼45 min towards a Hg vapor concentration of 10.55 mg/m3 balanced in either dry nitrogen or in streams containing up to 38% RH at near room temperature (28 °C). The stability of the developed sensor over 50 h of continuous testing towards Hg vapor under varying humidity levels indicates that a PPy/Pd(O2CCH3)2 thin layer is a good choice for near room temperature Hg vapor sensing applications.