PdCl2–Polyaniline Composite for CO Detection Applications: Electrical and Optical Response
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- Arafa, I.M., El-Ghanem, H.M. & Bani-Doumi, K.A. J Inorg Organomet Polym (2013) 23: 365. doi:10.1007/s10904-012-9785-6
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Different mass ratios of PdCl2 were incorporated into polyaniline emeraldine base (PdCl2–PANI) by sonication in acetonitrile. The PdII-doped PANI composites readily interact with CO gas at ambient conditions (1 atm, 27 °C) resulting in the reduction of PdII ions into metallic Pd0 and the release of HCl to afford Pd0–PANI·HCl. The dramatic structural changes associated with CO exposure were examined by different spectroscopic (UV–Visible, FT-IR), powder X-ray diffraction (P-XRD) and electrical conductivity (DC) techniques. The P-XRD data shows that the resulting nano-scale metallic Pd0 clusters (~10–15 nm) remain tightly bound to the PANI chains. The observed chemical transformation of PdCl2–PANI into Pd0–PANI·HCl as a function of exposure to CO gas was exploited to monitor this poisonous gas in CO/air mixture; the optical and DC electrical response functions were examined in solution and solid state, respectively. The DC electrical response signal is relatively ten-fold more sensitive to CO exposure (% Selectrical = 471–496 %) compared to the corresponding optical response (%Soptical at 460 nm = 40–51 %). This responsive action demonstrates that PdCl2–PANI composite can be employed as a feasible low-cost solid-state CO detecting material in chemical sensor devices.