PdCl2-Polyaniline Composite for CO Detection Applications: Electrical and Optical Response

Abstract

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. © 2012 Springer Science+Business Media New York.