Selective sensing of volatile organic compounds using novel conducting polymer–metalnanoparticle hybrids

Abstract

Conducting polymer–metal nanoparticle hybrids, fabricated by assembling metalnanoparticles on top of functionalized conducting polymer film surfaces using conjugatedlinker molecules, enable the selective sensing of volatile organic compounds (VOCs). Inthese conducting polymer–metal nanoparticle hybrids, selectivity is achieved by assemblingdifferent metals on the same conducting polymer film. This eliminates the need to developeither different polymers chemistries or device configurations for each specific analyte. Inthe hybrids, chemisorption of the analyte vapor induces charge redistribution inthe metal nanoparticles and changes their work function. The conjugated linkermolecule causes this change in the work function of the tethered nanoparticlesto affect the electronic states in the underlying conducting polymer film. Theresult is an easily measurable change in the resistance of the hybrid structure.The fabrication of these sensing elements involved the covalent assembly of nickel (Ni) and palladium(Pd) metal nanoparticles on top of poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid), poly(EDOT-co-TAA), films using 4-aminothiophenol linker molecules. The change inresistance of hybrid Pd/poly(EDOT-co-TAA) and Ni/poly(EDOT-co-TAA) hybrid films toacetone and toluene, respectively, is observed to be in proportion to their concentrations.The projected detection limits are 2 and 10 ppm for toluene and acetone, respectively. Anegligible response (resistance change) of the Pd/poly(EDOT-co-TAA) films to tolueneexposure confirmed its selectivity for detecting acetone. Similarly, lack of response toacetone confirmed the selectivity of the Ni/poly(EDOT-co-TAA) stacks for detectingtoluene. It is anticipated that the assembly of other metals such as Ag, Au and Cu on topof poly(EDOT-co-TAA) would provide selectivity for detecting and discriminating otherVOCs.