Development of polyaniline/zeolite a composite as a carbonmonoxide sensor

Abstract

Polyaniline (PANI) is one of the most promising conductive polymers. Despite all the advantages of polyaniline, such as its ease of synthesis, polyaniline has low selectivity when it is used as a gas sensor. Three types of zeolite LTA: KA, NaA and CaA, were chosen based on different effective pore size and polarity, and mixed with maleic acid MA-doped PANI (PANI-MA) in a dry mixing process to produce PANI/Zeolite A. The effects of acid dopant type, dopant concentration, zeolite type and zeolite A content on electrical conductivity responses when exposed to CO at room temperature are studied. At acid-aniline monomer mole ratio NA/NEB less than 2.0, HCl-doped polyaniline had a higher doping level than MA-doped polyaniline where the electrical conductivity increased dramatically with doping level. At acid-aniline monomer mole ratios greater 2.0, the doping levels and ℺ reached equilibrium values of ~ 100% and 4 S/cm, respectively. The CO sensitivity of the polyaniline sensor was found to obey the power law ∆℺ = a [CO]b, b ~ 0.35 0.75. PANI-10.0MA is suitable for use as a CO sensor because it has a high conductivity and sensitivity. The PANI-10MA/Zeolite A sensor had lower CO gas sensitivity than pre PANI-10MA. All zeolites A type reduced the CO gas sensitivity of the PANI-10MA sensor because of the decrease of PANI-10MA free volume.