PPY-CHOLIC ACID COMPOSITE FOR ETHANOL SENSING THROUGH IMPEDANCE SPECTROSCOPY MEASUREMENT

Partha P. D. Sharma, D. Sarkar

Abstract: Polymerization of pyrrole with cholic acid has been achieved by its oxidative polymerization in presence of dodecyl benzenesulphonic acid (DBSA). Incorporation of cholic acid in the composite is confirmed by SEM and FTIR results. The change is indicated by SEM and FTIR spectroscopy. The composite is used for sensing ethanol vapour which is visualized through change in electrical conductivity with applied dc bias 0-1V and low frequency ac bias of 0-5V. After ethanol exposure, resistivity of the composite is found to change from 3.03 to 0.71 Ohmcm. Low frequency dispersion is more prominently observed in the ethanol exposed composite, with a linear pattern at 50 Hz which gradually shows a non-linear trend with increasing frequency. Impedance shows a decreasing trend with increasing frequency on exposure to ethanol below the frequency of 500 Hz; but shows a completely different nature at applied frequency of 500Hz. Impedance is also found to decrease with increasing exposure time upto 10 minutes, beyond which change in impedance of the ethanol exposed composite is not so prominent. Specific interaction existing between PPy and cholic acid molecule in the composite, which may have directional property as well as the selective binding with the host molecule, are supposed to form the complimentary bonds between them which might become stronger with exposure to ethanol. The polymer composite also undergoes a chemical reaction on exposure to ethanol vapour. Non-covalent interaction takes place between the aromatic rings of the polymer composite and the ionic species of oxygen, give rise to ‘pstacking’ which eventually leads to changing electronic conductivity in terms of sensing behavior.

Keywords: SPECTROSCOPY

DOI: https://doi.org/10.15623/ijret.2017.0613007