Volatile organic compounds (VOCs) (e.g. acetone, ethanol, n-propanol, iso-propanol, propanal, dimethyl ether) are considered as major organic pollutants which cause severe harmful effects on environment due to their toxic nature. Some of the aforementioned VOCs exist in different isomeric forms. For example, n-propanol and iso-propanol are structural isomer; ethanol and dimethyl ether as well as acetone and propanal are functional isomers. The detection as well as discrimination of such isomers using simple and cost effective techniques is a challenging research issue. Herein, we made attempt to discriminate n-propanol and iso-propanol by analysing their interactions on zinc ferrite chemi-resistor. Zinc ferrite nano-particles are synthesized through wet chemical auto-combustion process and the phase formation behaviour and morphological features are studied. Operating temperature (250-325<sup>o</sup>C) dependent sensing characteristics are measured using a static flow gas sensing measurement set-up. The resistance transients of zinc ferrite sensor for the response of 200 ppm n-propanol and iso-propanol are found to vary significantly. The kinetic parameters are estimated by modelling the resistance transients in accordance to Langmuir-Hinshelwood mechanism. The activation energies for the interaction of n-propanol and iso-propanol over zinc ferrite sensor are estimated from the temperature dependence of kinetic parameters. For chemi-resistive type sensing, the adsorption, desorption, diffusion and interaction of gases is reflected through the respective change in resistance/ conductance transients of the sensors. Since n-propanol and iso-propanol differ in their structure, these interact differently on the sensor surface and produce distinct resistance transients. Therefore the analyses of the resistance transient using suitable kinetic algorithm can be useful to discriminate the isomeric VOCs.

Detection and discrimination of isomeric volatile organics on the surface of zinc ferrite chemi-resistor

256th National Meeting (2018)

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