Conducting polymer odour sensors

Elliott, Joanne Margaret (1997) Conducting polymer odour sensors. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

The development and characterisation of sixteen conducting polymer films suitable for use within an odour sensing array was undertaken. Ten of these polymers constituted a series of poly(aniline) alkyl sulfonate doped films, where the length of the alkyl chain varied from n = 4-16. Their rate of electropolymerisation was shown to increase with the size of the dopant molecule. The voltammetry of these films was shown to be typical of poly(aniline). The films were characterised using SEM and XRD, and were shown to be amorphous and to have a porous morphology. The size and density of the pores was found to vary depending upon the size of the dopant molecule. The smaller sized dopants produced films with larger sized pores.

The films were used to prepare odour sensors by electrochemical deposition onto five types of sensor substrate. Each sensor type was characterised in terms of their surface roughness, electrochemistry in sulfuric acid and reproducibility. The sensors were also characterised using Raman spectroscopy, where the nature of the polymer films was not shown to be possible. The Raman spectra of the polymers were shown to be sensitive to their environment. Upon exposure to ethanol the intensity of the spectra were observed to increase followed by a return to the original base line. Simultaneous measurements of polymer resistance indicated that an increase in polymer resistance was linked to an increase in the intensity of the spectrum.

The resistance of the polymers was shown to be sensitive to volatile odours and to several typical food flavour compounds. A system suitable for monitoring the constituents of human breath was developed and the detection and identification of two different chewing gums upon human breath during mastication was achieved.

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