Poly(2,5-dimethoxyaniline) based pH sensors

Walaiporn Prissanaroon-Ouajai, Nophawan Paradee, Sanirat Noreechai, Paul J. Pigram


Poly(2,5-dimethoxyaniline) (PDMA) has been prepared on stainless steel supportedelectrode through an electrochemical polymerization of 2,5-dimethoxyaniline. Oxalic acidwas chosen as a dopant. pH sensitivity of the PDMA-modified electrode has beeninvestigated with a combination of X-ray photoelectron spectroscopy (XPS) andpotentiometry. The potentiometric responses to pH change of the PDMA-modified electrodeappeared reversible and linear in the range from pH 2 to pH 8 with a sub-Nernstianpotentiometric response slope of 49.31 ± 6.1 mV/pH (28oC). The PDMA-modified electrodereadily responded to pH change and was stable in time over a period of a month. Theselectivity of hydrogen ion was also studied using a fixed interfering method. XPS revealedthat the potentiometric responses to pH change were related to the protonation anddeprotonation of the nitrogen atoms contained in the PDMA structure. The advantage of thisapproach is that the proposed pH sensor can be easily fabricated on the available stainlesssteel supported electrode. Surface modification of the PDMA-modified electrode possiblyimproves the potentiometric responding to pH change and it is the work in progress.

Keywords: Poly(2,5-dimethoxyaniline), Conducting polymer, Potentiometric sensor,pH sensor

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