Manufacturing of a Nafion-coated, Reduced Graphene Oxide/Polyaniline Chemiresistive Sensor to Monitor pH in Real-time During Microbial Fermentation

Selvaraj Chinnathambi, Gert-Jan Euverink*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

Here, we report the engineering of a solid-state micro pH sensor based on polyaniline-functionalized, electrochemically reduced graphene oxide (ERGO-PA). Electrochemically reduced graphene oxide acts as the conducting layer and polyaniline acts as a pH-sensitive layer. The pH-dependent conductivity of polyaniline occurs by doping of holes during protonation and by the dedoping of holes during deprotonation. We found that an ERGO-PA solid-state electrode was not functional as such in fermentation processes. The electrochemically active species that the bacteria produce during the fermentation process interfere with the electrode response. We successfully applied Nafion as a proton-conducting layer over ERGO-PA. The Nafion-coated electrodes (ERGO-PA-NA) show a good sensitivity of 1.71 Omega/pH (pH 4 - 9) for chemiresistive sensor measurements. We tested the ERGO-PA-NA electrode in real-time in the fermentation of Lactococcus lactis. During the growth of L. lactis, the pH of the medium changed from pH 7.2 to pH 4.8 and the resistance of the ERGO-PA-NA solid-state electrode changed from 294.5 Omega to 288.6 Omega (5.9 Omega per 2.4 pH unit). The pH response of the ERGO-PA-NA electrode compared with the response of a conventional glass-based pH electrode shows that reference-less solid-state microsensor arrays operate successfully in a microbiological fermentation.

Original languageEnglish
Article number58422
Number of pages8
JournalJournal of Visualized Experiments
Volume2019
Issue number143
DOIs
Publication statusPublished - Jan-2019

Keywords

  • Bioengineering
  • Issue 143
  • Reduced graphene oxide
  • polyaniline
  • chemiresistor
  • potentiometric pH sensor
  • microsensor
  • bacterial fermentation
  • ELECTROCHEMICAL SENSOR
  • POLYANILINE
  • GLUCOSE
  • NANOCOMPOSITE
  • VOLTAMMETRY
  • NANOSHEET
  • ELECTRODE
  • NANOWIRE
  • FILMS
  • ARRAY

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