pH-switched electrochemistry of pyrroloquinoline quinone at Au electrodes modified by functionalized monolayers

Eugenii Katz, Mazzi Lion-Dagan, Itamar Willner*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

Gold electrodes were modified with thiolate monolayers that included dissociative groups of different pKa values: cystamine, 4-aminothiophenol and 4-pyridyl disulfide. The electrochemistry of the redox probe pyrroloquinoline quinone (PQQ) was examined in a broad pH region using the different monolayer-modified electrodes. The redox probe PQQ reveals reversible electrochemical properties only in the presence of positively-charged monolayer-modified electrodes, owing to its electrostatic attraction to the monolayer|electrode interface. For the different monolayer-modified electrodes exhibiting different pKa values, the transition from a reversible to an irreversible electrochemical process for PQQ was observed at different pH values. The electrochemical response of the modified-electrode system can be reversibly switched between ON and OFF states by controlling the pH of the assemblies in a narrow range. The transduced amperometric signals at the different pH environments were amplified by the PQQ-electrocatalyzed oxidation of NADPH in the presence of Ca2+. The electrode systems represent novel examples of pH-controlled electrochemical ON-OFF systems.

Original languageEnglish
Pages (from-to)107-112
Number of pages6
JournalJournal of Electroanalytical Chemistry
Volume408
Issue number1-2
DOIs
StatePublished - 30 May 1996

Keywords

  • Charge effects
  • Electrocatalysis
  • Electrochemical kinetics
  • Electrode modification
  • pH-switchable electrodes
  • Pyrroloquinoline quinone (PQQ)

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