TY - JOUR
T1 - pH-switched electrochemistry of pyrroloquinoline quinone at Au electrodes modified by functionalized monolayers
AU - Katz, Eugenii
AU - Lion-Dagan, Mazzi
AU - Willner, Itamar
PY - 1996/5/30
Y1 - 1996/5/30
N2 - 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.
AB - 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.
KW - Charge effects
KW - Electrocatalysis
KW - Electrochemical kinetics
KW - Electrode modification
KW - pH-switchable electrodes
KW - Pyrroloquinoline quinone (PQQ)
UR - http://www.scopus.com/inward/record.url?scp=0030141649&partnerID=8YFLogxK
U2 - 10.1016/0022-0728(96)04525-1
DO - 10.1016/0022-0728(96)04525-1
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AN - SCOPUS:0030141649
SN - 1572-6657
VL - 408
SP - 107
EP - 112
JO - Journal of Electroanalytical Chemistry
JF - Journal of Electroanalytical Chemistry
IS - 1-2
ER -