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Toluidine blue covalently immobilized onto gold electrode surfaces: An electrocatalytic system for nadh oxidation
Author(s) -
Schlereth Daniela D.,
Katz Eugenii,
Schmidt HannsLudwig
Publication year - 1994
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/elan.1140060903
Subject(s) - toluidine , covalent bond , chemistry , cystamine , monolayer , electrochemistry , electrode , amperometry , electrode potential , adsorption , reference electrode , substrate (aquarium) , inorganic chemistry , organic chemistry , biochemistry , oceanography , geology
The electrochemical behavior of toluidine blue in solution has been studied and found to be strongly dependent on the electrode surface nature. Monolayers of cystamine (C) or 3‐mercaptopropionic acid (MP) chemisorbed onto gold electrode surfaces have been used as support for covalent attachment of toluidine blue (TOB) through its aromatic amino group in position 3 and the amino or carboxylic groups covering the elearode surface. After covalent attachment of TOB onto an MP monolayer, three different species remained stably attached to the electrode surface. Physically adsorbed TOB, which showed the same midpoint potential as in the solubilized state, E 1/2 = –245 mV (Ag/AgCl); covalently attached TOB, whose midpoint potential was shifted toward 120 mV more positive potentials; and an unknown species, probably physically adsorbed TOB dimers, with a midpoint potential, E 1/2 = +135 mV (Ag/AgCl). Toluidine blue modified electrodes started to oxidize catalytically NADH at –100 mV with an amperometric response dependent on the concentration of the substrate. An electrode fouling process was observed after successive additions of NADH leading to the loss of catalytic activity.