Elucidation of the Mechanism of Redox Grafting of Diazotated Anthraquinone

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Redox grafting of aryldiazonium salts containing redox units may be used to form exceptionally thick covalently attached conductingfilms, even in the micrometers range, in a controlled manner on glassy carbon and gold substrates. With the objective to investigate the mechanism of this process in detail, 1-anthraquinone (AQ) redox units were immobilized on these substrates by electroreduction of 9,10-dioxo-9,10-dihydroanthracene-1-diazo-nium tetrafluoroborate. Electrochemical quartz crystal microbalance was employed to follow the grafting process during a cyclic voltammetric sweep by recording the frequency change. The redox grafting is shown to have two mass gain regions/phases: an irreversible one due to the addition of AQ units to the substrate/film and a reversible one due to the association of cations from the supporting electrolyte with the AQ radical anions formed during the sweeping process. Scanning electrochemical microscopy was used to study the relationship between the conductivity of thefilm and the charging level of the AQ redox units in the grafted
film. For that purpose, approach curves were recorded at a platinum ultramicroelectrode for AQ-containing films on gold and glassy carbon surfaces using the ferro/ferricyanide redox system as redox probe. It is concluded that thefilm growth has its origin in electron transfer processes occurring through the layer mediated by the redox moieties embedded in the organic film
Original languageEnglish
JournalLangmuir
Volume28
Issue number25
Pages (from-to)9573–9582
ISSN0743-7463
DOIs
StatePublished - 2012

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