Characterization of polymeric film of a new manganese phthalocyanine complex octa-substituted with 2-diethylaminoethanethiol, and its use for the electrochemical detection of bentazon
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Date
2009-07-26
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ELsevier
Abstract
Manganese acetate octakis-(2-diethyaminoethanethiol) phthalocyanine (AcMnODEAETPc) was newly
synthesized and characterized by spectroscopic and electrochemical methods. Solution electrochemistry
of the complex showed three redox processes assigned to MnIIIPc−1/MnIIIPc−2, MnIIIPc−2/MnIIPc−2 and
MnIIPc−2/MnIIPc−3 species. The new molecule was polymerized onto a glassy carbon electrode (GCE)
to form thin films of different thickness, giving poly-10-AcMnODEAETPc-GCE, poly-20-AcMnODEAETPcGCE and poly-30-AcMnODEAETPc-GCE, where 10, 20 and 30 represent the number of voltammetry scans
during polymerization. Three distinct redox processes were observed on the modified electrode in 0.1 M
phosphate buffer solution, pH 5, which confirmed the formation of the polymer. The current signal due
to the herbicide, bentazon, was dependent on film thickness; the best signal was obtained on poly20-AcMnODEAETPc-GCE while poly-10-AcMnODEAETPc-GCE gave the least signal. However, the signals
due to the herbicide were better on the different films compared to the bare electrode. Electrochemical
impedance spectroscopy (EIS) technique revealed that differences in film thickness offered different
charge transfer resistances, Rct, hence difference in current signals for bentazon oxidation were observed
on these films. A Tafel slope of 77 mV/decade, obtained for the herbicide on poly-20-AcMnODEAETPcGCE, denotes a fast one electron transfer followed by a slow chemical step in the electro-oxidation of
bentazon. The voltammetry signals of the herbicide on the films indicated the likely involvement of
ring-based redox processes in the detection of the herbicide. A plot of background corrected current
response, on this film, versus the concentration of bentazon was linear within the range 50–750 M with
a detection limit of 2.48 × 10−7 M.
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Akinbulu, I. A., & Nyokong, T. (2009). Characterization of polymeric film of a new manganese phthalocyanine complex octa-substituted with 2-diethylaminoethanethiol, and its use for the electrochemical detection of bentazon. Electrochimica Acta, 55(1), 37-45.