Hydrophobicity effects in iron polypyridyl complex electrocatalysis within Nafion thin-film electrodes

Uday Pratap Azad, Dharmendra Kumar Yadav, Vellaichamy Ganesan, Frank Marken

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Four polypyridyl redox catalysts Fe(bp)3 2+, Fe(ph)3 2+, Fe(dm)3 2+, and Fe(tm)3 2+ (with bp, ph, dm, and tm representing 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine, and 3,4,7,8-tetramethyl-1,10-phenanthroline, respectively) are investigated for the electrocatalytic oxidation of three analytes (nitrite, arsenite, and isoniazid). The poly-pyridyl iron complex is exchanged into a Nafion film immobilized on a glassy carbon electrode, which is then immersed in 0.1 M Na2SO4. Cyclic voltammetry is employed for the evaluation of the mechanism and estimation of kinetic parameters. The electrocatalytic behaviour going from low to high substrate concentration is consistent with the Albery-Hillman cases of "LEty" switching to "LEk" (changing from the first order in the substrate to half order in the substrate), denoting a process that occurs in a reaction zone close to the electrode surface with diffusion of charge (from the electrode surface into the film) and of anionic or neutral analyte (from the Nafion-solution interface into the film). The relative hydrophobicity of the iron polypyridyl catalyst within the film is shown to affect both the diffusion of charge/electrons and analyte within the film with Fe(tm)3 2+ providing the mildest catalyst. All three analytes, nitrite, isoniazid, and arsenite, exhibit linear calibration ranges beneficial for analytical applications in the micro-molar to the milli-molar range.

Original languageEnglish
Pages (from-to)23365-23373
Number of pages9
JournalPhysical Chemistry Chemical Physics
Issue number33
Publication statusPublished - 7 Sept 2016


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