title: Hydrophobicity effects in iron polypyridyl complex electrocatalysis within Nafion thin-film electrodes.
abstract: 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.
authors: Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi-221005, India. velganesh@yahoo.com velgan@bhu.ac.in.
authors: Uday Pratap
authors: UP
authors: Azad
authors: Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi-221005, India. velganesh@yahoo.com velgan@bhu.ac.in.
authors: Dharmendra Kumar
authors: DK
authors: Yadav
authors: Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi-221005, India. velganesh@yahoo.com velgan@bhu.ac.in.
authors: Vellaichamy
authors: V
authors: Ganesan
authors: Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. f.marken@bath.ac.uk.
authors: Frank
authors: F
authors: Marken