Av. Kashevskii et al., Behaviors of H2TPP and CoTPPCl in Nafion((R)) film and the catalytic activity for nitric oxide oxidation, J ELEC CHEM, 510(1-2), 2001, pp. 86-95
The behavior of meso-tetraphenylporphyrin (H2TPP) and its Co(III)-complex (
CoTPPCl) in Nafion((R)) film has been studied by cyclic voltammetry and vis
ible spectroscopy. Buffer titration of H4TPP2+ in the film showed only the
dication-free-base equilibrium (H4TPP2+ reversible arrow H2PP + 2H(+)) and
the apparent equilibrium constant, pK(3.4), was determined to be 4.12. Inse
rtion of cobalt(III) into the H2TPP core in the film has been realized at r
oom temperature by immersion of H2TPP-containing Nafion((R)) film into CoCl
2 solution. The electrocatalytic activity of the resulting film toward NO o
xidation at a glassy carbon (GC) electrode has been monitored in comparison
with other Nafion((R)) films doped with H2TPP or free CoCl2 A GC electrode
coated with Nafion((R)) film doped with CoTPPCl exhibited the highest cata
lytic activity, confirming the involvement of the Co site in a catalytic cy
cle of NO oxidation. In amperometric detection of NO in phosphate buffer so
lution at pH 7.4 this electrode demonstrated a linear response to the NO co
ncentration increment. The detection limit at a signal-to-noise ratio of 3
was 1.2 nM. (C) 2001 Elsevier Science B.V. All rights reserved.