In this study sonovoltammetry, voltammetry in the presence of
power ultrasound, is used to investigate aspects
of cytochrome c redox processes at conventional-sized
electrodes under extreme mass transport conditions
comparable to those found in microelectrode steady state experiments.
A new small volume sonovoltammetry
cell (10−20 mL) equipped with a high-intensity 3 mm diameter titanium
horn was built and characterized.
By variation of the electrode-to-horn separation, a range of
accessible average diffusion layer thicknesses
from typically 1 to 7 μm was determined and an approximate mass
transport model based on a “uniformly
accessible electrode” is suggested. On gold electrodes modified
with 4,4‘-bipyridyl disulfide, well-defined
“steady state” sonovoltammograms for the reduction of
ferricytochrome c corresponding to very fast
electron
transfer (k
s
> 0.1 cm
s-1) were obtained, although the activity of
the electrode surface was found to be
sensitive to the applied potential and to some degree to the period and
intensity of insonation. A model
based on the adsorption of cytochrome c on bare gold and
surface modified gold [Szucs et al. Electrochim.
Acta
1992, 37, 403] is used to explain
irreversible and reversible electrode deactivation
processes.
Voltammograms obtained on glassy carbon, basal, and edge plane
pyrolytic graphite in the presence of
ultrasound under high mass transport conditions were ill-defined
possibly due to competing adsorption of
impurities or the effect of high shear forces induced by
ultrasound.
A very large assembly of more than 8000 carbon fibre microdisk electrodes was used to study direct electron transfer to cytochrome c. Near steady-state cyclic voltammograms were observed, which exhibited excellent signal-to-noise ratios despite the low concentrations of cytochrome c employed (1-50 microM). The high resolution of the voltammograms allowed the formal potential of the native form of cytochrome c to be determined over a range of solution pH.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.