Biomedical Engineering Reference
In-Depth Information
mechanism, involving dissociative adsorption of H
2
O
2
with the formation
of OH radicals, followed by 1-electron reduction of these radicals to OH
-
.
At a higher concentration of H
2
O
2
, and especially at a higher pH (pH 7.3),
the second process appears rate limiting. h e analytical implications are
that a linear dependence of cathodic current on H
2
O
2
concentration should
be observed within the narrow peroxide concentration range associated
with biosensor applications in neutral solutions, as has been reported in
practice [17, 15].
In a parallel paper [27], electrocatalytic reduction of H
2
O
2
at electrodes
modii ed by electro-deposited layers of PB were studied with an in-situ
Raman spectro-electrochemical technique. During the cathodic reduc-
tion of H
2
O
2
, PW appeared to turn partially into its oxidized form (PB;
see
Figure 12.4
) even at electrode potentials corresponding to the reduced
form of a modii er. h e ratio of PB/PW within the modii er layer was
shown to depend on H
2
O
2
concentration, indicating that electrocataly-
sis proceeds within the modii er layer rather than at an outer modii er-
electrolyte interface. In contrast, electrooxidation of AA did not af ect the
in-situ Raman spectra, indicating an outer interface as the most probable
site for AA oxidation.
More recently, PB and its analogues have been combined with a variety
of novel materials for electrocatalytic detection of H
2
O
2
. For example, a PB
composite with graphene oxide and chitosan (Chi) gave a detection limit
of 100 nM H
2
O
2
[28] and cobalt hexacyanoferate nanoparticles (CoHCF/
NPs) modii ed with carbon nanotubes (CNT) showed a synergic ef ect
toward H
2
O
2
detection [29]. In this way Han
et al.
, 2013, reported a com-
posite of CoHCF and platinum nanoparticles on carbon nanotubes pro-
vided a sensor with a linear response up to 1.25 mM H
2
O
2
, also with a
detection limit of 100 nM, and a fast response time (< 2 s) [30]. Controlled
synthesis of mixed nickel-iron hexacyanoferrate nanoparticles (~35 nm
average size) has been shown to be an excellent material for selective elec-
troanalytical applications for H
2
O
2
and glutathione sensing [31]. A number
of these novel, mostly nanoparticle-based materials, have been exploited to
develop sensitive and selective devices for electroanalysis, including glu-
cose biosensors [32, 33] and immunosensors [34].
12.4
Prussian Blue: Biosensor Applications
During the last two decades some authors have suggested the use of electro-
catalytic i lms to detect H
2
O
2
in biosensing applications [8, 10]. Based on this
approach, Karyakin and Chaplin [8] proposed to modify the transduction
