Chemistry Reference
In-Depth Information
behavior of one of these modified electrodes. In turn, the copolymer
coimmobi-
lized with GOx on a Pt electrode, has been also used as amperometric sensor for
glucose determination. The results obtained indicate that both anodic and cathodic
operation mode may be used with the copolymer, which acts as electrocatalyst in
either oxidation or reduction of the hydrogen peroxide arisen in the enzyme-catalyzed
reaction. The sensitivities and detection limits found with both polymers were
comparable or even better than other ferrocene-modified polymers-mediated elec-
trodes. On other hand, the homopolymer
39
was used to prepare an enzyme electrode
incorporatingHRP. The redox polymer was coimmobilizedwithHRP on Pt electrodes
using glutaraldehyde and BSA and applied as amperometric biosensor for the
determination of hydrogen peroxide and organic peroxides. It was possible to operate
at a low potential (
40
50mV vs. SCE) and a good linear response and protection from
interferences was found.
8.3.4.2 Block Copolymers We have applied the electrocatalytic properties of
diferrocenylsilane units attached to other different type of supramolecular struc-
tures. Three different block copolymers containing interacting ferrocenyl moieties
were synthesized (Scheme 8.12). The anionically prepared diblock copolymers
41-43
consist of a polystyrene (PS) block and a polybutadiene (PB) block
functionalized with diferrocenylsilane by Karstedt-catalyzed hydrosilylation [122].
It has been found that the presence of polystyrene blocks confers long-term stability
and reproducibility to the electrodes modified with block-copolymer films, which is
attributable to the excellent film forming properties of the polystyrene blocks.
NAD/NADH-dependent dehydrogenases need the freely diffusing cofactor NAD
รพ
to catalyze the oxidation of the substrates. The major problem in practical
applications of dehydrogenases is the difficulty in the regeneration of the nico-
tinamide coenzyme since the electrooxidation of NADH on solid electrodes usually
requires high potentials.
Electrodes modified with appropriate mediators can be used to shuttle the
electrons fromNADH to the electrode in order to reduce the overpotential. Another
H
Si
H
3
C
Fe
Fe
n
-
p
m
p
m
n
Karstedt's cat.
To l u e n e , 1 0 0
o
C
Si
H
3
C
Fe
m
= 615,
n
= 53,
p
= 39
41
Fe
m
= 375,
n
= 92,
p
= 76
42
43
m
= 455,
n
= 204,
p
= 170
SCHEME 8.12
Synthesis of block copolymers
41-43
.
