Chemistry Reference
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d
n
3
r
4
n
g
|
4
Figure 11.5
SEM image (a) and TEM image (b) of the hierarchical TiO
2
nanostruc-
ture and current-time curve (c) for successive addition of 0.15 mM of
glucose aliquots at -0.45 V (adapted from ref. 31 with permission).
response time of 5 s at an applied potential of
0.45 V. The sensitivity was
improved 2-3-fold compared to other TiO
2
-based glucose sensors. Further-
more, it was interesting to observe a saturated current at a higher glucose
concentration due to enzymatic behavior as shown in Figure 11.5(c).
The 2-3 mesh-like hierarchical structure of Mn
3
O
4
was fabricated on 3D
graphene foam using an electrochemical deposition method.
32
This flexible
and freestanding hierarchical Mn
3
O
4
composite was used for the non-
enzymatic detection of glucose and hydrogen peroxide (H
2
O
2
) which are key
analytes in the health care and food industries. The glucose sensor showed a
sensitivity of 360 mAcm
2
(mM)
1
on a linear range of 0.1 to 8 mM, a re-
sponse time of less than 5 s and an LOD of 10 mM at an applied potential
voltage of 0.4 V. On the other hand, the H
2
O
2
sensor had a sensitivity of
1030 mAcm
2
(mM)
1
on a linear range of 2 mM to 6.5 mM, a response time
of 3 s and an LOD of 1 mM without applying a potential voltage. The authors
suggested that the direct electrooxidation of glucose could be catalyzed by
MnO
2
, resulting in a positive current flow. However, MnO
2
experienced a
series of redox mechanisms leading to a cathodic current peak, which was
seen as a negative current. Noh et al.
33
reported a 1-2 dendrite hierarchical
nanostructure of a Cu-Co alloy as shown in Figure 11.6(a) and (b) by elec-
trochemical synthesis followed by application to a biosensor that measured
either glucose or H
2
O
2
. The sensor for glucose showed a linear range of
.
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