Chemistry Reference
In-Depth Information
0.0
0. 0
21
22
24
−
0.5
−
0. 5
−
1.0
−
1.5
−
1. 0
−
2.0
i
(
μ
A)
i
(
μ
A)
−
2.5
−
1. 5
−
3.0
21
22
24
(b)
−
2. 0
(a)
−
3.5
−
4.0
−
2. 5
0
2
4
6
8
10
0
2
4
6
8
10
Gluco se (mM)
Glucose (mM)
FIGURE 8.20
(a) Glucose calibration plots of monoenzymatic sensors of dendrimers
21
,
22
,
and
24
(
G
3
10
9
mol ferrocene/cm
2
thickness films). Steady-state anodic currents mea-
sured at 400mV (vs. SCE) applied potential in O
2
saturated phosphate buffer (pH
¼
7.0).
(b) Glucose calibration plots of bienzymatic sensors of dendrimers
21
,
22
, and
24
(
G
2
10
9
mol ferrocene/cm
2
thickness films). Steady-state current measured at a 100mV applied
potential in O
2
saturated phosphate buffer (pH 7.0). Adapted from Losada et al. [117].
These sensors were applied to the determination of glucose under aerobic
conditions [117]. The results obtained (Figure 8.20) indicate that the sensitivity of
both mono and bienzymatic biosensors based on octamethylferrocenyl dendrimers
increases with the increasing dendrimer generation. Thus, the dendrimer generation
demonstrates to play a significant role in the electrocatalytic activity.
The increase of flexibility of the dendrimer backbone, which is a function of the
length of the dendrimer branches, together with the shorter separation between
ferrocenyl neighbors, increase the electron transfer efficiency between ferrocene
moieties and cause a higher catalytic response of the sensors based on the higher
generation dendrimers. On other hand, the analysis of SEMmicrographs (Figure 8.21)
shows that films of the higher generation dendrimers have a more permeable structure
that facilitates diffusion of glucose, minimizing the barrier to transport, and also
contributes to signal enhancement.
As expected, the octamethylated ferrocenyl dendrimeric mediators enable the
use of lower working potentials for glucose measurements than sensors with
FIGURE 8.21
SEM micrographs of a platinum wire electrode modified with films of (a)
dendrimer
21
and (b) dendrimer
24
. From Losada et al. [117].
