Biomedical Engineering Reference
In-Depth Information
60
41.5
55
as prepared
50
PAH-1
PSS-2
PSS-4
41.0
45
PAH-5
40
PSS-6
35
40.6
PSS-8
PA H - 7
as prepared
PA H
PSS
30
25
40.0
PA H - 3
20
15
2.5
2.0
1.5
1.0
0.5
0.0
0.5
1.16
1.14
1.12
1.10
1.08
1.06
1.04
1.02
1.00
0.98
(a)
Voltage (V)
Voltage (V)
120
44
100
n-Si-SiO 2
50 mV
24 mV
80
40
60
before immobilization
40
36
after immobilization
before hybridization
after hybridization
20
0
1.5
1.0
0.5
0.0
0.5
1.0
1.5
0.85
0.80
0.75
0.70
0.65
0.60
0.55
(b)
Voltage (V)
Voltage (V)
FIGURE 7.11 (a) C-V curves of a capacitive p-Si-SiO 2 (30 nm)-Ta 2 O 5 (60 nm) FED - as prepared, and
after adsorption of PAH and PSS polyelectrolyte layers (left), and resulting potential shifts in the depletion
region (right); measurement frequency: 1 kHz; 0.1 M NaCl, pH 6 solution. (b) C-V curves of a capacitive
n-Si-SiO 2 (30 nm) FED before and after ssDNA immobilization in buffer pH 4.6 and before and after cDNA
hybridization in buffer pH 7.24 (left), and resulting potential shifts in the depletion region (right); measure-
ment frequency: 1 kHz.
adsorbed PE multilayer containing a relatively large amount of water molecules and
small ions.
The label-free DNA immobilization and hybridization detection for an n-Si-SiO 2
FED is presented in Fig. 7.11b. The C-V curves of the FED have been recorded before
and after the ssDNA immobilization as well as before and after cDNA hybridization.
The observed large shifts in the C-V curve along both the capacitance and voltage axis
can be attributed to the different values of pH and electrolyte conductivity of immobili-
zation (pH 4.6, ionic strength 0.5 M) and hybridization (pH 7.24, ionic strength 0.02 M)
buffers. When considering these effects, the remaining shifts of the immobilization
 
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