Electrochemical sensors based on carbon nanotubes - Electrochemical Sensors, Biosensors and Their Biomedical Applications - page 480

6

4

2

0

2

1

4

6

5

8

10

0.8 0.6 0.4 0.2 0.0 0.2

E /V vs Ag/AgCl

FIGURE 15.16 Cyclic voltammograms of [GOx/CNT] n immobilized on PDDA/GC electrodes in 0.1 M
phosphate buffer solution (pH 7.4) at 0.1 V s 1 , indicating an increasing response of [GOx/CNT] n with layer
number from 1 to 5 (unpublished results, J. Zhang, M. Feng, and H. Tachikawa) (see Plate 17 for color version).

constructed using a GC or carbon fi ber microelectrode responds even more sensitively
to glucose than the GC/GOx electrode modifi ed with Pt nanoparticles or CNTs alone.
The response time and detection limit of this biosensor is 3 s and 0.5

M, respectively
[110]. A glucose biosensor based on the adsorption of GOx on Pt nanoparticle-modifi ed
CNT electrode that is fabricated by growing CNTs directly on the graphite substrate
has also been reported [111]. Joshi et al. [112] have constructed a glucose biosensor
by incubating the enzyme in a CNT solution and cross-linking with a redox polymer
poly[(vinylpyridine)Os(bipyridyl) 2 Cl 2 /3 ] fi lm. This glucose sensor showed a three-
fold increase of the glucose oxidation current (1 mA cm 2 ). Moreover, new CNT-based
glucose electrochemical sensors are still attracting much interest as a model enzyme
biosensor. Salimi et al. have fabricated a glucose biosensor prepared by immobilizing
GOx into a sol-gel composite at the surface of a graphite electrode modifi ed with CNTs
[42]. A disposable glucose biosensor based on CNTs and screen-printed carbon elec-
trodes has been developed [113]. Li et al. formed covalently linked composites of CNTs
and GOx with a high function density in order to use as a biosensing interface [114].
These sensors show some excellent properties for glucose determination, such as high
sensitivity, quick response, good reproducibility, and long-term stability.
Other enzymes have also been immobilized on CNTs for the construction of elec-
trochemical biosensors. Deo et al. [115] have described an amperometric biosensor for
organophosphorus (OP) pesticides based on a CNT-modifi ed transducer and OP hydro-
lase, which is used to measure as low as 0.15

µ

µ M paraoxon and 0.8 µ M parathion with