An experimental sensor using the design principles explained above is shown in
Figure 2.16; this design uses SnO 2 as the sensing material, while the contacts and
contact leads are made from platinum.
The response of this sensor is heavily dependent on the size of the SnO 2 particles
used as the sensing material, there being a clear increase in the sensitivity of
detection for carbon monoxide (CO) with decreasing grain size (see Figure 2.17).
Such behavior may occur for either of two reasons: (i) that there is a reduced
diffusion time, according to Eq. (2.3) and (ii) that there is an enlarged surface,
thereby accelerating exchange with the surrounding atmosphere.
For the successful operation of a thick-film sensor, it is a necessary prerequisite
that the sensing layer be prepared from nanoparticles consisting of a highly porous
structure that allows a relatively rapid diffusion of the gas to be sensed. A scanning
electron microscopy image of the characteristic structure of such a SnO 2 thick-film
Figure 2.16 Gas sensor in which a SnO 2 thick film made from nanoparticles is applied as the
sensing element (Barunovic and Hahn,TU Darmstadt, private communication).
4
5
6
7
8
9
10 11 12 13 14
grain diameter [nm]
0
2
4
6
8
10
12
14
16
sensitivity
[a.u.]
Figure 2.17 Sensitivity of CO determination of a gas sensor designed according to Figure 2.16.
A significant increase in sensitivity is achieved with decreasing grain size (Barunovic and Hahn,
TU Darmstadt, private communication).
18j 2 Nanomaterials and Nanocomposites
Figure 2.16; this design uses SnO 2 as the sensing material, while the contacts and
contact leads are made from platinum.
The response of this sensor is heavily dependent on the size of the SnO 2 particles
used as the sensing material, there being a clear increase in the sensitivity of
detection for carbon monoxide (CO) with decreasing grain size (see Figure 2.17).
Such behavior may occur for either of two reasons: (i) that there is a reduced
diffusion time, according to Eq. (2.3) and (ii) that there is an enlarged surface,
thereby accelerating exchange with the surrounding atmosphere.
For the successful operation of a thick-film sensor, it is a necessary prerequisite
that the sensing layer be prepared from nanoparticles consisting of a highly porous
structure that allows a relatively rapid diffusion of the gas to be sensed. A scanning
electron microscopy image of the characteristic structure of such a SnO 2 thick-film
Figure 2.16 Gas sensor in which a SnO 2 thick film made from nanoparticles is applied as the
sensing element (Barunovic and Hahn,TU Darmstadt, private communication).
4
5
6
7
8
9
10 11 12 13 14
grain diameter [nm]
0
2
4
6
8
10
12
14
16
sensitivity
[a.u.]
Figure 2.17 Sensitivity of CO determination of a gas sensor designed according to Figure 2.16.
A significant increase in sensitivity is achieved with decreasing grain size (Barunovic and Hahn,
TU Darmstadt, private communication).
18j 2 Nanomaterials and Nanocomposites