Octaaniline sensor

The reversibility (-99.7%) of the octaaniline sensor is excellent as shown in Figure 21. The environmental stability of the sensor is most satisfying. As can be seen from Figure 22, sensitivity, on exposure to a toluene/air mixture as discussed above, is reduced fairly rapidly during the first day of exposure to laboratory air, but then essentially stabilizes after a few days. 

Figure 21. Typical 120 seconds resistance responses of an octaaniline sensor to normal laboratory air, laboratory air saturated with toluene vapor at room temperature ( 26 torr 35,000ppm) and normal laboratory air.

Figure 22. Change in sensitivity (AR%) of an octaaniline sensor to saturated toluene vapor (25°C, -26.8 torr, 35,000ppm) as a function of number of days exposure of the sensor to ambient laboratory air at room temperature. Reproduced from reference 10.

Figure 23. Effect of water vapor in air at 25°C (23.7 torr 31,300ppm) on an octaaniline sensor. Reproduce with permission from Synthetic Metals (in press). Copyright 1998 Elsevier Science Ltd.

MacDiarmid et al. [332,333] reported the synthesis of octaani-line, an oligomer of aniline, and its use in a device to detect organic vapors such as toluene. The reversibility of the octaaniline sensor toward toluene vapors was observed to be excellent (99.7%) with a satisfactory environmental stability after a few days. 

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