Polypyrrole Sensor

To enhance the response of the polypyrrole sensor towards DMMP, acid dopants were added to the polypyrrole structure. The rational for doping polypyrrole was to introduce secondary doping sites for DMMP in the structure. Secondary doping... 

Han, G.Y., and G.Q. Shi. 2004. Gonducting polymer electrochemical actuator made of high-strength three-layered composite films of polythiophene and polypyrrole. Sensor Actuator B-Chem 99 525. 

Hamilton, S. Hepher, M. J. Sommerville, J. Detection of Serpula lacrymans infestation with a polypyrrole sensor array. Sens. Actuators B Chem. 2006, 2, 989-997. 

We report studies on polypyrrole sensors (8, 49, 50), the prime objective of which was to attain reversibility of response and to demonstrate that selectivity to chemically inert VOCs could be realized. Less extensive studies were performed on polythiophene (8, 50), The unexpectedly promising properties of sensors containing oligomers of aniline are also reported. 

Polypyrrole Sensors (8,49,50). The soluble polypyrrole (59) used in the sensors in Examples 1-7 inclusive in Figure 17 was spun onto interdigitated gold electrode... 

We had initially limited our studies to polypyrrole based sensors with several different chemically inert VOCs and to polythiophene sensors with toluene analyte. However, because of the relatively low sensitivity of the polypyrrole sensors and because of photosensitivity of the polythiophene sensors we have recently directed our attention to a new type of oligomer of aniline which we have recently synthesized and characterized (67, 62). 

Shoa T, Madden JDW et al (2010b) Electromechanical coupling in polypyrrole sensors and actuators. Sens Actuators A 161(1-2) 127-133... 

Figure 3. Qualitative DC resistance response characteristic at room temperature of a conducting polypyrrole sensor to pulses of (a) ammonia and (b) niotrogen dioxide.

The quantitative response of a polypyrrole sensor to a sequence of pulses of 0.1% nitrogen dioxide on the same timescale is shown at Figure 5. Again the response (in this case a resistance decrease) is sustained over eight pulses during a two hour period, but the background resistance shows a progressive increase. 

Figure 4. AC (1 kHz) resistivity changes at room temperature for a conducting polypyrrole sensor exposed to eight 15 minute pulses of 0.1% ammonia in air over a period of 4 hours.

Figure 7. Room temperature AC (1 kHz) resistance changes for a (inducting polypyrrole sensor exposed to 15 minute pulses of (a) 0.01%, (b) 0.1% and (c) 1% ammonia in air.

An important parameter to be considered during an assessment of the potential utility of new materials in gas sensing is the variation in response with gas concentration. Figure 7 shows the reproducibility of the polypyrrole sensor to pulses of ammonia at three different concentrations. There is clearly a useful response over a wide concentration range. 

Ozkorucuklu SP, Sahin Y, Alsancak G (2008) Voltammetric behaviour of sulfamethoxazole on electropolymerized-molecularly imprinted overoxidized polypyrrole. Sensors 8 8463-8478... 

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