Abstract
Polypyrrole (Ppy) was synthesized using Ferric Chloride (FeCl3) as oxidant. The ratio of monomer to oxidant was 1:2.4. The polymerization was carried out at 5。C. Attempts were made to increase the electrical conduc-tivity by using various dopants viz. Lithium per Chlorate (LiClO4), para-Toluene Sulfonate (p-TS) and Nap-thalene Sulfonic acid (NSA). The materials were characterized using FTIR, X-Ray diffraction and SEM. The electrical conductivity was measured by two probe method and was found to be in the range of 10-3 to 10-2 S/cm. Thin films of these preparations were casted on the interdigited electrodes to study the detection of gases such as ammonia and LPG. It was found that for the pure Ppy and one doped with LiClO4, when ammonia gas was allowed to flow in, there was a sudden increase in the current, which decreased rapidly when gas was stopped. This behavior is in contradiction to that observed in earlier investigations where Ppy was prepared by electrochemical method. However when Ppy doped with p-TS and NSA were used, the trend was reversed. Similarly it was noted that for pure Ppy and one doped with LiClO4, p-TS and NSA there was an increase in the current when LPG gas was brought in. However the response to LPG was somewhat low as compared ammonia gas.
Highlights
Electroactive conducting polymers have assumed a great importance in several technologies such as Display devices, Solar cells, Gas sensors and Actuators [1,2,3]
In the present paper we report preparation of polypyrrole in pure form and by using dopants such as LiClO4, para-Toluene Sulfonate (p-TS) and Napthalene Sulfonic acid (NSA)
It was observed that the electrical conductivity of polypyrrole increased when dopants such as LiClO4, p-TS and NSA were used with FeCl3 as oxidant the conductivities were found in the range of 10−3 S/cm to 10−2 S/cm
Summary
Electroactive conducting polymers have assumed a great importance in several technologies such as Display devices, Solar cells, Gas sensors and Actuators [1,2,3] Their ease of processing together with their chemically tunable properties makes them useful in electro-mechanical devices. Most of the conducting polymers are doped/undoped by redox reactions When such conducting polymeric material is brought in contact with either a gas or a liquid, transfer of electrons from or to the analyte takes place. Gases such as NO2 and I2 which are electron acceptors can remove electrons from the aromatic ring of polypyrrole When this occurs, for a p-type conductive polymer, the doping level as well as electric conductance of the conductive polymers is enhanced. The response of these materials, when exposed to ammonia and LPG is being reported
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