When considering new sensory technologies one should look to nature for guidance. Indeed, living organisms have developed the ultimate chemical sensors. Many insects can detect chemical signals with perfect specificity and incredible sensitivity. Mammalian olfaction is based on an array of less discriminating sensors and a memorized response pattern to identify a unique odor. It is important to recognize that the extraordinary sensory performance of biological systems does not originate from a single element. In actuality, their performance is derived from a completely interactive system wherein the receptor is served by analyte delivery and removal mechanisms, selectivity is derived from receptors, and sensitivity is the result of analyte-triggered biochemical cascades. Clearly, optimal artificial sensory sys-

Conjugated polymer-based chemical sensors.

The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

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Gas Sensors Based on Conducting Polymers

Conducting polymers in chemical sensors and arrays

Semiconductor Junction Gas Sensors

We report the synthesis, electrical characterization and ammonia gas sensing with single nanowire of conducting polypyrrole. Three hundred nanometer in diameter and 50 to 60 mm long polypyrrole nanowires were synthesized by chemical polymerization inside SiO2 coated alumina membranes. Temperature dependent electrical resistance studies established that the chemically synthesized nanowires were more ordered compared to electrochemically synthesized nanowires. We further demonstrated that gas sensors based on single polypyrrole nanowire exhibited good sensitivity towards ammonia, and provided a reliable detection at concentration as low as approximately 40 ppm.

K. Potje-Kamloth

Papers

Electrical and chemical sensing properties of doped polypyrrole/gold Schottky barrier diodes

Electrical and NOx gas sensing properties of metallophthalocyanine-doped polypyrrole/silicon heterojunctions

Electrical properties of doped polypyrrole/silicon heterojunction diodes and their response to NOx gas

Dimorphite based gas sensitive thin films

Molecular interaction of DMMP and water vapor with mixed self-assembled monolayers studied by IR spectroscopy and SAW devices