Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

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Detection of harmful gases is important to ensure human and environmental health. Industrial waste gases such as CO, NO 2 , H 2 S, and NH 3 are of typical focus among researchers over the years. Chemiresistive sensors are suitable for detecting these harmful gases. One suitable candidate material for this sensor is the conducting polymer, which offers the advantage of room-temperature operation. This review focuses on the overall development of conducting polymer as chemiresistive sensing materials. Effects of different parameters influencing sensor performance such as response, gas concentration, response time, and recovery time of conducting polymers are explored. Different conducting polymers are compared and their affinities to specific gases are determined. An understanding of pure conducting polymers assists further exploration of these polymers in composite form. A comprehensive understanding based on an overview of literature will facilitate researchers in selecting appropriate conducting polymers for different gas sensing applications and is expected to encourage further progress in this area.

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