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In the present study, ZnO nanotube arrays were synthesized from hydrothermally grown ZnO nanowires by selective chemical etching, using KCl as dissolving solution. Synthesized ZnO nanotube arrays were characterized using X-ray diffraction, scanning electron microscopy, UV-visible and Raman spectroscopy. Room temperature gas sensing properties of these arrays were investigated towards various toxic gases and the results were compared to that of ZnO nanowire arrays. Samples of ZnO nano tube arrays showed better sensor response to both H2S (4.2 for 5 ppm) and NO2 (13 for 1.5 ppm) as compared to samples of ZnO nanowires array which exhibited a sensor response of ~ 3.7 towards 5 ppm H2S and ~1 towards 1.5 ppm NO2. The enhancement of sensor response in nanotube arrays can be attributed to the hollow morphology of the ZnO NT which offers higher surface area. Oxygen adsorption in this case takes place on both inner and outer surfaces of the tube resulting in larger change in resistance.. [ABSTRACT FROM AUTHOR]

Dependence of the resistance of metal-oxides thin films on environment is generally used to detect toxic gases at ppm levels. In order to obtain a fast response and recovery, sensing films are heated to high temperatures (upto 300°C). The heater assembly used to raise the film temperature not only makes the sensor bulky but also consumes high power. In our efforts to reduce the size of sensors, we have deposited SnO2: CuO thin film directly onto low-temperature co-fired ceramic (LTCC) substrates with integrated heater and temperature sensor. Sensor films were investigated for their compatibility with LTCC substrate and results show a stable response towards hydrogen sulphide gas for over a year. The stability of heater and thermistor embedded in LTCC substrate has also been monitored. The results of our study show films on LTCC substrate can be successfully applied in sensor technology. [ABSTRACT FROM AUTHOR]

Hydrothermal growth of ZnO nanowires were performed using ZnO nanoparticles as a seed layer. The growth was found to depend strongly on the reaction duration. These nanowires detected H2S with faster response and recovery time of 13 and 78 s, respectively towards 20 ppm at 350° C. The lowest detection limit was improved to 0.6 ppm upon annealing in O2 flow of 50 sccm. The response time was further improved to just 6 s towards 20 ppm of H2S at 350° C. The enhanced response characteristics have been attributed to the high surface area to volume ratio of nanowires. Photoluminescence (PL) studies showed increase in the green emission related to defect states in ZnO. This is also expected to contribute for the improved sensing characteristics. [ABSTRACT FROM AUTHOR]

Gas sensing properties of pure and Au incorporated WO3 thin films towards H2S and Cl2 have been investigated. The sensor films were able to detect H2S and Cl2 selectively at an operating temperature of 150 and 200 °C, respectively. Effect of gas concentration and Au loading have been investigated and correlated with the observed sensitivity values. Pure WO3 films exhibited better sensing characteristics towards H2S (S = 17, 10 ppm, 150 °C) while sensor film containing Au thickness of 21.6 nm exhibited a maximum sensitivity towards Cl2 (S = 89, 10 ppm, 200 °C).. [ABSTRACT FROM AUTHOR]