Tiny methane sniffers
doi:10.1038/nindia.2008.130 Published online 27 February 2008
How can you detect even a small amount of highly inflammable methane gas in air? Researchers have now created nano-sized sensors out of zinc oxide that can sniff methane in air. The sensor may help avert mine explosions caused by methane.
The main drawback of the existing tiny gas detecting devices is that they operate only at high temperatures. In recent years, zinc oxide has emerged as a more chemically sensitive, non-toxic and cost effective material for gas sensors. The new sensor is different from existing sensors as it uses a metal-insulator-metal device configuration to reduce the methane detection time to about two seconds.
The researchers chose a thin sheet of zinc, as electrode (anode) and placed a platinum electrode (cathode) 18 mm apart. Through anodization — dipping zinc sheets in a solution of oxalic acid separately in the absence and presence of ultraviolet (UV) light — the team changed the microscopic texture and crystal structure of the metal surface. Finally, they manufactured the nanoporous zinc oxide sensor through platinum contact.
The sensors grown in presence of UV light were better than the ones grown in its absence. In studies with methane in nitrogen and methane in synthetic air, both types of sensors showed maximum response at 240°C. The sensor was stable for 16 hours with a minimum fluctuation of current at 0.4 Volt.
"These sensors will be handy in countries like India and China where 80 per cent of the mine mishaps take place due to explosions caused by methane," says lead researcher Sukumar Basu from the Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata.
- Basu, P. K. et al. Methane Sensing Properties of Platinum Catalysed Nano Porous Zinc Oxide Thin Films Derived by Electrochemical Anodization. Sens. Lett. 6, 219-225 (2008)