Optically transparent, electrically conducting single walled carbon nanotubes random networks for room temperature ammonia vapor sensing

Optically transparent and electrically conducting single walled carbon nanotubes (SWCNT) random networks have been fabricated on glass using the spray coating technique. SWCNT random network were characterized by the scanning electron microscopy, micro-Raman and UV-vis-NIR spectroscopy and used as sensors. Change in electrical resistance of the random networks against the ammonia vapor concentration from 0 to 1000 ppm was studied at room temperature. The sensors showed logarithmic response. Fast, reversible and highly selective nature of the sensor towards ammonia among methanol, ethanol and acetone vapors is accomplished. The sensor having 93% of optical transparency at 550 nm showed maximum response of 181 for 62.5 ppm ammonia concentration with high signal to noise ratio value of 3240. Sensing of ammonia was attributed to charge transfer from ammonia molecules to the SWCNT. The sensor response and recovery times were calculated as 215 and 548 s respectively for 62.5 ppm ammonia. The present study has the theoretical detection limit up to 5 ppb. (C) 2015 Elsevier Ltd. All rights reserved.