Room temperature ammonia sensors based on zinc oxide and functionalized graphite and multi-walled carbon nanotubes

In this work, different techniques are proposed to realize ammonia (NH3) sensors working at room temperature and a preliminary electrical characterization under water vapor and in NH3 atmospheres is presented. Three families of ceramic planar sensors based on a zinc oxide (ZnO) layer overlapped by screen-printed Pd-doped carboxyl groups functionalized multi-walled carbon nanotubes (Pd-COOH-MWCNTs) or by blocks of vertically aligned MWCNTs or by graphite as such and functionalized with fluorinated or nitrogenous functional groups were studied. These sensors were almost insensitive to humidity, while all of them gave a good response in NH3 atmosphere, starting from about 45 ppm in the case of zinc oxide with fluorinated or nitrogenous MWCNTs and graphite or 50 ppm for Pd-COOH-MWCNTs sensors. These results are not actually as good as those reported in the literature, but this preliminary work proposes simpler and cheaper processes to realize NH3 sensor for room temperature applications. (C) 2010 Elsevier B.V. All rights reserved.