Application of ink-jet printing and spray coating for the fabrication of polyaniline/poly(N-vinylpyrrolidone)-based ammonia gas sensor

We report on the preparation of thin conducting films from the poly(N-vinylpyrrolidone) stabilized polyaniline dispersions for the ammonia gas sensor applications. The dispersion is waterbased and prepared by means of relatively simple chemical oxidation polymerization of aniline. Two processes were used for the ink deposition, the ink-jet printing and the spray-coating technique. With the former one, the ink was at first tested on the poly(ethylene terephthalate) foil to find a suitable combination of ink formulation and print parameters. After that, the final ammonia gas sensors were fabricated by both deposition techniques and compared. The aspects of the ink preparation and alteration, as well as the active layer properties, are analyzed by means of UV-vis spectroscopy, optical microscopy, atomic force microscopy, profilometry and electrical measurements. The results obtained from each deposition technique are discussed. In both cases, the sensitivity to the ammonia gas has been demonstrated, making the proposed ink in combination with the two named deposition processes feasible for the potential large-area sensor production.