Gasochromic response of nanocrystalline vanadium pentoxide films deposited from ethanol dispersions

Vanadium pentoxide (V₂O₅) nanocrystals having few tens nanometers average size, are obtained from ammonium metavanadate (NH₄VO₃) in the presence of oleic acid, and treating the reaction product at 400 °C. Nanocrystalline films, deposited from stable ethanol suspensions of the V₂O₅ nanopowder, adhere strongly to different kinds of substrates, without the need of any thermal post processing. At room temperature, the films are found to bleach when exposed to ammonia. Bleaching originates from the formation of ammonium metavandate, and is reversible, as after annealing in air at 350 °C, ammonium metavanadate converts back to V₂O₅. Formation of ammonium metavanadate, clearly evidenced by remarkable changes in infrared spectrum of V₂O₅ films exposed to ammonia, is a valuable detection mechanism, promising in view of developing highly selective ammonia sensors operating at room temperature.