Vanadium pentoxide (V(2)O(5)) nanocrystals having few tens nanometers average size, are obtained ammonium metavanadate (NH(4)VO(3)) in the presence of oleic acid, and treating the reaction 400 degrees C. Nanocrystalline films, deposited from stable ethanol suspensions of the V(2)O(5) strongly to different kinds of substrates, without the need of any thermal post processing. temperature, the films are found to bleach when exposed to ammonia. Bleaching originates formation of ammonium metavandate, and is reversible, as after annealing in air at 350 C, metavanadate converts back to V(2)O(5). Formation of ammonium metavanadate, clearly remarkable changes in infrared spectrum of V(2)O(5) films exposed to ammonia, is a valuable mechanism, promising in view of developing highly selective ammonia sensors operating temperature. (C) 2010 Elsevier B.V. All rights reserved.