Abstract
VO2(B), VO2(M), and V2O5 are the most famous compounds in the vanadium oxide family. Here, their gas-sensing properties were investigated and compared. VO2(B) nanoflakes were first self-assembled via a hydrothermal method, and then VO2(M) and V2O5 nanoflakes were obtained after a heat-phase transformation in nitrogen and air, respectively. Their microstructures were evaluated using X-ray diffraction and scanning and transmission electron microscopies, respectively. Gas sensing measurements indicated that VO2(M) nanoflakes were gas-insensitive, while both VO2(B) and V2O5 nanoflakes were highly selective to ammonia at room temperature. As ammonia sensors, both VO2(B) and V2O5 nanoflakes showed abnormal p-type sensing characteristics, although vanadium oxides are generally considered as n-type semiconductors. Moreover, V2O5 nanoflakes exhibited superior ammonia sensing performance compared to VO2(B) nanoflakes, with one order of magnitude higher sensitivity, a shorter response time of 14–22 s, and a shorter recovery time of 14–20 s. These characteristics showed the excellent potential of V2O5 nanostructures as ammonia sensors.
Highlights
In many industries, hazardous gases have become increasingly important raw materials, and for this reason it has become very important to develop highly sensitive gas sensors to monitor them in the manufacturing process
Self-assembled VO2(B) nanoflakes were synthesized via a simple hydrothermal method, and VO2(M) and V2O5 nanoflakes were obtained through a high-temperature phase transition in nitrogen and air, respectively
Sensors based on the three famous vanadium oxide
Summary
Hazardous gases have become increasingly important raw materials, and for this reason it has become very important to develop highly sensitive gas sensors to monitor them in the manufacturing process. Vanadium oxides have been considered as new candidates for gas sensors Their sensing properties for inorganic/organic gases such as nitrogen oxides [27,28], ethanol [1,29,30,31], butyl-amine [32], and ammonia [33,34,35] have been reported. The gas-sensing properties of vanadium oxide nanostructures are strongly dependent on the actual synthesis environment and closely correlated with material morphologies, surface states, and microstructures. With regard to p-type MOS gas sensors, the direction of resistance change is opposite due to the combination of holes with electrons released from the surface reaction.
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