NO 2 selective sensor based on α-Fe 2 O 3 nanoparticles synthesized via hydrothermal technique

In the present work, hematite (α-Fe 2 O 3 ) nanopowders were successfully prepared via a hydrothermal route. The morphology and microstructure of the synthesized nanopowders were analyzed by using scanning and transmission electron microscopy (SEM and TEM, respectively) analysis and X-ray diffraction. Gas sensing devices were fabricated by printing α-Fe 2 O 3 nanopowders on alumina substrates provided with an interdigitated platinum electrode. To determine the sensor sensitivity toward NO 2 , one of the main environmental pollutants, tests with low concentrations of NO 2 in air were carried out. The results of sensing tests performed at the operating temperature of 200 ◦ C have shown that the α-Fe 2 O 3 sensor exhibits p-type semiconductor behavior and high sensitivity. Further, the dynamics exhibited by the sensor are also very fast. Lastly, to determine the selectivity of the α-Fe 2 O 3 sensor, it was tested toward different gases. The sensor displayed large selectivity to nitrogen dioxide, which can be attributed to larger affinity towards NO 2 in comparison to other pollutant gases present in the environment, such as CO and CO 2 .