Abstract
In the present work, hematite (α-Fe2O3) 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-Fe2O3 nanopowders on alumina substrates provided with an interdigitated platinum electrode. To determine the sensor sensitivity toward NO2, one of the main environmental pollutants, tests with low concentrations of NO2 in air were carried out. The results of sensing tests performed at the operating temperature of 200 °C have shown that the α-Fe2O3 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-Fe2O3 sensor, it was tested toward different gases. The sensor displayed large selectivity to nitrogen dioxide, which can be attributed to larger affinity towards NO2 in comparison to other pollutant gases present in the environment, such as CO and CO2.
Highlights
Metal oxides, such as ZnO, NiO, SnO2, and others, have been used for a long time as an active layer in gas sensors to detect toxic and hazardous environmental gases, such as CO, CO2, and NO2, because they have a low cost in comparison to other sensing technologies, are robust, have a small size, and are lightweight
In this work, we report efforts made in synthesizing α-Fe2 O3 nanoparticles by hydrothermal method, focusing on the development of a selective sensor for NO2 gas for applications in the field of environmental monitoring
Hematite Fe2O3 nanoparticles were successfully prepared by hydrothermal technique
Summary
Metal oxides, such as ZnO, NiO, SnO2 , and others, have been used for a long time as an active layer in gas sensors to detect toxic and hazardous environmental gases, such as CO, CO2 , and NO2 , because they have a low cost in comparison to other sensing technologies, are robust, have a small size, and are lightweight. More research is still necessary to develop further improvements in gas-sensing properties, especially the sensitivity and selectivity [11] These characteristics are of utmost importance for environmental applications where the target gas is usually present in low concentrations in a complex gaseous mixture. Α-Fe2 O3 prepared as thin films showed a selective detection for NO2 [22], while α-Fe2 O3 nanowires are more sensitive to CO gas [26], and flowerlike α-Fe2 O3 exhibited better performance regarding ethanol [27] This shape dependence of sensor sensitivity towards gases is attributed to the variation of the available nanocrystal facets in contact with target gas [28]. In this work, we report efforts made in synthesizing α-Fe2 O3 nanoparticles by hydrothermal method, focusing on the development of a selective sensor for NO2 gas for applications in the field of environmental monitoring
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