Highly sensitive NO2 gas sensor based on hematite nanoparticles synthesized by sol–gel technique

• Published in: Journal of materials science. Materials in electronics Vol. 31; no. 6; pp. 5025 - 5031
• Main Author: Hjiri, M.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.03.2020; Springer Nature B.V
• Subjects: Ammonia; Characterization and Evaluation of Materials; Chemistry and Materials Science; Crystallites; Ethanol; Gas sensors; Gases; Hematite; Low concentrations; Materials Science; Morphology; Nanomaterials; Nanoparticles; Nitrogen dioxide; Operating temperature; Optical and Electronic Materials; Selectivity; Sensors; Sol-gel processes; Synthesis; Transmission electron microscopy
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-020-03069-4

The sol–gel technique was utilized to synthesize α-Fe 2 O 3 nanoparticles in supercritical conditions of ethanol. The morphology and microstructure were investigated by scanning and transmission electron microscopy (SEM and TEM) analysis and X-ray diffraction (XRD).The average crystallite size estimated by sherrer’s equation was 60 nm. TEM images show that the obtained powder is composed of agglomeration of irregular shaped (between oval and spherical) grains. The prepared nanomaterial was used as sensing layer in gas sensing device. The sensor has been tested towards low concentrations in air of NO 2 at different temperatures from 200 to 350 °C. We noticed that 225 °C was the best operating temperature. At this temperature, the obtained results indicated that the realized sensor has a high response towards 1 ppm of NO 2 gas. The response and recovery times are 26 and 48 s, respectively. To show the selectivity of the sensor, we have tested it with different gases such as CO, CO 2 , and NH 3 . We found that hematite sensor exhibits high selectivity towards NO 2 gas.