Synthesis of Maghemite nanoparticles for highly sensitive and selective NO2 sensing

Abstract We report a simple and efficient method for the synthesis of highly sensitive and selective Maghemite (γ-Fe2O3) nanoparticles from magnetite (Fe3O4). Maghemite nanoparticles were obtained by optimizing the annealing temperature. The annealing temperature was found critical for obtaining Maghemite phase (γ) from magnetite. The structure, morphology, and chemical bonding of obtained Maghemite nanoparticles were annealed at 300 °C-600 °C temperature. These samples were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), and Fourier-transform infrared spectroscopy (FT-IR), etc. The structural property of all the annealed samples revealed the formation of Maghemite (γ-Fe2O3) and hematite (α-Fe2O3) phases. Moreover, the sensing properties of all the samples were carried out for various oxidizing and reducing gases like acetone ((CH3)2CO), ammonia (NH3), ethanol (C2H6O), carbon dioxide (CO2), nitrogen dioxide (NO2). The fabricated cubic Maghemite sensor annealed at 300 °C-was found to be more sensitive and selective towards NO2 gas at 150 °C of operating temperature. Additional parameters like operating temperature, linearity, response time (SRes) and, recovery time (SRec) were also evaluated, which shows typical sensing behavior. These typical properties of fabricated Maghemite sensor were useful to study the behaviour of the gas sensor. Thus, the present effort depicts the exemplary sensing behaviour of Maghemite annealed at 300 °C nanoparticles over different phases of iron oxide nanoparticles. This work strongly recommends an efficient approach to fabricate Maghemite sensors with highly sensitive and selective towards NO2 gas detection than ever in the reported literature.