Semiconducting and gas sensing performance of Magnetite nanoparticle systems of different morphologies

Abstract

Magnetite nanoparticle systems with uniform morphological features were synthesized through co-precipitation and forced hydrolysis without using any surfactants or additives. The selected batches of the synthesized particle systems were calcined at 1200 °C for phase transformation. The as-synthesized and calcined samples were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectrometry (FTIR), and X-ray Diffraction (XRD). In addition, the as-prepared and commercial magnetite particles were then employed as gas sensors to detect ammonia. Furthermore, the semiconducting properties of the synthesized (magnetite-I magnetite-II & magnetite-III) and commercial magnetite-based sensors were studied in the temperature range from 30 °C to 270 °C which indicated the n-type semiconducting nature of the magnetite particles. While commercial magnetite did not show any response in the employed temperature range. Furthermore, the synthesized magnetite nanoparticle-based sensors showed good and highly reproducible performance toward 10 ppm ammonia with a gas response of 58.44%, 64.39%, and 59.02%, respectively. For instance, magnetite-II and III were more sensitive toward the detection of ammonia with quick response/recovery times of 2s/5.8s and 2.4s/6.2s than 40s/17s for magnetite-I-based sensors. In contrast, the commercial magnetite-based sensor showed a response of 13.59% and significantly longer response/recovery time at room temperature and did not respond to ammonia concentration even at high temperatures. It was attributed to the remarkable uniformity in morphology, porosity, and good crystallinity of the as-prepared nanoparticles compared to the commercial-based sensor. This study unfolds that morphological features of the gas sensor’s material could be the key factors for controlling their sensing properties.