3D hollow mesoporous α-Fe2O3 sensor detecting liquified petroleum gas and humidity for diagnosing sleep hypopnea-apnea syndrome

Sensors utilizing mesoporous materials have garnered significant interest; however, they are primarily designed for detecting a single analyte. In this study, we successfully synthesized a three-dimensional (3D) hollow mesoporous α-Fe₂O₃ using a nanocasting process for the purpose of sensing LPG and humidity. The α-Fe₂O₃ obtained in this study maintained the cubic framework structure of MCM-48, demonstrating a mesoporous and hollow architecture. The Liquified Petroleum Gas (LPG) sensing characteristics of mesoporous α-Fe₂O₃ were examined at different operating temperatures (170–210 °C). The gas sensing response was optimized 99.3 % at 190 °C and the response/recovery time comes out to be 11.79 s & 0.84 s respectively. The humidity sensor's traits were evaluated at room temperature, with relative humidity (RH%) ranging from 11 % to 98 %, using mesoporous α- Fe₂O₃. The response/recovery time of mesoporous α-Fe₂O₃ as a humidity sensor comes out to be 6.3 s & 7.2 s respectively. The highly sensitive nature of the sensor along with negligible hysteresis, excellent repeatability and considerable stability for 30 days makes it a promisable candidate for real-time subtle respiration monitoring. Meanwhile, mesoporous α-Fe₂O₃ humidity sensor is also utilized for evaluation of sleep hypopnea-apnea syndrome.