Novel Yttrium Iron Garnet (Y₃Fe₅O₁₂) Based Chemiresistive Highly Sensitive Selective Ultrafast CO Gas Sensor

Carbon monoxide (CO) sensors are critical for safety applications in residential settings, industrial workplaces, environmental monitoring, and healthcare diagnostics. Additionally, CO serves as a biomarker for respiratory and inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD). Therefore, the development of a highly sensitive CO sensor capable of detecting trace concentrations is of significant importance. In this study, we present, for the first time, a highly selective and stable chemiresistive CO sensor based on yttrium iron garnet (Y₃Fe₅O₁₂). The material was synthesized via a sol-gel method under varying pH conditions and characterized using XRD, FESEM, EDX, XPS, BET, and UV-vis spectroscopy. XRD analysis confirmed that a pure garnet phase formed under highly acidic conditions, whereas a mixed phase appeared at neutral or less acidic pH. Gas sensing studies demonstrated that the phase-pure Y₃Fe₅O₁₂ sensor exhibited an ultrafast response (3 s) and recovery (4 s) with a ∼37-fold p-type sensing response toward 100 ppm CO. It maintained high sensitivity even at 500 ppb CO (∼5-fold response) and showed exceptional selectivity against common interfering gases. The sensor remained stable for over 120 days, highlighting its potential for real-world applications in environmental monitoring and medical diagnostics.