CuO/M(OH)₂ (M = Mg, Ca) heterostructures with in-situ oxygen vacancies enable room-temperature ultrahigh triethylamine sensing

Room-temperature gas sensors are crucial for detecting toxic gases and volatile organic compounds (VOCs). Conventional metal oxide semiconductor (MOS)-based sensors, however, often require high-temperature operation and suffer from low sensitivity. Here, we present a one-step mini-mechanochemical synthesis of CuO/M(OH) 2 (M = Mg, Ca) heterostructures that exhibit exceptional room-temperature sensing performance towards triethylamine (Et 3 N). Our results reveal a tenfold enhancement in the sensor response to Et 3 N compared to pristine CuO. This remarkable improvement is attributed to the in-situ formation of oxygen vacancies in CuO induced by the incorporation of M(OH) 2 , as evidenced by X-ray photoelectron spectroscopy (XPS), positron annihilation spectroscopy (PAS), and electron paramagnetic resonance (EPR). Notably, CuO/Mg(OH) 2 demonstrates superior long-term stability, while CuO/Ca(OH) 2 suffers from performance decay due to environmental carbonation. Furthermore, we developed a portable Et₃N analysis device based on the CuO/Mg(OH) 2 sensor, which enables real-time monitoring with Wi-Fi capability and achieves an accuracy within 6 % error across a 1 to 100 ppm detection range. This study not only provides a cost-effective and scalable fabrication method for CuO-based gas sensors but also highlights the potential of CuO/M(OH)₂ in practical applications for environmental monitoring and food safety assessment.