A highly sensitive gas sensor for ethylene glycol: leveraging p-type NiO/ZnO composite and micro-hotplate structure

A high-sensitivity and stable ethylene glycol sensor was successfully developed by employing a facile hydrothermal method and annealing process to fabricate flower-shaped NiO/ZnO hierarchical nanostructures. The flower-shaped NiO/ZnO was integrated as the sensing material into a Microelectromechanical Systems (MEMS) gas sensor. The MEMS-based hotplate provided favorable heating conditions for the sensitive nanomaterial. Gas-sensing tests demonstrated excellent sensing performance of the sensor based on the flower-shaped NiO/ZnO heterostructure towards ethylene glycol. At the optimal operating temperature of 300 °C, the sensor to 10 ppm of ethylene glycol exhibited a response value of approximately 17.46 with response and recovery times of approximately 18 and 150 s, respectively. Moreover, its selectivity towards ethylene glycol was significantly higher than other common volatile organic compounds. This enhanced sensing performance is primarily attributed to the formation of p-n heterojunctions at the interface, the porous structure of NiO nanosheets, and their effective catalytic activity, resulting in a remarkable enlargement of the surface depletion region and an increase in barrier height. This study provides a simple synthetic process not only applicable to the preparation of other semiconductor oxide composite materials but also offers an effective method for ethylene glycol detection.