Novel Co(OH)F/Zn(OH)F heterostructures for acetone gas sensor applications: Materials synthesis, characterization, and sensor performance evaluation

The detection of acetone gas using a gas sensor provides a non-invasive means for monitoring diabetes patients. Various Co-based materials have been developed as acetone-sensing materials. In this work, we developed novel heterostructured materials consisting of metal fluoride hydroxides, Co(OH)F, and Zn(OH)F using a microwave-assisted hydrothermal synthesis process. The ratio between the Co(OH)F microflowers and Zn(OH)F nanorods (3:1) and the mixing conditions (120 °C for 20 min) were optimized. A gas sensor based on the heterostructured material prepared under the optimized conditions demonstrated a significant enhancement in gas response compared with the sensor based on pristine Co(OH)F microflowers. The optimized gas sensor exhibited a very high response of 7.6 toward 5 ppm of acetone gas at an operating temperature of 150 °C, with good selectivity and stability. Considering the energy band diagrams confirmed that the formation of p–n junctions at the interface led to an improvement in the gas response compared with that of the pristine Co(OH)F microflowers.