Rational design of hierarchical ZnO microspheres for high-performance acetone gas detection
摘要
The rational design of sensing materials with tailored morphologies is an effective strategy for enhancing the performance of metal oxide semiconductor (MOS) gas sensors. In this study, the hydrothermal method was used to synthesize three types of ZnO nanospheres with distinct structural morphologies, namely nanospheres assembled from rod-like subunits, nanospheres assembled from flake-like subunits, and nanospheres assembled from needle-like subunits. Notably, the amount of sodium hydroxide (NaOH) added was adjusted to regulate the pH of the reaction system: this pH modulation directly influenced the growth orientation of ZnO secondary structures, with an optimal pH range inducing the formation of flake-like subunits-a key structural feature contributing to superior sensing performance. The research results demonstrate that the sensor based on nanospheres assembled from flake-like subunits exhibited superior performance in acetone detection. At an optimal operating temperature of 223 °C, the sensor achieved a high response value of 108 to 100 ppm acetone, a rapid response time of 2 s, and excellent selectivity. This enhanced performance is mainly attributed to the hierarchical structure composed of flake-like subunits, which offers a large specific surface area (16.52 m2/g) and a high density of surface oxygen vacancies (30.4%). Furthermore, the sensor exhibited stable sensitivity to acetone over a four-week period, demonstrating its good long-term reliability. This study demonstrates the effectiveness of hierarchical structural engineering in the development of high-performance and fast-response acetone gas sensors.