Ionic liquid assisted synthesis of snowflake ZnO for detection of NOx and sensing mechanism

Snowflake ZnO mesoporous material with a small amount of ionic liquid residual remained was synthesized under the assistance of ionic liquid [Bmin][BF4] via hydrothermal reaction cembined with 650 °C calcination. A small amount of residual ionic liquid produces defects on the surface of the ZnO material. More active sites and larger specific surface area improve the selectivity of the ZnO sensor to NOx and increase the adsorption-desorption ability for the NOx gas molecules. The sensor exhibits superior sensing performance to 10 ppm NOx at an optimum operating temperature of 170 °C (S = 73.4). The sensor offers significant advantages in terms of lower detection limit (50 ppb) and shorter recovery time (10 s). DFT calculation and GC–MS technology explain the good desorption performance of snowflake ZnO to NOx gas and clarify the NOx sensing mechanism of the sensor.