High Sensitivity NO₂ Gas Sensor Based on 3D WO₃ Microflowers Assembled by Numerous Nanoplates.

Tungsten oxide microflowers (WO₃ MFs) were fabricated by a simple hydrothermal process through adjusting the pH of the solution by HCl. These MFs possess the outer diameters of about 2 μm and are composed of numerous nanoplates with the average pore size of 10.9 nm. Chemiresistive activity of as-fabricated WO₃ MFs sensor was attempted towards oxidizing and reducing target gases, revealing a superior selectivity to NO₂ with a maximum response of 22.95 (2 ppm NO₂) @105 °C compared to other target gases. One of the key features of as-fabricatedWO₃ MFs sensor is the lower detection limit of 125 ppb and operating temperature of 105 °C to NO₂ with better reproducibility, signifying commercial prospective of the developed sensor materials. Finally, the gas sensing mechanism of WO₃ MFs sensor has been proposed.