Nanoscale Ag/WO₃ Multilayered Fabry–Perot Cavities for Colorimetric NO₂ Sensing

High-performance gas sensors with low operating temperatures are of emerging research interest. They do not require heaters, thus guaranteeing cost-effectiveness and low power consumption. This is a study to demonstrate the possibility of fabricating a high-performance sensor through a simplified mechanism based on the surface property changes of a Fabry–Perot cavity. Here, the upper metal reacts independently, allowing accurate analyses to be performed while minimizing errors due to external factors. The proposed sensor rapidly responds to corrosive gases; it shifts the absorption wavelength by over 45 nm, that is, from 552 to 597 nm within 15 min at room temperature, significantly changes the color from purple to blue, and can be fabricated in bulk using conventional electron-beam physical vapor deposition. NO2 gas experiments verify the sensor's superior performance and productivity potential, demonstrating its applicability in urban areas and factories.