Anomalous Scaling Of Response Time Of Chemical Sensors With Concentration Of Unstable Gases

Gas sensors are critical for industrial and public safety. A good sensor should have high sensitivity and a small response time especially for gases identified as harmful to human health. However, most sensors face a tradeoff of increased response time when detecting trace amounts of a gas. In particular, unstable gases, that decay alongside diffusing in the sensor chamber, can limit the flux reaching the sensor. Here, we incorporate such decay phenomena within the framework of diffusion-limited gas detection to address the anomalous scaling of response times with the target gas concentration (in tune with recent experiments on lead-halide perovskite-based ozone sensors). This analysis could lead to better design of sensor chambers through optimization of detection conditions and sensor structure to ensure reasonable response times. In addition, we explore the relation between the response times and the decay time constants to propose an empirical method for decay time constant characterization.