Fig. 4: Performance evaluation of the SnO₂-CuO-based SAW sensor under practical operating conditions.

a Relationship between the SAW sensor response and humidity change. b Long-term stability of SnO2-CuO to 0.5 vol% CO2 at room temperature (25 °C). c Sensor selectivity for 0.5 vol% CO2 and 200 ppm of other gases at room temperature (25 °C)