Low-working-temperature, fast-response-speed NO2 sensor with nanoporous-SnO2/polyaniline double-layered film

A SnO2/polyaniline (PANI) double-layered film sensor for NO2 detection was fabricated using nanoporous SnO2 and PANI layers. The double layered film sensor has high selectivity and high response to NO2 gas even with low concentration. Furthermore, the double layered film sensor also has a low optimum working temperature (140 °C) and high stability over a long working time period. The response and recovery time of sensor S5P500 is as short as about 17 s and 25 s to 37 ppm NO2 at 140 °C, respectively. The experiment results show that the porous characteristics of nanoporous SnO2 and the thickness of PANI have effect on the sensor response of double layered film sensors. The improved sensing properties mainly attributes to the formation of depletion layer at the p–n junction interface in SnO2/PANI double layered film sensor, which makes great resistivity difference in air and NO2 gas. Thus, the combination of n-type SnO2 thick film and p-type PANI thick film provides an effective strategy to design high property gas sensors.