Fig. 6

a Selectivity tests of the response of the S1–S5 NW gas sensors to 5 ppm hydrogen sulfide, ammonia, 1-hexanol, acetone, nitrogen dioxide, toluene, ethanol, and methanol at the corresponding optimal operating temperature (390, 380 350, 320, and 340 °C, respectively). b Stability tests of the S1–S5 NW gas sensors in the presence of 1 ppm acetone (tested every 5 days) at the corresponding optimal operating temperature