Investigating NiO nanostructures in ethanol vapor sensing by changing the morphology

The NiO nanostructures were simply synthesized through the hydrothermal method at different hydrothermal temperatures of 100 and 180 °C. The XRD results in association with SEM and TEM images indicate that morphology of NiO crystals varied from irregular nanoparticles to nanorods by increasing the hydrothermal temperature from 100 to 180 °C. Also, it was seen from FTIR results that a negligible amount of surface functional groups is mounted on calcinated samples. The lack of impurities and other unwanted phases were also confirmed using XRD and Raman spectroscopies. The gas response of the samples showed that NiO nanorod samples give at least 2–3 times better sensitivity than NiO nanoparticle sample which was attributed to its porous structure. Also, it was shown that gas response value against ethanol vapor concentration follows from one-order exponential function.