Solution-processed Synthesis-in-Place Method of Hematite Nanorods for Selective Ethanol and Acetone Sensors

Abstract

Integrating highly crystalline hematite nanorods with patterned substrates is an effective design strategy for taking advantage of one-dimensional nanorod structures such as high surface-to-volume ratio and long-term reliability, but many challenges remain in synthesis. Here we report a facile synthesis-in-place method for hematite nanorod films on patterned substrates without additional process and the application of the films to gas sensors. Vertically standing hematite nanorods are synthesized with hydrothermal method. The morphology of hematite nanorods is controlled by changing synthesis time. It is shown that the response of vertically standing hematite nanorods to 50 ppm ethanol at 350oC is 4 times higher than that of collapsed nanorods and the theoretical detection limit is estimated to be about 20 ppb. This is explained with gas accessibility to the bottom region of the oxide layer, so called, utility factor. The nanorod sensor shows selective responses to ethanol at 300-375 oC and to acetone at 400oC. Our results demonstrate that the morphology control using the facile synthesizing method is an effective strategy for making ethanol or acetone sensors based on the earth-abundant semiconducting oxide, hematite.