High selectivity humidity sensors of functionalized graphite oxide with more epoxy groups

With large amounts of functional groups, graphene oxide (GO) is a promising sensing material for detecting gas molecules. Due to the different binding abilities between different oxygen-containing functional groups and target gas molecules, the selective response of the target gas can be realized through the regulation of functional groups in the GO structure. Herein, a new kind of GO with abundant epoxy groups was prepared by adding water as the activator in the low-temperature stage. The structure, spectral characteristics, and humidity sensitivity were systematically investigated by the XRD, FT-IR, XPS and sensitivity curves. The results showed that epoxy groups in GO structures could be effectively controlled with the addition of activator. Besides, the GO with more epoxy groups exhibited excellent selective sensitivity for humidity. At a 32.8% RH environment, the sensitivity of this kind of GO could reach 40.1%, and the response and recovery curves almost kept the same during five response and recovery cycles.