Humidity Sensor Based on High Proton Conductivity of Graphene Oxide

This paper explores the performance of graphene oxide (GO) as humidity sensor. GO was synthesized using modified Hummers and Offeman method, and the sensing layer was characterized using optical microscope, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The sensor devices were fabricated by drop-casting of GO on patterned gold electrodes on Si/SiO₂ substrate. GO-based sensor was exposed to six different relative humidity (RH%), and the response of our sensor was found to be excellent due to large proton conduction. The sensor response varied from ∼180 times (40% RH) to ∼1200 times (88% RH). Our GO-based humidity sensor also showed ultrafast response and recovery times with extremely good repeatability. Also, the role of functional groups in humidity sensing was explored by fabricating the sensor devices by thermally reducing GO for different time durations. We believe GO could potentially be used to develop new-generation ultrasensitive humidity sensor.