Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) Based Humidity Sensors

Humidity sensors are critical in a wide range of applications ranging from automotive, biomedical, chemical, and electronics industries, to scientific research laboratories. Here we discussed widely acclaimed synthesis techniques for the preparation of graphene and its derivatives. Graphene, along with its analogues GO, and rGO shows improved surface properties making it sensitive to fractional change in ambient surroundings. GO/rGO-based sensory materials owing to their distinctive physio-chemical features appeared as a competitive sensor in comparison to the widely used metal oxides. The enhancement in the merits of GO-based humidity sensors is ascribed to the various functionalized groups on the GO surface. Pristine GO is employed as a capacitive sensor, whereas reduced GO (rGO) with improved conductivity is extensively utilized as a chemiresistive humidity sensor. Similarly, Graphene quantum dots (GQDs) and 2D- layered graphene have been explored as humidity sensors due to their massive scope of manipulation in properties. The chemiresistive humidity sensor gains an advantage over any type of available sensor owing to its cost-effective fabrication, easier integration with the CMOS platform, and efficient operation. This review aims to establish the evaluability of GO and rGO humidity sensors and their role in the progress of the next generation of flexible sensors for the Internet of Things (IoT).