▎ 摘　　要

Graphene oxide (GO) is regarded as one of the potential candidates for gas and humidity sensor applications owing to its excellent water adsorption capabilities. However, there is a lack of understanding the response of GO to humidity. Some authors believe the water adsorption leads to p-type response while other think it to be n-type. The present work demonstrates the mechanism of water adsorption and n- to p-type response inversion of GO to humidity. The GO suspension was synthesised by modified Hummers' method and then drop-casted onto the substrates having already patterned gold interdigital electrodes (IDE). The sensors can detect wide humidity range (5-95 %RH) with a low voltage 0.1 V leading to low power consumption < 10(-5) W. It is also found that rGO samples annealed at temperature below 150 degrees C show n-type (e.g. Rair/RRH -1.29 x 10(5) for rGO-40) while the samples annealed above this temperature demonstrate p-type humidity response (e.g. RRH/Rair -40 for rGO-150). The static test response time is 8 s, while recovery time is 13 s with excellent long-term stability and RH accuracy value (+/- 4% RH). Further characterization are performed to elucidate the physio-chemical model of the sensing mechanism as well as n- to p-type conductivity inversion under humidity.