An encapsulation strategy of graphene humidity sensor for enhanced anti-interference ability

Abstract

Humidity sensors are widely used in agriculture. Graphene and reduced graphene oxide (rGO) have become high-performance humidity-sensitive materials. However, there are many interferences in agricultural production, such as smoke from burning stalks and animal waste. In fact, graphene and rGO are sensitive to a variety of gases, resulting in poor anti-interference ability of existing humidity sensors. In this work, by simply spraying a layer of graphene oxide (GO) on the surface of rGO, the cross-sensitivity to 3.4 ℃ temperature rise reduces from −0.3%/RH% to −0.2%/RH%, the cross-sensitivity to 683 ppm ammonia significantly reduces from 2.5%/RH% to 0.08%/RH%, and the cross-sensitivity to 34 ppm ethanol reduces from −0.2%/RH% to nearly 0. The encapsulated sensor still maintains the high sensitivity (0.37%/% RH) and fast response (1.8 s response/4.5 s recovery) of the original humidity sensor. The resistance to temperature interference is due to GO's weak thermal conductivity. The resistance to gas interference stems from that the adsorbed water molecules between the GO interlayers block the entry of other gases to some extent. Finally, field tests show that the encapsulated rGO humidity sensor can resist the interference of straw smoke and pig manure, which has great practical application value.