Effect of oxygen on ammonia sensing of large area graphene

Abstract

The high specific surface area of graphene is an important factor to enable a large molecular adsorption on the surface, thus enabling direct sensing on a versatile surface. A large area graphene sensor (1 cm²) is fabricated using a transfer method for the detection of ammonia (NH₃) gas under ambient conditions. The ambient atmosphere contains 21% oxygen (O₂), and thus it is crucial to understand its impact on the sensing of ammonia gas. The sensing response is analyzed under both the inert nitrogen (N₂) gas and condensed dry air (CDA) containing 78.08% N₂, 20.95% of O₂, and 0.93% of argon gas. Upon interaction with the graphene, both NH₃ and O₂ resulted in opposite electrical responses. Thus, this finding reveals a polarity dependent interaction of gases with the graphene.