Ammonia gas has been recognized by the United States Environmental Protection Agency
(USEPA) as one of the primary gases that are detrimental to conserving air quality. As such, trace levels of ammonia must be detected in any quality-controlled atmospheric conditions, such as space stations, manned space vehicles, submarines, healthcare facilities, pharmaceutical manufacturing, and food processing. The high specific surface area of graphene is an important factor in enabling large molecular adsorption on the surface and thus, enabling a direct sensing on a versatile surface. A large-area graphene sensor (1 cm^2) is fabricated using a transfer method for the detection of ammonia gas under ambient condition. The ambient atmosphere contains 21% of oxygen (O2), thus it is crucial to understand its impact on sensing of ammonia gas. The sensing response is analyzed under both the inert nitrogen gas and condensed dry air (CDA) containing 78.08% nitrogen, 20.95% of oxygen, and 0.93% of argon gases. Upon interaction with the graphene, both ammonia and Oxygen resulted in opposite electrical responses. Thus, finding reveals a polarity dependent interaction of gases with the graphene.
Our findings demonstrated that graphene sensors have distinct responses towards ammonia and oxygen, which can primarily interfere with gas present in the atmosphere. Thus, the graphene sensor provides a polarity-dependent response due to the presence of chemical doping during the growth and transfer process. These types of versatile sensors have also been shown to have applications in wearable biomonitoring. Further details can be found here: https://doi.org/10.1039/D4NJ02686A
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