Abstract
We report low-cost conductometric gas sensors that use an ultrathin film made of graphene oxide (GO) nanoflakes as transducing element. The devices were fabricated by lift-off metallization and near-room temperature, atmospheric pressure electrospray printing using a shadow mask. The sensors are sensitive to reactive gases at room temperature without requiring any post heat treatment, harsh chemical reduction, or doping with metal nanoparticles. The sensors’ response to humidity at atmospheric pressure tracks that of a commercial sensor, and is linear with changes in humidity in the 10%–60% relative humidity range while consuming <6 μW. Devices with GO layers printed by different deposition recipes yielded nearly identical response characteristics, suggesting that intrinsic properties of the film control the sensing mechanism. The gas sensors successfully detected ammonia at concentrations down to 500 ppm (absolute partial pressure of ∼5 × 10−4 T) at ∼1 T pressure, room temperature conditions. The sensor technology can be used in a great variety of applications including air conditioning and sensing of reactive gas species in vacuum lines and abatement systems.
Highlights
Conductometric gas sensors, based on semiconducting metal oxide films, are widely used due to their simplicity, flexibility in production, and broad applicability to many fields [1]
Electrosprayed graphene, graphene oxide (GO), and reduced graphene oxide (rGO) thin-film structures have been reported for supercapacitor electrodes [24], resistive switch applications [25], and humidity sensors [26]
In comparison to the published work on electrosprayed rGO humidity sensors [26], our sensors were fabricated with GO nanoflakes in an aqueous suspension versus rGO in isopropanol; our sensors implement a four-point probe electrode structure with a total active area that is an order of magnitude smaller than the rGO two-point structure reported in [26]; our sensors stabilized more than 30 times quicker at 50% relative humidity (RH), and were shown to detect ammonia in addition to RH in air
Summary
Conductometric gas sensors, based on semiconducting metal oxide films, are widely used due to their simplicity, flexibility in production, and broad applicability to many fields [1]. Electrosprayed graphene, GO, and rGO thin-film structures have been reported for supercapacitor electrodes [24], resistive switch applications [25], and humidity sensors [26].
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