Porous metal-graphene oxide nanocomposite sensors with high ammonia detectability

Nickel oxide-graphene oxide (NiO-GO), zinc oxide-graphene oxide (ZnO-GO) and bismuth oxide-graphene oxide (Bi₂O₃-GO) metal oxide-graphene oxide nanocomposite (MO-GO NC) sensors, operable at room temperature, were synthesized via a simple and cost-effective microwave-assisted combustion method for chemiresistive gas sensor applications. From the measured structural, morphological, and elemental detection properties, the sensors are found capable of detecting various gases. The Bi₂O₃-GO NC sensor exhibited excellent response over NiO-GO (~20 at 50 ppm) and ZnO-GO NC (~60 at 50 ppm) sensors for detecting NH₃. The response of the Bi₂O₃-GO NC sensor at 50 ppm NH₃ in just 14 s operation duration was ~81.23, which is improved 25-fold and 13-fold compared to pristine GO sensors. Additionally, the as-developed Bi₂O₃-GO NC sensor demonstrates outstanding repeatability and recovery kinetics, attributed to porosity and the combined effects of MO and GO. The sensing mechanism of the Bi₂O₃-GO NC gas sensors is proposed herein. The superior sensing performance, including quick response and recovery of the Bi₂O₃-GO NC sensor is attributed to favorable charge transfer across the Bi₂O₃ and GO interface. The significance of relative humidity on sensing potential of the Bi₂O₃-GO NC sensor has also been studied and the sensor is confirmed to be unaffected by relative humidity.