Environment-sensitive and fast room temperature CO2 gas sensor based on ZnO, NiO and Ni-ZnO nanocomposite materials

In contrast to other ZnO and NiO-based sensors, ZnO, NiO, and Ni-ZnO-based sensors were fabricated for this work in order to enhance CO₂ gas sensing properties at various concentrations. Nanomaterials were synthesized using the sol-gel technique. XRD, SEM, UV-visible spectroscopy, Raman spectroscopy, FTIR, and EDS were used to examine the structures, morphology, optical characteristics, rotational and vibrational frequencies, transmittance, and elemental content of the nanomaterials. Investigation findings revealed that the sensor response increased with the increase in CO₂ concentration. The typical response of a Ni-ZnO-based CO₂ gas sensor for various concentrations (500, 1000, 1500, and 2000 ​ppm) was investigated using the Keithley electrometer sensing set-up. Different sensing parameters (response time, recovery time, sensitivity) were estimated at ambient temperature for all three fabricated sensors and the result/sensitivity of the sensors was 0.0024, 0.0025 and 0.003 sensor response ppm-1 for ZnO, NiO, and Ni-ZnO respectively at 500 ​ppm. This result indicates that the sensors based on nanomaterials show good sensing parameters. All the fabricated sensors show a response time ranging from 14 ​s to 41 ​s, and a recovery time between 15 ​s and 44 ​s. The mechanism of sensing behind all the fabricated sensors, which are based on nanomaterials for CO₂ gas at various concentrations and at ambient temperatures is briefly discussed in this present report.