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Synthesis and Characterization of Ni-Doped ZnO Nanoparticles for CO2 Gas Sensing

In this research, we synthesised nickel (Ni)-doped zinc oxide (ZnO) nanoparticles (NZ) with various atomic ratios of [Ni]/[Zn], i.e., 0.02, 0.04 and 0.06 using a simple sol–gel method. The synthesized materials were examined by different techniques such as X-ray diffraction (XRD),
 scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The observed XRD results confirmed that all the prepared samples exhibited a hexagonal wurtzite structure with no additional secondary phases, confirming that
 Ni ions were successfully incorporated into the lattices of ZnO crystals. The average size of the synthesized nanoparticles is in the range of 30–80 nm, as was confirmed from the TEM observations. The synthesized Ni-doped ZnO nanoparticles were used as functional material to fabricate
 efficient CO2 gas sensors. The gas detection results demonstrated an improvement in the response of the Ni-doped ZnO sensor towards CO2 gas. The data obtained at 350 ˚C working temperature reveal that this sensor has a modest reaction to CO2. With increasing
 Ni doping, we noticed that the baseline and the dynamic responses rises. Based on the obtained results, a plausible sensing mechanism towards CO2 gas sensor based on Ni-doped ZnO nanoparticles is also proposed and presented in this paper.