Enhanced NO₂ Gas Sensing Using Ce-doped ZnO Nanostructures

This study investigates the NO2 gas detection capabilities of cerium-doped zinc oxide and the effects of varying the cerium concentration. The experiment utilized spray pyrolysis, X-ray diffraction (XRD), and infrared (IR) spectroscopy, along with a mesh aluminum electrode, on thin film samples. Thermocouples monitored the heat variance with gas levels inside a sealed gas chamber using an internal gas sensor, and the sample resistance was continuously measured and recorded. XRD analysis of ZnO nanostructures revealed a hexagonal wurtzite crystal structure with distinct alignment along specific crystallographic planes. The introduction of Ce dopants caused a red shift in the absorption edge of ZnO toward higher wavelengths, extending its absorption into the visible light spectrum. The bandgap value was shifted via doping, which showed for ZnO and Ce/ZnO were 3.32, 3.24, and 3.22 eV, respectively. The FTIR spectrum revealed the presence of hydroxyl groups (OH) associated with water molecules, which can be attributed to the combined influence of two overlapping vibrational modes. The NO2 gas is a byproduct of chemical operations, with a vibrational wavenumber of 1526 cm-1. The discernible fingerprint bond of Ce–O was identified as a stretching vibration in the range of 740 cm-1 and 655 cm-1. The position of the Zn–O stretching vibration band varies depending on factors such as the dimensions, structure, and crystallinity of the ZnO nanoparticles. The gas sensing data were obtained using methods capable of detecting concentrations as low as 10 to 100 ppm. The specimen containing 10% Ce/ZnO exhibited the highest sensitivity among all samples.