Synthesis of nanostructured NiO by hydrothermal route and its gas sensing properties

A hydrothermal process was used for the synthesis of nanostructured NiO with and without capping reagent (surfactant). Nickel Chloride (NiCl₂) a precursor of Nickel and Thioglycerol, a capping reagent, was used for this preparation. The structure, morphology and crystalline phase of the nickel oxide nanocrystal have been investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). TEM images showed that the nickel oxide nanoparticles have hexagonal structure with uniform size distribution around 20-38 nm for NiO with capping agent and 23-100 nm for NiO without capping agent. Phase pure, cubic nickel oxide formation was identified from the XRD data. The thick films of NiO were prepared by screen-printing technique to study their gas sensing properties. The gas sensing performance of NiO thick films (with and without surfactant) were tested to H₂S, LPG, H₂, NH₃, Ethanol, CO, CO₂, and O₂, to operating temperature ranging from 100 °C to 450 °C, they showed maximum response to H₂S for 10 ppm gas concentration at 150 °C. The response and recovery values upon the exposures to 10 ppm H₂S gas and air were 4 s and 58 s for NiO (with surfactant) thick film sensor, while those were 10 s and 64 s for NiO (without surfactant) thick film sensor respectively. The NiO thick films have potential applications in H₂S gas sensor applications. The results are discussed and presented in this paper.