Green synthesized ZnO/NiO heterostructures based quick responsive LPG sensor for the detection of below LEL with DFT calculations

Abstract

The current research work reports on the detection of liquefied petroleum gas (LPG) at room temperature. The ZnO/NiO heterostructure was synthesized via green method and characterized by various techniques. The surface morphological and structural analysis has been performed by scanning electron microscope, transmission electron microscope and X-ray diffractometer. The Rietveld refinement analysis confirmed the polycrystalline nature of ZnO/NiO and existing hexagonal (ZnO) and cubic (NiO) crystal structures. The optical properties were analyzed by UV–visible spectroscopy and optical band gap of ZnO, NiO and ZnO/NiO were found to be 3.62 eV, 3.81 eV and 3.71 eV respectively. The DFT analysis was performed by B3LYP/LAN2DZ basis set with the interaction from LPG of ZnO, NiO and ZnO/NiO composite for better understanding of the sensing characteristics of devices. The ZnO, NiO, and ZnO/NiO were investigated for the detection of the LPG from below lower explosion limit (LEL) i.e. 0.5 vol% to 2.5 vol%. Sensor response of ZnO/NiO heterostructure-based sensor was found 7.72 at 2.5 vol% which is 2.6 times higher than pure ZnO and NiO. The fast response and recovery times of ZnO/NiO were found to 7.83 s and 11.01 s, respectively at 0.5 vol% LPG. Also, the ZnO/NiO is highly selective for LPG in comparison to other analytes like ethanol, acetone, ammonia, and CO2 etc. Thus ZnO/NiO heterostructures can be effectively used for the detection of LPG at room temperature against below LEL.

Keywords

• Metal oxide
• ZnO/NiO heterostructure
• Green synthesis
• LPG sensor
• DFT calculations