Microwave Assisted Growth of ZnO Nanorods and Nanopolypods Nanostructure Thin Films for Gas and Explosives Sensing

Abstract

The growth of uniformly distributed and densely packed array of zinc oxide (ZnO) nanorods (NRs) and nanorods (NRs)/nanopolypods (NPPs) was successfully achieved through microwave-assisted chemical route at low temperature. The ZnO NRs and NRs/NPPs were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX), and UV-Vis absorption spectroscopy. The ZnO NRs were of 100–150 nm diameter and 0.5–1 μm length, while the NPPs were of diameter about 150–200 nm and 1.5–2 μm pod length. The prepared films are polycrystalline in nature and highly oriented along (002) plane with a hexagonal wurtzite structure. These films were studied for the sensing properties of liquefied petroleum gas (LPG), oxygen, and hazardous explosives, that is, 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramines (RDX), in the temperature ranges of 25–425 °C and 100–200 °C, respectively. The grown nanostructure films showed reliable stable response to several on-off cycles, and reduction in sensor recovery time was found with the increase in temperature. ZnO NRs and NRs/NPPs showed better sensitivity and recovery time for both LPG and oxygen, as compared to the literature-reported results for ZnO thin films.