Nanocrystalline ZnO obtained from pyrolytic decomposition of layered basic zinc acetate: Comparison between conventional and microwave oven growth

The pyrolytic decomposition of layered basic zinc acetate (LBZA) nanobelts (NBs) and nanosheets (NSs) into nanocrystalline ZnO NBs/NSs has been investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Photoluminescence (PL). We also report on the gas sensing response of the resulting ZnO nanomaterials to CO. The LBZA NBs were grown at 65°C for 9h in an aqueous solution of zinc acetate dehydrate and the LBZA NSs were grown in 2min in a standard microwave oven. AFM, SEM and XRD showed as-grown products possess the characteristic layered structure of LBZA crystals. XRD results showed that annealing as-grown products a 400°C in air caused a transformation from zinc acetate to nanocrystalline ZnO via thermal decomposition and that the crystalline domain size increased with temperature. The thickness of the NBs and NSs, determined via AFM, ranged from 10 to 50 nm. PL shows a larger defect band for ZnO NBs, compared to NSs. Gas sensors fabricated from 400°C annealed NBs showed a response of 1.62 when exposed to 200ppm of CO in dry air at 400°C. The same response was observed at 325°C for the NSs, which also had better response at lower concentrations. Our results indicate that ZnO nanostructures obtained by thermal decomposition of LBZA NBs/NSs could provide a cost effective route to high sensitivity gas sensors.