Abstract
A facile thermal-treatment route was successfully used to synthesize ZnO nanosheets. Morphological, structural, and optical properties of obtained nanoparticles at different calcination temperatures were studied using various techniques. The FTIR, XRD, EDX, SEM and TEM images confirmed the formation of ZnO nanosheets through calcination in the temperature between 500 to 650°C. The SEM images showed a morphological structure of ZnO nanosheets, which inclined to crumble at higher calcination temperatures. The XRD and FTIR spectra revealed that the samples were amorphous at 30°C but transformed into a crystalline structure during calcination process. The average particle size and degree of crystallinity increased with increasing calcination temperature. The estimated average particle sizes from TEM images were about 23 and 38 nm for the lowest and highest calcination temperature i.e. 500 and 650°C, respectively. The optical properties were determined by UV–Vis reflection spectrophotometer and showed a decrease in the band gap with increasing calcination temperature.
Highlights
Nanoscale particles possess several unique properties such as large surface areas, unusual adsorptive properties, surface defects and fast diffusivities
The polyvinyl pyrrolidone (PVP) content and undesired anions were completely removed from the sample and gradually high purity Zinc oxide (ZnO) nanosheets begun to conform with increasing calcination temperature
The average particle size at calcination temperatures of 500, 550, 600 and 650uC is about 23, 26, 30 and 38 nm, respectively, which were found to be in good agreement with the XRD measurements. These results indicate that the attained particle size has increased with increasing calcination temperature due to the fact that as the temperature went high, many neighbouring particles were prone to fuse together to form larger particle sizes by melting their surfaces [37]
Summary
Nanoscale particles possess several unique properties such as large surface areas, unusual adsorptive properties, surface defects and fast diffusivities. When zinc oxide approaches nanoscale sizes accompanied by intriguing properties due to quantum confinement effect [8] as compared to bulk counterparts, its usage can further expand to cover applications as in optical devices including blue-violet and UVlight emitting diodes [9], laser diodes [10], biosensors [11], piezoelectric transducers, solar cells [12], transparent electrodes, electroluminescent devices and photocatalytic materials [13] Because it has been chemically and optically stable with offering low toxicity, its use as a fluorescent label for bioimaging in medical application has been anticipated [14]. The chemical materials were above 99% in purity and used without further purification
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