Synthesis and characterization of zinc oxide quantum dots using an acidic precursor

Zinc oxide (ZnO) quantum dots (QDs) exhibit large exciton binding energy as a wide-bandgap semiconductor. They have a great advantage for catalytic processes due to their large surface area, which is extremely important in many fields of science and industry. In the present work, the focus was on zinc oxide QDs prepared through a simple direct-precipitation process that uses zinc acetate (ZnC4H6O4) and sodium hydroxide (NaOH). The characterizations showed variations in optical bandgap, particle size, morphology and elemental composition among the QDs. The optical absorption showed distinct excitonic features at 362 nm and an optical bandgap at 3.14 eV. The X-ray diffraction results indicated that the synthesized zinc oxide QDs had pure wurtzite structures. The crystal size obtained was 1-18 angstrom, along with a d-spacing of 1.83 angstrom. Scanning electron micrographs specifically showed aggregation, with a particle diameter of 44.00 +/- 0.32 nm. From transmission electron microscopy-selected area energy diffraction analysis, the diameter of the QDs was 3.42 +/- 0.17 nm, showing that zinc oxide excitons are comparatively near Bohr's radius.