ZnO, due to its semiconducting, piezoelectric, and pyroelectric multiple properties, has found numerous electronic and optoelectronic applications in solar cells, gas sensors, and liquid crystal displays. These applications depend on the particle size and morphology, whichin turn are dependent of the preparation method. In this context, we are reporting the effect of [Zn2+] within the range of 0.02-0.38 M on the morphology of Zn(OH)2 and ZnO, prepared by our room-temperature procedure without using any surface ligand or template in theaqueous medium. The obtained Zn(OH)2 and ZnO materials were characterized by XRD, UV-vis, and SEM. XRD showed hexagonal wurtzite structure of ZnO for all materials, calcinedat 550�C. However, for the highest [Zn2+] of 0.38 M, ZnO was precipitated at room temperature, while orthorhombic wulfingite structure of Zn(OH)2 was detected by XRD for the other [Zn2+] concentrations. These XRD results are in agreement with the pH effect on determining the form of Zn-containing material. UV-Vis absorption revealed that all obtainedZnO materials have an Eg of ~3.1 eV, which is comparable to the value of 3.2 eV for the bulk ZnO, irrespective of [Zn2+]. SEM analysis explicitly revealed a strong influence of [Zn2+] on the morphology of the precipitated materials at room-temperaturethe, which was maintained for the ZnO materials, obtained upon calcination. Connected-spherical along with chunky particles were obtained for the highest [Zn2+] of 0.38 M. Aggregated sheet-like morphology wasobtained for when applying [Zn2+] of 0.19 M. On the other hand, the other three lower [Zn2+]resulted in octahedron particles with well-defined surfaces and edges. This featurewas evidently observed upon calcination. The observed morphology of the ZnO materials, prepared in this work, could be ascribed to the 'oriented attachment', where the colloidalparticles assemble themselves into larger aggregates or secondary particles in the micrometer regime.

Dependence of ZnO morphology on Zn<sup>2+</sup> concentration

248th National Meeting (2014)

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Dependence of ZnO morphology on Zn2+ concentration

Dependence of ZnO morphology on Zn²⁺ concentration