Growth of self-aligned ZnO nanorods by hydrothermal process

Abstract

The present paper discuss the growth mechanisms of ZnO nanorods thin-films using the hydrothermal process. This was achieved on a ZnO seed layer prepared by sputtering and spray pyrolysis. ZnO nanorods were prepared using various precursors, including zinc nitrate [Zn(NO3)2.6H2O], zinc chloride [ZnCl2], and zinc acetate [Zn(CH3COO)2.2H2O, to investigate the effect of salt source. The morphological and structural properties of ZnO NRs were investigated using x-ray diffraction (XRD) and a scanning electron microscopy (SEM). The deposited film consist of highly oriented crystalline ZnO NRs along the [002] axis. We found that the seed layer preparation method alters the nanorods alignment. SEM observation revealed that, regardless of the seed layer preparation method, the nature of salt source play a key role in the nanorods size. We concluded that the ZnO nanorods diameter increases in the following order with respect to zinc salt source: ZnAc <zinc nitride <zinc chloride. The mechanism of of ZnO nanorods formation is correlated with bath solution viscosity and surface tension properties. We emphasized that, in a solution with a larger viscosity and surface tension, such as zinc chloride, the motion and transfer towards the substrate, of species participating in ZnO formation, is hindered by the friction force due to the viscosity. When using a solution with lower viscosity and surface tension, such as zinc acetate, the species forming the ZnO nanorods can easily reach the substrate, which leads to a larger nucleation center, yielding low-diameter ZnO nanorods.

Cutting-edge developments in zinc oxide nanoparticles: synthesis and applications for enhanced antimicrobial and UV protection in healthcare solutions

“…Whether it's catalysis, sensors, biomedical devices, or optoelectronics, hydrothermal synthesis offers the versatility needed to fine-tune ZnO nanoparticles for optimal performance. 43,44 …”

“… 42 The controlled reaction kinetics ensure the formation of nanoparticles with uniform size distribution and high crystallinity, essential for achieving desired functionalities. 43 Moreover, the hydrothermal process allows for the formation of complex nanostructures, such as nanorods, nanowires, and nanosheets, which further expand the range of potential applications. 44 …”

“…Whether it's catalysis, sensors, biomedical devices, or optoelectronics, hydrothermal synthesis offers the versatility needed to ne-tune ZnO nanoparticles for optimal performance. 43,44 In this method, the hydrothermal environment provides the ideal conditions for the nucleation and growth of ZnO crystals. 42 The controlled reaction kinetics ensure the formation of nanoparticles with uniform size distribution and high crystallinity, essential for achieving desired functionalities.…”

“…42 The controlled reaction kinetics ensure the formation of nanoparticles with uniform size distribution and high crystallinity, essential for achieving desired functionalities. 43 Moreover, the hydrothermal process allows for the formation of complex nanostructures, such as nanorods, nanowires, and nanosheets, which further expand the range of potential applications. 44 Overall, hydrothermal synthesis stands as a cornerstone in the realm of nanomaterial fabrication, offering researchers a powerful tool to engineer ZnO nanoparticles with tailored properties and enhanced performance for a myriad of technological advancements and scientic endeavors.…”