Selective synthesis and shape-dependent microwave electromagnetic properties of polymorphous ZnO complex architectures

A simple one-pot hydrothermal approach that allowed the selective synthesis of complex ZnO architectures with varying configurations without using any surfactants and/or solid templates is proposed in this paper. The ZnO configurations include spherical aggregates, nanosheet-based flowers, microrod-composed flowers, and nanopetal-built flowers. Kinetic factors (i.e., the base type and base/Zn2+ molar ratio) can be easily utilized to control the oriented attachment and growth of [Zn(OH)](2-) on the (001) polar planes, thereby regulating the morphology of ZnO architectures. The ZnO architectures were characterized by scanning electron microscopy, transmission electron microscopy, selected-area electron diffraction, x-ray diffraction, and specific surface area. The relationships between the structures and microwave electromagnetic properties were established. Enhanced dielectric and absorption properties were exhibited by ZnO flowers composed of large-aspect-ratio microrods. Such properties could be attributed to the improved microcurrent attenuation and interface scattering rather than the dielectric relaxation and microantenna radiation. This study provides a guide for creating and synthesizing highly efficient microwave absorbing materials.