Enhanced reactive oxygen species (ROS) yields and antibacterial activity of spongy ZnO/ZnFe₂O₄ hybrid micro-hexahedra selectively synthesized through a versatile glucose-engineered co-precipitation/annealing process

In this study, sponge-like ZnO/ZnFe₂O₄ hybrid micro-hexahedra with diverse textures and compositions were fabricated by the thermal decomposition of hexahedral zinc/iron oxalate precursors, starting from a glucose-engineered co-precipitation process. The resulting ZnO/ZnFe ₂O₄ micro-hexahedra were systematically characterized by X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electronic microscopy, transmission electron microscopy (TEM), high-resolution TEM, and surface area analysis. Moreover, modulation in crystal size, composition, and textural properties of spongy ZnO/ZnFe₂O₄ micro-hexahedra was easily achieved by varying the Zn²⁺/Fe ³⁺ feeding ratio and the annealing temperature. The antibacterial property of the products was analyzed by testing ATP (adenosine triphosphate) and inhibition zones. Results showed that oxidative stress was the governing mechanism for the antibacterial activity of ZnO/ZnFe₂O₄ hybrid materials. Moreover, we found that the higher reactive oxygen species yields and the resulting antibacterial activity were exhibited by the ZnO/ZnFe₂O₄ micro-hexahedra formed at lower sintering temperatures rather than the pure ZnO and Fe₂O₃. The enhanced antibacterial properties were likely caused by the spongy ZnO/ZnFe ₂O₄ heterostructures, improving the probability of photoinduced charge separation and broadening the visible-light absorption.