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/ZnFe2O4 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+/Fe3+ 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/ZnFe2O4 heterostructures, improving the probability of photoinduced charge separation and broadening the visible-light absorption.