Structural, Electronic and Antibacterial Properties of Hydrothermally Grown Nano- and Microcrystalline Fe:ZnO

The antibacterial activity of nano- and microcrystalline ZnO is well documented, however, the underlying mechanisms that cause its cytotoxicity remain the subject of debate. In our research, we proposed a model of the antibacterial action of ZnO, which is based on the dissolution of the material mediated by surface defects. To further validate this model, we modify the surface layers of hydrothermally synthesized nano- and microparticles of ZnO in order to change their antibacterial efficacy in a controlled manner. Our results suggest that the instability of ZnO in antibacterial assays arises from defect-rich reconstructions of its polar surfaces with strong intrinsic dipole moment within the wurtzite lattice. Theoretically, doping of ZnO with Fe can inhibit this dipole and stabilize the free surface without disturbing the wurtzite structure. Importantly, iron ions are physiologically acceptable for bacterial cells and therefore do not have an additional effect on the overall level of cytotoxicity. We modify the hydrothermal synthesis protocol to produce Fe:ZnO micro- and nanoparticles with controlled doping concentrations. We perform systematic optoelectronic and structural characterization of our specimens as well as antibacterial assays.