Stabilization Mechanism of ZnO Nanoparticles by Fe Doping

Surprisingly low solubility and toxicity of Fe-doped ZnO nanoparticles is elucidated on the basis of first-principles calculations. Various ZnO surfaces that could be present in nanoparticles are subject to substitutional Fe doping. We show that Fe stabilizes polar instable surfaces, while nonpolar surfaces, namely (1010) and (1120), remain intact. Polar surfaces can be stabilized indirectly through Fe2+ - Fe3+ pair-assisted charge transfer, which reduces surface polarity and therefore, the solubility in polar solvents.