A surface study of ultrathin ceria nanoparticles decorated with transition-metal ions

A wide range of nanoparticles’ properties can be tuned by changing their surface characteristics, especially when dealing with ultrathin nanomaterials. Surface modification with transition-metal ions may effect a variety of nanoparticles’ properties including the surface charge, the electronic structure and the electrical and optical characteristics. In this work, a surface study of ceria (CeO₂) nanoparticles modified by adsorption of various transition-metal ions to their surface is conducted. Characterization of the decorated particles as well as of the modifying transition-metal ion was carried out using zeta potential in organic solution, UV-Vis absorption, and electron paramagnetic resonance measurements, together with X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. All measurements confirmed the attachment of the cation to the surface of ceria, both in solid state and in colloidal suspension. We show that the metallization process had a significant effect on the surface charge of the nanoparticles by consistently shifting the zeta potential to more positive values and on the optical properties of the modifying transition-metal ions by red-shifting their absorption peak. The modification of ultrathin nanoparticles with transition-metal ions can be used to improve their catalytic and electronic properties.