A Surface Study of Ultrathin Ceria Nanoparticles Decorated with Transition-Metal Ions

A wide range of nanoparticle properties can be tuned by changing their surface characteristics, especially when dealing with ultrathin nanomaterials. Surface modification with transition-metal ions may affect a variety of the nanoparticles' properties including the surface charge, the electronic structure, and the electrical and optical characteristics. In this work, a surface study of ceria nanoparticles modified by attachment of various transition-metal ions to their surface is conducted. Characterization of the decorated particles as well as of the modifying transition-metal ion is carried out using zeta potential in organic solution, UV–Vis absorption, and electron paramagnetic resonance measurements, together with isothermal titration calorimetry, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. All measurements confirm the attachment of the cation to the surface of ceria, both in solid state and in colloidal suspension. It is suggested that the modifying ion-complex attaches to ceria both via chemical or strong physical interactions and weak physical interactions, demonstrated by a case-study modification of ceria using a copper-oleylamine complex. The metalization has a significant effect on the surface charge of the nanoparticles by 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.