*3.1. Characterization of nCeO2*

The results of the physicochemical characterization of *n*CeO2 are reported in Table 1 and Figure 1A. In particular, the relative Z—averages are reported in Table 1, together with the relative polydispersity index (PDI) and the ζ—potentials of the particles. The Hd distribution of both the materials is in agreemen<sup>t</sup> with the value provided by the supplier. Both *n*CeO2 25 nm and 50 nm exhibit a monodisperse size particle distribution in the nanometric range with relatively low PDI, and the main size peak at 62.0 nm and 91.0 nm, respectively. The relative Z-averages were found to be much larger than these values; this was probably due to the presence of particle aggregates. Since a high net surface charge is typically associated with weak nanoparticle interactions and aggregation, these data are coherent with the higher Z-average detected for sample *n*CeO2 50 nm with respect to *n*CeO2 25 nm [39]. Figure 1B,C reports fields of TEM observation of *n*CeO2 25 and 50 nm suspensions.



**Figure 1.** (**A**) Particle size distribution measured by dynamic light scattering (DLS) on suspensions of *n*CeO2 25 nm and 50 nm; (**B**) transmission electron microscopy (TEM) image of *n*CeO2 25 nm; (**C**) TEM *n*CeO2 50 nm.
