Figure 1.

Abiotic generation of reactive oxygen species (ROS) by the rare earth oxide (REO) particles in deionized water measured after 24-h incubation with fluorescent dyes DCFH-DA (A) and HPF (B). Mn₃O₄ (A) and Fenton reaction (B) were included as positive controls. Concentrations are shown in the insets and are nominal, in mg compound/L. Dotted line indicates background fluorescence = 1.0. The asterisk (*) marks significant difference (p < 0.05); (**) highly significant difference (p < 0.01), and (***) very highly significant difference (p < 0.001) from the control.