Figure 2.

Bactericidal action of studied (doped) rare earth oxides (A) and salts of respective rare earth elements and dopants (B) to Vibrio fischeri. Bactericidal properties were evaluated by determining the colony-forming ability of the bacteria after exposure to suspensions of the particles in 2% NaCl for 24 h at room temperature, 22–23 °C. After exposure, 3 μL of bacterial suspension was transferred onto toxicant-free agarized nutrient medium and plates were incubated for 72 h at 22–23 °C. The concentrations are in mg compound/L (REO) or mg metal/L (REE salts), and nominal. Blue-green spots are bioluminescent bacterial colonies photographed in the dark. Minimal bactericidal concentration, MBC, is the lowest tested concentration that inhibited the bacterial ability to grow (form a colony on nutrient agar). MBC of La₂NiO₄ = 25 mg/L. For other REOs MBC > 500 mg/L. See also Table 2.