Fig. 6. Emission spectra (λ_ex = 464 nm) of [A336][NO₃] loaded with increasing concentrations of Eu³⁺ (0.1 to 0.3 mol L⁻¹, sample [A336][NO₃]-a to [A336][NO₃]-e), and [P₆₆₆₁₄][NO₃] loaded with Eu³⁺ (0.5 mol L⁻¹), water-saturated ([P₆₆₆₁₄][NO₃]-a) and dry ([P₆₆₆₁₄][NO₃]-b), by extraction from a nitrate solution.