Fig. 3. (a) PL excitation spectra (dash-dotted line, λ_em = 650 nm) and PL emission spectra (solid line, λ_ex = 470 nm) of the annealed CaS:0.06%Eu²⁺ and CaS:0.06%Eu²⁺, 0.006%Sm³⁺ NCs. (b) PersL emission spectra and (c) PersL decay curves (λ_em = 650 nm) of the NCs after illumination with a white LED for 5 min. The insets in (b) show the PersL photographs of (top) CaS:0.06%Eu²⁺ and (below) CaS:0.06%Eu²⁺, 0.006%Sm³⁺ NCs recorded at 1 min after the cease of excitation. TL glow curves and the corresponding wavelength-temperature contour plots of (d and f) CaS:0.06%Eu²⁺ and (e and g) CaS:0.06%Eu²⁺, 0.006%Sm³⁺ NCs. (h) PL rise curves (λ_ex = 470 nm, λ_em = 650 nm) of CaS:0.06%Eu²⁺ and CaS:0.06%Eu²⁺, 0.006%Sm³⁺ NCs after emptying the traps by heating the samples at 350 °C for 10 min.