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Normalized UV/visible absorption (black solid line) and phosphorescence spectra (red, orange, and green lines) of complex Ir under different oxygen concentrations in toluene and upconversion luminescence spectra of NaYF4: 20 mol% Yb/0.2 mol% Tm@NaYF4 core–shell UCNPs (blue solid line). The spectra were measured at 25 °C.
