Fig. 5: Analysis on upconversion efficiency influenced by power.

a Consolidated UCL (400–850 nm) log-log plotted with 980 nm laser irradiance for the core–shell–shell NaYF4:x% Tm3+@NaYbF4@NaYF4 (x = 4, 8, 16, 32, 50, 70 and 100) UCNPs. b Average single particle UCL brightness for all the core–shell–shell samples under laser irradiance of 20 MW/cm2; note that UCL from the core–shell–shell samples with 0.5, 1, and 2% Tm3+ is marked by dotted box, as these samples were not bright enough to be measured. The 800 nm luminescence (760-850 nm) intensity is marked with a gray stripe pattern. Luminescence intensity at 20 MW/cm2 in (b) was determined by single particle measurements, while the variation of each saturation curve in (a) was given by multi-particle investigations31. Source data are provided as a Source Data file.