Figure 2.

Loading Ce6 inside UCNPs clusters. a) The molecular structure of Ce6. b) The high stacking model of UCNPs clusters with different packing UCNPs number (from 4 to 5). The number in parentheses signifies the average space number surrounded by four UCNPs. c) Theoretical maximum Ce6 loading quantity within UCNPs clusters packed with different UCNPs number. d) UCNPs clusters with and without Ce6 loading. The picture on the left was taken in standard lighting, and the right photo was taken in a 365 nm UV environment. e) UV absorption of UCNPs clusters with and without Ce6 loading. f) Emission spectra of UCNPs clusters in water solution (with and without loaded Ce6) excited with 980 nm laser. g) UV absorption of different UCNPs clusters loaded with Ce6 formed at different polymer/UCNPs weight ratio. The total concentration of UCNPs clusters is 1 mg mL⁻¹.