Fig. 1.

Design of UCNP-fluorophore conjugates for efficient upconverted energy transfer. (a) Yb³⁺, Er³⁺-doped core/shell UCNPs encapsulated in fluorophore-conjugated amphiphilic polymers. (b) Energy diagram for energy transfer from UCNPs complexed with fluorophore Cy3. UCNP energy pathways calculated as in ref [7]. (c) Z-contrast STEM image of 8-nm β-NaYF₄: 20% Yb, 20% Er UCNPs with 2-nm NaYF₄ shells. Scale bar is 20 nm. (d) Incoherent Z-contrast STEM image of 10-nm NaErF₄ UCNPs with 2-nm NaYF₄ shell. Scale bar is 6 nm. (e) Absorbance and emission spectra of Cy3 overlaid with visible UCNP emission spectrum from 980 nm excitation.