• • Yb3+ sensitizer exhibits an absorption cross-section of ~10^-20 cm^2, which is 10^-4 to 10^-6 times weaker than organic dyes (10^-16 to 10^-17 cm^2) and quantum dots (10^-14 to 10^-15 cm^2), necessitating high-power excitation (>100 W cm^-2) for conventional UCNPs.
• • Dye-sensitized UCNPs suffer from photobleaching and interfacial energy losses, limiting photoconversion performance; triplet-induced singlet oxygen photobleaching has been identified as a key degradation pathway (Wang et al., Nano Lett, 2023).
• • Core/active shell architectures and heavy-atom effects (e.g., CsLu2F7:Yb/Er) enhance dye-triplet-sensitized upconversion emission, with reported improvements in emission intensity and photostability (Zhang et al., Angew Chem Int Ed, 2022).
• • Achieving photostability in dye-sensitized UCNPs enables their use in Fenton-type photocatalysis, demonstrating practical applicability beyond bioimaging (Kaur et al., Nanoscale, 2023).