Insights into Nd^III to Yb^III Energy Transfer and Its Implications in Luminescence Thermometry

This work challenges the conventional approach of using (NdF3/2)-F-III 4 lifetime changes for evaluating the experimental Nd-III -> Yb-III energy transfer rate and efficiency. Using near-infrared (NIR) emitting Nd:Yb mixed-metal coordination polymers (CPs), synthesized via solvent-free thermal grinding, we demonstrate that the Nd-III [H-2(11/2) -> I-4(15/2)] -> Yb-III [F-2(7/2) -> F-2(5/2)] pathway, previously overlooked, dominates energy transfer due to superior energy resonance and J-level selection rule compatibility. This finding upends the conventional focus on the Nd-III [F-4(3/2) -> I-4(11/2)] -> Yb-III [F-2(7/2) -> F-2(5/2)] transition pathway. We characterized Nd0.890Yb0.110(BTC)(H2O)(6) as a promising cryogenic NIR thermometry system and employed our novel energy transfer understanding to perform simulations, yielding theoretical thermometric parameters and sensitivities for diverse Nd:Yb ratios. Strikingly, experimental thermometric data closely matched the theoretical predictions, validating our revised model. This novel perspective on Nd-III -> Yb-III energy transfer holds general applicability for the Nd-III/Yb-III pair, unveiling an important spectroscopic feature with broad implications for energy transfer-driven materials design.