general, sensitization of lanthanide(III) ions by organic sensitizers is regarded to take place via the triplet state of the sensitizers. Herein, we show that in dansyl- and lissamine-functionalized Nd3+ complexes energy transfer occurs from the singlet state of the sensitizers to the Nd3+ center. No sensitized emission was observed in the corresponding complexes with Er3+, Yb3+, and Gd3+ ions. Furthermore, the fluorescence of the sensitizers was quenched only in the Nd3+ complex and not in the complexes with the other ions. Only Nd3+ centers can accept energy from the singlet state of the dyes, because the excited states of Nd3+ have a high spectral overlap with the fluorescence of the dansyl and lissamine sensitizers, and because the selection rules allow a fast energy transfer, which apparently is competitive with the fluorescence.
Hebbink, G. A., Klink, S. I., Grave, L., Oude Alink, P. G. B., & van Veggel, F. C. J. M. (2002). Singlet Energy Transfer as the Main Pathway in the Sensitization of Near-Infrared Nd3+ Luminescence by Dansyl and Lissamine Dyes. ChemPhysChem, 3(12), 1014-1018. https://doi.org/10.1002/cphc.200290002