Color-Tunable Luminescence of Eu-Doped LaF3 Particles Sensitized by d–f Energy Transfer from a Two-Photon Absorbing Ir(III) Complex

Abstract

The surface of Eu0.3La0.7F3 submicron particles is functionalized with a blue-emitting Ir(III) complex (1) specifically designed to coordinate lanthanide(III) ions efficiently through a carboxylic unit. In this Eu0.3La0.7F3@1 composite, the Ir(III) complexes are randomly coordinated to either superficial La(III) ions or Eu(III) ions (Ir-Lasurface and Ir-Eusurface pairs, respectively) and its color emission, a balance between blue (Ir-based) and red (Eu-based) light, can be tuned as a function of the excitation wavelength. Irradiation at the maximum of the excitation band in 1 promotes blue emission from Ir-Lasurface pairs and red emission from Eusurface ions sensitized by Ir → Eusurface energy transfer (EnT). At λexc = 396 nm (maximum of the Eu(III) 5L6 ← 7F0 absorption band) the red emission from inner Eu(III) ions becomes dominant. Excitation of 1 can also be achieved by two photon-absorption (TPA) since this complex has a moderate cross-section of σ2 = 9.4 ± 1.0 GM at 780 nm (σ2 = 5.8 ± 0.6 GM at 800 nm). Phosphorescence lifetime imaging (PLIM) allows the emission of individual particles to be visualized and the Ir-, Eusurface-, and Eucore-based emissions can be distinguished due to the significant differences in their respective emission lifetimes.