Heteronuclear lanthanide titanium‐oxygen cluster luminescence thermometer with adjustable operating range and sensitivity

Abstract Given customizable crystal structure and intriguing optical properties, lanthanide titanium‐oxygen clusters (LTOCs) with atomic‐level accuracy have gained a lot of interest. In this study, we prepared [Ln 9 Ti 2 (μ 4 –O)(μ 3 –OH) 14 (acac) 17 (CH 3 O) 2 (CH 3 OH) 3 ] (Ln = Tb x Eu 9− x ( x = 0, 4, 6, 7, 8, 9), Hacac = acetylacetone), Tb 3+ and Eu 3+ co‐doped LTOCs, to modify the optical properties for the luminescence thermometer. In detail, the serial LTOCs display dual characteristic emission peaks of 5 D 4 → 7 F 5 for Tb 3+ and 5 D 0 → 7 F 2 for Eu 3+ at 548 and 616 nm, respectively, under 330 nm excitation. Effective energy transfer (ET) between Tb 3+ ions and Eu 3+ ions was revealed in terms of both emission spectra and luminescence lifetime. The 5 D 0 → 7 F 2 emission intensity of Eu 3+ ions at 616 nm is maximally enhanced (by a factor of 11.2) with a change in the relative molar ratio of Tb 3+ to Eu 3+ , along with a change in the ET efficiency of Tb 3+ → Eu 3+ . In addition, the luminescent color changes from red, orange, yellow, to green. This precise control of the ET process between rare‐earth ions allows {Tb 6 Eu 3 Ti 2 } to reach a maximum relative sensitivity of 1.241 K −1 at 355 K, which is an enhancement of up to 4.6‐fold with respect to the previously reported homonuclear emission, holding great potential in the optical thermometers.