Issue 34, 2023

Crystalline-to-semicrystalline transition in lanthanide trifluoroacetates: implications for optical pressure and temperature sensing

Abstract

We report the serendipitous discovery of a pressure-dependent, crystalline-to-semicrystalline, reversible transition in the solid solution Eu1−xTbx(tfa)3(H2O)3 (tfa = CF3COO). This transition is observed across the entire composition range upon reducing pressure from atmospheric to sub-100 mTorr levels. In the case of mixed-metal trifluoroacetates, switching from the atmospheric to the low-pressure phase leads to a drastic reduction in the intensity of green emission from Tb3+ and enhanced red emission from Eu3+. The low-pressure phase shows not only enhanced Tb-to-Eu energy transfer but also a multisite distribution of lanthanide emitters. The crystalline-to-semicrystalline transition results from a disruption of hydrogen bonds and van der Waals interactions responsible for the long-range order observed in the atmospheric phase, likely driven by chemical changes such as vacuum-induced removal of terminal acuo ligands. The distinct luminescence responses of the atmospheric and low-pressure phases of Eu1−xTbx(tfa)3(H2O)3 have direct implications for the potential of mixed-metal trifluoroacetates as optical sensors. On the one hand, this contrast could be exploited to realize a two-state luminescent pressure sensor, though with the limitations imposed by the kinetics of the pressure-dependent transition, which takes about a day to complete in either direction under the experimental conditions observed in this work. On the other hand, the much weaker intensity of the emission from Tb3+ relative to that of Eu3+ in the low-pressure phase (≈2 orders of magnitude) limits the robustness of the red-to-green ratio as a thermometric parameter for luminescent thermometry.

Graphical abstract: Crystalline-to-semicrystalline transition in lanthanide trifluoroacetates: implications for optical pressure and temperature sensing

Supplementary files

Article information

Article type
Paper
Submitted
02 Jun 2023
Accepted
02 Aug 2023
First published
09 Aug 2023

J. Mater. Chem. C, 2023,11, 11552-11563

Author version available

Crystalline-to-semicrystalline transition in lanthanide trifluoroacetates: implications for optical pressure and temperature sensing

R. G. Szlag and F. A. Rabuffetti, J. Mater. Chem. C, 2023, 11, 11552 DOI: 10.1039/D3TC01924A

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