Energy Transfer in Mixed Lanthanides Complexes: Toward High-Performance Pressure Sensors Based on the Luminescence Intensity Ratio

In this study, a reversible pressure-sensing material with high sensitivity is presented. Mixed beta-diketonate complexes of Tb3+ and Eu3+ [(Ln)(acac)3phen] are synthesized with phenanthroline as an ancillary ligand. The organic ligands provide the antenna effect to make the Ln3+ complex excitable at 405 nm. Eu3+ emission results from efficient energy transfer (ET) from Tb3+. Under 405 nm excitation, the emission intensity of Tb3+ decreases whereas the emission intensity of Eu3+ increases with pressure, making this complex a potential pressure sensor based on luminescent-intensity-ratio (LIR) up to 700 MPa. This study then discusses the application of this Tb3+/Eu3+ complex for pressure sensing depending on measurement conditions. The addition of the optically neutral ion Y3+ to the system can reduce the impact of pressure-induced structural defects on the emission, thus improving the reversibility of the LIR variation as a function of pressure. Therefore, a self-calibrating, reliable, and reversible pressure-sensing material is proposed here, with remarkable pressure sensitivity compared to a peak shift-based pressure sensor. A highly sensitive reversible pressure sensor designed for short-range applications (below 700 MPa) is demonstrated, using a luminescent mixed lanthanide complex. This mononuclear complex, containing terbium, europium, and yttrium enables pressure-sensitive Tb3+/Eu3+ energy transfer with reversibility. As pressure increases, the relative intensity of Tb3+/Eu3+ emission decreases, leading to exceptional pressure sensitivity based on luminescence intensity ratios.image