Luminescence properties and NIR-II ratiometric thermometry of Er³ ⁺/Ho³ ⁺/Yb³ ⁺-doped Bi₄Ti₃O₁₂ perovskite

A RE-doped Bi 4 Ti 3 O 12 perovskite-based luminescence material is developed. • Dual NIR-II emissions of Ho 3+ /Er 3+ are achieved under 980 nm excitation. • High performance (Sr=1.3% K-1) phonon-assisted ratiometric thermometer is constructed. High-performance optical thermometers operating in the second near-infrared (NIR-II) window hold great promise for biomedical applications due to their tissue penetration depth and minimal autofluorescence. However, developing reliable NIR-II thermometers with high sensitivity and robust performance across a wide temperature range remains a challenge. Herein, the luminescence properties and NIR-II ratiometric thermometric performance of Er 3+ , Ho 3+ , Yb 3+ co-doped Bi 4 Ti 3 O 12 (BTO) perovskite oxide were investigated. Upon 980 nm excitation, NIR-II emission from Er 3+ at 1560 nm ( 4 I 13/2 → 4 I 15/2 ) and Ho 3+ at 1200 nm ( 5 I 6 → 5 I 8 ) was achieved. A ratiometric thermometer was constructed using the temperature-dependent intensity ratio, I Er /I Ho . Relying on the thermal dependence of this ratio, the BTO system exhibits a relative sensitivity (S r ) of 1.3% at 333 K. Furthermore, the results suggest that phonon characteristics of the BTO host influence energy-transfer processes and NIR-II thermometric performance, highlighting importance of host properties in designing rare-earth-doped NIR-II thermometric materials. Download: Download high-res image (154KB) Download: Download full-size image A high-sensitivity NIR-II ratiometric thermometer is achieved in Bi 4 Ti 3 O 12 : Yb 3+ , Ho 3+ , Er 3+ Perovskites via a unique phonon-assisted energy transfer pathway.