Charge Transfer-Triggered Bi³⁺Near-Infrared Emission in Y₂Ti₂O₇for Dual-Mode Temperature Sensing

Abstract

Trivalent bismuth is a popular main group ion showing versatile luminescent behaviors in a broad spectral range from ultraviolet to visible, but barely in the near-infrared (NIR) region. In this study, we have observed unexpected NIR emission at ∼744 nm in a Bi3+-doped pyrochlore, Y2Ti2O7 (YTOB). Our first-principles electronic structure calculation and analysis of the Bi local structure via extended X-ray absorption fine structure indicate that only Bi3+ species appears in YTOB and it has a similar local environment to that of Y3+. The NIR emission is assigned to a Ti4+ → Bi3+ metal-to-metal charge transfer process. Moreover, we have demonstrated dual-mode luminescence thermometry based on the luminescence intensity ratio (LIR) and lifetime (τ) in 0.5% Bi3+ and 0.5% Pr3+ co-doped Y2Ti2O7 (YTOB0.5P0.5). It exhibits high thermometric sensitivity simultaneously in the cryogenic temperature range from 78 to 298 K based on τ of the NIR emission of Bi3+ at 748 nm and in the temperature range of 278–378 K based on the LIR of Bi3+ to Pr3+ emissions (I 748/I 615). As a novel LIR-τ dual-mode thermometric material over a wide temperature range, the maximum relative sensitivities of the YTOB0.5P0.5 reach 3.53% K–1 at 298 K from the τ mode and 3.52% K–1 at 318 K based on the LIR mode. The dual-mode luminescence thermometry with high responsivity from our Bi3+-based pyrochlore Y2Ti2O7 phosphor opens a new avenue for more luminescent materials toward multi-mode thermometry applied in complex temperature-sensing conditions.

Broadband emitting phosphor Sr6Sc2Al4O15:Cr3+ for near-infrared LEDs

“…Sr 3 Li 4 Si 2 N 6 :Eu 2+ , 12 MgGeO 3 :Pr 3+ , 13 and La 3 Si 6 N 11 :Yb 3+ 14 ); (ii) main group elements ( e.g. Cs 2 ZnCl 4 :Sb 3+ , 15 Y 2 Ti 2 O 7 :Bi 3+ , 16 and FAPbI 3 :Sn 2+ 17 ); and (iii) transition metals ( e.g. MgAl 2 O 4 :Mn 2+ , 18 Sr 2 InSbO 6 :Fe 3+ , 19 and LiGaP 2 O 7 :Cr 3+ 20 ).…”

A Multimodal Ratiometric Luminescent Thermometer Based on a Single-Dysprosium Metal–Organic Framework

“…They operate in a single mode and are highly dependent on the precise control and optimization of the ratio of the two lanthanide ions. Their sensing performance becomes worse at higher temperatures since the energy transfer between the lanthanide ions tends to saturate. − A more robust and reliable strategy is to introduce multiple optical emissions into a thermostable single-lanthanide MOF (S’LnMOF) to construct multiple thermometric parameters operating in certain temperature regions, thus realizing the multimode luminescent thermometers with improved sensing performance at elevated temperatures. − In principle, the emission intensity between the thermally coupled energy levels (TCELs) of single-lanthanide centers, such as Dy 3+ , Er 3+ , and Nd 3+ , can serve as a reliable ratiometric parameter to determine the temperatures. − In addition, the temperature dependence of the energy transfer between the organic linker and the lanthanide center in an S’LnMOF can also be another parameter for temperature measurement. , In this regard, if both the TCELs’ emissions of lanthanide ions and the ligand’s fluorescence can be integrated into an S’LnMOF, one can make use of the temperature-dependent behaviors of the multiple emissions, i.e., the emissions between the TCELs of lanthanide or between the ligand and lanthanide ions, to form a multimodal luminescent ratiometric MOF thermometer for high-temperature sensing. To our knowledge, no multimodal S’LnMOFs have been realized so far for temperature detection.…”

Novel color tunable LaCaGaO4:Bi3+,Eu3+ phosphors for high color rendering warm white LEDs

“…There are many kinds of oxide compounds, such as spinel type AB 2 O 4 , olivine type ABCO 4 , chalcocite type A 2 BCO 6 , etc., determined by different combinations of three cations, A, B, and C. LaCaGaO 4 is one of the olivine type ABCO 4 (A = La, Ga, Lu, Y; B = Ca, Sr, Ba; C = Al, Ga), and the crystal structure consists of LaO 6 /CaO 6 octahedra and GaO 4 tetrahedra, suitable for the doping of activator ions such as Bi 3+ and Eu 3+ . Bi 3+ ions have gained much attention as a well‐known non‐rare‐earth metal ion because its bare 6s and 6p electrons are particularly sensitive to the crystal environment 16–19 . In general, Bi 3+ ‐doped phosphors have a wide excitation band in the n‐UV region, which is due to the spin‐allowed 1 S 0 → 3 P 1 transition 20 .…”

“…Bi 3+ ions have gained much attention as a well-known non-rare-earth metal ion because its bare 6s and 6p electrons are particularly sensitive to the crystal environment. [16][17][18][19] In general, Bi 3+ -doped phosphors have a wide excitation band in the n-UV region, which is due to the spin-allowed 1 S 0 → 3 P 1 transition. 20 Due to the sensitivity to the environment when Bi 3+ ion is employed as an activator, various hosts emit different colors, and the emission range from the 3 P 1 → 1 S 0 transition can encompass the whole visible area.…”