Tm³⁺Ion Blue Emission Quenching by Pd²⁺Ions in Barium Phosphate Glasses: Fundamental Analysis toward Sensing Applications

Abstract

The quenching effect of Pd2+ ions on the blue emission from Tm3+ was investigated for the first time using barium phosphate glass as model matrix. Glasses containing fixed Tm2O3 at 0.5 mol % and PdO up to 0.3 mol % (added relative to P2O5) were prepared by melting and first characterized for basic structural properties by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Thermal properties were then evaluated by differential scanning calorimetry (DSC). The focus was thereafter on evaluating the optical properties by absorption and photoluminescence (PL) spectroscopy with decay kinetics assessment. XRD confirmed the amorphous nature of the glasses synthesized. The vibrational spectroscopy assessment consistently exhibited the IR- and Raman-active bands characteristic of phosphate glasses, showing no significant variation with PdO codoping. The DSC analysis revealed all glasses possessed high thermal stability assessed by the differences (ΔT = T g – T x ≥ 154 °C) between glass transition temperatures (T g) and onset of crystallization (T x). A tendency of the T g values to increase with PdO contents was however exhibited. In addition, specific enthalpies of crystallization showed magnitudes decreasing with increasing PdO concentration, thus suggesting crystallization suppression by Pd2+. Concerning the optical properties, it was observed that codoping the glasses with PdO (0.1–0.3 mol %) led to the development of the visible Pd2+ d–d absorption band (peak ≈415–410 nm). In addition, drastic PL quenching of the Tm3+ blue emission around 452 nm (1D2 → 3F4 transition) was induced by Pd2+. Analyzing PL decay curves obtained by exciting Tm3+ ions at 359 nm while monitoring 452 nm emission revealed decreased 1D2 state lifetimes. Thus, a potential of Tm3+ for analytical sensing of Pd2+ in various matrices was suggested. Ultimately determining quenching constants from the PL data and based on the comparison of results from emission intensity and decay rates, likely Tm3+ → Pd2+ energy transfer processes underlying the PL quenching were proposed.

XANES analysis of phosphate glasses melted with Tb4O7 and SnO: evaluating the impact of valence states on structural, thermal, and luminescent properties

“…The implied stability factor is thus Δ T = 149 °C, which is somewhat lower than that reported for a similar 0.5 mol% Tm 2 O 3 -doped barium phosphate glass with Δ T of 169 °C, given the T g , T x and T c of 499, 668 and 699 °C, respectively. 22 The slightly lower glass stability in the Tb glass prepared herein may be due to the use of overall marginally higher rare-earth content when using 0.5 mol% Tb 4 O 7 . The 1SnTb glass then shows in Fig.…”

“…The assignment for the various features is achieved in agreement with the literature as reported for similar phosphate-based glasses. 22,23,32,33 Taken as reference, the Tb glass exhibits towards the low energy region a band around 685 cm −1 credited to the in-chain symmetric stretching vibrations in P–O–P bridges, ν s (POP), in Q 2 tetrahedral units (PO 4 tetrahedra with 2 bridging oxygens, BOs). The small feature observed around 1006 cm −1 is attributed to the symmetric stretch, ν s (PO 3 2− ), in non-bridging oxygens (NBOs) pertaining to Q 1 units (PO 4 tetrahedra with 1 BO).…”

“…A binary barium phosphate glass matrix previously studied with other metals and rare-earths was used as host. [21][22][23] The glasses were synthesized by melt-quenching with fixed Tb 4 O 7 amounts at 0.5 mol% and increasing SnO content added up to 5 mol% (both relative to network former P 2 O 5 ). The glasses were then characterized by X-ray diffraction (XRD) to confirm amorphous nature, and by X-ray absorption near-edge structure (XANES) spectroscopy at the Sn K-edge and Tb L 3 -edge for tin and terbium speciation analysis.…”

Understanding the correlation between extraction and luminescence behavior of Eu(iii) in a biphasic system in the presence of Co-extracting metal ions

“…2B, wherein D Eu ( iii ) increases steadily with an increase in Pd(NO 3 ) 2 concentration in the aqueous phase, it is adequate to mention that the severe quenching behavior of Pd( ii ) strongly affects the fluorescence intensity of Eu( iii ). 40–44 Pd( ii ) is known to be an efficient quenching agent like the transition metal ions wherein the tails of the d–d absorption bands mostly have lower energy than the 5 D 0 excited state of Eu( iii ), and the quenching constants ( K sv ) of Pd( ii ) and other platinum group metal ions are reported to be highest among transition metal ions and main group metal cations. 45,46…”

“…2B, wherein D Eu (III) increases steadily with an increase in Pd(NO 3 ) 2 concentration in the aqueous phase, it is adequate to mention that the severe quenching behavior of Pd(II) strongly affects the fluorescence intensity of Eu(III). [40][41][42][43][44] Pd(II) is known to be an efficient quenching agent like the transition metal ions wherein the tails of the d-d absorption bands mostly have lower energy than the 5 D 0 excited state of Eu(III), and the quenching constants (K sv ) of Pd(II) and other platinum group metal ions are reported to be highest among transition metal ions and main group metal cations. 45,46 Due to the d 8 configuration of Pd(II), photo-induced energytransfer (PET) or photo-induced electron-transfer (PeT) occurs between the fluorophore (e.g., Eu(III))-Pd(II) interactions, and this electron transfer happens in the time scale of subpicoseconds, many orders of magnitude faster than the luminescence decay time.…”