Silicon-Induced UV Transparency in Phosphate Glasses and Its Application to the Enhancement of the UV Type B Emission of Gd³⁺

Abstract

The silicon route to improve the ultraviolet (UV) transparency in phosphate glasses is investigated and further exploited to enhance the UV type B (280-320 nm) emission of gadolinium(III) relevant for biomedical applications. The glasses were synthesized with a barium phosphate composition by melt-quenching in ambient atmosphere and the optical properties investigated by optical absorption and photoluminescence (PL) spectroscopy including emission decay kinetics. An improvement in the UV transparency was gradually developed for the glasses melted merely with increasing amounts of Si powder. A particular PL in the visible was also exhibited for such glasses under excitation at 275 nm, consistent with the presence of Si-induced defects. For Si-Gd codoped glasses, the UV transparency was likewise manifested, while the UV emission from Gd around 312 nm was enhanced with the increase in Si concentration (up to ∼6.7 times). Moreover, along with the Gd PL intensity enhancement, a linear correlation was revealed between the increase in decay times for the GdP-emitting state and the amount of silicon. It is then suggested that the improved PL properties of gadolinium(III) originate from the increased UV transparency of the host and the consequent precluding of a nonradiative energy transfer from Gd to the matrix. Accordingly, a role of Si as PL quenching inhibitor is supported. The demonstrated efficacy of the Si-Gd codoping concept realized by a facile glass synthesis procedure may appeal to the application of the UV-emitting glasses for phototherapy lamps.

Field-Induced Single Molecular Magnetism and Photoluminescence in Rare Cocrystals of Isomorphic Lanthanide(III) Coordination Compounds with Fully Substituted Pyridine-4-carboxamide Ligand

“…The excitation spectra (Figure S41) suggests that both antenna effect from the organic ligand and direct f – f excitations are involved in the sensitization mechanisms. From the luminescence data, it is expected that triplet state energy of ligand L will lie (2500–4500 cm –1 ) higher than the 5 D 4 (20 449 cm –1 ) and 4 F 9/2 (20 746 cm –1 ) excitation state energies in Tb­(III) and Dy­(III), respectively, and much lower than the 6 P 7/2 (32 000 cm –1 ) excitation level of Gd­(III) . A schematic diagram representing the observed transitions and images for solid-state luminescence images under a 365 nm UV lamp for compounds 1 – 3 are shown in Figure .…”

“…It is well-known that for Gd(III) ion, the energy gap between the ground state ( 8 S 7/2 ) and the excited state ( 6 P 7/2 ) is very large (∼32 000 cm −1 ) which makes energy transfer impossible from the triplet state of ligand to the excited state of the metal ion. 66 For compound 2, peaks are clearly visible at 489 nm (20 449 cm −1 ), 544 nm (18 382 cm −1 ), 583 nm (17 152 cm −1 ), and 622 nm (16 077 cm −1 ) including less intense peaks at 650 nm (15 384 cm −1 ), 668 nm (14 970 cm −1 ), and 679 nm (14 727 cm −1 ) upon excitation wavelength 365 nm (Figure 10b). These correspond to 5 D 4 → 4 F 6 , 5 D 4 → 4 F 5 , 5 D 4 → 4 F 4 , and 5 D 4 → 4 F 3 and less intense (Figure 10b (inset)) 5 D 4 → 4 F 2 , 5 D 4 → 4 F 1 , and 5 D 4 → 4 F 0 .…”

“…From the luminescence data it is expected that triplet state energy of ligand L will lie (2500-4500 cm -1 ) higher than the 5 D 4 (20449 cm -1 ), 4 F 9/2 (20746 cm -1 ) excitation state energies in Tb(III) and Dy(III), respectively and much lower than 6 P 7/2 (32000 cm -1 ) excitation level of Gd(III). 66 A schematic diagram representing the observed transitions and images for solid-state luminescence images under 365nm UV lamp for compound 1-3 are shown in Figure 11. Solid-state UV absorbance spectra for the ligand is shown in ESI Figure S42.…”

Synergistic thermo‐Raman and calorimetric kinetic study of the cation modifier's role in binary metaphosphate glasses

“…[1] A high glass stability, that is, low tendency for devitrification can be also realized by appropriate choice of modifiers, as with the MO:P 2 O 5 (M = Ba 2+ , Ca 2+ ) glasses explored in relation to noble metal inclusion and rare-earth doping. [7,10,13,14] Moreover, it is the choice of metal oxide and modifier ions that often times allows the distinction of the glass as useful for a particular application. For instance, although phosphate glasses are known for their susceptibility to chemical attack by water in connection with oxygen-bonded P 5+ within the network, phosphate glasses melted together with iron oxide show the superior hydrolytic stability needed for nuclear waste encapsulation.…”

“…The fifth valence electron is promoted to a 3d orbital where strong π-bonding molecular orbitals are formed with oxygen 2p electrons. [14][15][16][17] The P-tetrahedra link through covalent bridging oxygens (BOs) to form polymeric phosphate anions varying in length. The modifier cations provide ionic bonds with the polymeric anions, holding the matrix together while preventing it from crystallization.…”