Photoluminescence properties of novel Ba2Lu5B5O17:Eu3+ red emitting phosphors with high color purity for near-UV excited white light emitting diodes

A new melilite-type rare-earth borate CdTbGaB2O7 and multicolor tunable emission in the CdTb1-xSmxGaB2O7 (0 ≤ x ≤ 0.2) phosphors

A new mixed metal borate, CdTbGaB₂O₇, was successfully synthesized using the high-temperature solution method and its crystal structure was determined by single-crystal X-ray diffraction with the following unit-cell data: P4̄2₁m, a = b = 7.3487(1) Å, c = 4.7247(1) Å, V = 255.150(9) ų, and Z = 2. It belongs to a new member of the melilite family, which features a 3D framework consisting of alternately stacked [Ga(B₂O₇)]_n^5n- tetrahedral layers and (Cd²⁺/Tb³⁺) cationic layers that are interconnected via B(Ga)-O-(Cd/Tb) bridges. In addition, the solid solutions of CdTb_1-xSm_xGaB₂O₇ (0 ≤ x ≤ 0.2) were prepared via the solid-state reaction method. The combined techniques of XRD, SEM, IR/Raman, XPS and PLE/PL were employed to characterize the products. It was found that the CdTb_1-xSm_xGaB₂O₇ phosphors simultaneously showed green emission of Tb³⁺ at 545 nm and orange emission of Sm³⁺ at 603 nm under excitation at 370 nm. The emission color can be adjusted from green to orange-red by varying the Sm³⁺ doped content via an energy transfer mechanism. For CdTb_0.995Sm_0.005GaB₂O₇, a QY of 13.22% was obtained, and its emission intensity at 423 K was 94% of that at 303 K. These results show that the prepared materials can act as potential color-tunable phosphors for UV w-LEDs.

Structural and Optical properties of a new Milarite type Na3 Mg4 LiSi12 O30 :Eu3+ phosphor

A new red-emitting Eu³⁺ (1-17mol%) doped Na₃ Mg₄ LiSi₁₂ O₃₀ (NMLS) phosphor was prepared by conventional solid state reaction method at low temperature. The prepared samples belong to a hexagonal structure with well-matched JCPDS card No.73-0934. The photoluminescence (PL) emission spectrum showed an intense peak at 612nm when excited at 393nm. The variation of electric dipole transition (⁵ D₀ -⁷ F₂ ) emission intensity with increasing Eu³⁺ ion concentration was investigated. The concentration quenching at 11mol% is due to dipole-dipole interaction mechanism in the NMLShost. The optimized NMLS:Eu³⁺ phosphor shows 2.18 times higher luminescence intensity than the (Y,Gd)BO₃ (YGB) commercial phosphor. The NMLS:Eu³⁺ showed an intense red emission having CIE coordinates (0.6280, 0.3691) and color purity of 99.2%. The resulting phosphor exhibits good thermal stability of 80% at 423K. The magnified images of fingerprint showed various minute features such as bridges, sweat pores, ridge end, bifurcation, island and core with better visualization under 393 nm excitation. Furthermore, the optimized NMLS:Eu³⁺ was employed for pc-LED, latent fingerprints and anti-counterfeit applications as a promising red phosphor.

Revealing Eu3+-doped yttrium pyrogermanate as a soft UV excitable phosphor: retaining the pros of the commercial phosphor and compensating for the cons

This article presents the synthesis of a single-phase red emitting Y2Ge2O7:Eu3+ soft-UV excitable phosphor with up to 10% Eu3+ content. Experimental and theoretical exploration has established its relative potential with respect to the commercial Y2O3:Eu3+ phosphor.

Europium-Pyridinedicarboxylate-Adenine Light-Up Fluorescence Nanoprobes for Selective Detection of Phosphate in Biological Fluids

Phosphate (Pi) plays important roles in various physiological processes. Its quantification in biological fluids is highly crucial for timely warning of Pi accumulation. Herein, an europium (Eu)-based coordination polymer nanoprobe (Eu/DPA/Ade) is prepared by coordinating 2,6-pyridinedicarboxylic acid (2,6-DPA) and adenine (Ade) with Eu³⁺. Eu/DPA/Ade exhibits light-up fluorescence response to Pi. The strong coordinating interaction between Eu³⁺ and O atoms in the Pi group not only shortens the Eu³⁺-ligand distance to improve the energy transfer from 2,6-DPA to Eu³⁺ but also attenuates the fluorescence quenching from water molecules in the coordinating sphere of Eu³⁺. Eu/DPA/Ade produces red emission at λ_em 618 nm via the "antenna effect". The coligand Ade further promotes the fluorescent emission. The selective recognition of Pi within 10-60 μM is achieved with a detection limit of 4.65 μM. In addition, a certain level of Pi (100-170 μM) causes an exponential increment on the fluorescence of Eu/DPA/Ade and makes it feasible for visual estimation of Pi under irradiation by an ultraviolet lamp at 254 nm. The quantitative detection and visual estimation of Pi in human urine and saliva have been demonstrated.

The novel borate Lu5Ba6B9O27 with a new structure type: synthesis, disordered crystal structure and negative linear thermal expansion

Single crystals of Lu₅Ba₆B₉O₂₇ were obtained by cooling from a melt and polycrystals of the borate were prepared using a multi-step solid-state synthesis. The crystal structure was determined from single-crystal X-ray diffraction data. The borate crystallizes in a new structure type in the monoclinic crystal system in space group C2/c, with cell parameters a = 13.0927 (3), b = 9.9970 (2) and c = 20.4884 (4) Å, β = 106.827 (1)°, V = 2566.86 (9) ų and Z = 4. It is described as a framework composed of rings consisting of vertex-sharing [BO₃] triangles and [LuO₆] octahedra. The Ba atoms are in the cavities of the framework. The structure is disordered: one of the B atoms is surrounded by six O atoms with partial occupancies of 0.5. The thermal properties of Lu₅Ba₆B₉O₂₇ were investigated by thermal analysis and high-temperature X-ray powder diffraction. Its thermal expansion is highly anisotropic. The negative expansion (contraction) is along the b axis, i.e. parallel to the planes of the largest number of [BO₃] triangles. The coefficient of negative linear expansion ranges from -1.42 (at 20°C) to -5.57 × 10^-6 °C^-1 (at 1000°C). Thermal deformation of the ac plane is described in terms of the theory of shear deformation of monoclinic crystals. The Lu₅Ba₆B₉O₂₇ sample melts at 1170°C.