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A series of lanthanide-based metal–organic frameworks (Ln-MOFs) with significantly improved and tunable upconversion emissions were prepared. Y-MOFs co-doped with Yb3+/Er3+ ions have exhibited characteristic upconversion emissions at 520, 545, and 658 nm under 980 nm laser excitation, the intensities of which vary with Yb3+/Er3+ concentrations. In addition, experimental results have indicated that an excited state absorption mechanism is responsible for the upconversion process of Y-MOF:Yb/Er materials. This study has provided a novel design principle and experimental basis for the preparation of luminescent Ln-MOF materials. [ABSTRACT FROM AUTHOR]

Eu 2+ /Eu 3+ -doped fluorophosphate Na 5 Al(PO 4 ) 2 F 2 was synthesized by the high-temperature solid-state reaction. The structural XRD refinement was used to investigate the phase formation and structure. The photoluminescence (PL) excitation and emission spectra were measured. The host accommodates two kinds of Eu-centers in the lattices, i.e., Eu 3+ and Eu 2+ , which were confirmed by the emission spectra and decay curves. Under the excitation of UV and near-UV light, the broad emission peaked at 420 nm and 530 nm from the 4 f 6 5 d –4 f 7 transition of Eu 2+ and narrow peaks at 592 nm, 615 nm from the 4 f –4 f transitions of Eu 3+ ions were detected. The luminescence color could shift from blue to white and red by mixing the luminescence from the coexistence of Eu 2+ /Eu 3+ ions in the single-phase phosphor. [ABSTRACT FROM AUTHOR]

A series of novel Y 2 Mo 4 O 15 : x Sm 3+ ( (0.01 ≤ x ≤ 0.20) phosphors for white light-emitting (W-LEDs) were successfully prepared by the solid state reaction technology at 973 K for 12 h. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectra of the Y 2 Mo 4 O 15 :Sm 3+ phosphors consisted of some sharp emission peaks of Sm 3+ ions centered at 565 nm, 605 nm, 650 nm, and 712 nm. The strongest one is located at 605 nm due to 4 G 5/2 – 6 H 7/2 transition of Sm 3+ , generating bright orange–red light. The optimum dopant concentration of Sm 3+ ions in Y 2 Mo 4 O 15 : x Sm 3+ is around 5 mol% and the critical transfer distance of Sm 3+ is calculated as 23.32 Å. The CIE chromaticity coordinates of the Y 2 Mo 4 O 15 :0.05Sm 3+ phosphors were located in the orange reddish region. The Y 2 Mo 4 O 15 :Sm 3+ phosphors may be potentially used as red phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]

A series of orange-red emitting Ba 2 Y 3 (SiO 4 ) 3 F: x Sm 3+ (0.003≤ x ≤0.08) fluorosilicate apatite phosphors was synthesized by the convenient solid-state reaction. X-ray diffraction and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectra of the Ba 2 Y 3 (SiO 4 ) 3 F:Sm 3+ phosphors consisted of some sharp emission peaks of Sm 3+ ions centered at 564, 601, 648, and 710 nm. The strongest one is located at 601 nm due to 4 G 5/2 – 6 H 7/2 transition of Sm 3+ , generating bright orange-red light. The optimum dopant concentration of Sm 3+ ions in Ba 2 Y 3 (SiO 4 ) 3 F: x Sm 3+ is around 3 mol% and the critical transfer distance of Sm 3+ is calculated as 26 Å. The quenching temperature is above 500 K. The CIE chromaticity coordinates of the Ba 2 Y 3 (SiO 4 ) 3 F:0.03Sm 3+ phosphors is located in the orange reddish region. The Ba 2 Y 3 (SiO 4 ) 3 F:Sm 3+ phosphors may be potentially used as red phosphors for white light-emitting diodes. [ABSTRACT FROM AUTHOR]