High-efficiency energy transfer in the strong orange-red-emitting phosphor CeO2:Sm3+, Eu3

High-efficiency energy transfer (ET) from Sm3+ to Eu3+ leads to dominant red emission in Sm3+, Eu3+ co-doped single-phase cubic CeO2 phosphors. In this work, a series of Sm3+ singly and Sm3+/Eu3+ co-doped CeO2 cubic phosphors was successfully synthesized by solution combustion followed by heat treatment at 800 °C in air. The crystal structure, morphology, chemical element composition, and luminescence properties of the obtained phosphors were investigated using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoluminescence analysis. Under 360 nm excitation, the Sm3+ singly doped CeO2 phosphor emitted strong yellow-red light at 573 nm (4G5/2-6H5/2) and 615 nm (4G5/2-6H7/2). Meanwhile, the CeO2:Sm3+, Eu3+ phosphors showed the emission characteristic of both Sm3+ and Eu3+, with the highest emission intensity at 631 nm. The emission intensity of Sm3+ decreased with increasing Eu3+ content, suggesting the ET from Sm3+ to Eu3+ in the CeO2:Sm3+, Eu3+ phosphors. The decay kinetics of the 4G5/2-6H5/2 transition of Sm3+ in the CeO2:Sm3+, Eu3+ phosphors were investigated, confirming the high-efficiency ET from Sm3+ to Eu3+ (reached 84%). The critical distance of energy transfer (RC = 13.7 Å) and the Dexter theory analysis confirmed the ET mechanism corresponding to the quadrupole-quadrupole interaction. These results indicate that the high-efficiency ET from Sm3+ to Eu3+ in CeO2:Sm3+, Eu3+ phosphors is an excellent strategy to improve the emission efficiency of Eu3+.

Extensive tailoring of REPO4 and REVO4 crystallites via solution processing and luminescence

This article highlighted the recent achievements in crystal engineering of REPO4 and REVO4via solution processing, with an emphasis on solution chemistry, the role of chelate ion, crystallization mechanism and luminescence properties.

One-step surfactant-free controllable synthesis and tunable up-conversion/down-shifting white light emissions of Sr2YF7 crystals doped with Ln3+ ions

In this work, uniform and monodisperse Sr₂YF₇ spheres were successfully synthesized via a facile one-step hydrothermal route without employing any surfactant.

Dicarboxylate mediated efficient morphology/phase tailoring of YPO4:Ln3+ crystals and investigation of down-/up-conversion luminescence

Both hexagonal (h-) and tetragonal (t-) structured YPO₄ crystals with multiform morphologies of high uniformity were selectively synthesized by using dicarboxylates as morphology/structure modifiers.

EDTA-assisted phase conversion synthesis of (Gd0.95RE0.05)PO4 nanowires (RE = Eu, Tb) and investigation of photoluminescence

Hexagonal (Gd_0.95RE_0.05)PO₄·nH₂O nanowires ~300 nm in length and ~10 nm in diameter have been converted from (Gd_0.95RE_0.05)₂(OH)₅NO₃·nH₂O nanosheets (RE = Eu, Tb) in the presence of monoammonium phosphate (NH₄H₂PO₄) and ethylene diamine tetraacetic acid (EDTA). They were characterized by X-ray diffraction, thermogravimetry, electron microscopy, and Fourier transform infrared and photoluminescence spectroscopies. It is shown that EDTA played an essential role in the morphology development of the nanowires. The hydrothermal products obtained up to 180 °C are of a pure hexagonal phase, while monoclinic phosphate evolved as an impurity at 200 °C. The nanowires undergo hexagonal→monoclinic phase transformation upon calcination at ≥600 °C to yield a pure monoclinic phase at ~900 °C. The effects of calcination on morphology, excitation/emission, and fluorescence decay kinetics were investigated in detail with (Gd_0.95Eu_0.05)PO₄ as example. The abnormally strong ⁵D₀→⁷F₄ electric dipole Eu³⁺ emission in the hexagonal phosphates was ascribed to site distortion. The process of energy migration was also discussed for the optically active Gd³⁺ and Eu³⁺/Tb³⁺ ions.

Luminescence and energy transfer of a color tunable phosphor: Tb3+ and Eu3+ co-doped ScPO4

The PL spectra of ScPO₄:0.03Tb³⁺, yEu³⁺ (y = 0–0.05) phosphors under N-UV excitation (λ_ex = 370 nm) and the tunable luminescence.

Synthesis, crystal structure and photoluminescence properties of Eu2+-activated RbCaGd(PO4)2 phosphors

RbCaGd(PO₄)₂:Eu²⁺ was prepared by the Pechini-type sol–gel method. The crystal structure was determined in the first time. The dipole–dipole interaction plays a major role in the mechanism of concentration quenching of Eu²⁺ in this phosphor.

Hydrothermal conversion of layered hydroxide nanosheets into (Y0.95Eu0.05)PO4 and (Y0.96−xTb0.04Eux)PO4 (x = 0–0.10) nanocrystals for red and color-tailorable emission

Anion-exchange of NO₃⁻-LRH nanosheets with phosphate has led to (Y,Tb,Eu)PO₄ nanocrystals showing color-tailorable emissions.

Recent progress in low-voltage cathodoluminescent materials: synthesis, improvement and emission properties

Nowadays there are several technologies used for flat panel displays (FPDs) and the development of FPDs with enhanced energy efficiency and improved display quality is strongly required. Field emission displays (FEDs) have been considered as one of the most promising next generation flat panel display technologies due to their excellent display performance and low energy consumption. For the development of FEDs, phosphors are irreplaceable components. In the past decade, the study of highly efficient low-voltage cathodoluminescent materials, namely FED phosphors, has become the focus of enhancing energy efficiency and realizing high-quality displays. This review summaries the recent progress in the chemical synthesis and improvement of novel, rare-earth and transition metal ions activated inorganic cathodoluminescent materials in powder and thin film forms. The discussion is focused on the modification of morphology, size, surface, composition and conductivity of phosphors and the corresponding effects on their cathodoluminescent properties. Special emphases are given to the selection of host and luminescent centers, the adjustment of emission colors through doping concentration optimization, energy transfer and mono- or co-doping activator ions, the improvement of chromaticity, color stability and color gamut as well as the saturation behavior and the degradation behavior of phosphors under the excitation of a low-voltage electron beam. Finally, the research prospects and future directions of FED phosphors are discussed with recommendations to facilitate the further study of new and highly efficient low-voltage cathodoluminescent materials.

Two series of novel 3D potentially porous heterometallic Cu–Ln coordination frameworks assembled by 3,4-pyridinedicarboxylic acid with different topologies and channels: syntheses, structures, luminescence and magnetic properties

Two series of heterometallic Cu–Ln coordination frameworks assembled by 3,4-pyridinedicarboxylic acid with different topologies and channels.

Unique lanthanide frameworks with 63 topology based on 1,5-naphthalenedisulfonate and 1H-imidazo[4,5-f][1,10]-phenanthroline: syntheses, crystal structure, photoluminescence, and white light emission

Lanthanide complexes with a 6³ net topology were synthesized. White light emissions were realized by the Sm(iii) complex and Ln(iii)-doped Eu(iii) complexes.

Efficient energy transfer from inserted CdTe quantum dots to YVO₄:Eu³⁺ inverse opals: a novel strategy to improve and expand visible excitation of rare earth ions

Rare earth (RE)-based phosphors demonstrate sharp emission lines, long lifetimes and high luminescence quantum yields; thus, they have been employed in various photoelectric devices, such as light-emitting diodes (LEDs) and solar spectral converters. However, their applications are largely confined by their narrow excitation bands and small absorption cross sections of 4f-4f transitions. In this paper, we demonstrate a novel strategy to improve and expand the visible excitation bands of Eu(3+) ions through the interface energy transfer (ET) from CdTe quantum dots (QDs) to YVO₄:Eu(3+) inverse opal photonic crystals (IOPCs). The significant effects observed in the CdTe QDs/YVO₄:Eu(3+) IOPCs composites were that the excitation of Eu(3+) ions was continuously extended from 450 to 590 nm and that the emission intensity of the (5)D₀-(7)FJ transitions was enhanced ∼20-fold, corresponding to the intrinsic (7)F₁-(5)D₁ excitation at 538 nm. Furthermore, in the IOPC network, the ET efficiency from the QDs to YVO₄:Eu(3+) was greatly improved because of the suppression of energy migration among the CdTe QDs, which gave an optimum ET efficiency as high as 47%. Besides, the modulation of photonic stop bands (PSBs) on the radiative transition rates of the QDs and Eu(3+) ions was studied, which showed that the decay lifetime constants for Eu(3+) ions were independent of PSBs, while those of QDs demonstrated a suppression in the PSBs. Their physical nature was explained theoretically.