Significant effort has been made in the exploration of novel lanthanide‐activated phosphors with multicolor emission over the last decade, especially highly efficient and emission tunable phosphor ...systems, to optimize the performance of white light‐emitting diodes with regard to their positive impact on energy efficiency, their correlated color temperature, and their color rendering index. Therefore, a research focus in recent years has been the modification and tailoring of the photoluminescence of phosphors, enabling the acquisition of new phosphors with tunable emission colors. This review aims to highlight the prevailing strategies used for tuning the photoluminescence of lanthanide‐activated phosphors. Remarkable examples of newly designed emission‐tunable phosphor materials based on these prevailing strategies are introduced in this review. A comprehensive understanding of these strategies can provide an extensive guide for the discovery and fabrication of highly efficient phosphors with tunable emission colors in the future.
White light‐emitting diodes are an ideal green lighting source for the next‐generation lighting industry due to the excellent advantages of energy saving, high luminous efficiency, fast switching, etc. This tutorial review systematically discusses the prevailing strategies for photoluminescence tuning of lanthanide‐activated phosphors, which may provide a feasible guide for the highly efficient phosphor screening and photoluminescence tuning in the future.
A new, highly efficient deep red-emitting phosphor Ca14Al10Zn6O35:Mn4+ was developed as a component of solid-state white light-emitting diodes (LEDs). The structural and optical characterization of ...the phosphor is described. The phosphor exhibits strong emission in the range of 650–700 nm when excited by 460 nm excitation, with a quantum efficiency approaching 50%. Concentration dependence of Mn4+ luminescence in Ca14Al10Zn6O35:Mn4+ is investigated. Attempts to understand the thermal stability on the basis of the thermal quenching characteristics of Ca14Al10Zn6O35:Mn4+ is presented. The results suggest that phosphors deriving from Ca14Al10Zn6O35:Mn4+ have potential application for white LEDs. In addition, influence of cation substitution on the luminescence intensity of these phosphors is elucidated.
A series of single-component red/white-emitting CaScAlSiO6:Ce3+,Tb3+,Mn2+ phosphors have been synthesized by a solid-state reaction. It is observed that CaScAlSiO6:Ce3+,Tb3+ phosphors exhibit two ...dominating bands situated at 380 and 542 nm, originating from the allowed 5d → 4f transition of the Ce3+ ion and the 5D4 → 7F J = (J = 6, 5, 4, 3) transition of the Tb3+ ion, respectively. As for CaScAlSiO6:Ce3+,Mn2+, our results indicate that Mn2+ may occupy not only a Ca2+ site to generate an orange emission Mn2+(I) at 590 nm but also a Sc3+ site to generate a red emission Mn2+(II) at 670 nm. Both energy transfers from Ce3+ to Tb3+ and from Ce3+ to Mn2+ in the CaScAlSiO6 host are investigated and have been demonstrated to be of the resonant type via a dipole–dipole mechanism. By proper tuning of the relative composition of Tb3+/Mn2+, white light can also be achieved upon excitation of UV light, indicating that the developed phosphor may potentially be used as a single-component red/white-emitting phosphor for UV-light-emitting diodes.
Abstract Here, we report the covalently conjugation of lanthanide doped NaGdF4 :Yb3+ , Er3+ @NaGdF4 upconverting nanoparticles (UCNPs) on methylphosphonate functionalized silica nanospheres (pSi NPs) ...for in vivo upconversion luminescence (UCL), T1 -weighted magnetic resonance (MR), and X-ray computed tomography (CT) multi-modality imaging. The nanocomposites (pSi@UCNPs) were synthesized by a facile ligand exchange strategy. The hydrophobic pSi@UCNPs were transferred into aqueous solution by surface coating Pluronic F127. The Pluronic F127 coated pSi@UCNPs (pSi@UCNPs@F127) exhibit excellent stability in biological medium, inappreciable cytotoxicity and negligible organ toxicity. The pSi@UCNPs@F127 also shows brighter UCL, and higher CT/MR enhancements than that of Pluronic F127 coated NaGdF4 :Yb3+ , Er3+ @NaGdF4 UCNP. In detail, the capability of pSi@UCNPs@F127 as high performance contrast agents for in vivo multi-modality (UCL/MR/CT) imaging is evaluated successfully through small-animal experiments.
Well-shaped Y2O3:Eu hollow microspheres have been successfully prepared on a large scale via a urea-based homogeneous precipitation technique in the presence of colloidal carbon spheres as hard ...templates followed by a subsequent heat treatment process. XRD results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure cubic phase of Y2O3. TEM and SEM images indicate that the shell of the uniform hollow spheres, whose diameters are about 250 nm, is composed of many uniform nanoparticles with diameters of about 20 nm, basically consistent with the estimation of XRD results. Furthermore, the main process in this method was carried out in aqueous condition, without the use of organic solvents or etching agents. The as-prepared hollow Y2O3:Eu microspheres show a strong red emission corresponding to the 5D0−7F2 transition of the Eu3+ ions under ultraviolet or low voltage excitation, which might find potential applications in fields such as light phosphor powders, advanced flat panel displays, field emission display devices, and biological labeling.
Well-dispersed, uniform Gd2O3 hollow microspheres have been successfully fabricated via a urea-based homogeneous precipitation method in the presence of colloidal melamine formaldehyde (MF) ...microspheres as templates, followed by subsequent heat treatment. The main process was carried out under aqueous conditions without any organic solvents, surfactants, or etching agents. The as-obtained Gd2O3 microspheres with a spherical shape and hollow structure are uniform in size and distribution, and the thickness of the shell is about 200 nm. The lanthanide ion (Ln3+)-doped Gd2O3 hollow microspheres exhibit bright down- and upconversion luminescence with different colors coming from different activator ions under ultraviolet or 980 nm light excitation, which might find potential applications in fields such as drug delivery or biological labeling because of their excellent dispersing and luminescence properties. Furthermore, this synthesis route may be of great significance in the preparation of other hollow spherical materials.
In this work, we developed the surfactant-free aqueous synthesis of novel polyethylene glycol (PEG) coated Ba2GdF7:Yb3+, Er3+ upconversion nanoparticles (named as, Ba2GdF7:Yb3+, Er3+@PEG UCNPs) for ...in vivo multimodality imaging including upconversion luminescence (UCL), X-ray computed tomography (CT), and T 1-weighted magnetic resonance (MR). The as-prepared Ba2GdF7:Yb3+, Er3+@PEG UCNPs not only present bright UCL and reasonably high CT/MR enhancements but also exhibit excellent colloidal stability, inappreciable cytotoxicity, and negligible organ toxicity. In particular, the Ba2GdF7:Yb3+, Er3+@PEG UCNPs emit red UCL with high intensity in the tumor site after intravenous injection via the tail vein of a nude mouse. The Ba2GdF7:Yb3+, Er3+@PEG UCNPs as contrast agents exhibit high-performance for in vivo trimodality (UCL/CT/MR) imaging of a tumor during HepG2 tumor-bearing nude mouse experiments.
Non-rare earth doped oxide phosphors with far-red emission have become one of the hot spots of current research due to their low price and excellent physicochemical stability as the red component in ...white light-emitting diodes (W-LEDs) and plant growth. Herein, we report novel Mn4+-doped La2CaSnO6 and La2MgSnO6 phosphors by high-temperature solid-phase synthesis and analyzed their crystal structures by XRD and Rietveld refinement. Their excitation spectra consist of two distinct excitation bands with the dominant excitation range from 250 to 450 nm, indicating that they possess strong absorption of near-ultraviolet light. Their emission is located around 693 and 708 nm, respectively, and can be absorbed by the photosensitive pigments Pr and Pfr, proving their great potential for plant growth. Finally, the prepared samples were coated with 365 nm UV chips to fabricate far-red LEDs and W-LEDs with low correlation color temperature (CCT = 4958 K/5275 K) and high color rendering index (Ra = 96.4/96.6). Our results indicate that La2CaSnO6:Mn4+ and La2MgSnO6:Mn4+ red phosphors could be used as candidate materials for W-LED lighting and plant growth.
A series of Eu(3+), Tb(3+), Tm(3+) singly and triply doped Ca3Bi(PO4)3 (CBP) phosphors were synthesized by solid-state reaction. Their structure and photoluminescence (PL) properties were first ...investigated in detail. Rietveld refinement analysis confirmed that the CBP has a cubic unit cell. Its space group was determined to be I4combining macron3d with cell parameters a = b = c = 9.941 Å and Z = 4. In addition, the Ca3Bi(PO4)3 shows both cation disorder and oxygen sublattice disorder. For the CBP:Eu(3+) phosphor, the charge transfer bands in the PLE spectra were different at 293 K and 4.3 K, and a model was presented to give a possible explanation for this phenomenon. CBP:Eu(3+) shows intense red emission due to (5)D0-(7)F2 transition and its integral emission intensity and quantum efficiency are higher than the commercial Y2O3:Eu(3+) phosphor under irradiation of 397 nm, indicating that the CBP:Eu(3+) phosphor might have potential application in the NUV range for solid-state lighting. The CBP:Tb(3+) and CBP:Tm(3+) phosphors show intense green and blue emission due to (5)D4-(7)F2 transition of the Tb(3+) ions and the (1)D2-(3)F4 transition of the Tm(3+) ions, respectively. The energy transfer from the Tb(3+) to Eu(3+) ions was also validated by the spectra and decay curves of the Tb(3+) ions. Tunable emission colors were obtained by triply doping Eu(3+), Tb(3+) and Tm(3+) activators in a single host and adjusting their relative ratio.
