Tuning white light emission using single-component tetrachroic Dy3+ metallacrowns: the role of chromophoric building blocks

White light production is of major importance for ambient lighting and technological displays. White light can be obtained by several types of materials and their combinations, but single component emitters remain rare and desirable towards thinner devices that are, therefore, easier to control and that require fewer manufacturing steps. We have designed a series of dysprosium(iii)-based luminescent metallacrowns (MCs) to achieve this goal. The synthesized MCs possess three main structural types LnGa4(L')4(L'')4 (type A), Ln2Ga8(L')8(L''')4 (type B) and LnGa8(L')8(OH)4 (type C) (H3L', HL'' and H2L''' derivatives of salicylhydroxamic, benzoic and isophthalic acids, respectively). The advantage of these MCs is that, within each structural type, the nature of the organic building blocks does not affect the symmetry around Dy3+. By detailed studies of the photophysical properties of these Dy3+-based MCs, we have demonstrated that CIE coordinates can be tuned from warm to neutral to cold white by (i) defining the symmetry about Dy3+, and (ii) choosing appropriate chromophoric building blocks. These organic building blocks, without altering the coordination geometry around Dy3+, influence the total emission profile through changing the probability of different energy transfer processes including the 3T1 ← Dy3+* energy back transfer and/or by generating ligand-centered fluorescence in the blue range. This work opens new perspectives for the creation of white light emitting devices using single component tetrachroic molecular compounds.

Preparation of ZnGa2O4 nanoflowers and their full-color luminescence properties

Gallate material, a luminescent matrix with excellent performance is normally prepared by vapor deposition or solid phase sintering method at high temperature. However, it has not been solved to prepare gallate-based fluorescent materials with full-color luminescent properties at low temperature. In this paper, ZnGa2O4 undoped or doped with Cr or Mn nanoflowers composed of nanosheet-level structure were prepared by hydrothermal method at low temperature. Under ultraviolet light irradiation, ZnGa2O4, ZnGa2O4:Mn2+ and ZnGa2O4:Cr3+ display three primary colors of blue, green and red luminescence through self-excitation, Mn2+ and Cr3+ excitation respectively. The solid fluorescence yields of blue, green, and red colors are 32.3, 36.5, and 40.7%, respectively. It is highly expected to be applied to color display, biological imaging, white light devices.

{HPO3} and {WO4} Simultaneously Induce the Assembly of Tri-Ln(III)-Incorporated Antimonotungstates and Their Photoluminescence Behaviors

A double template agent strategy has been adopted to prepare a group of triacetate-adorned tri-Ln(III)-incorporated trimeric antimonotungstates (AMTs) K₃Na₂₁H[Ln₃(CH₃COO)₃(HPO₃)(WO₄)][B-α-SbW₉O₃₃]₃·36H₂O [Ln = Eu³⁺ (1), Dy³⁺ (2), Ho³⁺ (3), or Er³⁺ (4)] in a CH₃COOH-CH₃COONa buffer system. Therein, H₃PO₃ and Na₂WO₄·2H₂O have been, respectively, transformed into the capped {HPO₃} and {WO₄} tetrahedra during the assembly process, which are situated at the center of polyoxoanions of 1-4 and simultaneously perform as structure-directing templates to induce the assembly of 1-4. The hexahedral configuration supramolecular stacking is the same as the shape of a crystal of 1, which illustrates that the supramolecular stacking mode plays a significant role in forming the crystal shape of 1-4. Under the Ln³⁺ f-f excitation, the photoluminescence behaviors involving the emission spectrograms and fluorescence decay curves of 1-4 were systematically researched. The modulation of the excitation wavelength has realized the emission color tuning from blue to red, blue to green, blue to yellow, and green to yellow for 1-4. On the basis of the excitation of O → W charge transfer (OWCT), the energy-transfer procedure from AMT units to Eu³⁺ centers in 1 is mainly accomplished in the form of energy reabsorption. This work proposes a typical case for the construction of a new type of AMT clusters by using the double template agent strategy and confirms the great potential of Ln-containing AMTs in optic applications.

Utilizing the adaptive precursor [As2W19O67(H2O)]14– to support three hexanuclear lanthanoid-based tungstoarsenate dimers

The photoluminescence properties and polyanionic structures of hexanuclear lanthanoid-based tungstoarsenate dimers.

Tb3+, Eu3+ Co-doped CsPbBr3 QDs Glass with Highly Stable and Luminous Adjustable for White LEDs

Herein, we have introduced rare-earth cations Tb³⁺ and Eu³⁺ into CsPbBr₃ QDs glass by conventional melt-quenching. Rare-earth cations like Tb³⁺ emit green light, causing the main peak of bromide lead cesium to exhibit some redshift, owing to the energy transfer between CsPbBr₃ and Tb³⁺. To achieve adjustable light, Eu³⁺ emits red light, which was doped in this glass with different proportions to solve the problem of red deficiency. More importantly, Tb³⁺ and Eu³⁺ co-doped CsPbBr₃ QDs glass shows a series of desirable characteristics due to the energy transfer between Tb³⁺ and Eu³⁺. Interestingly, the blue light radiated by blue chip can excite Tb³⁺, Eu³⁺, and CsPbBr₃ perovskite effectively. We acquired high-performance white light-emitting diodes with color-rendering index, color coordinate transformation, and luminous efficiency of 85.7, 4945 K, and 63.21 lm/W under the current of 20 mA. This acquired Tb³⁺, Eu³⁺ co-doped CsPbBr₃ QDs glass proved the significant feasibility of luminescent materials in solid warm light source.

Highly stable and tunable white luminescence from Ag-Eu3+ co-doped fluoroborate glass phosphors combined with violet LED

Ag-Eu³⁺ co-doped fluoroborate glass phosphors doped with various Eu³⁺-concentrations were prepared by a melt-quenching technique. The luminescent properties of these glass phosphors were characterized by excitation and emission spectra. Broad excitation and emission bands located, respectively, at 300-450 nm and 390-700 nm originating from silver aggregates were observed. Strong red emissions were detected under 404 nm violet light-emitting diode (LED) excitation for those Ag-Eu³⁺ co-doped samples. It was found that these red emissions of Eu³⁺ well compensated the deficiency of the red spectral components in glasses containing Ag aggregates. In addition, it was confirmed that stable white light could be achieved from the combination of a specific Ag-Eu³⁺ co-doped fluoroborate glass phosphor and LEDs with different output wavelengths. By adjusting the luminescence intensity ratio of the glass phosphor to the 404 nm violet LED, tunable emitting color was realized, and the studied glass phosphors showed excellent emitting color stability toward LED drive currents. Our results demonstrated that this kind of easy fabrication, low-cost, and highly stable Ag-Eu³⁺ co-doped fluoroborate glass phosphors had potential application in white LED.

Self-assembled hierarchical architecture of tetragonal AgLa(MoO4)2 crystals: hydrothermal synthesis, morphology evolution and luminescence properties

Tetragonal AgLa(MoO₄)₂ microcrystals with novel discal hierarchical architectures were successfully synthesized via a one-step hydrothermal route.

Syntheses, structures and fluorescence properties of three rare-earth containing docosatungstates

Three rare-earth containing docosatungstates Na₃H₂[RE(H₂O)₄][RE(H₂O)₅]₂[W₂₂O₇₄H₂]·36H₂O [RE=Dy^III (1), Ho^III (2), Y^III (3)] have been synthesized by reaction of Na₂WO₄·2H₂O, dimethylamine hydrochloride (DMAHC) and RE(NO₃)₃·6H₂O in the aqueous solution and characterized by elemental analyses, IR spectra, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1-3 are isomorphous and each molecular unit consists of a S-shaped docosatungstate [W₂₂O₇₄H₂]^14- polyoxoanion with two supporting [RE(H₂O)₅]³⁺ cations and one disordered [RE(H₂O)₄]³⁺ cation. The [W₂₂O₇₄H₂]^14- polyoxoanion can be viewed as combination of two hendecatungstate [W₁₁O₃₈H]^9- subunits in the staggered fashion by sharing two μ₂-O atoms. The TG curves of 1-3 reveal the one-step weight loss between 25°C to 700°C. Moreover, both 1 and 2 demonstrate the characteristic luminescence emission behaviors of the corresponding RE³⁺ ions and their lifetime decay curves can be well fitted to the double exponential function. In addition, the CIE chromaticity coordinates of 1 and 2 have been obtained based on their corresponding emission spectra, and their dominant wavelengths and color purities have been also calculated.

Hydrothermal synthesis, characterization and luminescence properties of CaGd2(MoO4)4:Eu3+ ovoid like structures

Red light emission from CaGd₂(MoO₄)₄:0.06Eu³⁺ phosphor by EDTA assisted hydrothermal route at 200 °C for 24 h.

One-step hydrothermal synthesis of Sc2Mo3O12:Ln3+ (Ln = Eu, Tb, Dy, Tb/Eu, Dy/Eu) nanosheets and their multicolor tunable luminescence

The energy transfer of MoO₄²⁻ → Tb³⁺ (Dy³⁺) → Eu³⁺ and multicolor tunable emission occurred in Sc₂Mo₃O₁₂ nanosheets prepared by one-step hydrothermal synthesis.

Controllable synthesis of uniform CaMoO4:Eu3+,M+ (M = Li, Na, K) microspheres and optimum luminescence properties

High-quality and monodisperse CaMoO₄:Eu³⁺,M⁺ (M = Li, Na, K) microspheres have been synthesized with the assistance of poly-(diallyldimethylammonium chloride) (PDDA) via a facile coprecipitation hydrothermal route.

Synthesis and thermometric properties of shuttle-like Er3+/Yb3+ co-doped NaLa(MoO4)2 microstructures

SEM of shuttle-like NaLa(MoO₄)₂:Yb³⁺,Er³⁺ microcrystals, temperature-dependent UC spectra and sensitivity of samples without (A, C) and with (B, D) calcinations.

A new single-phase white-light-emitting CaWO4:Dy3+ phosphor: synthesis, luminescence and energy transfer

A new single-phase white-emitting CaWO₄:Dy³⁺ phosphor has been successfully synthesized and the photoluminescence properties and energy-transfer mechanism have been carefully investigated.