Tunable White Light Emission Research Articles

A highly connected (5,5,18)-c trinodal MOF with a 3D diamondoid inorganic connectivity: tunable luminescence and white-light emission

A highly connected (5,5,18)-c trinodal MOF featuring a 3D diamondoid inorganic connectivity was synthesized. Tunable color and white light emission can be achieved by inclusion of Eu3+ into the framework.

Photoluminescence and white-light emission in two series of heteronuclear Pb(ii)–Ln(iii) complexes

Tunable photoluminescence and single component white light emission is achieved in Pb(ii)–Eu(iii) heteronuclear complexes.

Tunable white light emission of Eu,Tb,Zn-containing copolymers by RAFT polymerization

In this work, a novel copolymer PS–Eu–Tb–Zn, which can match a 365 nm UV chip, was synthesized by the RAFT polymerization of Tb(p-BBA)3UA, Eu(TTA)2(Phen)MAA, Zn(BTZ)UA and styrene.

Photo-facilitated aggregation and correlated color temperature adjustment of single component organic solid state white-light emitting materials

A pyridinium derivative with photo-facilitated aggregation and intra-/intermolecular charge transfer synergy-induced dual emission has been presented. The correlated color temperature tunable white-light emission can be realized in different states.

Ca8NaY(PO4)6F2:Eu2+,Mn2+: a potential color-tunable phosphor for white LEDs applications

Eu2+- and/or Mn2+-activated Ca8NaY(PO4)6F2 phosphors have been prepared via a combustion-assisted synthesis route. The powder X-ray diffraction measurement revealed that Ca8NaY(PO4)6F2 crystallized in a hexagonal crystal system with the space group P63/m (176). The photoluminescence spectrum of the Eu2+ single-doped phosphor shows a broad blue emission band peaking at 451 nm under the excitation of UV irradiation. The Eu2+-/Mn2+-codoped phosphors show a blue emission band and an orange emission band, and the corresponding CIE coordinates intuitively indicate the tunable colors from blue to yellow area. The energy transfer from the Eu2+ to Mn2+ ions is demonstrated to be a quadrupole–quadrupole mechanism in terms of the experimental results and analysis of PL spectra and decay curves of the phosphors. The developed phosphors can be efficiently excited in the UV region and exhibit a tunable white-light emission, making them attractive as single-component white-light-emitting conversion phosphors for UV-based white LEDs.

Luminescence properties and energy transfer mechanism of Ce3 +/Sm3 + co-doped Na2O-Y2O3-SiO2 glass for white light emission

A series of Ce3+/Sm3+ doped glasses were prepared in this study and their luminescence properties were analyzed. A combination of blue and orange-red emission band was observed from these glasses, and tunable white light emission could be observed by adjusting concentration ratio of Ce3+ to Sm3+ under UV light excitation. Energy transfer (ET) from Ce3+ to Sm3+ is discovered by directly observing significant overlap of the excitation spectrum of Sm3+ and the emission spectrum of Ce3+ ions. The energy transfer from Ce3+ to Sm3+ via a dipole–dipole mechanism was confirmed by the luminescence spectra, the decay lifetime and the calculation of energy transfer efficiency of the glasses. Based on the results in this study, the Ce3+/Sm3+ doped glasses could be used as a potential matrix material for ultraviolet light emitting diode (LED) chip based white LEDs.

Tunable white light emission from single-phased Li2 SrSiO4 :Dy(3+) phosphors by co-doping with Eu(3+).

A series of single-phase full-color emitting Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) phosphors were synthesized by solid-state reaction and characterized by X-ray diffraction and photoluminescence analyses. The samples showed emission peaks at 488 nm (blue), 572 nm (yellow), 592 nm (orange) and 617 nm (red) under 393 nm excitation. The photoluminescence excitation spectra, comprising the Eu-O charge transfer band and 4f-4f transition bands of Dy(3+) and Eu(3+) , range from 200 to 500 nm. The Commission Internationale de I'Eclairage chromaticity coordinates for Li2 Sr0.98-x SiO4 :0.02Dy(3+) ,xEu(3+) phosphors were simulated. By manipulating Eu(3+) and Dy(3+) concentrations, the color points of Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) were tuned from the greenish-white region to white light and eventually to reddish-white region, demonstrating that a tunable white light can be obtained by Li2 Sr1-x-y SiO4 :xDy(3+) ,yEu(3+) phosphors. Li2 Sr0.98-x SiO4 :0.02Dy(3+) , xEu(3+) can serve as a white-light-emitting phosphor for phosphor-converted light-emitting diode.

Aggregation-induced white-light emission from the triple-stranded dinuclear Sm(iii) complex.

A novel bis-β-diketone ligand, 4,4'-bis(4,4,4-trifluoro-1,3-dioxobutyl)(phenoxy)-1,1'-binaphthalene (BTPB), is designed for synthesis of a white light emissive lanthanide complex. The ligand bears two benzoyl β-diketonate sites linked by a 1,1'-binaphthoxy spacer. Reaction of the doubly negatively charged bis-bidentate ligand with lanthanide ions forms triple-stranded dinuclear complexes Sm2(BTPB)3(H2O)4 () and Gd2(BTPB)3(H2O)4 (), which have been fully characterized by various spectroscopic techniques. UV-Vis absorption and emission spectroscopic techniques are used to investigate photophysical properties of the ligand and its complexes in THF and CHCl3. In some cases aggregation of the ligand results in the appearance of a new luminescence band at about 510 nm in addition to the monomer fluorescence. In complex , partial energy transfer from BTPB results in Sm(iii)-based red light emission in addition to the BTPB-based blue/green emission. With the variation of the excited wavelength and concentration of the solution, complex shows a tunable white light emission with the balance of three primary colors. This is an unusual case of observation of white light emission from a single molecule Sm(iii) complex.

Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-to-Make Porous Conjugated Polymer

Separating silver (Ag(+)) from lead (Pb(2+)) is one of the many merits of the porous polymer framework reported here. The selective metal binding stems from the well-defined chelating unit of N-heterocycles, which consists of a triazine (C3N3) ring bonded to three 3,5-dimethylpyrazole moieties. Such a rigid and open triad also serves as the distinct building unit in the fully conjugated 3D polymer scaffold. Because of its strong fluorescence and porosity (e.g., BET surface area: 355 m(2)/g), and because of the various types of metal species that can be readily taken up, this versatile framework is especially fit for functionalization. For example, with AgNO3 loaded, the framework solid exhibits a brown color in response to water solutions of H2S, even at the dilution of 5.0 μM (0.17 ppm); whereas cysteine and other biologically relevant thiols do not cause notable change in color. In another example, tunable white-light emission was produced when an Ir(III) complex was doped (e.g., about 0.02% of the polymer weight) onto the framework. Mechanistically, the bound Ir(III) centers become highly emissive in the orange-red region, complementing the broad, bluish emission from the polymer host to result in the overall white-light quality: the color attributes of the emission are therefore easily tunable by the Ir(III) dopant concentration. With this exemplary study, we intend to highlight metal uptake as an effective approach to modify and enrich the properties of porous polymer frameworks and to stimulate interest in further examining metal-polymer interactions in the context of sensing, separation, catalyzes, and other applications.

Synthesis, structure and tunable white-light emission of dinuclear Eu(III) Schiff base complex

The structures and photophysical properties of Ln(III) [europium(III), terbium(III) and gadolinium(III)] complexes with the Schiff base ligands L: (E)-N′-((2-hydroxynaphthalen-1-yl)methylene)acetohydrazide have been investigated. Single crystal X-ray structure of the Eu(III) complex shows two unsymmetrical metal centers that are directly linked by three, near symmetrical phenoxo bridges. The complex exhibits extensive intramolecular stacking interactions between the naphthalene rings that lead to the formation of an excimer. By proper tuning of solvent's polarity and molecular aggregation, excitation of the Eu(III) complex in dichloromethane exhibits white emission expanding the visible region composed of blue (ligand), green (excimer) and red (sensitized Eu(III) centre) luminescence.

Anionic porous metal–organic framework with novel 5-connected vbk topology for rapid adsorption of dyes and tunable white light emission

A novel porous metal–organic framework, {[Zn2(L)·H2O]·3H2O·3DMAc·NH2(CH3)2}n (Zn(II)–MOF), was synthesized under solvothermal conditions using a flexible multicarboxylic acid (H5L = 3,5-bis(1-methoxy-3,5-benzene dicarboxylic acid)benzoic acid). Zn(II)–MOF contains 1D nanotubular channels of 13.8 A × 16.4 A and exhibits a rare 5-connected vbk net with a Schlafli symbol of {45.65} topology. Notably, Zn(II)–MOF can adsorb toluidine blue fast and effectively, and trap lanthanide ions such as Eu3+ and Tb3+ to sensitize their emissions in the solid state through a Ln3+-exchanged approach. Furthermore, we successfully obtained white light emitting materials.

Generation of tunable white light in blue-green self-activated Ba2TiSi2O8 phosphor by doping Sm3+ or Eu3+ ions

Tunable white light emission was generated in blue-green self-activated Ba2TiSi2O8 phosphor by doping Sm3+ or Eu3+ ions, which emit orange-red light. The white light was attributed to the color mixture of blue-green and orange-red emission, which originates from the charge transfer (CT) transition emission of Ti4+–O2− and the transition emission of dopants (Sm3+ or Eu3+) respectively. The dependence of emission properties on the concentration of Eu3+ dopants and the energy transfer between the Ti4+–O2− CT and the dopants were investigated. White light with tunable correlated color temperature (CCT) and color rendering index (CRI) for Ba2TiSi2O8:Eu3+ phosphors were demonstrated by simply controlling the content of dopants, suggesting the potential application in white light emitting devices.

Tunable white light from photo- and electroluminescence of ZnO nanoparticles

Tunable white light emission was obtained from ZnO nanorods with lengths ranging from 125 to 165 nm and quantum dots with an average size of 5 nm, synthesized with dodecylamine (DCA) as surfactant. It was possible to tailor the emission from cool to warm white light by changing the concentration of DCA in the synthesis process. The CIE coordinates for the white light obtained were (0.33, 0.32) in the case of photoluminescence and (0.31, 0.33) for electroluminescence from ZnO-based LEDs with a turn-on voltage of 4 and 6 V and a maximum current consumption of 2.32 mA at 10 V.

Tunable white-light emission in single-phase Ca_9Gd(VO_4)_7:Tm^3+, Eu^3+

A series of Tm3+ and/or Eu3+ doped Ca9Gd(VO4)7 single composition phosphors were synthesized by a solid state reaction method, and their luminescence properties were investigated. Tm3+ and Eu3+ co-doped Ca9Gd(VO4)7 phosphors showed a blue with the peak at 477 nm and red with the stronger peak at 620 nm dual emission bands under the UV excitation, which originates from the f-f transitions of Tm3+ and Eu3+ ions, respectively. The energy transfer from O2--V5+ CT (charge transfer) energy to Tm3+ and Eu3+ ions as well as the energy transfer from Tm3+ to Eu3+ ions were investigated. The photoluminescence intensity ratio of blue and red emission could be tuned by adjusting the concentration of Tm3+ and Eu3+ ions and as a result the emission color varies from blue to white to red. The white-light emission is realized in single phased phosphor of Ca9Gd(VO4)7:Tm3+, Eu3+ by combining the Tm3+-emission and the Eu3+-emission.

Efficient and tunable white-light emission of metal–organic frameworks by iridium-complex encapsulation

Metal–organic frameworks (MOFs) are well known for their tunable structure and porosity. Many studies have shown they are promising for various important applications, for which their performance can be further enhanced by encapsulating functional species, such as luminescent guest molecules, within the frameworks. Although numerous MOFs are luminescent, very few emit white light and their quantum yield is usually low. Here we report a strategy to achieve efficient white-light emission by encapsulating an iridium complex in the MOF cavity. A mesoporous blue-emitting MOF is prepared as host to encapsulate a yellow-emitting iridium complex, [Ir(ppy)2(bpy)]+. The resultant composites emit bright white light with good colour quality (for example, Commission International de I’Eclairage coordinates, colour-rendering index and correlated colour temperature of (0.31, 0.33), 84.5 and 5409 K, respectively), and high quantum yield up to 115 °C. This strategy may open new perspectives for developing high-performance energy-saving solid-state lighting materials.

Tunable luminescence and white light emission of novel multiphase sodium calcium silicate nanophosphors doped with Ce3+, Tb3+, and Mn2+ ions

This study reports the sol–gel synthesis of sodium calcium multiphase silicate (SCMS) nanophosphors. X-ray powder diffraction indicated the crystallization of devitrite (Na2Ca3Si6O16), wollastonite-2M (CaSiO3), and cristobalite (SiO2) phases that consistently occurred together upon repeated syntheses. The multiphase silicate system was used as a host matrix for varied concentrations of Ce3+, Tb3+, and Mn2+ dopant ions which resulted in tunable photoluminescence. A broad violet/UV emission band of Ce3+ (350–425nm) combined with blue-green emissions of Tb3+ (488 and 545nm) and a yellow-orange emission of Mn2+ (560nm) resulted in the observance of white light (x=0.31, y=0.32, TC=6624K) under midwave UV excitation (300–340nm). Energy transfer from Ce3+→Tb3+ and Ce3+→Mn2+ was confirmed by steady state and time-resolved emission spectra, lifetime, and quantum yield measurements. The structural properties, morphology, and elemental composition of the nanophosphors were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS).

Tunable white-light emission of SiAlON-base crystal/glass composite phosphor by variation of excitation wavelength

Abstract Tunable white light of Eu 2+ doped SiAlON crystal/glass composite phosphor with blue-yellow dual-emissions was demonstrated by variation of excitation wavelength in this work. The excitation properties of blue emission originated from the transition of Eu 2+ ions in the Si–Al–B–O–N glass matrix and that of yellow emission originated from the transition of Eu 2+ ions in the SiAlON lattice were investigated, respectively. By varying the excitation wavelength in the range of 330–380 nm, white emission was tuned from cool white to warm white for this SiAlON crystal/glass composite phosphor owing to the various excitation properties of these two emission bands. Presented results indicate that this tunable SiAlON crystal/glass composite white-light phosphor might be applied in white LED, combining with UV chips with different emitting wavelengths in the range of 330–380 nm.

Highly Thermostable One-Dimensional Lanthanide(III) Coordination Polymers Constructed from Benzimidazole-5,6-dicarboxylic Acid and 1,10-Phenanthroline: Synthesis, Structure, and Tunable White-Light Emission

Three novel isostructural lanthanide(III) coordination polymers (LnCPs), {[Ln3(bidc)4(phen)2(NO3)]·2H2O}n (Ln = Gd (1), Eu (2), Tb (3); H2bidc = benzimidazole-5,6-dicarboxylic acid, and phen = 1,10-phenanthroline), were synthesized via hydrothermal reaction and characterized. The complexes crystallize in the chiral space group P212121. They possess 1D structures based on lanthanide trinuclear clusters containing Ln(1)O9, Ln(2)O6N2, and Ln(3)O6N2 polyhedra by bidc linkers, and phen and nitrate act as terminal ligands. The bidc and phen ligands provide efficient energy transfer for the sensitization of Eu(III) and Tb(III) complexes. The complexes 2 and 3 emit red and green light, respectively. Lifetimes and quantum yields of luminescence are 0.86 ms and 13.20% for 2 and 0.32 ms and 2.08% for 3. Tuning of white-light emission by adjusting the doping concentration of Eu(III) and Tb(III) ions in the Gd(III) complex was achieved.

Tunable white light emission from γ-irradiated Ag/Eu co-doped phosphate glass phosphor

We report a new tunable white light emission from γ-irradiated Ag/Eu co-doped phosphate glass phosphor. The appearance of Eu2+ and silver aggregates after γ-irradiation was confirmed via Electron paramagnetic resonance (EPR), absorption, and emission spectra. The effects of Ag/Eu doping concentration and excitation wavelengths on white light emission were discussed. A pure white light emission with the chromaticity coordinates (X = 0.331, Y = 0.329) was generated using the optimal sample under excitation at 360 nm.

Tunable white light-emission of a CaW1−x Mo x O4:Tm3+, Tb3+, Eu3+ phosphor prepared by a Pechini sol–gel method

A white light-emitting CaW1−x Mo x O4:Tm3+, Tb3+, Eu3+ phosphor was prepared by a Pechini sol–gel method. The incorporation of Mo6+ into the CaWO4 host matrix can broaden its excitation range and promote tunability to its emission. When the CaW1−x Mo x O4 system is triply-doped with Tm3+, Tb3+, and Eu3+ ions, energy transfer occurs from both WO4 2− and MoO4 2− groups to Tm3+ and Tb3+ ions. A significant red-shift in the excitation of Eu3+ allows the resulting emission to be tunable between cool, natural, and warm white light by varying the excitation wavelength. The undoped and triply-doped CaW1−x Mo x O4 phosphors were characterized by X-ray diffraction, scanning electron microscopy, photoluminescence excitation and emission spectra, and CIE chromaticity (x, y) coordinates.