Luminescence Tuning and White‐Light Emission of Co‐doped Ln–Cd–Organic Frameworks

Four new three‐dimensional isostructural lanthanide–cadmium metal–organic frameworks (Ln–Cd MOFs), [LnCd₂(imdc)₂(Ac)(H₂O)₂]?H₂O (Ln=Pr ( 1 ), Eu ( 2 ), Gd ( 3 ), and Tb ( 4 ); H₃imdc=4,5‐imidazoledicarboxylic acid; Ac=acetate), have been synthesized under hydrothermal conditions and characterized by IR, elemental analyses, inductively coupled plasma (ICP) analysis, and X‐ray diffraction. Single‐crystal X‐ray diffraction shows that two Ln^III ions are surrounded by four Cd^II ions to form a heteronuclear building block. The blocks are further linked to form 3D Ln–Cd MOFs by the bridging imdc^3? ligand. Furthermore, the left‐ and right‐handed helices array alternatively in the lattice. Eu–Cd and Tb–Cd MOFs can emit characteristic red light with the Eu^III ion and green light with the Tb^III ion, respectively, while both Gd–Cd and Pr–Cd MOFs generate blue emission when they are excited. Different concentrations of Eu³⁺ and Tb³⁺ ions were co‐doped into Gd–Cd/Pr–Cd MOFs, and tunable luminescence from yellow to white was achieved. White‐light emission was obtained successfully by adjusting the excitation wavelength or the co‐doping ratio of the co‐doped Gd–Cd and Pr–Cd MOFs. These results show that the relative emission intensity of white light for Gd–Cd:Eu³⁺,Tb³⁺ MOFs is stronger than that of Pr–Cd:Eu³⁺,Tb³⁺ MOFs, which implies that the Gd complex is a better matrix than the Pr complex to obtain white‐light emission materials.     

Luminescence of Eu3+ and Tb3+ Complexes of Two Macrobicyclic Ligands Derived from a Tetralactam Ring and a Chromophoric Antenna

Two macrobicyclic ligands derived from an 18‐membered tetralactam ring and 2,2′‐bipyridine or 2,6‐bis(pyrazol‐1‐yl)pyridine moieties, 1 and 2 , respectively, form stable complexes with Gd^III, Eu^III, and Tb^III ions in aqueous solution. The ligand‐based luminescence is retained in the Gd^III cryptates, whereas this radiative deactivation is quenched in the Eu^III and Tb^III cryptates by ligand‐to‐metal energy transfer, resulting in the usual metal‐centered emission spectra. Singlet‐ and triplet‐state energies, emission‐decay lifetimes, and luminescence yields were measured. [Tb⊂ 1 ]³⁺ cryptate shows a long luminescence lifetime (τ=1.12 ms) and a very high metal luminescence quantum yield (Φ=0.25) in comparison with those reported in the literature for Tb³⁺ complexes sensitized by a bipyridine chromophore. By comparison to [Ln⊂ 1 ]³⁺, [Ln⊂ 2 ]³⁺ presents markedly lower luminescence properties, due to worse interaction between the 2,6‐bis(pyrazol‐1‐yl)pyridine unit and the metal ion. Moreover, the luminescent metal and the triplet ligand energy levels of [Eu⊂ 2 ]³⁺ do not match. The effects of H₂O molecules coordinated to the metal centre and of thermally activated decay processes on nonradiative deactivation to the ground‐state are also reported.     

Mechanistic Insight into Energy-Transfer Dynamics and Color Tunability of Na4CaSi3O9:Tb3+,Eu3+ for Warm White LEDs

In this work, a latent energy-transfer process in traditional Eu³⁺,Tb³⁺-doped phosphors is proposed and a new class of Eu³⁺,Tb³⁺-doped Na₄CaSi₃O₉ (NCSO) phosphors is presented which is enabled by luminescence decay dynamics that optimize the electron-transfer energy process. Relative to other Eu³⁺,Tb³⁺-doped phosphors, the as-synthesized Eu³⁺,Tb³⁺-doped NCSO phosphors show improved large-scale tunable emission color from green to red upon UV excitation, controlled by the Tb³⁺/Eu³⁺ doping ratio. Detailed spectroscopic measurements in the vacuum ultraviolet (VUV)/UV/Vis region were used to determine the Eu³⁺–O²⁻ charge-transfer energy, 4f–5d transition energies, and the energies of 4f excited multiplets of Eu³⁺ and Tb³⁺ with different 4f^N electronic configurations. The Tb³⁺→Eu³⁺ energy-transfer pathway in the co-doped sample was systematically investigated, by employing luminescence decay dynamics analysis to elucidate the relevant energy-transfer mechanism in combination with the appropriate model simulation. To demonstrate their application potential, a prototype white-light-emitting diode (WLED) device was successfully fabricated by using the yellow luminescence NCSO:0.03Tb³⁺, 0.05Eu³⁺ phosphor with high thermal stability and a BaMgAl₁₀O₁₇:Eu²⁺ phosphor in combination with a near-UV chip. These findings open up a new avenue to realize and develop multifunctional high-performance phosphors by manipulating the energy-transfer process for practical applications.     

Photophysical Properties of Metal Ion Functionalized NaY Zeolite

A series of luminescent ion exchanged zeolite are synthesized by introducing various ions into NaY zeolite. Monometal ion (Eu³⁺, Tb³⁺, Ce³⁺, Y³⁺, Zn²⁺, Cd²⁺, Cu²⁺) exchanged zeolite, rare‐earth ion (Eu³⁺, Tb³⁺, Ce³⁺) exchanged zeolite modified with Y³⁺ and rare‐earth ion (Eu³⁺, Tb³⁺, Ce³⁺) exchanged zeolite modified with Zn²⁺ are discussed here. The resulting materials are characterized by Fourier transform infrared spectrum radiometer (FTIR), XRD, scanning electronic microscope (SEM), PLE, PL and luminescence lifetime measurements. The photoluminescence spectrum of NaY indicates that emission band of host matrix exhibits a blueshift of about 70 nm after monometal ion exchange process. The results show that transition metal ion exchanged zeolites possess a similar emission band due to dominant host luminescence. A variety of luminescence phenomenon of rare‐earth ion broadens the application of zeolite as a luminescent host. The Eu³⁺ ion exchanged zeolite shows white light luminescence with a great application value and Ce³⁺ exchanged zeolite steadily exhibits its characteristic luminescence in ultraviolet region no matter in monometal ion exchanged zeolite or bimetal ions exchanged zeolite.     

Three Lanthanide Metal‐Organic Frameworks Based on an Ether‐Decorated Polycarboxylic Acid Linker: Luminescence Modulation,CO2 Capture and Conversion Properties

Three new isostructural 3D lanthanide metal–organic frameworks (Ln‐MOFs), {H[LnL(H₂O)]?2 H₂O}_n ( 1‐Ln ) (Ln=Eu³⁺, Gd³⁺ and Tb³⁺), based on infinite lanthanide‐carboxylate chains were constructed by employing an ether‐separated 5,5′‐oxydiisophthalic acid (H₄L) ligand under solvothermal reaction. 1‐Eu and 1‐Tb exhibit strong red and green emission, respectively, through the antenna effect, as demonstrated through a combination of calculation and experimental results. Moreover, a series of dichromatic doped 1‐Eu_xTb_y MOFs were fabricated by introducing different concentrations of Eu³⁺ and Tb³⁺ ions, and they display an unusual variation of luminescent colors from green, yellow, orange to red. 1‐Eu with channels decorated by ether O atoms and the open metal sites displays good performance for CO₂ capture and conversion between CO₂ and epoxides into cyclic carbonates.     

A Lanthanide‐Complex‐Based Ratiometric Luminescent Probe Specific for Peroxynitrite

A lanthanide‐complex‐based ratiometric luminescence probe specific for peroxynitrite (ONOO^?), 4′‐(2,4‐dimethoxyphenyl)‐2,2′:6′,2′′‐terpyridine‐6,6′′‐diyl]bis(methylenenitrilo)tetrakis(acetate)‐Eu³⁺/Tb³⁺ ([Eu³⁺/Tb³⁺(DTTA)]), has been designed and synthesized. Both [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] are highly water soluble with large stability constants at ≈10²⁰, and strongly luminescent with luminescence quantum yields of 10.0 and 9.9 %, respectively, and long luminescence lifetimes of 1.38 and 0.26 ms, respectively. It was found that the luminescence of [Tb³⁺(DTTA)] could be quenched by ONOO^? rapidly and specifically in aqueous buffers, while that of [Eu³⁺(DTTA)] did not respond to the addition of ONOO^?. Thus, by simply mixing [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] in an aqueous buffer, a ratiometric luminescence probe specific for time‐gated luminescence detection of ONOO^? was obtained. The performance of [Tb³⁺(DTTA)] and [Eu³⁺/Tb³⁺(DTTA)] as the probes for luminescence imaging detection of ONOO^? in living cells was investigated. The results demonstrated the efficacy and advantages of the new ratiometric luminescence probe for highly sensitive luminescence bioimaging application.     

Preparation,Characterization and Luminescence Study of Chitosan Membrane and Powder Forms with Eu3 + and Tb3 +

Chitosan membranes with trivalent lanthanide ion Eu^{3 +} were prepared at a ratio of 3:1 w/w (chitosan:lanthanide). There was no membrane formation at a ratio of 1:1 w/w (chitosan: Eu^{3 +} or Tb^{3 +}); in this case a white solid powder was obtained. Both chitosan compounds were characterized by elemental analysis (CHN), thermal analysis (TG/DTG), scanning electron microscopy (SEM) and luminescence spectroscopy. CHN analysis was performed only for chitosan compounds in powder form, suggesting that these compounds have the general formula QUILn.6H₂O, where QUI = Chitosan and Ln = Eu^{3 +} or Tb^{3 +}. The results of TG/DTG curves for chitosan membranes with Eu^{3 +} ion indicate that the introduction of this metal into the chitosan structure causes gradual degradation in residual carbons, showing lower weight loss in the Eu^{3 +} membranes compared to pure chitosan membrane. Analysis of luminescence demonstrated that chitosan membranes with Eu^{3 +} ion exhibit emission in the visible region, showing emission bands from chitosan and Eu^{3 +} moieties. For chitosan with Eu^{3 +} and Tb^{3 +} ions compounds, in powder form, the analysis of luminescence suggested that chitosan is not transferring energy to the lanthanide ion; however, the chemical region where the lanthanide ion is found breaks the selection rules and favors the emission of these ions.     

Upconversion Luminescence through Cooperative and Energy-Transfer Mechanisms in Yb3+-Metal-Organic Frameworks

Lanthanide-doped metal–organic frameworks (Ln-MOFs) have versatile luminescence properties, however it is challenging to achieve lanthanide-based upconversion luminescence in these materials. Here, 1,3,5-benzenetricarboxylic acid (BTC) and trivalent Yb³⁺ ions were used to generate crystalline Yb-BTC MOF 1D-microrods with upconversion luminescence under near infrared excitation via cooperative luminescence. Subsequently, the Yb-BTC MOFs were doped with a variety of different lanthanides to evaluate the potential for Yb³⁺-based upconversion and energy transfer. Yb-BTC MOFs doped with Er³⁺, Ho³⁺, Tb³⁺, and Eu³⁺ ions exhibit both the cooperative luminescence from Yb³⁺ and the characteristic emission bands of these ions under 980 nm irradiation. In contrast, only the 497 nm upconversion emission band from Yb³⁺ is observed in the MOFs doped with Tm³⁺, Pr³⁺, Sm³⁺, and Dy³⁺. The effects of different dopants on the efficiency of cooperative luminescence were established and will provide guidance for the exploitation of Ln-MOFs exhibiting upconversion.     

Photophysical Properties of Lanthanide (Eu3+, Tb3+) Hybrid Soft Gels of Double Functional Linker of Ionic Liquid–Modified Silane

Four kinds of luminescent hybrid soft gels have been assembled by introducing the lanthanide (Eu³⁺, Tb³⁺) tetrakis β‐diketonate into the covalently bonded imidazolium‐based silica through electrostatic interactions. Here, the imidazolium‐based silica matrices are prepared from imidazolium‐derived organotriethoxysilanes by the sol–gel process, in which the imidazolium cations are strongly anchored within the silica matrices while anions can still be exchanged following application for functionalization of lanthanide complexes. The photoluminescence measurements indicated that these hybrid soft gels exhibit characteristic red and green luminescence originating from the corresponding ternary lanthanide ions (Eu³⁺, Tb³⁺). Further investigation of photophysical properties reveals that these soft gels have inherited the outstanding luminescent properties from the lanthanide tetrakis β‐diketonate complexes such as strong luminescence intensities, long lifetimes and high luminescence quantum efficiencies.     

A new disordered langbeinite‐type compound,K2Tb1.5Ta0.5P3O12, and Eu3+‐doped multicolour light‐emitting properties

For the first time, a new langbeinite‐type phosphate, namely potassium terbium tantalum tris(phosphate), K₂Tb_1.5Ta_0.5(PO₄)₃, has been prepared successfully using a high‐temperature flux method and has been structurally characterized by single‐crystal X‐ray diffraction. The results show that its structure can be described as a three‐dimensional open framework of [Tb_1.5Ta_0.5(PO₄)₃]_∞ interconnected by K⁺ ions. The Tb^III and Ta^V cations in the structure are disordered and occupy the same crystallographic sites. The IR spectrum, the UV–Vis spectrum, the morphology and the Eu³⁺‐activated photoluminescence spectroscopic properties were studied. A series of Eu³⁺‐doped phosphors, i.e. K₂Tb_1.5–xTa_0.5(PO₄)₃:xEu³⁺ (x = 0.01, 0.03, 0.05, 0.07, 0.10), were prepared via a solid‐state reaction and the photoluminescence properties were studied. The results show that under near‐UV excitation, the luminescence colour can be tuned from green through yellow to red by simply adjusting the Eu³⁺ concentration from 0 to 0.1, because of the efficient Tb³⁺→Eu³⁺ energy‐transfer mechanism.     

Rare earth complexes chemiluminescence catalyzed by gold nanoparticles for fast sensing of Tb3+ and Eu3+

Developing multiplex sensing technique is of great significance for fast sample analysis. However, the broad emissions of most chemiluminescence(CL) luminophores make the multiplex CL analysis be difficult. In this work, a simple and sensitive CL analytical method has been developed for the simultaneous determination of Tb³⁺and Eu³⁺thanking to their narrow band emission. The technique was based on a mixed CL system of periodate(IO₄^-)-hydrogen peroxide(...     

The Series of Rare Earth Complexes [Ln2Cl6(μ‐4,4′‐bipy)(py)6], Ln=Y,Pr, Nd,Sm‐Yb: A Molecular Model System for Luminescence Properties in MOFs Based on LnCl3 and 4,4′‐Bipyridine

A series of 12 dinuclear complexes [Ln₂Cl₆(μ‐4,4′‐bipy)(py)₆], Ln=Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, ( 1 – 12 , respectively) was synthesized by an anhydrous solvothermal reaction in pyridine. The complexes contain a 4,4′‐bipyridine bridge and exhibit a coordination sphere closely related to luminescent lanthanide MOFs based on LnCl₃ and 4,4‐bipyridine. The dinuclear complexes therefore function as a molecular model system to provide a better understanding of the luminescence mechanisms in the Ln‐N‐MOFs ${\hbox{}{{\hfill 2\atop \hfill \infty }}}$ [Ln₂Cl₆(4,4′‐bipy)₃] ? 2(4,4′‐bipy). Accordingly, the luminescence properties of the complexes with Ln=Y, Sm, Eu, Gd, Tb, Dy, ( 1 , 4 – 8 ) were determined, showing an antenna effect through a ligand–metal energy transfer. The highest efficiency of luminescence is observed for the terbium‐based compound 7 displaying a high quantum yield (QY of 86 %). Excitation with UV light reveals typical emission colors of lanthanide‐dependent intra 4f–4f‐transition emissions in the visible range (Tb^III: green, Eu^III: red, Sm^III: salmon red, Dy^III: yellow). For the Gd^III‐ and Y^III‐containing compounds 6 and 1 , blue emission based on triplet phosphorescence is observed. Furthermore, ligand‐to‐metal charge‐transfer (LMCT) states, based on the interaction of Cl^? with Eu^III, were observed for the Eu^III compound 5 including energy‐transfer processes to the Eu^III ion. Altogether, the model complexes give further insights into the luminescence of the related MOFs, for example, rationalization of Ln‐independent quantum yields in the related MOFs.     

A rht-Type Luminescent Zn (II)-MOF Constructed by Triazine Hexacarboxylate Ligand: Tunable Luminescent Performance and White-light Emission Regulation through doping Eu3+/Tb3+

White-light emitting materials have become a hot research field of luminescent MOF (Metal–Organic Framework) because of its high practical application value. Herein, we successfully synthesized and characterized a rht-type fluorescent MOF Zn-TDPAT [H₆TDPAT = 2,4,6-tris(3,5-dicarboxylphenylamino)-1,3,5-triazine] with a topology of (3, 24) connected nodes. A series of MOFs materials x%Tb + y%Eu@Zn-TDPAT were prepared by incorporating different concentrations of green emission center Tb³⁺ and red emission center Eu³⁺ into the blue-emitting Zn-MOF. The luminescence properties of MOFs materials x%Tb + y%Eu@Zn-TDPAT can be effectively adjusted by incorporating different concentrations of Tb³⁺ and Eu³⁺ and can obtain multi-color luminescence properties from blue, blue-green, green, yellow green, yellow, blue-red, yellow-red and white. According to trichromatic mechanism, by reasonably matching the intensity of blue light, green light and red light emitted by x%Tb + y%Eu@Zn-TDPAT at 420, 543 and 616 nm, MOFs materials 0.75%Tb + 5%Eu@Zn-TDPAT, 0.65%Tb + 5.5%Eu@Zn-TDPAT and 0.5%Tb + 7.5%Eu@Zn-TDPAT with white-light emission are obtained. Their CIE coordinates are 0.3162, 0.3345 (0.3162, 0.3345), (0.3138, 0.3339) and (0.3329, 0.3222), respectively, which are very close to ideal white-light emission (0.3333,0.3333).     

Development of a ratiometric time-resolved luminescence sensor for pH based on lanthanide complexes

Time-resolved luminescence bioassay technique using lanthanide complexes as luminescent probes/sensors has shown great utilities in clinical diagnostics and biotechnology discoveries. In this work, a novel terpyridine polyacid derivative that can form highly stable complexes with lanthanide ions in aqueous media, (4′-hydroxy-2,2′:6′,2′′-terpyridine-6,6′′-diyl) bis(methylenenitrilo) tetrakis(acetic acid) (HTTA), was designed and synthesized for developing time-resolved luminescence pH sensors based on its Eu³⁺ and Tb³⁺ complexes. The luminescence characterization results reveal that the luminescence intensity of HTTA–Eu³⁺ is strongly dependent on the pH values in weakly acidic to neutral media (pK_a = 5.8, pH 4.8–7.5), while that of HTTA–Tb³⁺ is pH-independent. This unique luminescence response allows the mixture of HTTA–Eu³⁺ and HTTA–Tb³⁺ (the HTTA–Eu³⁺/Tb³⁺ mixture) to be used as a ratiometric luminescence sensor for the time-resolved luminescence detection of pH with the intensity ratio of its Tb³⁺ emission at 540 nm to its Eu³⁺ emission at 610 nm, I_540 nm/I_610 nm, as a signal. Moreover, the UV absorption spectrum changes of the HTTA–Eu³⁺/Tb³⁺ mixture at different pHs (pH 4.0–7.0) also display a ratiometric response to the pH changes with the ratio of absorbance at 290 nm to that at 325 nm, A_290 nm/A_325 nm, as a signal. This feature enables the HTTA–Eu³⁺/Tb³⁺ mixture to have an additional function for the pH detection with the absorption spectrometry technique. For loading the complexes into the living cells, the acetoxymethyl ester of HTTA was synthesized and used for loading HTTA–Eu³⁺ and HTTA–Tb³⁺ into the cultured HeLa cells. The luminescence imaging results demonstrated the practical utility of the new sensor for the time-resolved luminescence cell imaging application.     

Tailoring of polychromatic emissions in Tb3+/Eu3+ codoped NaYbF4 nanoparticles via energy transfer strategy for white light-emitting diodes

The polychromatic emission and wide-range color tuning in the luminescent nanoparticles are currently of crucial importance, due to the development of color and white light-emitting diode (LED) devices, based on such lanthanide-doped nanostructured materials. By utilization of precipitation method, Tb³⁺-doped and Tb³⁺/Eu³⁺-codoped NaYbF₄ nanoparticles (i.e. NPs) are synthesized. For Tb³⁺-doped NaYbF₄ NPs excited by 377 nm, green emission originating from Tb³⁺ is observed, where its optimum state is obtained when Tb³⁺ content is 25 mol% and the concentration quenching mechanism is found by electric dipole-dipole interaction. Moreover, due to the existence of energy transfer between Tb³⁺ and Eu³⁺, polychromatic emissions are realized in Tb³⁺/Eu³⁺-codoped NaYbF₄ NPs as Eu³⁺ content increases. Through analyzing emission decay times and emission spectra, it was confirmed that the energy transfer mechanism in the synthesized NPs is governed mainly by electric dipole-dipole interaction. Furthermore, the resultant NPs also own strong resistance to temperature, which is verified by temperature-dependent emission spectra, and the activation energies of Tb³⁺ and Eu³⁺ are 0.206 and 0.207 eV, respectively. In addition, by employing designed NPs as yellow-emitting components, the fabricated white-LED emits brightness warm white light with color coordinate of (0.385, 0.380), high color rendering index of 84.3 and low correlated color temperature of 3903 K. This work does not only offer an available route to develop NPs with polychromatic emissions but also devise promising luminescent materials for improving the performance of the phosphor-converted white-LED.     

Synthesis,Structure, and Photoluminescence Properties of Novel KBaSc2(PO4)3:Ce3+/Eu2+/Tb3+ Phosphors for White‐Light‐Emitting Diodes

A series of novel KBaSc₂(PO₄)₃:Ce³⁺/Eu²⁺/Tb³⁺phosphors are prepared using a solid‐state reaction. X‐ray diffraction analysis and Rietveld structure refinement are used to check the phase purity and crystal structure of the prepared samples. Ce³⁺‐ and Eu²⁺‐doped phosphors both have broad excitation and emission bands, owing to the spin‐ and orbital‐allowed electron transition between the 4f and 5d energy levels. By co‐doping the KBaSc₂(PO₄)₃:Eu²⁺ and KBaSc₂(PO₄)₃:Ce³⁺ phosphors with Tb³⁺ ions, tunable colors from blue to green can be obtained. The critical distance between the Eu²⁺ and Tb³⁺ ions is calculated by a concentration quenching method and the energy‐transfer mechanism for Eu²⁺→Tb³⁺ is studied by utilizing the Inokuti–Hirayama model. In addition, the quantum efficiencies of the prepared samples are measured. The results indicate that KBaSc₂(PO₄)₃:Eu²⁺,Tb³⁺ and KBaSc₂(PO₄)₃:Ce³⁺,Tb³⁺ phosphors might have potential applications in UV‐excited white‐light‐emitting diodes.     

Ambient‐Pressure Stabilization of β‐GdB3O6 by Doping with Bi3+ and Color‐Tunable Emissions by Co‐Doping with Tb3+ and Eu3+: The First Photoluminescence Study of a High‐Pressure Polymorph

Rare‐earth borates are good candidates for optical applications. To date, however, the high‐pressure/high‐temperature technique has produced a large number of novel borates with optical properties that have rarely been investigated due to the severe problem of substantial defects. We targeted the high‐pressure polymorph of β‐GdB₃O₆ and synthesized three solid solutions of β‐Gd_0.75−x Bi_0.25Tb_x B₃O₆ (0≤x ≤0.75), β‐Gd_0.75−y Bi_0.25Eu_y B₃O₆ (0≤y ≤0.75), and β‐Gd_0.50−z Bi_0.25Tb_0.25Eu_z B₃O₆ (0≤z ≤0.05) by using typical solid‐state reactions at 820 °C. Here, the function of Bi³⁺ is to stabilize the high‐pressure phase by lowering the synthetic temperature and being the sensitizer to promote the green and red emissions of Tb³⁺ and Eu³⁺. The multiple energy transfer paths were investigated by using lifetime decay experiments and photoluminescent spectra, and both efficiency and mechanism were determined. Eventually, color‐tunable and white emissions were achieved by rational doping of Bi³⁺, Tb³⁺, and Eu³⁺ into β‐GdB₃O₆, that is, the CIE chromaticity coordinate for β‐Gd_0.44Bi_0.25Tb_0.30Eu_0.01B₃O₆ is (0.318, 0.365) with a correlated color temperature of 6101 K.     

The luminescence of mercury-like ions in and the crystal structure of SrLaBO4

The crystal structure of SrLaBO₄ contains triangular borate groups. The luminescence of mercury-like ions (Sn²⁺, Sb³⁺, Tl⁺, Pb²⁺, Bi³⁺) in this host lattice is characterized by a large Stokes shift. The Pb²⁺ is a very efficient activator at room temperature. The luminescent properties are discussed in terms of earlier models related to an off-center position of the metal ion. The emission of Eu³⁺ shows that the crystal structure has a disordered nature and confirms an off-center position. Energy transfer from Pb²⁺ to Eu³⁺ and Tb³⁺ was studied and found to be inefficient.     

Mono- and Mixed Metal Complexes of Eu3+, Gd3+, and Tb3+ with a Diketone,Bearing Pyrazole Moiety and CHF2-Group: Structure,Color Tuning,and Kinetics of Energy Transfer between Lanthanide Ions

Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely [LnL₃(H₂O)₂], Ln = Eu, Gd and Tb, were synthesized, and, according to single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes [Eu_xTb_1-xL₃(H₂O)₂] (Eu_xTb_1-xL₃), [EuxGd_1-xL₃(H₂O)₂] (Eu_xGd_1-xL₃), and [Gd_xTb_1-xL₃(H₂O)₂] (Gd_xTb_1-xL₃), were studied. The Eu_xTb_1-xL₃ complexes exhibit the simultaneous emission of both Eu³⁺ and Tb³⁺ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu³⁺. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb³⁺ and Eu³⁺ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.     

Synthesis,Persistent Luminescence,and Thermoluminescence Properties of Yellow Sr3SiO5:Eu2+,RE3+ (RE=Ce,Nd, Dy,Ho, Er,Tm, Yb) and Orange‐Red Sr3−xBaxSiO5:Eu2+, Dy3+ Phosphor

Sunlight‐excitable orange or red persistent oxide phosphors with excellent performance are still in great need. Herein, an intense orange‐red Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ persistent luminescence phosphor was successfully developed by a two‐step design strategy. The XRD patterns, photoluminescence excitation and emission spectra, and the thermoluminescence spectra were investigated in detail. By adding non‐equivalent trivalent rare earth co‐dopants to introduce foreign trapping centers, the persistent luminescence performance of Eu²⁺ in Sr₃SiO₅ was significantly modified. The yellow persistent emission intensity of Eu²⁺ was greatly enhanced by a factor of 4.5 in Sr₃SiO₅:Eu²⁺,Nd³⁺ compared with the previously reported Sr₃SiO₅:Eu²⁺, Dy³⁺. Furthermore, Sr ions were replaced with equivalent Ba to give Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ phosphor, which shows yellow‐to‐orange‐red tunable persistent emissions from λ=570 to 591 nm as x is increased from 0 to 0.6. Additionally, the persistent emission intensity of Eu²⁺ is significantly improved by a factor of 2.7 in Sr_3?xBa_xSiO₅:Eu²⁺,Dy³⁺ (x=0.2) compared with Sr₃SiO₅:Eu²⁺,Dy³⁺. A possible mechanism for enhanced and tunable persistent luminescence behavior of Eu²⁺ in Sr_3?xBa_xSiO₅:Eu²⁺,RE³⁺ (RE=rare earth) is also proposed and discussed.