Efficient Luminescence Properties Research Articles

Structural Phase Transition in 0D (3,5-DMP)2Bi1-xSbxCl5 Metal Halides: Expression of the Lone Pair Effect and Polyhedral Distortion.

Low-dimensional Bi/Sb-based organic-inorganic metal halides (OIMHs) have attracted immense attention from the research community because of their structural diversity and efficient luminescence properties. Further understanding of the relationship between the structure and luminescence properties of these materials is of utmost importance for tuning the luminescence properties for various practical applications. Herein, we have synthesized two lead-free Bi/Sb-based novel OIMHs, (3,5-DMP)2BiCl5 and (3,5-DMP)2SbCl5 [(3,5-DMP) = 3,5-dimethylpiperidine], with zero-dimensional (0D) structures and crystallizing in triclinic (P space group) and monoclinic (P21/c space group) crystal systems, respectively. Both the compounds behave as typical semiconductors with indirect optical band gaps of 3.34 and 3.36 eV for pristine Bi and Sb compounds. These compounds exhibit higher environmental and thermal stability at ambient conditions. Gradual substitution of Sb at the Bi site in (3,5-DMP)2Bi1-xSbxCl5 resulted in the introduction of structural strain due to the significant expression of the lone pair effect, thus leading to a structural transition from the triclinic to monoclinic phase. The effect of the structural phase transition on the optical properties is also studied in (3,5-DMP)2Bi1-xSbxCl5. This work may offer new direction and guidance for exploring various 0D hybrid metal halides and tuning the structures for improvement in the luminescence properties.

Boosting Blue Self-Trapped Exciton Emission in All-Inorganic Zero-Dimensional Metal Halide Cs2ZnCl4 via Zirconium (IV) Doping.

Low-dimensional metal halides with efficient luminescence properties have received widespread attention recently. However, nontoxic and stable low-dimensional metal halides with efficient blue emission are rarely reported. We used a solvothermal synthesis method to synthesize tetravalent zirconium ion-doped all-inorganic zero-dimensional Cs2ZnCl4 for the first time. Bright blue emission in the range of 370 nm-700 nm with a emission maximum at 456 nm was observed in Zr4+:Cs2ZnCl4 accompanied by a large Stokes shift, which was due to self-trapped excitons (STEs) caused by the lattice vibrations of the twisted structure. Simultaneously, the PLQY of Zr4+:Cs2ZnCl4 achieve an impressive 89.67%, positioning it as a compelling contender for future applications in blue-light technology.

Elucidation of the structural features and photoluminescence properties of a hydrothermally-synthesized γ-KEu(MoO4)2 microcrystal phosphor with metastable orthorhombic structure and differences in the luminescence properties by structure transition due to Y3+-dilution

Potassium europium molybdate, KEu(MoO4)2, is an intriguing material known for its efficient luminescence properties attributed to Eu3+ ions and its polymorphic nature.

In Situ TEM/STEM Investigation of Crystallization in Y3Al5O12:Ce at High Temperatures Inside a Transmission Electron Microscope.

Y3Al5O12:Ce (YAG:Ce) phosphors are extensively used in the field of white light-emitting diodes (LEDs) due to their efficient luminescent properties. To optimize the performance of YAG:Ce phosphors, a comprehensive understanding of their synthesis and structural evolution is essential. This paper presents a direct in situ transmission electron microscopy (TEM) /scanning TEM (STEM) investigation on the transformation process of a precursor comprising nanocrystalline CeO2 dispersed in an amorphous Y-Al oxide matrix into crystalline YAG:Ce particles. The study reveals that nanocrystalline CeO2 particles dissolve completely in the Y-Al oxide matrix at a temperature above 900 °C, while YAlO3 (YAP)-type crystalline particles with Al2O3 phase in grain boundaries are observed above 1000 °C. Finally, YAG:Ce-type crystalline particles are formed above 1180 °C. Atomic-resolution energy-dispersive X-ray spectroscopy (EDS) elemental mapping demonstrates that the doped cerium (Ce) atoms occupy the same atomic sites as yttrium (Y). Photoluminescence measurements validate the efficient luminescent properties of the obtained YAG:Ce phosphor.

Efficient resonance energy transfer study of BaClF: Ce3+ to Tb3+

Ce3+/Tb3+ co-doped BaClF luminescent materials with highly efficient green luminescent properties. The phosphor was synthesized by a co-precipitation hydrothermal method, and the structure and morphology of the phosphor were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS). The photoluminescence properties of the prepared products were investigated and the energy transfer efficiencies were calculated for BaClF:3.0 mol% Ce3+, ymol% Tb3+ ( y = 0–0.5). By adjusting the doping concentration of Tb3+ ions in BaClF: Ce3+, Tb3+ phosphors, the luminescent color of the phosphor can be easily changed from blue to green. The Ce3+ and Tb3+ co-doped BaClF phosphor shows strong PL emission in the green region due to the resonance energy transfer from Ce3+ to Tb3+. The energy transfer mechanism of Ce3+ and Tb3+ co-doped BaClF samples was analyzed based on the energy level relationship between Ce3+ and Tb3+. The energy transfer efficiency from Ce3+ to Tb3+ was calculated and found to be up to 89.63%. These results suggest that BaClF: Ce3+, Tb3+ fluorescent material can be a potential green luminescent material for optoelectronic applications.

Coordination-Induced Conformational Control Enables Highly Luminescent Metallo-Cages.

In recent years, luminescent materials have received a great deal of attention due to their wide range of applications. However, exploring a simple solution to overcome the fluorescence quenching resulting from the aggregation of conventional organic fluorophores remains a valuable area of investigation. In this study, we successfully constructed two metallo-cages, namely, SA and SB, through coordination-driven self-assemblies of the triphenylamine (TPA)-based donor L with different diplatinum(II) acceptors LA and LB, respectively. These metallo-cages take advantage of their steric nature and curved conformation to more effectively limit the free rotation of the benzene ring and hinder π-π stacking in the solid state, which successfully inhibited fluorescence quenching and realizing highly efficient luminescent properties. Therefore, this work offers a new design strategy for preparing materials with excellent luminescent properties.

Antimony(III) based hybrid materials toward stable and highly efficient white LED

Zero-dimensional (0D) organic-inorganic hybrid materials have attracted extensive attention due to their facile preparation and excellent optical characteristics. However, achieving superior photophysical properties and excellent stability is still desirable for their practical application. Sb(III)-based metal halides owning 5 S2 lone-pair are prone to form deformable building units, which is beneficial for efficient self-trapped excitons (STE) emission. Herein, a 0D Sb(III)-based metal halides DIPA2SbCl5 (DIPA+ = 4-amino-3,5-diiodopyridin-1-ium) was obtained by solvothermal method at room temperature, which exhibited highly efficient broadband emission at 652 nm with a photoluminescence quantum yield (PLQY) of 87.1% and outstanding stability against moisture. Then, a white-light-emitting diode (WLED) was fabricated by mixing DIPA2SbCl5 with green phosphor ((Sr, Ba)2SiO4: Eu2+) and blue phosphor (BaMgAl10O17:Eu2+), with the CIE coordinates of (0.351, 0.371), a correlated color temperature of 4183 K and a color rendering index of 93.3. This work provides a universal solution to obtain hybrid materials with efficient luminescence properties and potential applications.

Preparation and Applications of Rare-Earth-Doped Ferroelectric Oxides

Ferroelectric oxides possess abundant fascinating physical functionalities, such as electro-optic, acousto-optic, and nonlinear optical characteristics, etc. However, most pristine ferroelectric oxides exhibit no efficient luminescent properties due to the indirect and wide bandgap. Rare-earth-doped phosphors demonstrate advantages such as sharp emission bandwidths, large Stokes shift, high photonstability, and low toxicity. The combination of rare-earth ions and ferroelectric oxides has shown great potential in optical sensing, lighting, solar cells, and other applications. Rare-earth-doped ferroelectric oxides exhibit efficient upconversion or downconversion luminescence in the range of ultraviolet (UV) to near-infrared (NIR) regions. In this article, the preparation process of rare-earth-doped ferroelectric oxides and the preparation methods of thin films are introduced. Their recent applications in optical sensing, lighting, and solar cells are highlighted. The review concludes with a brief summary of all related branches and discusses the potential direction of this field.

Lanthanopolyoxometalate‐Silica Core/Shell Nanoparticles as Potential MRI Contrast Agents

AbstractThe NMR relaxivities of the decatungstolanthanoate core‐shell nanoparticles, prepared by encapsulating [Ln(W5O18)2]9− polyoxometalates (LnPOM) within amorphous silica shells (K9[Ln(W5O18)2]@SiO2), were studied along the Ln series. The relaxivity of GdPOM is slightly higher than for Gd‐DTPA due to second‐sphere relaxation effects, but the values for the other paramagnetic LnPOMs are much smaller due to the short T1e values of their Ln3+‐ions. The NPs have core‐shell spherical structures, with LnPOM‐containing cores with 9.5–28 nm diameters, and 4.0–11.0 nm thick amorphous silica shells. In water suspensions, the NPs have negative zeta potentials (−32.5 to −40.0 mV) and time‐dependent hydrodynamic diameters (31–195 nm) reflecting the formation of aggregates. The relaxivities of GdPOM@SiO2 NPs suspensions (r1=10.97 (mM Gd)−1 s−1, r2=12.02 (mM Gd)−1 s−1, 0.47 T, 25 °C) are considerably larger than for the GdPOM solutions, indicating that their silica shell is significantly porous to water. This increase is limited by the agglomeration of the complexes in the NPs core, limiting their access to water to those at the core surface. Replacing half of the Gd3+ ions by Eu3+ decreases the NPs r1 and r2 relaxivities at 0.47 T to 20 % and 35 % of their initial values, which are still considerable, but does not affect the efficient luminescence properties of the Eu3+ centers. This indicates that the mixed NPs have potential as dual modality MRI/optical imaging contrast agents.

A multivariate luminescent MOF based on dye covalently modification serving as a sensitive sensor for Cr2O72−, CrO42− anions and its applications

In this work, a multivariate metal-organic framework (MOF) (9-1-MOF-253-NH2) with mixed ligands is firstly constructed through solid solution approach under solvothermal conditions. Then, a Rhodamine B (RhB)-functionalized compound (RhB@9-1-MOF-253-NH2) with bright red fluorescence is obtained by covalent post-synthetic modification (PSM). Due to possessing efficient and stable luminescent properties and robust framework, the sensing application of this material (RhB@9-1-MOF-253-NH2) is explored. Remarkably, the water-tolerance and reusable RhB@9-1-MOF-253-NH2 can specifically recognize and detect Cr2O72−/CrO42− based on fluorescence quenching mechanism. Moreover, the sensor shows many excellent sensing performances for Cr2O72−/CrO42− including high selectivity, good anti-jamming ability, great sensitivity (0.863 μM and 0.789 μM, respectively), and fast response speed. More importantly, the RhB@9-1-MOF-253-NH2 can act as a fluorescent probe using for the detection of the Cr2O72−/CrO42− content in milk and tap water samples with good accuracy and sensitivity. Furthermore, the possible sensing mechanisms of RhB@9-1-MOF-253-NH2 towards Cr2O72−/CrO42− are investigated in detail.

Visible and NIR Upconverting Er3+–Yb3+ Luminescent Nanorattles and Other Hybrid PMO‐Inorganic Structures for In Vivo Nanothermometry

AbstractLanthanide‐doped luminescent nanoparticles are an appealing system for nanothermometry with biomedical applications due to their sensitivity, reliability, and minimal invasive thermal sensing properties. Here, four unique hybrid organic–inorganic materials prepared by combining β‐NaGdF4 and PMOs (periodic mesoporous organosilica) or mSiO2 (mesoporous silica) are proposed. PMO/mSiO2 materials are excellent candidates for biological/biomedical applications as they show high biocompatibility with the human body. On the other hand, the β‐NaGdF4 matrix is an excellent host for doping lanthanide ions, even at very low concentrations with yet very efficient luminescence properties. A new type of Er3+–Yb3+ upconversion luminescence nanothermometers operating both in the visible and near infrared regime is proposed. Both spectral ranges permit promising thermometry performance even in aqueous environment. It is additionally confirmed that these hybrid materials are non‐toxic to cells, which makes them very promising candidates for real biomedical thermometry applications. In several of these materials, the presence of additional voids leaves space for future theranostic or combined thermometry and drug delivery applications in the hybrid nanostructures.

The crucial impact of cerium reduction on photoluminescence

Rare earth-based inorganic phosphors are of great interest for solid-state lighting because some of them present very efficient luminescence properties. However, their performances strongly depend on several parameters. For multivalent dopants such as cerium, a widely used activator in the lighting industry, a synthesis in reducing atmosphere is often required to stabilize the dopant in its lower oxidation state. Surprisingly, this crucial step is not much considered, and the presence of the reduced state only is often assumed. However, the presence of the dopants oxidized form has been previously evidenced after such reductions. In this case, a question remains open about the impact of the Ce3+/Ce4+ ratio on the materials optical properties. As an example, different CaSc2O4:Ce samples were prepared and their Ce3+/Ce4+ ratios were probed by diffuse reflection and XANES. The evolution of their photoluminescence properties was investigated to rationalize the progressive reduction of dopants.

A three-dimensional cuprous lead bromide framework with highly efficient and stable thermochromic luminescence properties.

Herein, by using a structural design strategy of incorporating hetrometallic halide blocks, we prepared the first 3D bimetallic halide of [H2DABCO]2Cu6PbBr12 with new topological network based on two types of 6-connected nodes. Remarkably, this 3D framework displays highly efficient thermochromic luminescence from broadband yellow to green light emissions with remarkable stability.

Efficient luminescent properties and cation recognition ability of heavy group 13 element complexes of N2O2- and N2O4-type dipyrrins.

The first mononuclear 1 : 1 complexes of heavy group 13 elements (Ga and In) and N2O2/N2O4-type dipyrrins were synthesized and characterized. The N2O2-type complexes showed efficient luminescent properties even in polar solvents. The N2O4-type complexes exhibited fluorometric responses to alkaline earth metal ions.

Low temperature molten salt synthesis of CeF3 and CeF3:Tb3+ phosphors with efficient luminescence properties

CeF3 and CeF3:Tb3+ particles have been successfully synthesized in a low temperature by the facile molten salt synthesis (MSS) method using NaNO3 and KNO3 as the reaction medium. The phase, morphology, photoluminescence and cathodoluminescence properties of the samples were investigated systematically. The substitution of Tb3+ ions in the CeF3 lattice has a significant influence on the phase, microstructure and photoluminescent intensity. The emission intensity of CeF3: Tb3+ increases with the concentration of Tb3+, reaching a maximum at 20%Tb mol. The excitation peaks suggest the energy transfer from Ce3+ to Tb3+, and the maximal energy transfer rate is estimated to be 98.2%. Under the excitation of the low voltage electron beams, the CeF3:Tb3+ phosphor shows the characteristic emissions of Tb3+ which is similar to the photoluminescence properties. The outstanding luminescence properties make the as-obtained samples highly potential in displays, sensors and telecommunications.

Reaching Biocompatibility with Nanoclays: Eliminating the Cytotoxicity of Ir(III) Complexes.

Cyclometalated IrIII complexes are promising candidates for biomedical applications but high cytotoxicity limits their use as imaging and sensing agents. We herein introduce the use of Laponite as carrier for triplet-emitting cyclometalated IrIII complexes. Laponite is a versatile nanoplatform because of its biocompatibility, dispersion stability and large surface area that readily adsorbs functional nonpolar and cationic molecules. These inorganic-organic hybrid nanomaterials mask cytotoxicity, show efficient cell uptake and increase luminescent properties and photostability. By camouflaging intrinsic cytotoxicity, this simple method potentially extends the palette of available imaging and sensing dyes to any metal-organic complexes, especially those that are usually cytotoxic.

Electrospinning preparation and luminescence properties of Eu2(PBT)3(NO3)3/PMMA composite nanofibers

A new luminescent europium(III) bis-β-diketonate complex, Eu2(PBT)3(NO3)3 (PBT = 1,1-(pyridine-2,6-diyl)bis(4,4,4-trifluoro-1,3-dione), was incorporated into the poly(methylmethacrylate) (PMMA) matrix and formed nanofibers via electrospinning technology. The different characterization techniques were adopted to reveal the effect of Eu2(PBT)3(NO3)3 on the spatial structure and optical properties of the nano-composite fibers obtained. The doping enhances the thermal stability and filament-forming properties for a series of PMMA-supported composite nanofibers Eu/PMMA, and in particular, the doping concentrations of 11 wt% also showed more efficient luminescence properties. Furthermore, the Judd-Ofelt theory was applied in this study to explain the effect of the distribution of Eu2(PBT)3(NO3)3 and the mutual effect of the Eu2(PBT)3(NO3)3 coordination compound and surrounding fractions of PMMA.

Efficient energy transfer and luminescence properties of green–blue emission in Ce/Tb Co-doped Sr3NaY(PO4)3F phosphors

Ce3+ and Ce3+/Tb3+-activated Sr3NaY(PO4)3F phosphors are synthesized by the high temperature solid-state reaction, which can be efficiently excited by near ultraviolet (NUV) light-emitting diode (LED) chips. The X-ray diffraction profiles (XRD), photoluminescence(PL) spectra, the decay curves, thermal properties and energy transfer of the phosphors were systematically investigated in detail. The PL spectrum of Sr3NaY(PO4)3F:Ce3+/Tb3+ shows a broad hump ranging from 300 to 450 nm of Ce3+ ions and characteristic line of Tb3+ ions. The emission intensity of Tb3+ increased and that of Ce3+ decreased with the increase of content of Tb3+. The color of the Sr3NaY(PO4)3F:Ce3+/Tb3+ phosphors can shift from blue to green by varying Tb3+ content. The decay curves of Sr3NaY(PO4)3F:Ce3+/Tb3+ indicated that energy transfer process from Ce3+ to Tb3+ existed in the host and the quadrupole–quadrupole interaction to be demonstrated for energy transfer mechanism. In addition, the Sr3NaY(PO4)3F:Ce3+/Tb3+ phosphor exhibits excellent thermal stability, 90% initial emission intensity still remained at temperatures over 100 °C. The obtained results reveal that Sr3NaY(PO4)3F:Ce3+/Tb3+ phosphors can be served as a green-emitting candidate material for phosphor-converted white-light NUV-LEDs.

Terbium‐Doped Layered Yttrium Hydroxide Nanocone: Controlled Synthesis, Structure Variations, Phase Conversion to Oxide/Oxysulfate Nanocone and Their Luminescence Properties

AbstractIt is demonstrated herein that a series of terbium ions (Tb3+)‐doped layered yttrium hydroxide (LYH:Tb) nanocones (NCs) intercalating dodecyl sulfate (C12H25SO4, DS) anions can be successfully synthesized in large quantities through a facile hydrothermal strategy. The DS anions in the interlayer gallery of LYH:Tb NCs can be readily modified with various anions (such as NO3 −, Cl−, and CH3COO−) through a convenient anion‐exchange procedure. The luminescent properties of LYH:Tb NCs are sensitively influenced by the dopant concentration and the interlayer anions. In particular, the original DS−‐intercalated form and the anion‐exchanged product can be topotactically converted into oxysulfates and oxides with original conical features through a calcination process at 750 °C for 2 h, respectively. Compared with Y2O3:Tb NCs, Y2O2SO4:Tb NCs exhibit efficient luminescent properties due to the stronger deformation of the crystal field. More interestingly, the conical structures also exhibit superior luminescent properties over the lamellar objects, originating from the extreme curvature and perturbation of crystal field, which are promising candidates for potential applications in optical and display devices.

Exploring the optical properties of Vernier phase yttrium oxyfluoride thin films grown by pulsed liquid injection MOCVD.

In this work, we report on the first successful deposition of Vernier phase yttrium oxyfluoride (V-YOF) thin films on Si (100) wafers using pulsed liquid injection metal organic chemical vapor deposition (PLI-MOCVD). The formation of V-YOF has been confirmed by X-ray diffraction measurements and electron probe microanalysis. The infrared phonon modes of V-YOF thin films and their corresponding optical constants as inferred from spectroscopic ellipsometry are reported here for the first time. The V-YOF thin films are featured by a broad absorption band centering around 370-373 cm-1; their refractive index is located between those of YF3 and Y2O3, and which shows an intimate relationship with the oxygen content in the film. The luminescence properties of Er3+ doped V-YOF thin films are finally examined and compared with that of YF3. Our results highlight that the as-deposited V-YOF thin films by PLI-MOCVD serve as promising candidates as efficient host material for spectral conversion for photovoltaic applications.