Bright Red Luminescence Research Articles

Modulated upconversion luminescence of water-dispersed NaErF4@NaYF4 nanoparticles by introducing Tm3+/Ho3+ as energy capture centers under multi-wavelength NIR excitation

Water-dispersed red upconversion nanoparticles (UCNPs) have great application prospects in the biomedical field. Thus, a series of Er3+-based upconversion nanoparticles (Er-UCNPs) with excellent red upconversion luminescence under three-wavelength NIR excitation (808/980/1550 nm) were prepared by a simple thermal decomposition method, and then further functionalized by PAA to achieve good water dispersibility. Compared with NaErF4 bare core, the emission intensity of Er-UCNPs samples doping of 0.5%Tm3+ and 0.5%Ho3+ as energy capture centers was significantly enhanced, and further improved after coating with NaYF4 inert shell. Meanwhile, among all Er-UCNPs@NaYF4 samples, NaErF4@NaYF4 exhibited the highest emission intensity and longest luminescence lifetime due to the efficient suppression of luminescence quenching effect, while NaErF4:0.5%Tm3+@NaYF4 showed highest red luminescence purity owing to the energy transfer process between Tm3+(3H5) and Er3+(4I13/2). The hydrophilic Er-UCNPs@NaYF4@PAA samples still maintained good red luminescence under multi-wavelength excitation. The luminescence enhancement mechanism in Er-UCNPs@NaYF4 was discussed in detail based on spectral characteristics. The as-prepared water-dispersed Er-UCNPs@NaYF4@PAA with bright red luminescence under multi-wavelength NIR excitation will have potential applications in targeted therapy and deep tissue imaging.

Multishell Silver Indium Selenide-Based Quantum Dots and Their Poly(methyl methacrylate) Composites for Application in Red-Light-Emitting Diodes.

In this work, the production of novel multishell silver indium selenide quantum dots (QDs) shelled with zinc selenide and zinc sulfide through a multistep synthesis precisely designed to develop high-quality red-emitting QDs is explored. The formation of the multishell nanoheterostructure significantly improves the photoluminescence quantum yield of the nanocrystals from 3% observed for the silver indium selenide core to 27 and 46% after the deposition of the zinc selenide and zinc sulfide layers, respectively. Moreover, the incorporation of the multishelled QDs in a poly(methyl methacrylate) (PMMA) matrix via in situ radical polymerization is investigated, and the role of thiol ligand passivation is proven to be fundamental for the stabilization of the QDs during the polymerization step, preventing their decomposition and the relative luminescence quenching. In particular, the role of interface chemistry is investigated by considering both surface passivation by inorganic zinc chalcogenide layers, which allows us to improve the optical properties, and organic thiol ligand passivation, which is fundamental to ensuring the chemical stability of the nanocrystals during in situ radical polymerization. In this way, it is possible to produce silver-indium selenide QD-PMMA composites that exhibit bright red luminescence and high transparency, making them promising for potential applications in photonics. Finally, it is demonstrated that the new silver indium selenide QD-PMMA composites can serve as an efficient color conversion layer for the production of red light-emitting diodes.

Circularly polarised luminescence of cholesteric polymer composite with high concentration of europium complex

ABSTRACT A novel method has been developed for fabricating cholesteric liquid crystal polymer composite containing a luminescent europium complex. It involves creating porous cholesteric polymer networks, introducing the europium complex into the pores and encapsulating it through the UV-induced polymerisation of a nematic diacrylate. The resulting composite exhibits bright red luminescence upon excitation by UV light which is strongly circularly polarised. Such materials have potential applications in display technologies, counterfeit protection and other fields.

Thermally activated delayed fluorescence emitters for efficient sensitization of europium(III).

We demonstrate for the first time a unique approach to efficiently sensitize lanthanides(III) using photosensitizer ligands that show thermally activated delayed fluorescence (TADF). TADF ligands have very small singlet (S1) and triplet (T1) excited state energy splitting and S1/T1 energy levels are in optimum energy to the acceptor level of Eu(III) to enable high energy transfer efficiency. The synthesized Eu(III) coordination polymers with TADF ligands showed bright red luminescence with an outstanding sensitization efficiency of 90-94% and Φtot of 79-85% in poly(methyl methacrylate) encapsulated films. This rational approach of efficiently sensitizing lanthanides with TADF ligands demonstrates their great potential for imaging and optical communications applications.

Dual-mode luminous and afterglow Ca3Al2Ge3O12:Yb3+, Er3+ phosphors for anti-counterfeiting and fingerprint verification

Generally, traditional anti-counterfeiting fluorescent materials usually show a single peak under single wavelength excitation, which cannot meet the security of authentication information. Therefore, the simultaneous realization of multicolor, multiexcitation and multimodal luminescence properties remains a fascinating goal, especially in a single host. In this work, the sustained luminescent materials Ca3Al2Ge3O12:Yb3+, Er3+ (CAG:Yb3+, Er3+) were obtained, which can exhibit bright red and green luminescence with Er3+ ions under the 490 nm and near-infrared (980 nm) light excitation. The red emission dominates under the 980 nm laser irradiation, and the sample showed excellent photoluminescence (PL) and persistent luminescence (PersL) performance under the 490 nm irradiation, and the afterglow can exceed 6h. The up-conversion mechanism and emission properties of the phosphors were analytically studied, and some fluorescence-safe anti-counterfeiting patterns and multifunctional latent fingerprint (LFP) afterglow time imaging were designed as potential applications for anti-counterfeiting aspects and information storage.

Understanding and Effective Tuning of Red‐to‐Green Upconversion Emission in Ho‐Based Halide Double Perovskite Microcrystals

AbstractHo‐based lead‐free double perovskite microcrystals (MCs), Cs2NaHo1‐xYbxCl6, are synthesized and demonstrated to be promising optical temperature sensing materials by understanding the concentration‐dependent upconversion (UC) luminescence mechanisms. By optimizing the dopant concentration, a dominant emission shifting from red to green is successfully achieved in an activator‐rich system. During this process, the red to green emission intensity ratio (R/G) can be changed from 12.5 (pure red light) to 0.14 (pure green light). It is clarified that the cross‐relaxation (CR) process between activator and the energy transfer process between Yb3+ and Ho3+ are the key mechanisms of UC luminescence intensity and R/G ratio variation. Moreover, the intensity of red and green UC emission shows strong dependence on temperature, resulting from the competition between CR and energy transfer in the emission levels. The high‐sensitivity Ho‐based thermometer can be obtained by Cs2NaHo0.99Yb0.01Cl6 MCs with bright red UC luminescence, whose fluorescence intensity ratio thermometer gains maximum relative sensitivities reaching 0.68% K−1 at 400 K. The multicolor UC luminescence quantitative modeling mentioned here is crucial for understanding the concentration‐dependence UC luminescence characteristics and to optimize the design of the Ho‐based thermometer. This study can be an extension of the application range for perovskite UC materials.

Bright Red Luminescence from Ag–In–Ga–S-Based Quantum Dots with the Introduction of Copper

Abstract This study presents cadmium-free, red-emission quantum dots (QDs) synthesized by incorporating Cu into silver indium gallium sulfide/gallium sulfide (Ag–In–Ga–S/Ga–S) core/shell QDs. By using a previous technique, in which the original Ag–In–Ga–S/Ga–S core/shell QDs exhibiting band-edge photoluminescence (PL) were improved to achieve a narrower emission and facile synthesis, we injected a mixture of Cu and Ag sources into a heated solution containing In, Ga, and S sources. This resulted in the formation of Ag–Cu–In–Ga–S quinary QDs without any precipitation. After being coated with a Ga–S shell, these QDs exhibit a red PL with a spectral full-width at half maximum of 55–60 nm. Although the PL wavelength was responsive to changes in In/Ga ratios, it was unaffected by variations in Cu/Ag ratios due to the transition between conduction band electrons and holes localized at Cu cites. Notably, the electroluminescence device exhibited high-purity red light that satisfies the recommendation ITU-R BT.2020 standard.

Synthesis of a europium complex with ultrahigh quantum yield and its application as an invisible luminescent additive in pigments for preservation of cultural relics

A europium coordination compound [Eu2(ppip)2(PhCOO)6] (ppip is 1,2-diphenylimidazo[4,5-f][1,10]phenanthroline) has been synthesized and structurally characterized. In this symmetric dinuclear complex of octa-coordinated Eu(III) atom, both hanging phenyl rings in the ppip are twisted dramatically from the imidazophenanthroline part, leading to strong edge-to-face (T-type) C–H∙∙∙π interaction. This pale yellow stable complex possesses an ultrahigh luminescence quantum yield (84.2 ± 0.2%) under excitation at 365 nm, and hence is explored to be utilized in the preservation pigments for traditional Chinese paintings as an luminescent additive, which looks invisible under normal light, but exhibits bright red luminescence under UV excitation at a rather low percentage (0.02% wt).

Facile preparation of dihydrolipoic acid-stabilized red-emitting silver nanoclusters as a sensitive fluorometric probe for sulfide ions detection

In this work, we report a smartphone-integrated paper-based sensor for the determination of sulfide ions (S2−) using water-soluble dihydrolipoic acid stabilized silver nanoclusters (DHLA-AgNCs) as a nanoprobe. The optical properties of red emitting fluorescent DHLA-AgNCs was confirmed by UV–visible, steady state flourometric spectroscopic studies. The HR-TEM analysis revealed that the morphology of DHLA-AgNCs was quasi spherical with a grain size of ∼ 5.2 nm. The DHLA-AgNCs exhibited bright red luminescence with strong emission band centered at 650 nm upon the excitation at 420 nm. The excellent fluorescence property of DHLA-AgNCs was further utilized for fluorometric determination of S2− ions. The DHLA-AgNCs can be effectively quenched by increasing concentration of S2− ions owing to the formation of Ag2S complex. The DHLA-AgNCs probe could detect S2− ions preferentially even in the presence of other possible interfering anions with a limit of detection of 32.71 nM. In addition, the proposed technique was effectively used to detect S2− ions in environmental water samples such as tap and drinking water. The detect S2− ions detection was assay and showed good agree compared with the conventional methylene blue approach and showed comparable results. Moreover, a smartphone-paper-based detection assay was developed using the DHLA-AgNCs probe for highly selective and sensitive determination of S2− ions.

Controlling Factors of Meteoric Diagenesis in Karst Reservoirs: An Example from the Majiagou Formation, Ordos Basin, China

Karst reservoirs have always been a key field of oil and gas exploration. However, quantifying the process of meteoric transformation remains a persistent challenge that limits the accuracy of reservoir quality prediction. To explore the controlling factors of meteoric cementation on karst reservoirs, the Majiagou Formation of the Ordos Basin in China was selected as an example. The petrology; carbon, oxygen, and strontium isotopes; and in situ major, trace, and rare earth elements were used, types and origins of calcite cements were analyzed in detail. The results revealed five types of calcite cements (Cal-1~Cal-5), four types of cathodoluminescence (CL) intensities (dull, dull red, deep red, and bright red luminescence), and six types of rare earth element patterns (Pattern-1~Pattern-6). These five types of calcite cements developed in three periods. Cal-1 (transition CL) and Cal-2 (dull CL) were precipitated during the Early Pennsylvanian period, the meteoric freshwater was clean; Cal-3 (transition CL) and Cal-4 (bright red CL) were precipitated at the end of the Late Carboniferous period, the fluids had strong dissolution ability and were polluted by terrigenous debris; Cal-5 (transition CL) was deposited during the burial period, the fluid was pure pore water or groundwater. The control of the cement on the reservoir during the burial period was much weaker than that of meteoric cements. Therefore, explorations of karst reservoirs should be focused on weak cementation during the epigenetic period.

Intrinsic- and Rare Earth Ion-Activated Luminescence in NbAlO4 with Wide Structure Channels.

Compounds with ordered and interconnected channels have versatile multifunctional applications in technological fields. In this work, we report the intrinsic- and Eu3+-activated luminescence in NbAlO4 with a wide channel structure. NbAlO4 is an n-type semiconductor with an indirect allowed transition and a band-gap energy of 3.26 eV. The conduction band and valence band are composed of Nb 3d and O 2p states, respectively. Unlike the common niobate oxide Nb2O5, NbAlO4 exhibits efficient self-activated luminescence with good thermal stability even at room temperature. The AlO4 tetrahedron effectively blocks the transfer/dispersion of excitation energy between NbO6 chains in NbAlO4, allowing for effective self-activated luminescence from NbO6 activation centers. Moreover, Eu3+-doped NbAlO4 displayed a bright red luminescence of 5D0 → 7F2 transition at 610 nm. The site-selective excitation and luminescence of Eu3+ ions in a spectroscopic probe were utilized to investigate the doping mechanism. It is evidenced that Eu3+ is doped in the structure channel in NbAlO4 lattices, not in the normal cation sites of Nb5+ or Al3+. The experimental findings are valuable in developing new luminescent materials and improving the understanding of the material's channel structure.

Highly Luminescent Europium(III) Complexes in Solution and PMMA-Doped Films for Bright Red Electroluminescent Devices.

This paper reports the synthesis, structure, photophysical, and optoelectronic properties of five eight-coordinate Europium(III) ternary complexes, namely, [Eu(hth)3(L)2], bearing 4,4,5,5,6,6,6-heptafluoro-1-(2-thienyl)-1,3-hexanedione (hth) as a sensitizer and L = H2O (1), dpso (diphenyl sulphoxide, 2), dpsoCH3 (4,4'-dimethyl diphenyl sulfoxide, 3), dpsoCl (bis(4-chlorophenyl)sulphoxide, 4), and tppo (triphenylphosphine oxide, 5) as co-ligands. The NMR and the crystal structure analysis confirmed the eight-coordinate structures of the complexes in solution and in a solid state. Upon UV-excitation on the absorption band of the β-diketonate ligand hth, all complexes showed the characteristic bright red luminescence of the Europium ion. The tppo derivative (5) displayed the highest quantum yield (up to 66%). As a result, an organic light-emitting device, OLED, was fabricated with a multi-layered structure-ITO/MoO3/mCP/SF3PO:[complex 5] (10%)/TPBi:[complex 5] (10%)/TmPyPB/LiF/Al-using complex 5 as the emitting component.

Influence of Ancillary Ligand on the Photosensitization and Photophysical Properties of Red Luminescent Tri-fluorinated Β-diketonate Eu(III) Complexes.

Highly emissive ternary Eu(III) complexes were synthesized with a tri-fluorinated β-diketone as principal ligand and heterocyclic aromatic compounds as ancillary ligands to assess their utility as an illuminating material for display devices and other optoelectronics.The general characterizations, regarding the coordinating facets of complexes were accomplished via various spectroscopic techniques. Thermal stability was investigated via TGA/DTA. Photophysical analysis was accomplished by PL studies, Band gap value, color parameters and J-O analysis. DFT calculations were performed adopting geometrically optimized structure of complexes.Superb thermal stability has been achieved in complexes, which decides their concrete candidature for display devices. The bright red luminescence of complexes is ascribed to 5D0 → 7F2 transition of Eu(III) ion. Colorimetric parameters unlocked the applicability of complexes as warm light source and J-O parameters adequately summarized the coordinating surrounding around the metal ion. Various radiative properties were also evaluated which suggested the prospective use of complexes in lasers and other optoelectronic devices. The band gap and Urbach band tail, procured from absorption spectra, revealed the semiconducting behavior of synthesized complexes. DFT studies rendered the energies of FMO and various other molecular parameters.It can be summarized from the photophysical and optical analysis of synthesized complexes that these complexes are virtuous luminescent materials and possess potentiality to be used in diverse domain of display devices.

Ultrahighly Efficient Narrowband Red Luminescence of Uniquely Distorted Mn4+ Octahedron in the Feldspar‐Type LED Phosphor

AbstractThe mineral structure‐inspired discovery of red phosphors has become a research hotspot that can help compensate for the missing red components in cold white light‐emitting diodes (WLEDs). Herein, first the feldspar‐type structure is utilized to develop narrowband red‐emitting CaAl2Si2O8:Mn4+/Mn4+, Mg2+ phosphors. Rietveld refinement results confirm the Mn4+ occupation of the distorted [Ca1O6] octahedron, resulting in a strong nephelauxetic effect, and thus exhibits bright red luminescence with a narrow full width at half maximum (43 nm). Compared with CaAl2Si2O8:Mn4+, the fluorescence intensity of CaAl2Si2O8:Mn4+, Mg2+ is further enhanced by up to 210% owing to the decreasing nonradiative decay rate from 2Eg excited state, which weakens the concentration quenching effect resulting from energy migration along the adjacently aggregated Mn4+. CaAl2Si2O8:Mn4+, Mg2+ shows preferable thermal stability with an ultrahigh quantum efficiency (90.3%), surpassing other current Mn4+‐doped oxide phosphors and UCr4C4‐type nitride phosphors. A fabricated prototype WLED obtains ideal warm white light with a low correlated color temperature (3081 K) and a wide color gamut covering 112% of the National Television System Committee standard. Guided by natural mineral‐type structural prototypes, this study demonstrates the possibility of designing a uniquely distorted local structure to achieve a superior luminescence performance of Mn4+ for warm WLEDs.

Construction of self-sensitized NaErF4@NaYF4 nanoparticles with multiple red upconversion luminescence for highly-sensitive optical temperature sensing

Efficient deep-penetrating red upconversion luminescent nanoparticles with ultra-small size are promising biological temperature probes. Herein, bright red upconversion luminescence are achieved in NaErF4@NaYF4 core-shell nanoparticles under multi-wavelength excitation of 808 nm, 980 nm, and 1550 nm. The core-shell structure engineering is constructed to minimize energy dissipation by surface quenchers. Furthermore, the established model explains the temperature dependence of thermally coupled energy levels in detail, confirming that the non-radiative relaxation is responsible for the quenching processes. Based on the luminescence intensity ratio technique, optical temperature sensing characteristics of thermally coupled (2H11/2/4S3/2) and non-thermally coupled energy levels (4F9/2/4S3/2) are investigated under the excitation of a relatively safe near-infrared wavelength for 1550 nm. The thermometer can maintain a maximum sensitivity of 35 × 10−3 K−1 over the entire temperature measurement region by fitting the non-thermally coupled energy levels, which is conducive to temperature monitoring in vivo due to high sensitivity and relatively safe excitation wavelength.

Controllable Fabrication of Organic Cocrystals with Interior Hollow Structure Based on Donor-Acceptor Charge Transfer Molecules

Fluorescent hollow organic molecular cocrystals comprised of (E)-4-(2(anthracen-9-yl)vinyl)pyridine-1,2,4,5-tetracyanobenzene (APE-TCNB) were prepared via a surfactant-mediated co-precipitation method. The size and morphology of these cocrystals could be easily tuned by varying the type and concentration of the surfactant, incubation time, and temperature. Moreover, optical fluorescence and scanning electron microscopy characterization indicated that the APE-TCNB microcrystals contained two symmetric empty cavities when 3-(N, N-dimethyldodecylammonio)propane sulfonate (BS12) was used as the surfactant. The cross-polarized microscope and powder X-ray diffraction (PXRD) measurements both showed that the prepared microcrystals exhibited high crystallinity. APE and TCNB molecules were found to align parallelly along the crystallographic a-axis in the crystal lattice, and the strong π–π intermolecular interactions facilitated the formation of unique crystal chambers. A series of measurements and characterization, including UV-Vis absorption spectroscopy, infrared spectroscopy, steady-state, and time-resolved fluorescence spectroscopy, also verified that strong charge–transfer (CT) interactions had been established in the APE-TCNB microcrystals. Moreover, these APE-TCNB microcrystals could emit bright red luminescence, which extended to the near-infrared region (~800 nm), displaying a strong charge-transfer property. Here, we have shown a general facile way to make organic cocrystals with complex structures and topologies using a self-assembly method.

Layered Gadolinium-Europium-Terbium Hydroxides Sensitised with 4-Sulfobenzoate as All Solid-State Luminescent Thermometers

Ternary layered gadolinium-europium-terbium basic chlorides were synthesised using a facile hydrothermal-microwave technique. A continuous series of solid solutions was obtained in a full range of rare earth concentrations. To sensitise the luminescence of Eu3+ and Tb3+, a 4-sulfobenzoate anion was intercalated in the ternary layered rare earth hydroxides using one of two methods—a high-temperature ion exchange or a single-stage synthesis. The luminescent colour of the materials was governed by the gadolinium content: at low and medium gadolinium concentrations (0–70%), layered Gd-Eu-Tb basic sulfobenzoate exhibited a bright red europium luminescence; at high gadolinium content (70–90%), a bright green terbium luminescence was observed. The colour coordinates of layered Gd-Eu-Tb basic sulfobenzoate luminescence depended on the temperature in the physiological range (20–50 °C). The relative thermal sensitivity of the obtained materials was up to 2.9%·K−1.

Zero-dimensional antimony(III) halides templated by ruthenium complexes: photoluminescence, thermochromism and photo/electrical performances

Zero dimensional antimony(III) halides have captured more and more attention as broadband emitters. Herein, Using photochemically active ruthenium complexes as templates, two new antimony(III) halide based hybrids have been prepared and structurally determined, i.e., [Ru(bipy)3](Sb2Cl6O) (1) and [Ru(phen)3](SbI5) (2). Both the (Sb2Cl6O)2- and (SbI5)2-are rare examples of antimony halides, in which Sb centers are in square pyramidal environments with stereochemically active lone pairs. The (Sb2Cl6O)2- ion bearing secondary Sb···Cl interactions are further stabilized by C-H···Cl hydrogen bonds to give a quasi-3D network. The (SbI5)2- anions are anchored in the 1D[Ru(phen)3]n 2n+ chains based on strong π···π stacking interactions among phenanthroline ligands, which are the reason for the formation of its square pyramid geometry.1 exhibits bright red luminescence but 2produces weak blue emission. This trend might be assigned to the larger conjugated system of phenanthroline in 2, which is dominant by ruling out the contribution of antimony(III) halide. Besides, reversible thermochromism can be found in 1. Furthermore, good electrical chemical and photocurrent performance can be detected. The photoluminescence modulation by controlling the conjugated degree of organic ligands is an efficient strategy for the precise preparation of new luminescent materials.

Synthesis and photoluminescence characterization of the complexes of samarium dibenzoylmethanates with 1,10-phenanthroline derivatives

The eight coordinated complexes of samarium were synthesized with dibenzoylmethane (DBM) and bidentate auxiliary ligand. Ternary complexes of samarium of the type [Sm(DBM)3L] (L = 1,10-Phenanthroline or its derivatives) were prepared by one step method. These complexes were characterized by spectroscopic techniques and thermo-gravimetric analysis. The proton-NMR data of all the complexes are reliable with the coordination of three DBM units and one neutral unit. Luminescence spectra of the complexes taken in powdered form, illustrate the bright red luminescence at 648 nm upon UV excitation that is accredited to the 4G5/2→6H9/2 transition of Sm3+ ion. The domination of hypersensitive transition corresponding to 648 nm reflects the asymmetric environment around samarium ion and their intensity undergoes significant change on variation in the binding environment about metal ion. The intense luminescence and color coordinates demonstrate that the complexes might be used as promising candidate in displays and light emitting devices.

Synthesis of core-shell nanoparticles based on interfacial energy transfer for red emission and highly sensitive temperature sensing.

Red up-conversion luminescence with both emission and excitation peaks within the "tissue transparency window" makes for ideal fluorescent labels for deep tissue penetration and low-background biological imaging. In this work, an efficient strategy is proposed to realize bright red up-conversion luminescence based on interfacial energy transfer (IET), and the luminescence centers (Er3+ and Tm3+) and sensitizers (Yb3+) are doped in separate layers to avoid deleterious cross-relaxation. The IET process between Yb3+ and Er3+ can enable bright red photon up-conversion under 980 nm excitation via fine control and manipulation of the lanthanide ion concentration and shell thickness. By appropriately employing the fluorescence intensity ratio technique, an optical thermometer based on non-thermally coupled energy levels demonstrates a superior relative sensitivity of 2.02% K-1 across the whole temperature region. NaYF4:Er3+,Tm3+@NaYF4:Yb3+ with strong red UC luminescence and highly sensitive performance exhibits potential for application in the field of non-contact temperature sensing.