Red-emitting Ca Research Articles

Realizing an impressive red-emitting Ca9MnNa(PO4)7 phosphor through a dual function based on disturbing structural confinement and energy transfer

A dazzling red light was achieved in the Ca9MnNa(PO4)7:Eu2+ phosphor based on disturbing structural confinement and energy transfer.

FRET-Based Nanobiosensors for Imaging Intracellular Ca²⁺ and H⁺ Microdomains.

Semiconductor nanocrystals (NCs) or quantum dots (QDs) are luminous point emitters increasingly being used to tag and track biomolecules in biological/biomedical imaging. However, their intracellular use as highlighters of single-molecule localization and nanobiosensors reporting ion microdomains changes has remained a major challenge. Here, we report the design, generation and validation of FRET-based nanobiosensors for detection of intracellular Ca2+ and H+ transients. Our sensors combine a commercially available CANdot®565QD as an energy donor with, as an acceptor, our custom-synthesized red-emitting Ca2+ or H+ probes. These ‘Rubies’ are based on an extended rhodamine as a fluorophore and a phenol or BAPTA (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid) for H+ or Ca2+ sensing, respectively, and additionally bear a linker arm for conjugation. QDs were stably functionalized using the same SH/maleimide crosslink chemistry for all desired reactants. Mixing ion sensor and cell-penetrating peptides (that facilitate cytoplasmic delivery) at the desired stoichiometric ratio produced controlled multi-conjugated assemblies. Multiple acceptors on the same central donor allow up-concentrating the ion sensor on the QD surface to concentrations higher than those that could be achieved in free solution, increasing FRET efficiency and improving the signal. We validate these nanosensors for the detection of intracellular Ca2+ and pH transients using live-cell fluorescence imaging.

Photoluminescence properties of Ca0.99Eu0.01(Mo1−xSix)O4 nanocrystals red-phosphors obtained by the hydrothermal method

Abstract In this paper, we report the obtention of a novel red-emitting Ca 0.99 Eu 0.01 (Mo 1− x Si x )O 4 nanocrystals phosphor synthesized by the hydrothermal method for the first time, and its photoluminescence (PL) properties were investigated for application to white-light-emitting diodes (W-LEDs). The as-synthesized phosphors were characterized by means of X-ray powder diffraction (XRD), transmission electron microscope (TEM), high-resolution transmission electron microcopy (HR-TEM), photoluminescence excitation (PLE) and PL emission spectra. XRD patterns, TEM images and PL emission indicated that the introduction of Si 4+ ions promotes the distortion and slight shrinking of the unit cell, narrow size distribution and the blue-shift of the charge transfer bands of Ca 0.99 Eu 0.01 MoO 4 red-phosphors. PL properties revealed that the optical brightness as well as the intensity ratio of 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 was highly dependent on the Si 4+ ions concentration. The morphological evolution was explained via a crystal growth mechanism. Introduction of 5 mol% Si 4+ ions into the crystal structure enhanced the PL emission brightness, and the nanocrystals Ca 0.99 Eu 0.01 (Mo 0.95 Si 0.05 )O 4 red-phosphors showed the relatively most promising PL performance with the most intense emission. The CIE chromaticity coordinates for nanocrystals Ca 0.99 Eu 0.01 (Mo 1− x Si x )O 4 red-phosphors were simulated and located in the red region. All the results imply that the studied Ca 0.99 Eu 0.01 (Mo 1− x Si x )O 4 nanophosphors could be potentially used as W-LEDs.

Characterization and photoluminescent properties of sol–gel-derived Ca2(1−x)La7.6+x(SiO4)6O2:Eu0.4, Lix phosphors

Abstract Red-emitting Ca 2(1− x ) La 7.6+ x (SiO 4 ) 6 O 2 :Eu 0.4 , Li x (CLS:Eu 0.4 , Li x ) phosphors were synthesized via a citric acid based sol–gel combustion method. The morphologies, crystal structures and optical properties of these phosphors were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), powder X-ray diffraction (PXRD) and photoluminescence (PL) spectroscopy, respectively. The CLS:Eu 0.4 based phosphors readily excited under UV light (387 nm), which makes them promising red-emitting candidates for commercial near-UV light emitting diodes (LEDs)-pumped white LEDs. After doping with Li + ions, the CLS:Eu 0.4 , Li x phosphors exhibited remarkably enhanced photoluminescent performances. Additionally, the emission intensity of CLS:Eu 0.4 , Li x phosphors generated using the sol–gel combustion method was found to be much higher than for those obtained using a solid-state reaction method. This finding indicated the sol–gel combustion method could be considered a versatile route for producing high-quality CLS:Eu 0.4 , Li x phosphors.

Luminescence properties of red-emitting Ca2Al2SiO7:Eu3+ nanoparticles prepared by sol-gel method

A series of red-emitting Ca(subscript 2-x)Al2SiO7:xEu(superscript 3+) (x=1 mol.%-10 mol. %) phosphors were synthesized by the sol-gel method. The effects of annealing temperature and doping concentration on the crystal structure and luminescence properties of Ca2Al2SiO7:Eu(superscript 3+) phosphors were investigated. X-ray diffraction (XRD) profiles showed that all peaks could be attributed to the tetragonal Ca2Al2SiO7 phase when the sample was annealed at 1000℃. Scanning electron microscopy (SEM) micrographs indicate that the phosphors have an irregularly rounded morphology with particles of about 200 nm. Excitation spectra showed that the strong broad band at around 258 nm and weak sharp lines in 350-490 nm were attributed to the charge transfer band of Eu(superscript 3+)-O(superscript 2-)and f-f transitions within the 4f^6 configuration of Eu(superscript 3+) ions, respectively. Emission spectra implied that the red luminescence could be attributed to the transitions from the 5D0 excited level to the 7F(subscript J) (J=0, 1, 2, 3, 4) levels of Eu(superscript 3+) ions with the main electric dipole transition 5D0→7F2(618 and 620 nm), and Eu(superscript 3+) ions prefer to occupy a lower symmetry site in the crystal lattice. Moreover, the photoluminescence (PL) intensity was strongly dependent on both the sintering temperature and doping concentration, and the highest PL intensity was observed at an Eu(superscript 3+) concentration x=7 mol. % after annealing at 1100℃. The obtained Ca2Al2SiO7:Eu(superscript 3+) phosphor may have potential application for the red lamp phosphor.

Synthesis and luminescence properties of a broad-band red phosphor Ca 3Si 2O 7:Eu 2+ for warm white light-emitting diodes

Single-phase broad-band red-emitting Ca 3Si 2O 7:Eu 2+ phosphors, with photoluminescence features that qualify them as candidates for white light-emitting diodes applications, were successfully synthesized via a modified solid-state reaction method that employed H 3BO 3 as a flux. The phosphors produced have an intense broad red emission band, with a peak at 603 nm, a full width at half maximum of 110 nm, and color coordinates of (0.550, 0.438). Concentration quenching occurred at 0.01 mol Eu 2+. The discussion of the results shows that Eu 2+ ions should be accommodated at the Ca-sites of the lattice, dipole–dipole interactions should predominantly govern the energy transfer mechanism among them, and the critical distance between them is ∼31 Å.

Improved luminescent properties of red-emitting Ca 0.54Sr 0.16Eu 0.08Gd 0.12(MoO 4) 0.2(WO 4) 0.8 phosphor for LED application by charge compensation

The red-emitting Ca 0.54Sr 0.16Eu 0.08Gd 0.12(MoO 4) 0.2(WO 4) 0.8 phosphor is improved in the emission charateristics by charge compensation, of which chromaticity coordinates (CIE) are x=0.66 and y=0.33. Three approaches to charge compensation are investigated, namely (a) 3Ca 2+/Sr 2+→2Eu 3+/Gd 3++vacancy, (b) 2Ca 2+/Sr 2+→Eu 3+/Gd 3++M +(M + is a monovalent cation like Li +, Na + and K + employed as a charge compensator) and (c) Ca 2+/Sr 2+→Eu 3+/Gd 3++N − (N − is a monovalent anion like F −, Cl −, Br − and I − employed as charge compensation ions). Through photoluminescent spectra analyzing the radiative and non-radiative relaxation mechanisms of luminescent system are obtained. Under 20 mA forward-bias current, one red-emitting LED is made by combining 390–405 nm-emitting LED chip and the phosphor. The red-emitting phosphor has broad prospects in LED application field.

A red-emitting Ca 8MgLa(PO 4) 7:Ce 3+,Mn 2+ phosphor for UV-based white LEDs application

Ca 8MgLa(PO 4) 7:Ce 3+,Mn 2+ phosphors have been prepared by a conventional solid state reaction under a weak reductive atmosphere. The crystal structure and photoluminescent properties were investigated. It was found that the red emission at 640 nm originated from the 4T 1( 4G) → 6A 1( 6S) transition of Mn 2+ increases dramatically by a factor of 6.4 with the optimum Ce 3+ co-doping. The energy transfer from Ce 3+ to Mn 2+ was proposed to be resonance-type via an electric dipole-dipole mechanism and the energy transfer efficiency was also calculated by the relative emission intensity. With the broadband ultraviolet (UV) absorption of Ce 3+ and the suitable color coordinates, Ca 8MgLa(PO 4) 7:Ce 3+,Mn 2+ phosphors might be a promising candidate as red phosphors in the field of UV-based white light-emitting diodes.

Synthesis and luminescence of Ca 4YO(BO 3) 3:Eu 3+ for fluorescent lamp application

The red-emitting Ca 4YO(BO 3) 3:Eu 3+ phosphor has been prepared at 1200 °C by the simple solid-state reaction. This preparation temperature is much lower than Y 2O 3:Eu 3+ (1400–1500 °C) for conventional solid-state reaction method. In particular, the complete process to produce high-quality phosphor particles was carried out through the single-step heat treatment of the mixture of corresponding oxide-type metal sources. For this material, the XRD, PL, PL excitation (PLE) and SEM features have also been investigated. The X-ray diffraction data indicate that pure phase of Ca 4YO(BO 3) 3:Eu 3+ can be successfully obtained. Among the different emission transitions 5D 0 → 7F J =0, 1, 2, 3, 4 of this phosphor, one particular transition ( 5D 0 → 7F 2) at 610 nm has been found. Besides carrying out these essential measurements, we have also made an attempt to observe a strong red emission performance displayed by this phosphor for use as coating material on compact fluorescent lamps (CFLs). The results clearly indicate that the life time based on Ca 4YO(BO 3) 3:Eu 3+ was found to be much longer than that using Y 2O 3:Eu 3+. The good performances of the CFLs demonstrate that this phosphor may be suitable for application on short ultraviolet fluorescent lamp.

Luminescence Properties of Ca(Y0.915−xGdxAl0.025Eu0.06)BO4 Phosphors Under VUV Irradiation

The major phase of post-treated Ca(Y(0.915-x)Gd(x)A10.025Eu0.06)BO4 (0 < or = x < or = 0.3) phosphors was solid solutions of the constituent oxides, which had an orthorhombic warwickite-like structure. The calculated crystallite size of the Ca(Y(0.915-x)Gd(x)Al0.025Eu0.06)BO4 phosphors was approximately 36 nm. The Gd additive significantly enhanced both the charge transfer (CT) transition of O2(-) -Eu3+ and the absorption of the host materials, thereby resulting in an increase in emission intensity. The Ca(Y(0.715)Gd0.2Al0.025Eu0.06)BO4 phosphor showed the highest emission intensity at 593 nm, which was over five times as strong as that of a Gd-free Ca(Y0.915Al0.025Eu0.06)BO4 phosphor. The addition of Gd was desirable for improving the photoluminescent properties of red-emitting Ca(Y0.915Al0.025Eu0.06)BO4 phosphors.