Epitaxial Synthesis of Uniform Cerium Phosphate One-Dimensional Nanocable Heterostructures with Improved Luminescence

Effect of Dopant Concentration on Luminescence Properties of Na3Ca2(SO4)3F: RE (RE = Eu3+, Dy3+) Phosphor for Solid-State Lighting

A fluoride material phosphor doped with rare earth ions Eu3+ and Dy3+ was studied for its photoluminescence (PL) properties. The material was synthesized using a combustion method and characterized using X-ray diffraction (XRD) and PL techniques. The Na3Ca2(SO4)3F: Eu3+ phosphor exhibits two distinct peaks at 593 nm (orange) and 615 nm (red) at an excitation wavelength of 395 nm. The PL excitation spectrum of the Na3Ca2(SO4)3F: Dy3+ phosphor showed series of peaks, corresponding to the 4f → 4f transitions of Dy3+ ions. Under 350-nm excitation, the PL emission spectrum revealed two prominent bands one at 483 nm (blue region) due to the 4F₉/₂ → 6H₁₅/₂ transition, and another at 573 nm (yellow region) resulting from the 4F₉/₂ → 6H₁₃/₂ transition. These blue and yellow emissions suggest potential applications in solid-state lighting, particularly for mercury-free excitation sources. Rare earth-doped Eu3+/Dy3+ materials exhibit highly efficient PL properties, making them suitable candidates for white light-emitting diodes (LEDs) or other solid-state lighting phosphors.

Structural, morphological, and photoluminescence properties of RE (RE = Dy3+ , Eu3+ , Sm3+ )-doped CaAlBO4 phosphor synthesized by combustion method

The CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor were prepared via combustion synthesis and studied by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) analysis, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectra and CIE coordinates. The phase formation of the obtained phosphor was analyzed by XRD and the result was confirmed by standard PDF Card No. 1539083. XRD data successfully indicated pure phase of CaAlBO4 phosphor. The crystal structure of CaAlBO4 phosphor is orthorhombic with space group Ccc2 (37). The SEM image of CaAlBO4 phosphor reveals an agglomerated morphology and non-uniform particle size. The EDS image provides evidence of the elements present and the chemical makeup of the materials. Under the 350 nm excitation, the emission spectrum of Dy3+ activated CaAlBO4 phosphor consists of two main groups of characteristic peaks located at 484 and 577 nm which are ascribed to 4 F9/2  → 6 H15/2 and 4 F9/2  → 6 H13/2 transition of Dy3+ respectively. The PL emission spectra of CaAlBO4 :Eu3+ phosphor shows characteristics bands observed around 591 and 613 nm, which corresponds to 5 D0  → 7 F1 and 5 D0  → 7 F2 transition of Eu3+ respectively, upon 395 nm excitation wavelength. The emission spectra of Sm3+ activated CaAlBO4 phosphor shows three characteristic bands observed at 565, 601 and 648 nm which emits yellow, orange and red color. The prominent emission peak at the wavelength 601 nm, which is attributed to 4 G5/2  → 6 H7/2 transition, displays an orange emission. The CIE color coordinates of CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor are calculated to be (0.631, 0.368), (0.674, 0.325) and (0.073, 0.185). As per the obtained results, CaAlBO4 :RE (RE = Dy3+ , Eu3+ , Sm3+ ) phosphor may be applicable in eco-friendly lightning technology.

Wet chemical synthesis of BiPO4 : Eu3+ phosphor for W-LED application

The synthesis of BiPO₄ : Eu³⁺ phosphors has been achieved via a wet chemical process. X-ray diffraction patterns show that the phase of as-prepared samples matches very well with the standard BiPO₄ structure. At 395 nm, the highest excitation intensity was observed. Following 395 nm excitation, two characteristic emission peaks at 592 nm and 616 nm were shown. At 0.5 mole percent of Eu³⁺ ions, concentration quenching occurred. The particle size is within the micrometer range, according to the SEM magnification. The chromaticity coordinates for wavelengths 592 nm and 616 nm are (X=0.586, Y=0.412) and (X=0.682, Y=0.317), respectively. The findings imply that prepared phosphor may be used to create white LEDs.

Bioinspired crystallization, sensitized luminescence and cytocompatibility of citrate-functionalized Ca-substituted europium phosphate monohydrate nanophosphors

Biocompatible nanosystems exhibiting long-lifetime (∼millisecond) luminescence features are particularly relevant in the field of bioimaging. In this study, citrate-functionalized calcium-doped europium phosphates nanophosphors of the rhabdophane type were prepared at different synthesis times by a bioinspired crystallization route, consisting in thermal decomplexing of Ca²⁺/Eu³⁺ /citrate/phosphate/carbonate solutions. The general formula of this material is Ca_αEu_1-α(PO₄)_1-α(HPO₄)_α·nH₂O, with α ranging from 0 to 0.58 and n ∼ 1. A thorough characterization of the nanoparticles has been carried out by XRD (including data processing with Topas 6.0), HR-TEM, TEM, FTIR, TG/DTA, ICP, dynamic light scattering (DLS), electrophoretic mobility, and fluorescence spectroscopy. Based on these results a crystallization mechanism involving the filling of cationic sites with Ca²⁺ions associated to a concomitant adjustment of the PO₄/HPO₄ ratio was proposed. Upon calcium doping, the aspect ratio of the nanoparticles as well as of the crystalline domains decreased and the relative luminescence intensity (R.L.I.) could be modulated. Neither the pH nor the ionic strength, nor the temperature (from 25 to 37 °C) affected significantly the R.L.I. of particles after resuspension in water, leading to rather steady luminescence features usable in a large domain of conditions. This new class of luminescent compounds has been proved to be fully cytocompatible relative to GTL-16 human carcinoma cells and showed an improved cytocompatibility as the Ca²⁺ content increased when contacted with the more sensitive m17. ASC murine mesenchymal stem cells. These biocompatible nanoparticles thus appear as promising new tailorable tools for biomedical applications as luminescent nanoprobes.

Transcription of Nanofibrous Cerium Phosphate Using a pH-Sensitive Lipodipeptide Hydrogel Template

A novel and simple transcription strategy has been designed for the template-synthesis of CePO₄·xH₂O nanofibers having an improved nanofibrous morphology using a pH-sensitive nanofibrous hydrogel (glycine-alanine lipodipeptide) as structure-directing scaffold. The phosphorylated hydrogel was employed as a template to direct the mineralization of high aspect ratio nanofibrous cerium phosphate, which in-situ formed by diffusion of aqueous CeCl₃ and subsequent drying (60 °C) and annealing treatments (250, 600 and 900 °C). Dried xerogels and annealed CePO₄ powders were characterized by conventional thermal and thermogravimetric analysis (DTA/TG), and Wide-Angle X-ray powder diffraction (WAXD) and X-ray powder diffraction (XRD) techniques. A molecular packing model for the formation of the fibrous xerogel template was proposed, in accordance with results from Fourier-Transformed Infrarred (FTIR) and WAXD measurements. The morphology, crystalline structure and composition of CePO₄ nanofibers were characterized by electron microscopy techniques (Field-Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy/High-Resolution Transmission Electron Microscopy (TEM/HRTEM), and Scanning Transmission Electron Microscopy working in High Angle Annular Dark-Field (STEM-HAADF)) with associated X-ray energy-dispersive detector (EDS) and Scanning Transmission Electron Microscopy-Electron Energy Loss (STEM-EELS) spectroscopies. Noteworthy, this templating approach successfully led to the formation of CePO₄·H₂O nanofibrous bundles of rather co-aligned and elongated nanofibers (10⁻20 nm thick and up to ca. 1 μm long). The formed nanofibers consisted of hexagonal (P6₂22) CePO₄ nanocrystals (at 60 and 250 °C), with a better-grown and more homogeneous fibrous morphology with respect to a reference CePO₄ prepared under similar (non-templated) conditions, and transformed into nanofibrous monoclinic monazite (P21/n) around 600 °C. The nanofibrous morphology was highly preserved after annealing at 900 °C under N₂, although collapsed under air conditions. The nanofibrous CePO₄ (as-prepared hexagonal and 900 °C-annealed monoclinic) exhibited an enhanced UV photo-luminescent emission with respect to non-fibrous homologues.

Luminescence of delafossite-type CuAlO2 fibers with Eu substitution for Al cations

CuAlO₂ has been examined as a potential luminescent material by substituting Eu for Al cations in the delafossite structure. CuAlO₂:Eu³⁺ nanofibers have been prepared via electrospinning for the ease of mitigating synthesis requirements and for future optoelectronics and emerging applications. Single-phase CuAlO₂ fibers could be obtained at a temperature of 1100 °C in air. The Eu was successfully doped in the delafossite structure and two strong emission bands at ~405 and 610 nm were observed in the photoluminescence spectra. These bands are due to the intrinsic near-band-edge transition of CuAlO₂ and the f-f transition of the Eu³⁺ activator, respectively. Further electrical characterization indicated that these fibers exhibit semiconducting behavior and the introduction of Eu could act as band-edge modifiers, thus changing the thermal activation energies. In light of this study, CuAlO₂:Eu³⁺ fibers with both strong photoluminescence and p-type conductivity could be produced by tailoring the rare earth doping concentrations.

High yield synthesis and optical properties of MgF2nanowires with high aspect ratios

Ultrapure highly crystalline magnesium fluoride (MgF₂) nanowires with high aspect ratios were successfully synthesized by utilizing ammonium boron trifluoride (NH₃BF₃) as a precursor material for the first time.

Photocatalytic activity enhancement of LaPO4via surface oxygen vacancies

The photocatalytic activity reached a maximum 350 °C with vacuum heat treatment and was almost 1.6 times higher than that of untreated LaPO₄. The v-LaPO₄ photocatalyst has good stability.

Enhanced electrochemical performance and thermal stability of a CePO4-coated Li1.2Ni0.13Co0.13Mn0.54O2 cathode material for lithium-ion batteries

CePO₄ coating via a simple precipitation method enhances the thermal stability of the layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode material.

Multifunctional LaPO4:Ce/Tb@Au mesoporous microspheres: synthesis, luminescence and controllable light triggered drug release

Uniform LaPO₄:Ce/Tb mesoporous microspheres were prepared by a facile co-precipitation process. Under UV irradiation, a rapid DOX release was derived from the overlap of the green emission of Tb³⁺ and the surface plasmon resonance (SPR) band of Au.

Controllable morphology and high photoluminescence of (Y, Gd)(V, P) O4:Eu3+ nanophosphors synthesized by two-step reactions

Multi-ion doped YVO(4):Eu(3+) nanophosphors with high photoluminescence intensity were successfully prepared by a two-step reaction process for the first time, including YVO(4):Eu(3+) seeds synthesized by hydrothermal reaction and co-doping P(5+) and Gd(3+) in a sol-gel process. X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and photoluminescence spectroscopy were adopted to detect the structure, grain size, morphology and optical properties of the nanophosphors, respectively. Owning to the template-induced effect of the seeds, the morphology and size of the nanophosphors could be controlled by adjusting the molar ratios between the seeds and doping ions. The size of these nanophosphors increased as P(5+) and Gd(3+) co-doped. However, most of the samples kept approximately spherical morphology and narrow size distribution. The composition-optimized (Y, Gd)(V, P)O(4):Eu(3+) nanophosphors with spherical morphology in the 80-100 nm range exhibit better red emission and superior color saturation under vacuum ultraviolet excitation compared with that of the commercial phosphor (Y, Gd)BO(3):Eu(3+).

Spatially resolved cathodoluminescence of individual BN-coated CaS:Eu nanowires

Luminescence properties of individual BN-coated CaS:Eu nanowires have been studied by high-spatial-resolution cathodoluminescence (CL) spectroscopy. A broad red light-emitting band from an individual nanowire has been observed. Detailed local CL studies on the nanowires reveal spatial variations of luminescence from the structure surfaces toward their cores. Such variations are attributed to the different Eu2+ ions surroundings within the surface and core nanowire regions. The attractive luminescence properties are meaningful for fundamental studies of nanoscaled luminescent materials and may be of interest for novel optoelectronic applications.

Synthesis and luminescence of CePO4:Tb/LaPO4 core/sheath nanowires

CePO(4):Tb/LaPO(4) nanowires with a core/sheath architecture have been successful synthesized by a facile aqueous chemical method mediated by original CePO(4):Tb aggregation seeds. The seed crystals serve as both a luminescence center and a nucleation site for epitaxial growth. The seed nanocrystals have an irregular sphere-like shape with an average size of around 6.8 nm and a narrow size distribution. When the seed crystals are coated with LaPO(4), the resulting core/sheath CePO(4):Tb/LaPO(4) nanowires have mean diameters of about 7.6 nm and lengths up to 331 nm. Both photo- and x-ray luminescence demonstrate that the LaPO(4) coating increases the luminescence efficiency. These core/sheath structured nanowires may find potential applications in solid state lighting, medical imaging and radiation detection.

Functionalized Mesoporous SBA-15 with CeF3: Eu3+ Nanoparticle by Three Different Methods: Synthesis, Characterization, and Photoluminescence

Luminescence functionalization of the ordered mesoporous SBA-15 silica is realized by depositing a CeF3: Eu3+ phosphor layer on its surface (denoted as CeF3: Eu3+/SBA-15/IS, CeF3: Eu3+/SBA-15/SI and CeF3: Eu3+/SBA-15/SS) using three different methods, which are reaction in situ (I-S), solution impregnation (S-I) and solid phase grinding synthesis (S-S), respectively. The structure, morphology, porosity, and optical properties of the materials are well characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, N2 adsorption, and photoluminescence spectra. These materials all have high surface area, uniformity in the mesostructure and crystallinity. As expected, the pore volume, surface area, and pore size of SBA-15 decrease in sequence after deposition of the CeF3: Eu3+ nanophosphors. Furthermore, the efficient energy transfer in mesoporous material mainly occurs between the Ce3+ and the central Eu3+ ion. They show the characteristic emission of Ce3+ 5d → 4f (200-320 nm) and Eu3+5D0 → 7FJ(J = 1-4, with 5D0 → 7F1 orange emission at 588 nm as the strongest one) transitions, respectively. In addition, for comparison, the mesoporous material CeF3: Eu3+/SBA-15/SS exhibits the characteristic emission of Eu3+ ion under UV irradiation with higher luminescence intensity than the other materials.

Synthesis of YVO(4):Eu/YBO(3) Heteronanostructures with Enhanced Photoluminescence Properties

Novel YVO(4):Eu(3+)/YBO(3) core/shell heteronanostructures with different shell ratios (SRs) were successfully prepared by a facile two-step method. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize the heteronanostructures. Photoluminescence (PL) study reveals that PL efficiency of the YVO(4):Eu(3+) nanocrystals (cores) can be improved by the growth of YBO(3) nanocoatings onto the cores to form the YVO(4):Eu(3+)/YBO(3) core/shell heteronanostructures. Furthermore, shell ratio plays a critical role in their PL efficiency. The heteronanostructures (SR = 1/7) exhibit the highest PL efficiency; its PL intensity of the (5)D(0)-(7)F(2) emission at 620 nm is 27% higher than that of the YVO(4):Eu(3+) nanocrystals under the same conditions.

Cerium phosphate nanotubes: synthesis, characterization and biosensing

Cerium phosphate (CeP) nanotubes have been synthesized and confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The 1D nanomaterial has a monoclinic crystal structure with a mean width of 15-20 nm and a length up to several micrometers. The nanotubes have been employed as electrode substrates for immobilization and direct electrochemistry of heme proteins/enzymes with myoglobin (Mb) as a model. The electrochemical characteristics of the Mb-CeP/GC electrode were studied by voltammetry. After being immobilized on the nanotubes, Mb can keep its natural structure and undergo effective direct electron transfer reaction with a pair of well-defined redox peaks at -(367 +/- 3) mV (pH 7.5). The apparent electron transfer rate constant is (9.1 +/- 1.4) s(-1). The electrode displays good features in the electrocatalytic reduction of H(2)O(2), and thus can be used as a biosensor for detecting the substrate with a low detection limit (0.5 +/- 0.05 microM), a wide linear range (0.01-2 mM), high sensitivity (14.4 +/- 1.2 microA mM(-1)), as well as good stability and reproducibility. CeP nanotubes can become a simple and effective biosensing platform for the integration of heme proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.

Facile preparation method for rare earth phosphate hollow spheres and their photoluminescence properties

We have developed a template-free hydrothermal method of constructing rare earth phosphate hollow spheres using H(6)P(4)O(13) as the PO(4) (3-) source. The mechanism of hollow spheres formation was proposed on the basis of Ostwald ripening. The resulting hollow spheres, especially with the aid of doping of other lanthanide cations, exhibit emission spanning the whole UV-visible wavelength range.

Ni/Ni3C core-shell nanochains and its magnetic properties: one-step synthesis at low temperature

One-dimensional Ni/Ni3C core-shell nanoball chains with an average diameter by around 30 nm were synthesized by means of a mild chemical solution method using a soft template of trioctylphosphine oxide (TOPO). It was revealed that the uniform Ni nanochains were capped with Ni3C thin shells by about 1-4 nm in thickness and each Ni core consists of polygrains. The coercivity of the core-shell nanochains is much enhanced (600 Oe at 5 K) and comparable with single Ni nanowires due to the one-dimensional shape anisotropy. Deriving from the distinctive structure of Ni core and Ni 3C shell, this architecture may possess a possible bifunctionality. This unique architecture is also useful for the study on the magnetization reversal mechanism of one-dimensional magnetic nanostructure.