Blue to Red Emission Tunable Bi3+ co-doped YPO4:Eu3+: Host Emission and Phase Change

Bi3+(0, 1, 3, 5, 7, 10, 12 and 15 at.%) co-doped YPO4:Eu3+ have been hydrothermally synthesized. Bi3+ (x ≥ 1 at.%) co-doping in YPO4:Eu3+ renders mixed crystalline phase of tetragonal to hexagonal. Pure tetragonal phase of Bi3+ co-doped YPO4:Eu3+ could be achieved upon annealing at 900 °C. The luminescence intensity is improved significantly upon annealing at 900 °C. This is due to the reduction of quenching pathways such as water molecules, dangling bonds, etc. The probability of magnetic dipole and electric dipole transitions is observed to be altered. As-prepared samples show near blue emission, while 900 °C annealed samples exhibit red emission, which could be a potential candidate for display, sensing and biological labelling, etc.

Impact of Structural Changes on Energy Transfer in the Anion-Engineered Re3+:Y2O3 Through Low-Temperature Synthesis Approach

Anion engineering has proven to be an effective strategy to tailor the physical and chemical properties of metal oxides by modifying their existing crystal structures. In this work, a low-temperature synthesis for rare earth (RE)-doped Y2O2SO4 and Y2O2S was developed via annealing of Y(OH)3 intermediates in the presence of elemental sulfur in a sealed tube, followed by a controlled reduction step. The crystal structure patterns (X-ray diffraction) and optical spectra (UV-IR) of Y2O2SO4, Y2O2S, and crystalline Y2O3 were collected throughout the treatment steps to correlate the structural transformations (via thermogravimetric analysis) with the optical properties. Local and long-range crystallinities were characterized by using X-ray and optical spectroscopy approaches. Systematic shifts in the Eu3+ excitation and emission peaks were observed as a function of SO42- and S2- concentrations resulting from a crystal evolution from cubic (Y2O3) to trigonal (Y2O2S) and monoclinic (Y2O2SO4), which can modify the local hybridization of sensitizer dopants (i.e., Ce3+). Ultimately, Tb3+ and Tb3+/Ce3+ doping was employed in these hosts (Y2O2SO4, Y2O2S, and Y2O3) to understand energy transfer between sensitizer and activator ions, which showed significant enhancement for the monoclinic sulfate structure.

Analysis of Excitation Energy Transfer in LaPO4 Nanophosphors Co-Doped with Eu3+/Nd3+ and Eu3+/Nd3+/Yb3+ Ions

Nanophosphors are widely used, especially in biological applications in the first and second biological windows. Currently, nanophosphors doped with lanthanide ions (Ln³⁺) are attracting much attention. However, doping the matrix with lanthanide ions is associated with a narrow luminescence bandwidth. This paper describes the structural and luminescence properties of co-doped LaPO₄ nanophosphors, fabricated by the co-precipitation method. X-ray structural analysis, scanning electron microscope measurements with EDS analysis, and luminescence measurements (excitation 395 nm) of LaPO₄:Eu³⁺/Nd³⁺ and LaPO₄:Eu³⁺/Nd³⁺/Yb³⁺ nanophosphors were made and energy transfer between rare-earth ions was investigated. Tests performed confirmed the crystal structure of the produced phosphors and deposition of rare-earth ions in the structure of LaPO₄ nanocrystals. In the range of the first biological window (650-950 nm), strong luminescence bands at the wavelengths of 687 nm and 698 nm (⁵D₀ → ⁷F₄:Eu³⁺) and 867 nm, 873 nm, 889 nm, 896 nm, and 907 nm (⁴F_3/2 → ⁴I_9/2:Nd³⁺) were observed. At 980 nm, 991 nm, 1033 nm (²F_5/2 → ²F_7/2:Yb³⁺) and 1048 nm, 1060 nm, 1073 nm, and 1080 nm (⁴F_3/2 → ⁴I_9/2:Nd³⁺), strong bands of luminescence were visible in the 950 nm-1100 nm range, demonstrating that energy transfer took place.

Praseodymium selective fluorescence recognition based on GdPO4: Tb3+ probe via energy transfer from Tb3+ to Pr3+ ions

A novel strategy is proposed based on the efficient energy transfer from Tb³⁺ to Pr³⁺ for the sensitive and selective discrimination of praseodymium ions due to the matched energy levels of ⁵D₄ (Tb³⁺) and ³P₀ (Pr³⁺). The electron of Tb³⁺ transfers from the ground state to the excited state under the excitation of ultraviolet light and relaxes to the ⁵D₄ level. In the presence of Pr³⁺ the electron has no time to return to the ground state, thus it transfers to the ³P₀ level of Pr³⁺ resulting in the quenching of Tb³⁺ luminescence. In the case of GdPO₄: Tb³⁺ nanowire, its fluorescence intensity at 545 nm linearly decreased when Pr³⁺ concentration ranged from 1 × 10^-7 to 1 × 10^-5 M, and the detection limit was 75 nM. To further investigate the sensing mechanism, CePO₄: Tb³⁺, YPO₄: Tb³⁺, and YBO₃: Tb³⁺ nanoparticles were also synthesized for Pr³⁺ ion detection. For all materials, similar fluorescence quenching by Pr³⁺ ions occurred, which confirmed the efficient energy transfer from Tb³⁺ to Pr³⁺ ions. Utilizing the matched energy levels of ⁵D₄ (Tb³⁺) and ³P₀ (Pr³⁺), for the first time, we proposed a novel strategy (taking GdPO₄: Tb³⁺ probe as the example) based on the efficient energy transfer from Tb³⁺ to Pr³⁺ for the sensitive and selective discrimination of praseodymium ions.

Lanthanide-Based Nanosensors: Refining Nanoparticle Responsiveness for Single Particle Imaging of Stimuli

Lanthanide nanoparticles (LNPs) are promising sensors of chemical, mechanical, and temperature changes; they combine the narrow-spectral emission and long-lived excited states of individual lanthanide ions with the high spatial resolution and controlled energy transfer of nanocrystalline architectures. Despite considerable progress in optimizing LNP brightness and responsiveness for dynamic sensing, detection of stimuli with a spatial resolution approaching that of individual nanoparticles remains an outstanding challenge. Here, we highlight the existing capabilities and outstanding challenges of LNP sensors, en-route to nanometer-scale, single particle sensor resolution. First, we summarize LNP sensor read-outs, including changes in emission wavelength, lifetime, intensity, and spectral ratiometric values that arise from modified energy transfer networks within nanoparticles. Then, we describe the origins of LNP sensor imprecision, including sensitivity to competing conditions, interparticle heterogeneities, such as the concentration and distribution of dopant ions, and measurement noise. Motivated by these sources of signal variance, we describe synthesis characterization feedback loops to inform and improve sensor precision, and introduce noise-equivalent sensitivity as a figure of merit of LNP sensors. Finally, we project the magnitudes of chemical and pressure stimulus resolution achievable with single LNPs at nanoscale resolution. Our perspective provides a roadmap for translating ensemble LNP sensing capabilities to the single particle level, enabling nanometer-scale sensing in biology, medicine, and sustainability.

Tb3+- and Yb3+-doped novel KBaLu(MoO4)3 crystals with disordered chained structure showing down- and up-conversion luminescence

Tb³⁺/Yb³⁺ co-doped KBaLu(MoO₄)₃ with a highly disordered structure consisting of chains induces high color purity of primary green luminescence.

Structure and photoluminescent properties of green-emitting terbium-doped GdV1-x Px O4 phosphor prepared by solution combustion method

Terbium-doped gadolinium orthovanadate (GdVO4 :Tb(3+) ), orthophosphate monohydrate (GdPO4 ·H2 O:Tb(3+) ) and orthovanadate-phosphate (GdV,PO4 :Tb(3+) ) powder phosphors were synthesized using a solution combustion method. X-Ray diffraction analysis confirmed the formation of crystalline GdVO4 , GdPO4 ·H2 O and GdV,PO4 . Scanning electron microscopy images showed that the powder was composed of an agglomeration of particles of different shapes, ranging from spherical to oval to wire-like structures. The chemical elements present were confirmed by energy dispersive spectroscopy, and the stretching mode frequencies were determined by Fourier transform infrared spectroscopy. UV-visible spectroscopy spectra showed a strong absorption band with a maximum at 200 nm assigned to the absorption of VO4 (3-) and minor excitation bands assigned to f → f transitions of Tb(3+) . Four characteristic emission peaks were observed at 491, 546, 588 and 623 nm, and are attributed to (5) D4  → (7) Fj (j = 6, 5, 4 and 3). The photoluminescent prominent green emission peak ((5) D4  → (7) F5 ) was centred at 546 nm. The structure and possible mechanism of light emission from GdV1-x Px O4 :% Tb(3+) are discussed. Copyright © 2016 John Wiley & Sons, Ltd.

Roles of solvent, annealing and Bi3+ co-doping on the crystal structure and luminescence properties of YPO4:Eu3+ nanoparticles

There are roles of solvent, annealing and Bi³⁺ co-doping on crystal structure and luminescence properties of YPO₄:Eu³⁺ nanoparticles.

Intense red emitting monoclinic LaPO4:Eu3+ nanoparticles: host–dopant energy transfer dynamics and photoluminescence properties

Visible host emission and dynamics of host–dopant energy transfer in LaPO₄:Eu phosphor is investigated using PL and complimented by DFT.

Energy-transfer from Gd(III) to Tb(III) in (Gd,Yb,Tb)PO4 nanocrystals

The photoluminescence properties of (Gd,Yb,Tb)PO4 nanocrystals synthesized via a hydrothermal route at 150 °C are reported. Energy-transfer from Gd(3+) to Tb(3+) is witnessed by the detailed analyses of excited-state lifetimes, emission quantum yields, and emission and excitation spectra at room temperature, for Tb(3+) concentrations ranging from 0.5 to 5.0 mol%. Absolute-emission quantum yields up to 42% are obtained by exciting within the (6)I7/2-17/2 (Gd(3+)) manifold at 272 nm. The room temperature emission spectrum is dominated by the (5)D4 → (7)F5 (Tb(3+)) transition at 543 nm, with a long decay-time (3.95-6.25 ms) and exhibiting a rise-time component. The (5)D3 → (7)F6 (Tb(3+)) rise-time (0.078 ms) and the (6)P7/2 → (8)S7/2 (Gd(3+)) decay-time (0.103 ms) are of the same order, supporting the Gd(3+) to Tb(3+) energy-transfer process. A remarkably longer lifetime of 2.29 ms was measured at 11 K for the (6)P7/2 → (8)S7/2 (Gd(3+)) emission upon excitation at 272 nm, while the emission spectrum at 11 K is dominated by the (6)P7/2 → (8)S7/2 transition line, showing that the Gd(3+) to Tb(3+) energy-transfer process is mainly phonon-assisted with an efficiency of ~95% at room temperature. The Gd(3+) to Tb(3+) energy transfer is governed by the exchange mechanism with rates between 10(2) and 10(3) s(-1), depending on the energy mismatch conditions between the (6)I7/2 and (6)P7/2 levels of Gd(3+) and the Tb(3+ 5)I7, (5)F2,3 and (5)H5,6,7 manifolds and the radial overlap integral values.

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.

Core/shell-type nanorods of Tb3+-doped LaPO4, modified with amine groups, revealing reduced cytotoxicity

ABSTRACT

A simple co-precipitation reaction between Ln³⁺ cations (Ln = lanthanide) and phosphate ions in the presence of polyethylene glycol (PEG), including post-treatment under hydrothermal conditions, leads to the formation of Tb³⁺-doped LaPO₄ crystalline nanorods. The nanoparticles obtained can be successfully coated with amorphous and porous silica, forming core/shell-type nanorods. Both products reveal intensive green luminescence under UV lamp irradiation. The surface of the core/shell-type product can also be modified with -NH₂ groups via silylation procedure, using 3-aminopropyltriethoxysilane as a modifier. Powder X-ray diffraction, transmission electron microscopy, and scanning electron microscopy confirm the desired structure and needle-like shape of the products synthesized. Fourier transform infrared spectroscopy and specific surface area measurements by Brunauer-Emmett-Teller method reveal a successful surface modification with amine groups of the core/shell-type nanoparticles prepared. The nanomaterials synthesized exhibit green luminescence characteristic of Tb³⁺ ions, as solid powders and aqueous colloids, examined by spectrofluorometry. The in vitro cytotoxicity studies reveal different degree toxicity of the products. LaPO₄:Tb³⁺@SiO₂@NH₂ exhibits the smallest toxicity against B16F0 mouse melanoma cancer cells and human skin microvascular endothelial cell lines, in contrast to the most toxic LaPO₄:Tb³⁺@SiO₂.