Synthesis and Rational design of Europium and Lithium Doped Sodium Zinc Molybdate with Red Emission for Optical Imaging

Glowing selenates: novel alkaline earth nanoparticles

Up to now, no selenate nanoparticles have been described even though much research has been done on respective oxidic compounds such as sulfates and phosphates. For the first time, alkaline earth selenates of the composition MSeO₄ (M = Ca, Sr, Ba) were synthesized as nanoparticles or nanorods as described in this publication. For this purpose, a micro emulsion method was applied using CTAB as a surfactant. Using X-ray diffraction measurements (XRD) phase purity of the materials could be proven. Furthermore, the nanoparticles were analyzed by raster electron microscopy (REM) and dynamic light scattering (DLS) measurements. Finally, the products were doped with small amounts of Eu³⁺ to obtain luminescent materials. Successful doping was demonstrated by luminescence investigations in the region of 18 000 to 14 000 cm^-1 (550-715 nm). Incorporation of Eu³⁺ led to strong red-emitting nanoparticles. Low temperature measurements at 10 K allowed conclusions about the site symmetry of Eu³⁺ ions located on the alkaline earth sites.

Excitation-Dependent Photoluminescence of BaZrO3:Eu3+ Crystals

The elucidation of local structure, excitation-dependent spectroscopy, and defect engineering in lanthanide ion-doped phosphors was a focal point of research. In this work, we have studied Eu³⁺-doped BaZrO₃ (BZOE) submicron crystals that were synthesized by a molten salt method. The BZOE crystals show orange-red emission tunability under the host and dopant excitations at 279 nm and 395 nm, respectively, and the difference is determined in terms of the asymmetry ratio, Stark splitting, and intensity of the uncommon ⁵D₀ → ⁷F₀ transition. These distinct spectral features remain unaltered under different excitations for the BZOE crystals with Eu³⁺ concentrations of 0-10.0%. The 2.0% Eu³⁺-doped BZOE crystals display the best optical performance in terms of excitation/emission intensity, lifetime, and quantum yield. The X-ray absorption near the edge structure spectral data suggest europium, barium, and zirconium ions to be stabilized in +3, +2, and +4 oxidation states, respectively. The extended X-ray absorption fine structure spectral analysis confirms that, below 2.0% doping, the Eu³⁺ ions occupy the six-coordinated Zr⁴⁺ sites. This work gives complete information about the BZOE phosphor in terms of the dopant oxidation state, the local structure, the excitation-dependent photoluminescence (PL), the concentration-dependent PL, and the origin of PL. Such a complete photophysical analysis opens up a new pathway in perovskite research in the area of phosphors and scintillators with tunable properties.

Luminescent lanthanide nanoparticle-based imaging enables ultra-sensitive, quantitative and multiplexed in vitro lateral flow immunoassays

Lateral Flow Assays (LFAs) have been extensively used on-site to rapidly detect analytes, possibly in complex media. However, standard gold nanoparticle-based LFAs lack sensitivity and cannot provide quantitative measurements with high accuracy. To overcome these limitations, we image lanthanide-doped nanoparticles (YVO₄:Eu 40%) as new luminescent LFA probes, using a homemade reader coupled to a smartphone and propose an original image analysis allowing strip quantification regardless of the shape of the test band signal. This method is demonstrated for the detection of staphylococcal enterotoxins SEA, SEG, SEH, and SEI. A systematic comparison to state-of-the-art gold nanoparticle-based LFA revealed an analytical sensitivity enhancement of at least one order of magnitude. We furthermore provided measurements of absolute toxin concentration over two orders of magnitude and demonstrated simultaneous quantitative detection of multiple toxins with unaltered sensitivity. In particular, we reached concentrations 100 times lower than the ones reported in the literature for on-site multiplexed LFA targeting enterotoxins. Altogether, these results highlight that our luminescent nanoparticle-based method provides a powerful and versatile on-site framework to detect multiple biomolecules with sensitivity approaching that obtained by ELISA. This paves the way to a change of paradigm in the field of analytical immunoassays by providing fast in situ quantitative high sensitivity detection of biomarkers or pathogens.

Structural, Electronic and Vibrational Properties of YAl3(BO3)4

The crystal structure of YAl₃(BO₃)₄ is obtained by Rietveld refinement analysis in the present study. The dynamical properties are studied both theoretically and experimentally. The experimental Raman and Infrared spectra are interpreted using the results of ab initio calculations within density functional theory. The phonon band gap in the Infrared spectrum is observed in both trigonal and hypothetical monoclinic structures of YAl₃(BO₃)₄. The electronic band structure is studied theoretically, and the value of the band gap is obtained. It was found that the YAl₃(BO₃)₄ is an indirect band gap dielectric material.

Role of alkali charge compensation in the luminescence of CaWO4:Nd3+ and SrWO4:Nd3+ Scheelites

The present work demonstrates the distinct role of alkali metal ion charge compensators on the luminescence of NIR-emitting Nd³⁺ Scheelite. The unit cell dimensions of the host lattice and excitation wavelength play a very important role.

Controlling the luminescence in K2Th(PO4)2:Eu3+ by energy transfer and excitation photon: a multicolor emitting phosphor

This work highlighted green, red, and white light emission from a single K₂Th(PO₄)₂ compound consisting of actinide and an alkali ion through defect, doping, excitation, and energy transfer manipulation.

Optical properties of undoped, Eu3+ doped and Li+ co-doped Y2Hf2O7 nanoparticles and polymer nanocomposite films

Li⁺ co-doping of Y₂Hf₂O₇:Eu³⁺ nanoparticles improve their quenching concentration, asymmetry ratio, quantum yield, and radioluminescence intensity due to the enhanced covalent character of Eu³⁺–O²⁻ bonding.