Inverse-Tunable Red Luminescence and Electronic Properties of Nitridoberylloaluminates Sr2-x Bax [BeAl3 N5 ]:Eu2+ (x=0-2).

The nitridoberylloaluminate Ba2 [BeAl3 N5 ]:Eu2+ and solid solutions Sr2-x Bax [BeAl3 N5 ]:Eu2+ (x=0.5, 1.0, 1.5) were synthesized in a hot isostatic press (HIP) under 50 MPa N2 atmosphere at 1200 °C. Ba2 [BeAl3 N5 ]:Eu2+ crystallizes in triclinic space group P 1 ‾ (no. 2) (Z=2, a=6.1869(10), b=7.1736(13), c=8.0391(14) Å, α=102.754(8), ß=112.032(6), γ=104.765(7)°), which was determined from single-crystal X-ray diffraction data. The lattice parameters of the solid solution series have been obtained from Rietveld refinements and show a nearly linear dependence on the atomic ratio Sr : Ba. The electronic properties and the band gaps of M2 [BeAl3 N5 ] (M=Sr, Ba) have been investigated by a combination of soft X-ray spectroscopy and density functional theory (DFT) calculations. Upon irradiation with blue light (440-450 nm), the nitridoberylloaluminates exhibit intense orange to red luminescence, which can be tuned between 610 and 656 nm (fwhm=1922-2025 cm-1 (72-87 nm)). In contrast to the usual trend, the substitution of the smaller Sr2+ by larger Ba2+ leads to an inverse-tunable luminescence to higher wavelengths. Low-temperature luminescence measurements have been performed to exclude anomalous emission.

Ultra-Narrow-Band Blue-Emitting Oxoberyllates AELi2 [Be4 O6 ]:Eu2+ (AE=Sr,Ba) Paving the Way to Efficient RGB pc-LEDs.

Highly efficient phosphor-converted light-emitting diodes (pc-LEDs) are popular in lighting and high-tech electronics applications. The main goals of present LED research are increasing light quality, preserving color point stability and reducing energy consumption. For those purposes excellent phosphors in all spectral regions are required. Here, we report on ultra-narrow band blue emitting oxoberyllates AELi2 [Be4 O6 ]:Eu2+ (AE=Sr,Ba) exhibiting a rigid covalent network isotypic to the nitridoalumosilicate BaLi2 [(Al2 Si2 )N6 ]:Eu2+ . The oxoberyllates' extremely small Stokes shift and unprecedented ultra-narrow band blue emission with fwhm ≈25 nm (≈1200 cm-1 ) at λem =454-456 nm result from its rigid, highly condensed tetrahedra network. AELi2 [Be4 O6 ]:Eu2+ allows for using short-wavelength blue LEDs (λem <440 nm) for efficient excitation of the ultra-narrow band blue phosphor, for application in violet pumped white RGB phosphor LEDs with improved color point stability, excellent color rendering, and high energy efficiency.

Sr[BeSi2 N4 ]:Eu2+ /Ce3+ and Eu[BeSi2 N4 ]: Nontypical Luminescence in Highly Condensed Nitridoberyllosilicates.

M[BeSi2 N4 ] (M=Sr,Eu), crystallizing in the hexagonal space group P6‾ 2c, was synthesized from Sr(NH2 )2 , Be3 N2 , and "Si(NH)2 " in W crucibles under a N2 atmosphere in a radio-frequency furnace. The crystal structure was solved from powder X-ray diffraction data by the charge-flipping method (Sr[BeSi2 N4 ]: a=4.86082(2), c=9.42264(4) Å, Z=2; Eu[BeSi2 N4 ]: a=4.85848(1), c=9.41615(4) Å). M[BeSi2 N4 ] contains a highly condensed rigid network of trigonal planar [BeN3 ] units that are connected to Si2 N7 double tetrahedra by common vertices. M[BeSi2 N4 ] (M=Sr,Eu) are the first examples of nitridoberyllosilicates and are isotypic to the oxoberyllate Sr[Be3 O4 ]. Eu2+ -doped Sr[BeSi2 N4 ] and Eu[BeSi2 N4 ] show orange-trapped exciton emission (λem =605 nm, fwhm ≈126 nm), whereas Ce3+ -doped samples of Sr[BeSi2 N4 ] show nontypical yellowish-orange luminescence. Sr[BeSi2 N4 ] has a large band gap of ≈4.4 eV and shows high chemical and thermal stability. Eu2+ -doped beryllates with regular 4f6 5d1 →4f7 -emission could be interesting for future application in LEDs upon doping with Eu2+ or Ce3+ due to large band gaps, rigid networks, and chemical and thermal stability.

Narrow-band red-emitting Sr[LiAl3N4]:Eu²âº as a next-generation LED-phosphor material.

To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

Labeling of anti-MUC-1 binding single chain Fv fragments to surface modified upconversion nanoparticles for an initial in vivo molecular imaging proof of principle approach.

In vivo optical Imaging is an inexpensive and highly sensitive modality to investigate and follow up diseases like breast cancer. However, fluorescence labels and specific tracers are still works in progress to bring this promising modality into the clinical day-to-day use. In this study an anti-MUC-1 binding single-chain antibody fragment was screened, produced and afterwards labeled with newly designed and surface modified NaYF(4):Yb,Er upconversion nanoparticles as fluorescence reporter constructs. The MUC-1 binding of the conjugate was examined in vitro and in vivo using modified state-of-the-art small animal Imaging equipment. Binding of the newly generated upconversion nanoparticle based probe to MUC-1 positive cells was clearly shown via laser scanning microscopy and in an initial proof of principal small animal optical imaging approach.