Different dominant transitions in holmium and ytterbium codoped oxyfluoride glass and glass ceramics originating from varying phonon energy environments.

Transparent oxyfluoride glass and glass ceramics doped with 0.5% Ho3+ and 1.0% Yb3+ ions have been prepared. X-ray diffraction and transmission electron microscopy demonstrated the formation of NaYF4 nanocrystals during the heat treatment process. Raman spectra indicated the variation of glass structure brought about by the formation of NaYF4 nanocrystals. XRD curves and Judd-Ofelt intensity parameters confirmed the incorporation of Ho3+ into NaYF4 nanocrystals. Significantly enhanced visible upconversion and 2.85 µm emissions were achieved in glass ceramic under 980 nm laser diode pumping. A broadband spectrum with a full-width at half-maximum close to 132 nm was obtained in the glass ceramic. Besides, the calculated peak emission cross section was 0.6 × 10-20 cm2, suggesting that the glass ceramic is a promising gain material that can be applied to broadband amplifiers in the mid-infrared region. Furthermore, energy transfer mechanisms in glass and glass ceramics were proposed based on visible to mid-infrared emission spectra. It was found that the change in the photon energy environment around rare earth ions induced different dominant transitions in glass and glass ceramic. Finally, the influence of phonon energy on the transition processes was further quantitatively investigated, which may provide useful guidance for obtaining highly efficient 2.85 µm emission of holmium.

Bright Transparent Scintillators with High Fraction BaCl2 : Eu2+ Nanocrystals Precipitation: An Ionic-Covalent Hybrid Network Strategy toward Superior X-Ray Imaging Glass-Ceramics.

Metal halide crystals are bright but hygroscopic scintillator materials that are widely used in X-ray imaging and detectors. Precipitating them in situ in glass to form glass ceramics (GCs) scintillator offers an efficient avenue for large-scale preparation, high spatial resolution, and excellent stability. However, precipitating a high fraction of metal halide nanocrystals in glass to maintain high light yield remains a challenge. Herein, an ionic-covalent hybrid network strategy for constructing GCs scintillator with high crystallinity (up to ≈37%) of BaCl2 : Eu2+ nanocrystals is presented. Experimental data and simulations of glass structure reveal that the Ba2+ -Cl- clustering promotes the high crystallization of BaCl2 nanocrystals. The ultralow phonon energy (≈200 cm-1 ) of BaCl2 nanocrystals and good Eu reduction effect enable high photoluminescence inter quantum efficiency (≈80.41%) in GC. GCs with varied crystallinity of BaCl2 : Eu2+ nanocrystals demonstrate efficient radioluminescence and tunable scintillator performance. They either outperform Bi4 Ge3 O14 single crystal by over 132% steady-state light yield or provide impressive X-ray imaging resolutions of 20 lp mm-1 . These findings provide a new design strategy for developing bright transparent GCs scintillators with a high fraction of metal halide nanocrystals for X-ray high-resolution imaging applications.

Fe3+-selective and sensitive "on-off" fluorescence probe based on the graphitic carbon nitride nanosheets.

An effective and facile "on-off" fluorescence sensing approach for the determination of Fe3+ ion using a large area and relatively uniform size graphitic carbon nitride nanosheets (GCNS) was developed. The prepared GCNS have blue and stable emission, as well as excellent water dispersion, and were applied as an effective fluorescent probe that based on the quenched fluorescence for selective and sensitive detection of Fe3+ ion. Herein, we explain the ambiguous fluorescence quenching mechanism between the GCNS and Fe3+, which mainly springs from the redox potential and empty d orbital of Fe3+. The redox potential and unfilled d orbit of Fe3+ endow it excellent binding force with GCNS, which generates most obvious fluorescence quenching effect with respect to other metal ions. The limit of detection (LOD) for Fe3+ was found to be about 2.06 µM. Therefore, the prepared GCNS has the potential to be used as a fluorescent probe for detection.

Correction: Core-shell like glass containing lanthanide doped nanocrystals for efficient luminescence.

Correction for 'Core-shell like glass containing lanthanide doped nanocrystals for efficient luminescence' by Qunhuo Liu et al., Chem. Commun., 2018, 54, 13092-13095.

Core-shell like glass containing lanthanide doped nanocrystals for efficient luminescence.

We constructed a core-shell like nanoarchitecture in Yb/Er ion and Yb/Ho SrTiO3 nanocrystal-codoped tellurite-borate glass. We demonstrated that the adverse energy transfer between Er3+ ions in the glass region and Ho3+ ions in the crystal region was effectively prohibited, which permits independent and highly efficient emission from Er3+ and Ho3+ ions.