Simple one pot synthesis of luminescent europium doped yttrium oxide Y2O3:Eu nanodiscs for phosphor converted warm white LEDs

Yttrium oxide (Y2O3) is considered as one of the best host lattices for europium (Eu3+) based red emitting phosphors because of its unit cell and good photo-saturation properties.

Resonance Energy Transfer to Track the Motion of Lanthanide Ions—What Drives the Intermixing in Core-Shell Upconverting Nanoparticles?

The imagination of clearly separated core-shell structures is already outdated by the fact, that the nanoparticle core-shell structures remain in terms of efficiency behind their respective bulk material due to intermixing between core and shell dopant ions. In order to optimize the photoluminescence of core-shell UCNP the intermixing should be as small as possible and therefore, key parameters of this process need to be identified. In the present work the Ln(III) ion migration in the host lattices NaYF4 and NaGdF4 was monitored. These investigations have been performed by laser spectroscopy with help of lanthanide resonance energy transfer (LRET) between Eu(III) as donor and Pr(III) or Nd(III) as acceptor. The LRET is evaluated based on the Förster theory. The findings corroborate the literature and point out the migration of ions in the host lattices. Based on the introduced LRET model, the acceptor concentration in the surrounding of one donor depends clearly on the design of the applied core-shell-shell nanoparticles. In general, thinner intermediate insulating shells lead to higher acceptor concentration, stronger quenching of the Eu(III) donor and subsequently stronger sensitization of the Pr(III) or the Nd(III) acceptors. The choice of the host lattice as well as of the synthesis temperature are parameters to be considered for the intermixing process.

Vibrational Spectroscopic Analyses of (en)2-Td-type Clathrates

The clathrates of Hofmann-(en)2-Td-type, M(en)2M’(CN)4.Aniline (M=Cu,Cd; M’=Cd,Zn) and their hosts were synthesized with the confirmation using FTIR spectra. Hydrogen bonding interaction between π-cloud of phenyl ring of the guest molecule and ethylenediamine(en) of the host lattices was deduced from the upward shift in ν(CH)out of plane bending mode of aniline. A second type of hydrogen bonding between C≡N group of the host lattice and NH2 of aniline guest was also inferred from the downward shift in ν(C≡N) of the clathrates. The relative strength of H-bonding in the clathrates was found to be Hofmann-(en)2-Type > Hofmann-(en)2-Td-Phenol > Hofmann-(en)2-Td-Aniline. The presence of major peaks corresponding to various modes of guest aniline, ligand en and cyanide group in FT Raman spectra also confirms the formation of clathrates. Attempts to synthesize Ni(en)2M’(CN)4.Aniline (M’=Cd,Zn) resulted in the formation of M’(en)2Ni(CN)4.2Aniline (M’=Cd,Zn) due to the exchange of metal ions and greater stability of Ni(CN)4 unit.

Composite host lattices of 4,4′-sulfonyldibenzoate water/boric acid in two tetrapropylammonium inclusion compounds

Two novel inclusion compounds of 4,4′-sulfonyldibenzoate anions and tetrapropylammonium cations with different ancillary molecules of water and boric acid, namely bis(tetrapropylammonium) 4,4′-sulfonyldibenzoate dihydrate, 2C12H28N+·C14H8O6S2−·H2O (1), and bis(tetrapropylammonium) 4,4′-sulfonyldibenzoate bis(boric acid), 2C12H28N+·C14H8O6S2−·2H3BO3 (2), were prepared and characterized using single-crystal X-ray diffraction. In the two salts, the host 4,4′-sulfonyldibenzoic acid molecules, which are converted to the corresponding anions under basic conditions, can be regarded as proton acceptors which link different proton donors of the ancillary molecules of water or boric acid. In this way, an isolated hydrogen-bonded tetramer is constructed in salt 1 and a ribbon is constructed in salt 2. The tetramers and ribbons are then packed in a repeating manner to generate various host frameworks, and the tetrapropylammonium guest counter-ions are contained in the cavities of the host lattices to give the final stable crystal structures. In these two salts, although the host anion and guest cation are the same, the difference in the ancillary small molecules results in different structures, indicating the significance of ancillary molecules in the formation of crystal structures.

The Impact of Different Alkali Metal Ions on Photoluminescence Properties of Ca10M(PO4)7:Eu2+ (M: Li, Na, K)

A series of novel luminescent materials Ca10M(PO4)7:Eu2+(M: Li, Na, K) were synthesized by the solid-state reaction. The previous literatures indicate that the doped different alkali metal ions can only lead to regular shift of the emission and excitation spectra. Howerver, in this paper, we found the result that these three kinds of phosphors showed huge differences between the emission spectra intensity as well as the positions of the excitation and emission spectra peaks. No any regulars can be found. In order to explore it, crystal structure, the performance of photoluminescence spectra and CIE coordinates have been systematically investigated and discussed. In Ca10Li (PO4)7, Ca10Na (PO4)7and Ca10K(PO4)7host lattices, the positions of the cations are different, leading to three different crystal structures. Besides, the coordination conditions of the luminescent centers Eu2+ions are also changed by the incorporation of the alkali metal ions. Thus the enormous disparity on the luminescence intensity as well as the excitation and emission peak positions may be ascribed to these three quite different crystal fields and different coordination numbers of the luminescent central ion in the Ca10M(PO4)7:Eu2+(M: Li, Na, K) phosphors.