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Hydrolysis of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP), a commonly used RNA model substrate, is examined in molybdate solutions by using NMR, Raman and Mo K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. The kinetic studies have shown that [[[Mo.sub.7][O.sub.24]].sup.6-] is the hydrolytically active complex and that the cleavage has occurred by a mechanism that is different to that of other commonly known hydrolytically active metal complexes.

The complex formation of the uranyl ion with chloride ions in acetonitrile is examined by factor analysis of ultraviolet-visible absorption and U [L.sub.3] edge EXAFS (extended X-ray absorption fine structure) spectra. The U(VI) coordination of the solution species [U[O.sub.2][Cl.sub.2]([H.sub.2]O)[(MeCN).sub.2]] has changed during the crystallization of replacing one MeCN molecule with a bridging [[mu].sub.3].O atom in the tetramer.

The article explains the magnetic alignment of the various rare-earth-containing liquid crystal complexes. Different crystals are found to exhibit different positive and negative values of magnetic anisotropy.

The unique absorption properties of the 9-hydroxyphenalen-1-one (HPHN) ligand are explored to obtain visible-light-sensitizable rare-earth complexes in 1:3 and 1:4 metal-to-ligand ratios. The X-ray crystal structures of the tris complexes have shown solvent coordination to the central rare-earth ion, whereas in the tetrakis complexes, the four [PHN.sup.-] ligands form a protective shield around the central ion, preventing small solvent molecules from coordinating to the rare-earth ion, at least in the solid state.

In this work, a series of novel NaLa1−xGdxCa4W2O12:Mn4+ (NL1−xGxCWO:Mn4+, x = 0–1) phosphors were synthesized using a high-temperature solid-state reaction approach. Unexpected intense red-far-red emissions were clearly observed after the ionic couple substitution of 2Ca2+ by Na+ + Ln3+ (Ln = La, Gd) in negligible-luminescence Ca6W2O12:Mn4+ upon ultraviolet (UV) excitation. Moreover, a maximal emission-tuning of Δλ = 28 nm (Δν = 582 cm−1) can be found by changing x from 0 to 1, which is ascribed to the different crystal field and covalence among them. In addition, the luminescence thermal quenching behaviors and thermal quenching mechanisms were investigated in detail in representative NLCWO:0.01Mn4+ and NGCWO:0.01Mn4+ phosphors. The results were used to initiate an ionic couple substitution strategy to enrich novel oxide hosts for Mn4+ luminescence and select an appropriate host with better thermal stability for plant-cultivation LED applications. [ABSTRACT FROM AUTHOR]

A novel dazzling far-red-emitting phosphor NaLaCaTeO6:Mn4+ (NLCTO:Mn4+) with superior photoluminescence properties was found via an ionic couple substitution strategy of Na+ + La3+ for 2Ca2+ in non-luminous Ca3TeO6:Mn4+ for the first time, which is originated from the significant distortion of TeO6 octahedra. The results indicate that the ionic couple substitution strategy is a feasible guide to explore novel Mn4+-involved oxide phosphors for potential application in plant cultivation LEDs. [ABSTRACT FROM AUTHOR]

In this work we report a novel lanthanide octamolybdate 1D chain type of structure formed with holmium, thulium and lutetium. This is a rare case of compounds built out of [Mo8O28]8− units. These compounds were prepared in a mild reaction synthesis starting from the commonly used heptamolybdate polyoxometalate (POM) [(NH4)6[Mo7O24]. Interestingly, in our previous study we have employed a very similar synthesis route for lanthanides with a larger ionic radius and obtained heptamolybdate clusters. For the lanthanides with a smaller ionic radius (Ho3+, Tm3+ and Lu3+) no crystals could be obtained under those conditions. Only when doubling the amount of the lanthanide salt, single crystals suitable for measurements were obtained. These crystals revealed yet a very different structure from those previously observed. Lanthanide octamolybdate 1D chains were formed. Doubling the amount of the salt for other lanthanide ions still yielded heptamolybdate compounds previously reported by us. The lutetium octamolybdate compound was doped with 1–7.5% of Eu3+ ions yielding emission colors ranging from blue to strong red. Additionally in these materials the excitation wavelength was varied, and it was observed that the materials emission color was excitation-wavelength dependent. [ABSTRACT FROM AUTHOR]

In this paper, a novel kind of tristrontium sodium antimony(v) oxide (NaSr3SbO6:Mn4+; NSSO:Mn4+) material was developed, whose crystal structure is different from the well-researched Mn4+-doped antimoniate double pervoskite materials. The optimal NSSO:0.006Mn4+ can be mainly excited using ultraviolet/near-ultraviolet (UV/n-UV) and partial blue lights with a high quantum yield of 46% upon 365 nm UV excitation and good temperature dependent performance. [ABSTRACT FROM AUTHOR]

In this work, we prepared a novel kind of Yb3+,Er3+/Ho3+ co-doped CsGd(MoO4)2 phosphors with a different structure from the reported ALn(MoO4)2 (A = Li, Na or K; Ln = La, Gd or Y) compounds using a high-temperature solid-state reaction method. X-ray diffraction showed that the as-prepared samples had a pure phase. Based on the efficient energy transfer from Yb3+ to Er3+/Ho3+, the up-conversion (UC) luminescence of the optimal CsGd(MoO4)2:0.30Yb3+,0.02Er3+ sample showed intensely green light with dominant emission peaks at 528 and 550 nm corresponding to Er3+ transitions 2H11/2→4I15/2 and 4S3/2→4I15/2, respectively, as well as a weak emission peak originating from 4F9/2→4I15/2 at 671 nm, under 975 nm laser excitation. The CsGd(MoO4)2:Yb3+,Ho3+ samples mainly displayed two emission bands around 540 and 660 nm together with a negligible one at 755 nm, which corresponded to Ho3+ transitions 4F4,5F2→5I8, 5F5→5I8 and 4F4,5F2→5I7, respectively, under 975 nm laser excitation. With increasing Yb3+ concentration in CsGd(MoO4)2:Yb3+,Ho3+ phosphors, the emission color could be tuned from orange red to light yellow due to the large energy gap between levels 4F4,5F2 and 5F5. In addition, the CsGd(MoO4)2:Yb3+,Er3+ showed green light under 376 nm UV irradiation similar to that upon 975 nm laser excitation. However, the emissions for CsGd(MoO4)2:Yb3+,Ho3+ samples under 358 nm UV or 449 nm blue excitation showed dominant emission peaks at 540 nm and weak 660 nm and 752 nm peaks, which were a bit different from those under 975 nm excitation. Interestingly, we observed efficient energy transfer phenomena (possible quantum cutting) from Er3+/Ho3+ to Yb3+ and a Yb3+–O2− charge transfer (CT) transition in the molybdates, which was deduced from the visible and near-infrared emission spectra and the decrease of the Er3+/Ho3+ luminescent lifetimes with increasing Yb3+ concentration in the CsGd(MoO4)2:Yb3+,Er3+/Ho3+ samples. The luminescence properties of these phosphors suggest their potential possibility for applications in solid-state lighting and displays as well as in c-Si solar energy conversion systems. [ABSTRACT FROM AUTHOR]

Owing to their remarkable optical properties, all-inorganic cesium lead halide perovskite CsPbX3 (X = Br, Cl, and I) quantum dots (QDs) have emerged as promising materials for a variety of applications, such as solar cells and light-emitting diodes. However, these perovskite QDs can only be excited under short-wavelength light with high power below 600 nm, which limits their applications. Herein, we demonstrate an effective strategy to realize near-infrared (NIR) pumping for CsPbBr3 QDs through energy transfer from lanthanide-doped upconversion nanoparticles (UCNPs). UCNP/QD pairs with different molar ratios were synthesized by an in situ growth method. Transmission electron microscopy images show that the configuration of the assembly is dependent on the molar ratio of the two units which are distributed homogenously with high surface contact. A high energy transfer efficiency ∼100% from the UCNP donors to the QD acceptors is achieved, leading to intense green emission from the perovskite CsPbBr3 QDs under NIR laser light even in a liquid suspension. Additionally, the high photostability of CsPbBr3 QDs under NIR irradiation suggests that this strategy can be a critical step for the development of perovskite-based functional emitters or devices with long-term operational stability. [ABSTRACT FROM AUTHOR]