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Novel temperature-sensitive luminescent materials, Ba 2 Gd 2 Ge 4 O 13 doped with Bi 3+ , Bi 3+ /Sm 3+ or Bi 3+ /Eu 3+ ions, have been prepared using a conventional solid-state reaction technique. The XRPD study has verified that all the synthesized germanates crystallize in the monoclinic system (space group C 2/ c , Z = 4). The crystal lattice of the compounds consists of zigzag chains of edge-sharing Me 2 O 7 (Me = Bi 3+ , Eu 3+ or Sm 3+ ) dimers, [Ge 4 O 13 ] units, and ten-coordinated Ba atoms. Under UV excitation the powders exhibit the luminescence corresponding to the 3 P 1 → 1 S 0 (310-550 nm) transition in Bi 3+ and 4 G 5/2 → 6 H J (550-730 nm) in Sm 3+ or 5 D 0 → 7 F J (570-720 nm) transitions in Eu 3+ ions. Heating of Ba 2 Gd 1.94 Bi 0.01 Sm 0.05 Ge 4 O 13 and Ba 2 Gd 1.89 Bi 0.01 Eu 0.1 Ge 4 O 13 phosphors leads to an irregular decrease in the intensity of the main emission lines. It has been found that the fluorescence intensity ratio between a wide band in the 310-530 nm region and peaks at longer wavelengths may be successfully used as a temperature-dependent characteristic. Absolute/relative sensitivity values for Ba 2 Gd 1.94 Bi 0.01 Sm 0.05 Ge 4 O 13 and Ba 2 Gd 1.89 Bi 0.01 Eu 0.1 Ge 4 O 13 germanates reach 0.19% K -1 /0.80% K -1 and 2.21% K -1 /0.58% K -1 , respectively. The above parameters indicate that Ba 2 Gd 2 Ge 4 O 13 :Bi 3+ /Sm 3+ or Bi 3+ /Eu 3+ samples can be used as potential luminescent materials for non-contact temperature measurement.

A new series of BaRE 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ) (RE = Tm, Yb, Lu) germanates and activated phases BaYb 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ): x Tm 3+ and BaLu 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ):12 y Yb 3+ , y Tm 3+ have been prepared using a solid-state reaction. An XRPD study has revealed that the compounds crystallize in the monoclinic system (space group P 2 1 / m , Z = 2). The crystal lattice consists of zigzag chains of edge-sharing distorted REO 6 octahedra, bowed trigermanate [Ge 3 O 10 ] units, [Ge 2 O 7 ] groups, and eight-coordinated Ba atoms. The density functional theory calculations have confirmed a high thermodynamic stability of the synthesized solid solutions. According to the results of vibrational spectroscopy studies and diffuse reflectance measurements, the BaRE 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ) germanates are promising compounds for the creation of efficient lanthanide ion activated phosphors. Under 980 nm laser diode excitation, the BaYb 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ): x Tm 3+ and BaLu 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ):12 y Yb 3+ , y Tm 3+ samples exhibit upconversion luminescence corresponding to the characteristic 1 G 4 → 3 H 6 (455-500 nm), 1 G 4 → 3 F 4 (645-673 nm) and 3 H 4 → 3 H 6 (750-850 nm) transitions in Tm 3+ ions. Heating of the BaLu 6 (Ge 2 O 7 ) 2 (Ge 3 O 10 ):12 y Yb 3+ , y Tm 3+ phosphor with the optimal composition up to 498 K leads to the enhancement of a broad band at 673-730 nm, caused by 3 F 2,3 → 3 H 6 transitions. It has been revealed that the fluorescence intensity ratio between this band and the band at 750-850 nm may be used for temperature sensing. The absolute and relative sensitivities in the studied temperature range reach 0.021% K -1 and 1.94% K -1 , respectively.

Aza -pinacol coupling of N -benzyl-1-phenylmethanimine using Zn dust affords a mixture of R , S- or R , R -diastereomers in a 1:1 ratio. The R , S -diastereomer is solid with an m.p. of 135 °C, while the R , R- diastereomer is liquid at room temperature. The configuration of stereocenters was determined by combining X-ray powder diffraction and density functional theory (DFT) modeling., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The sorption of copper(II) ions in a wide range of pH by two Russian carbon sorbents BAU-A and MIU-S was studied. Sorbents varied in structure, surface area, pH of the point of zero charge (pH ZPC ), and graphitization degree. The sorption studies were conducted in batch mode. The removal of copper(II) ions from a solution at pH 4, 5, 6, and 6.7 is described by the classical adsorption isotherms of Freundlich, Langmuir, and Dubinin-Radushkevich. With an increase in pH from 4 to 6.7, the sorption capacity of sorbents increases, from 0.910 to 7.163 mg/g for BAU-A, and from 0.265 to 3.307 mg/g for MIU-S. The relationship between the degree of crystallinity and the sorption properties of sorbents has been established.

Removal of heavy metal ions, in particular, divalent nickel ions from natural and wastewater, is of great importance for the environment. Nickel (II) ions are very toxic and provoke many diseases. The purpose of this work was to study the possibility of removing toxic nickel (II) ions from polluted water using an iron (III) chloride (FeCl3) coagulant. It is shown that the removal of nickel ions from aqueous solution by iron (III) hydroxide precipitate formed during the coagulation process at pH 7 and 8 is described with satisfactory accuracy by the classical adsorption isotherms of Freundlich, Langmuir, and Dubinin-Radushkevich. The studies performed with the use of X-ray powder diffraction and thermal analyses, IR, Raman, and Mössbauer spectroscopy have shown that the uptake of nickel ions by iron (III) hydroxide precipitate is due to simple physical adsorption and is not accompanied by the formation of mixed iron and nickel compounds. No alloying of the formed iron (III) hydroxide precipitate with nickel ions takes place either. The formed iron (III) hydroxide precipitate is a two-line ferrihydrite having the gross formula Fe 2 O 3  × 3H 2 O. Its sorption capacity for nickel ions is almost an order of magnitude higher than that of some mineral and carbon sorbents, and at pH 7 and 8, it is 60.5 and 141.9 mg/g, respectively. PRACTITIONER POINTS: Coagulant FeCl 3 cleans contaminated solutions from Ni(II) ions. Iron (III) hydroxide precipitated at pH 7 and 8 is a two-line ferrihydrite Fe 2 O 3  × 3H 2 O. Removing of Ni(II) ions is described by classical adsorption isotherms. The most complete removal of Ni(II) ions occurs at pH = 8., (© 2022 Water Environment Federation.)

A new series of Ba 2 RE 2 Ge 4 O 13 (RE = Pr, Nd, Gd, Dy) germanates and Ba 2 Gd 2-x Eu x Ge 4 O 13 (x = 0.1-0.8) solid solutions have been synthesized using the solid-state reaction technique and characterized by X-ray powder diffraction. All compounds crystallize in the monoclinic system, space group C2/c, Z = 4. The crystal lattice consists of RE 2 O 12 dimers, zigzag C 2 -symmetric [Ge 4 O 13 ] 10- tetramers, and ten-coordinated Ba atoms located in voids between polyhedra. The density-functional theory (DFT) calculations performed on a rich set of Ba 2 RE 2 Ge 4 O 13 compounds have confirmed the high thermodynamic stability of monoclinic modification. Under ultraviolet (UV) light excitation Ba 2 Gd 2-x Eu x Ge 4 O 13 phosphors exhibit an orange-red emission corresponding to the characteristic f-f transitions in Eu 3+ ions. The highest intensity of lines at 580 nm ( 5 D 0 → 7 F 0 ), 582-602 nm ( 5 D 0 → 7 F 1 ), 602-640 nm ( 5 D 0 → 7 F 2 ), 648-660 nm ( 5 D 0 → 7 F 3 ), and 680-715 nm ( 5 D 0 → 7 F 4 ) is observed for the samples with x = 0.4-0.6. The possibility of their application has been assessed by studying their color characteristics, quantum efficiency, and thermal stability. The obtained data indicate that Ba 2 Gd 2-x Eu x Ge 4 O 13 solids can be considered as promising materials for UV-excited phosphor-converted light-emitting diodes (LEDs) if an aluminum nitride substrate (λ ex = 255 nm) is used as a semiconductor chip.

Olivine-type phosphate LiMgPO4 doped with rare-earth elements is currently considered as a new dosimetric material suitable for both OSL and TSL applications and able to compete with top commercial detectors. In this work, the samples of LiMgPO4:Er3+ were synthesized by the conventional solid state reaction method. We first studied X-ray luminescence and thermally and optically stimulated luminescence in LiMgPO4:Er3+ in detail. Our studies included the structure refinement, DFT calculations, which predicted the preferred positions of both erbium and charge-compensating vacancies, and UV-vis spectroscopy. We showed that the thermoluminescence spectrum of irradiated LiMgPO4:Er3+ does not contain components caused by the 4f-4f transitions in erbium, but coincides with the spectrum of the phosphate matrix with two broad bands at 360 nm and 650 nm. We discovered a high OSL and TSL output in LiMgPO4:Er3+, despite the nonradiative deexcitation of erbium ions.

Polymeric carbon nitride materials have been used in numerous light-to-energy conversion applications ranging from photocatalysis to optoelectronics. For a new application and modelling, we first refined the crystal structure of potassium poly(heptazine imide) (K-PHI)-a benchmark carbon nitride material in photocatalysis-by means of X-ray powder diffraction and transmission electron microscopy. Using the crystal structure of K-PHI, periodic DFT calculations were performed to calculate the density-of-states (DOS) and localize intra band states (IBS). IBS were found to be responsible for the enhanced K-PHI absorption in the near IR region, to serve as electron traps, and to be useful in energy transfer reactions. Once excited with visible light, carbon nitrides, in addition to the direct recombination, can also undergo singlet-triplet intersystem crossing. We utilized the K-PHI centered triplet excited states to trigger a cascade of energy transfer reactions and, in turn, to sensitize, for example, singlet oxygen ( 1 O 2 ) as a starting point to synthesis up to 25 different N-rich heterocycles., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Two new lithium-magnesium phosphates LiMg 6 (PO 4 ) 3 (P 2 O 7 ) and Li(Mg 5.62 Sc 0.19 Li 0.19 )(PO 4 ) 3 (P 2 O 7 ) were synthesized by a solid-phase method. Using high-resolution time-of-flight neutron powder diffraction (TOF NPD) and X-ray powder diffraction (XRPD), we established that these phosphates have a Pnma orthorhombic structure with the cell parameters a = 9.14664(5) Å, b = 18.83773(8) Å, c = 8.27450(4) Å, and V = 1425.71(1) Å 3 and a = 9.14516(5) Å, b = 18.84222(9) Å, c = 8.28204(4) Å, and V = 1427.12(1) Å 3 , respectively. The crystal structures can be described by stacking of the [Mg 6 O 18 ] ∞ or [Mg 5.62 Sc 0.19 Li 0.19 O 18 ] ∞ wavy layers, which are parallel to the (100) direction and interconnected through PO 4 tetrahedra and P 2 O 7 groups to form a 3D-framework. The Li atoms are located in large tunnels formed in a 3D lattice, which contributes to lithium diffusion. AC impedance spectroscopy analysis shows that LiMg 6 (PO 4 ) 3 (P 2 O 7 ) and Li(Mg 5.62 Sc 0.19 Li 0.19 )(PO 4 ) 3 (P 2 O 7 ) have a Li ion conductivity of 3.6 × 10 -4 S cm -1 and 1.7 × 10 -4 S cm -1 at 950 °C, with an activation energy of 1.28 eV and 1.55 eV, respectively. NMR MAS studies confirmed the coexistence of pyro- and orthogroups in the structure of both phases and two lithium positions in Li(Mg 5.62 Sc 0.19 Li 0.19 )(PO 4 ) 3 (P 2 O 7 ). The first-principles method was used to study the electronic structure and stability of the two phases. The calculated formation enthalpies demonstrated that Sc is a stabilizing impurity in LiMg 6 (PO 4 ) 3 (P 2 O 7 ), while a strong destabilization of olivine LiMgPO 4 is observed upon doping with Sc. This explains the failure to synthesize Sc-doped olivine. The new phosphate LiMg 6 (PO 4 ) 3 (P 2 O 7 ) is a dielectric with a band gap of 5.35 eV, which decreases to 4.85 eV due to the appearance of a localized Sc 3d peak upon doping with Sc. These findings are consistent with the results obtained by UV-Vis spectroscopy. The new phase may be a good optical matrix similar to LiMgPO 4 .

Gallium-doped aluminum oxide (Al 1-x Ga x ) 2 O 3 with γ-Al 2 O 3 (spinel) structure has been synthesized by the precursor method using the formate Al 1-x Ga x (OH)(HCOO) 2 as a precursor. The examination of Al 1-x Ga x (OH)(HCOO) 2 (x = 0.0, 0.1, 0.2, 0.3, 0.4) was carried out by X-ray powder diffraction, Infrared, Raman spectroscopy and differential-thermal methods. The solid solutions γ-(Al 1-x Ga x ) 2 O 3 with х≤0.2 have been synthesized by thermolysis of precursors in helium atmosphere at 700 °C; they exhibit white-blue emission under UV excitation, whose intensity lowers with increasing dopant concentration. As an independent method, the DFT calculations confirmed thermodynamically the stability field of γ-(Al 1 -x Ga x ) 2 O 3 solid solutions and the NMR data on relative abundance of Al and Ga within the tetrahedral and octahedral sites in the metal sublattice. Furthermore, the structural and thermodynamic properties of carbon-containing impurities within these compounds were suggested theoretically as possible models of luminescence emission centers. The experimentally observed Ga-dependent quenching of luminescence was explained using the competition between C2p and Ga4p states within the band gap of γ-Al 2 O 3 ., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The apatite-like NaLa9(GeO4)6O2:Nd3+,Ho3+ phosphor is prepared using the solid-state method. Rietveld refinement of high-resolution time-of-flight neutron powder diffraction measurements indicate that this compound crystallizes in the hexagonal system with space group P63/m, Z = 1 and unit cell parameters a = 9.88903(6) Å, c = 7.25602(5) Å, V = 614.521(7) Å3 at room temperature. The 4f sites are statistically occupied by La, Nd and Na, while 6h sites are occupied by La and Nd. Luminescence in the near- and middle-IR range caused by the transitions in neodymium and holmium ions is excited under 808 nm laser diode radiation. The highest emission intensity in NaLa9-x-yNdxHoy(GeO4)6O2 is attained at trace amounts of holmium, and it decreases sharply when y increases to 0.01. The IR phosphors have a good thermal stability and exhibit a very weak upconversion emission in the red spectral range upon 808 nm excitation. A scheme of excitation and emission pathways involving ground/excited state absorption, energy transfer, cross-relaxation, nonradiative multiphonon relaxation processes in Nd3+ and Ho3+ ions has been proposed. The data analysis indicates that Nd3+ ions serve as sensitizers for Ho3+ ions in these compounds, stimulating intense 2.1 μm and 2.7 μm emissions. These apatite-related germanate phosphors are promising materials for near- and middle-infrared solid-state lighting applications.

Simultaneous emission lines around 1.05μm, 1.3μm, 1.8μm, 2.1μm and 2.7μm have been observed in Li 7 La 3-x Nd x Hf 2 O 12 :Ho 3+ (x=0.00-0.15) under 808nm laser diode excitation. Near-infrared luminescence due to holmium ions with residual concentration in the Li 7 La 3 Hf 2 O 12 host has been studied. The intensity of 2.1 and 2.7μm lines associated with 5 I 7 → 5 I 8 and 5 I 6 → 5 I 7 transitions in Ho 3+ depends on the neodymium codopant concentration. This result indicates that Nd 3+ ions can be potentially used as sensitizers for Ho 3+ ions to stimulate the intense near-infrared emission in this system. Possible energy transfer mechanisms between lanthanide ions have been briefly discussed., (Copyright © 2017 Elsevier B.V. All rights reserved.)

We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCo 3 V 4 O 12 double perovskite with the high-spin (HS) Co 2+ ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co 2+ ions in the direction perpendicular to the oxygen planes. Although this effect is reminiscent of a continuous HS → LS transformation of the Co 2+ ions, it did not result in the anticipated shrinkage of the cell volume because of a certain "stiffing" of the bonds of the Ca and V cations. We verified that the oxidation states of all the cations did not change across this crossover, and hence, no charge-transfer effects were involved. Consequently, we proposed that CaCo 3 V 4 O 12 could undergo a phase transition at which the large HS-Co 2+ ions were pushed out of the oxygen planes because of lattice compression. The antiferromagnetic transition in CaCo 3 V 4 O 12 at 100 K was investigated by neutron powder diffraction at ambient pressure. We established that the magnetic moments of the Co 2+ ions were aligned along one of the cubic axes, and the magnetic structure had a 2-fold periodicity along this axis, compared to the crystallographic one.

Ba7Li1.75Mn3.5O15.75 is a new hexagonal perovskite whose crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. It has been synthesized via a solid-state microwave route. The crystal structure was solved using a combination of X-ray and neutron diffraction data, which show that Ba7Li1.75Mn3.5O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) Å and c = 16.7467(1) Å (V = 465.063(4) Å(3)), with one formula unit, and can be described as columns of face-shared octahedra occupied by Mn(4+) and Li(+) cations and vacancies along the c axis separated in the ab plane by barium atoms. Every sixth layer, the coordination of Mn(5+) and Li(+) changes to tetrahedral. Additional local ordering of manganese and lithium atoms among cationic sites leading to the formation of a rhombohedral supercell has been observed by scanning transmission electron microscopy.