Blue,green,red upconversion luminescence and optical characteristics of rare earth doped rare earth oxide and oxysulfide

The cold isostatic press pretreatment process was adopted to prepare fine rare earth oxysulfide up-conversion phosphors with spherical shape, narrow size distribution and high luminescence efficiency. The upconversion optical characteristics and brightness of the blue (Y2O2SYb,Tm), green (Y2O2S: Yb,Er), red (Y2O3Yb,Er) emitter were also investigated, and a novel method was successfully developed for the brightness measurement of upconversion luminescence (UPL). It is shown that a white color can be obtained by the appropriate mixture of these primary blue, green and red emissions components. The Er3 ions exhibit different upconversion mechanism in Y2O2S and Y2O3 host materials. The rare earth oxysulfide is an efficient upconversion matrix. The UPL brightness of Y2O2S: Yb,Er is 6.5 times higher than that of Y2O3: Yb,Er, and Y2O2S: Yb,Er shows UPL brightness of 1100 cd/m2 under 5.56 W/cm2 power density using a 980 nm laser diode.     

~1H and ~(13)C NMR studies of TTHA complexes with diamagnetic rare earth ions

TTHA complexes with diamagnetic rare earth ions (La3+, Y3+ and Lu3+) were studied by 1H and 13C NMR spectroscopy. A symmetric structural model was suggested for La(TTHA) complex and an asymmetric model for Y(TTHA) and Lu(TTHA) complexes. The complex formation was dependent on the pH value of the solution. The interactions of La(TTHA) with the additional metal ions (La3+, Y3+ and Ca2+) were relatively weak, but relatively strong for that of Lu(TTHA) with the additional Lu3+.     

Decomposition process and kinetics of waste rare earth polishing powder TG–DTA–FTIR studies

The decomposition reaction process of waste rare earth (RE) polishing powder was monitored in real time by the thermogravimetry?Cdifferential thermal analysis (TG?CDTA) and Fourier transform infrared spectroscopy (FTIR). The results showed that the reaction was divided into two stages, and the thermal weight losses got to stable when the temperature was more than 400?°C. The releasing gas mainly contained H₂O and SiF₄, and the reaction kinetics during decomposition process was studied by the methods of Freeman-Carroll and Kissinger.     

Coordination complexes of rare earth metals with hydrazine and isomeric acetamidobenzoates as ligands– spectral,thermal and kinetic studies

The isomeric acetamido benzoic acids (abbreviated as acambH) on reaction with hydrazine hydrate and lanthanides, La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺ and Gd³⁺ form complexes of formulae, [Ln{x-C₆H₄(CH₃CONH)}₃(N₂H₄)] where x = 2 (or) 3 (or) 4, at pH 3–4.5 in (1:1) aqueous ethanolic medium, which are insoluble in water and organic solvents. They are characterized by using elemental analysis, IR, UV, ¹³C, ¹H NMR and mass spectroscopic, XRD, SEM-EDAX, thermal and conductance studies. The difference between IR bands of v_{C=O asym} (acid) and v_{C=O sym}(acid) range, 122–166 cm^?1 supports the bidental coordination of carboxylate ions to metal. v_N-N values of 955 to 980 cm^?1, substantiate bridging bidentate coordination of hydrazine to metal. v_C=O of amide group 1632 to1709 cm^?1 indicates its non-coordination with metal. The thermal studies reveal that complexes undergo dehydrazination between 52 and 180 °C and exothermic degradation into phthalate intermediate between 172 and 496 °C and further degradation to form microsized metal oxide around 600 °C. The magnetic susceptibility measurements indicated that the presence of metals in the same electronic state and electronic spectral assignments suggested that the coordination number is eight for the complexes. The conductance measurement results in DMSO medium indicated that the complexes are neutral. The ¹³C – NMR, ¹H- NMR and the LC-Mass techniques substantiated the composition of the complexes.     

Theoretical studies of the reactions of Cl atoms with CF3CH2OCH n F(3−n) (n = 1, 2, 3)

This paper presents the theoretical studies of the reactions of Cl atoms with CF₃CH₂OCH₃, CF₃CH₂OCH₂F and CF₃CH₂OCHF₂ using an ab initio direct dynamics theory. The geometries and vibrational frequencies of the reactants, complexes, transition states and products are calculated at the MP2/6-31+(d,p) level. The minimum energy path is also calculated at same level. The MC-QCISD method is carried out for further refining the energetic information. The rate constants are evaluated with the canonical variational transition state theory (CVT) and CVT with small curvature tunneling contributions in the temperature range 200–1,500 K. The results are in good agreement with experimental values.     

Signature of ferromagnetism,antiferromagnetism, charge ordering and phase separation by electron paramagnetic resonance study in rare earth manganites,Ln1−xAxMnO3 (Ln=rare earth,A=Ca,Sr)

Phase separation has been recognized as an important ingredient to create the colossal magnetoresistance (CMR). To be able to characterize the phase separation signature by electron spin resonance (ESR), a preliminary work has been undertaken in order to check typical ESR behaviours of prototype manganites. These behaviours are antiferromagnetism (A-type, CE-type), charge order, ferromagnetism and phase separation. Five compounds were chosen, each of them exhibiting a specific characteristic (e.g., Pr_0.4Ca_0.6MnO₃ undergoes a charge ordered state followed by a antiferromagnetic state at lower temperature). The onset of the transitions has been determined from the temperature dependence of four main parameters deduced from the ESR spectra, the g_eff factor, the linewidth ΔH_pp, the intensity and the line asymmetry.     

Nanostructural oxide “memory” of rare earth molybdates

The structural aspects of the acid-base interaction in the course of formation of molybdates in the binary systems Ln₂O₃-MoO₃ have been considered. The structures of rare earth molybdates inherit infinite bands of {[LnO _n ]-[LnO _n ]} dimers from the structures of Ln₂O₃ oxides. The nanostructural oxide “memory” of molybdates implies that the dimers in these bands retain approximately nanometer sizes and predominant mutual orientation despite the fact that, as the Mo formula content increases, the types of polyhedra in the dimers change and the contacts between dimers and, eventually, between the polyhedra in these dimers are lost.     

Chemical effects of (n, γ) nuclear reaction on (Mo6Cl8)Cl4

The chemical effects of⁹⁸Mo(n, )⁹⁹ Mo reaction on molybdenum(II) chloride [(Mo₆Cl₈)Cl₄] have been studied. Retention, thermal and radiolytical annealing were determined. It was found that this molybdenum compound has low retention, a negligible tendency to thermal annealing and a virtual insensitivity to hydrolysis. For practical application in the enrichment of⁹⁹Mo by the Shilard-Chalmers method, molybdenum(II) chloride [(Mo₆Cl₈)Cl₄] appears to offer good prospects.     

Coordination field analysis of rare earth complexes with triangular symmetry

The calculation of the complex matrixes in odd triangular symmetry was accomplished.The configurations of the coordination unit with various triangular symmetries and different ligand numbers were discussed.On the basis of the double-sphere coordination point-charge (DSCPCF) model,the detailed forms of the DSCPCF parameters Bmk and the expressions of the perturbation matrix elements in triangular field (D3,D3h,D3d) were derived.Thereby,the calculation scheme of coordination field perturbation energy of the rare earth complexes with triangular symmetry was constructed After the calculation scheme was programmed,the Stark energies of the crystalline TbAl3(BO3)4 were calculated The results were considerably close to the experimental values     

Rare earth metal complexes with 1,3-bis-(2-hydroxyphenyl)-1,3-propanedione. An example of anhydrous rare earth β-diketonates

Summary The interaction of non-anhydrous solutions of the ligand 1,3-bis-(2-hydroxyphenyl)-1,3-propanedione (bhppH₃) with hydrated rare earth chlorides resulted in the formation of anhydrous, non-solvated, complexes M(bhppH₂)₃ (M=Y, La, Nd, Pr, Sm or Yb). The complexes have been characterized by elemental analysis, t.g., i.r. and¹H n.m.r. spectroscopy. The evidence suggests that the coordination is through the -diketone site.     

Synthesis and NMR spectral studies of the 7-C₆₀-adduct of n,n-(tetrachlorophthaloyl) dehydroabietylamine

The 7-C??-adduct of N,N-(tetrachlorophthaloyl)dehydroabietylamine was synthesized for the first time and characterized by IR, UV-vis, mass and NMR spectral studies. The 1H-NMR and 13C-NMR resonance signals of the new compound are unambiguously assigned by using homo- and heteronuclear 2D NMR spectroscopic techniques such as COSY, ROESY, HSQC and HMBC. The C? symmetric structure with 6,6-junction of compound was determined.     

Crystal structures of the complexes of rare earth picrates with N, N, N'''', N''''-tetraphenyl-3, 6-dioxaoctanediamide

The complexes of rare earth picrate with N,N,N',N'-tetraphenyl-3,6-dioxaoctanediamide(TDD),Eu(picc(TDD)] 2CH3CN and [ Y(pic)3(TDD)],have been synthesized.The crystal structures reveal that TDD at is as n tetradentate ligand,forming a ring-like coordination structure with its oxygen atoms together with one oxygen atom of the bidentate pterate In the Eu(Ⅲ) complex,the europium ion with a larger ionic radius lies out of the ring,while in the Y(Ⅲ) complex,the yttrium ion with a smaller ionic radius enters the cavity of the ligand.The structures of the complexes are greatly affected by the ionic radii due to participation of the picrates in coordination.     

(n,γ)-radiolysis of magnesium iodate

The initial retention of thermal neutron irradiated magnesium iodate tetrahydrate was found to be 47% and increased to 54% for the dehydrated salt. The post irradiation isothermal annealing followed the characteristic pattern both in hydrated and dehydrated salts; the rate of increase in retention in the hydrated salt being faster than in the dehydrated form. At an annealing temperature of 453 K, 100% retention was achieved by the hydrated salt but the corresponding value for the dehydrated magnesium iodate was not higher than 88%. The role of water of crystallization in the retention studies of magnesium iodate is discussed.     

Synthesis,structure, spectroscopic,magnetic and electrochemical studies of a rare syn–anti acetate-bridged copper(II) complex

The structure, spectroscopy and electrochemical properties of a novel dinuclear copper(II) complex, [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ where phen = 1,10-phenanthroline, is reported. The crystal structure contains two independent Cu(II) ions, with different geometry around each copper center, which are bridged by an acetate anion. The acetate-bridged ligand shows a syn–anti coordination mode with a trigonal bipyramidal geometry for the Cu(1) center and a distorted square-based pyramidal geometry for the Cu(2) center. The angular structural index parameter τ for Cu(1) and Cu(2) is 0.9 and 0.33, respectively. The copper(II) atoms display a different geometry with a N₄O chromophore group and with Cu–O distances of 1.993(5)–1.996(5) Å and Cu–N distances which vary from 1.980(5) to 2.161(6) Å. The intra Cu…Cu separation is 4.9904(5) Å. The effective magnetic moment (μ_eff) of the complex was measured by the Evans method. The cyclic voltammogram of [{Cu(phen)₂}₂(μ-CH₃COO)][PF₆]₃ shows two waves at positive potential which are assigned to the two Cu(II/I) reduction couples.     

Determination of rare earth elements and other trace elements (Y, Mn, Co, Cr) in seawater using Tm addition and Mg(OH)₂ co-precipitation

This paper reports on a novel procedure for determining trace element abundances (REE and Y, Cr, Mn, Co) in seawater by inductively coupled plasma sector field mass spectrometry (ICP-SFMS). The procedure uses a combination of pre-concentration using co-precipitation onto magnesium hydroxides and addition of thulium spike. The validity of the method was assessed onto 25 ml volumes of certified reference materials (NASS- and CASS-4) and in house seawater standard. Procedural blanks were determined by applying the same procedure to aliquots of seawater previously depleted in trace elements by successive Mg(OH)₂ co-precipitations, yielding estimated contributions to the studied samples better than 1.1% for all elements, with the exception of Cr (<3.3%) and Co (up to 8%). The reproducibility of the method over the six month duration of the study was smaller than 11% RSD for all the studied elements. Results obtained for NASS-5 and CASS-4 agree well with published working values for trace elements.     

Catalytic Activity of Molecular Rhenium Sulfide Clusters [Re6S8(OH)6−n (H2O) n ](4−n)− (n = 0, 2, 4, 6) with Retention of the Octahedral Metal Frameworks: Dehydrogenation and Dehydration of 1,4-Butanediol

A series of molecular rhenium sulfide clusters [Re₆S₈(OH)_6?n (H₂O) _n ]^(4?n)? (n = 0, 2, 4, 6) catalyze dehydrogenation of alcohols, and hydrogenation of ketones and olefins in a hydrogen stream at 350 °C. The catalytic activities of the dianionic and neutral clusters (n = 2, 4) are lower than those of tetraanionic and dicationic clusters (n = 0, 6) for all the reactions. When 1,4-butanediol is allowed to react over K₄[Re₆S₈(OH)₆], dehydrogenation proceeds to yield 2-hydroxytetrahydrofuran and successively γ-butyrolactone above 300 °C. Over [Re₆S₈(H₂O)₆]SO₄ dehydration proceeds to yield tetrahydrofuran above 250 °C. The thermal activation mechanisms of these clusters were studied by powder X-ray diffraction analyses, Raman spectrometry, extended X-ray absorption fine structure spectrometry, thermogravimetry, and differential thermal analyses. The catalytically active site of K₄[Re₆S₈(OH)₆] is an uncoordinated metal site (Lewis acid site) developed by the loss of a water molecule from two hydroxo ligands. The active site of [Re₆S₈(H₂O)₆]SO₄ is a Brønsted acid site; the anhydrous aqua cluster dication disproportionates to a hydroxo cluster monocation and a proton. Both of the octahedral cluster frameworks are retained up to 500 °C.