首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 531 毫秒
1.
Supramolecular pillared oxides were prepared through the intercalation of M2+ cations into a MnO2 host matrix by the method of ion exchange between the precursor δ-K x MnO2 and the corresponding guest. The materials M-MnO2 crystallize in the hexagonal system, the same structure as the precursor, with a larger interlamellar spacing. In the case of ZrO-MnO2, extended X-ray absorption fine structure (EXAFS) determination indicates that the Zr atom locates between the MnO2 layers forming a stable structure. Compared with the precursor, the cycling property of M-MnO2 was improved distinctly, while the capacity decreased to some degree due to the strong interaction between pillars and the host matrix. Among these pillared materials, ZrO-MnO2 has an advanced reversible capacity of 161.5 mAh·g−1 and improved cycling behavior compared with the precursor.  相似文献   

2.
For the Er3+–Yb3+ codoped Al2O3 powders, the strong near-infrared photoluminescence (PL) centered at 1.535 μm derived from the energy transfer (ET) from Yb3+ to Er3+ was detected by a 978 nm laser diode excitation. Compared with that of Er3+ doped Al2O3 powders, the PL intensity enhanced about 9 times, the full width at half maximum (FWHM) extended from 82 to 90 nm, and the lifetime increased from 3.22 to 4.17 ms for Er3+–Yb3+ codoped Al2O3 powders at room temperature. The ET coefficient of 2.18 × 10−18 cm3 s−1 from Yb3+ to Er3+ was obtained based on the rate equations. The decrease of PL intensity with increasing temperature in the range of 298–733 K was observed, due to thermally enhanced nonradiative relaxation 4I13/2 → 4I15/2 dominated over thermally enhanced phonon-assisted ET in the Er3+–Yb3+ codoped Al2O3.  相似文献   

3.
Double complex salts (DCS) α-[Pd(NH3)4][IrF6]·H2O (P21/m, a = 6.3181(3) Å, b = 10.8718(5) Å, с = 7.4526(4) Å, β = 103.568(2)°), β-[Pd(NH3)4][IrF6]·H2O (P21/с, a = 8.5773(3) Å, b = 10.8791(4) Å, с = = 12.6741(3) Å, β = 122.497(2)°), [Pd(NH3)4]3[IrF6]2Cl2·H2O (P-1, a = 7.6080(2) Å, b = 7.6274(2) Å, с = 11.8070(3) Å, β = 122.497(2)°), and [Pd(NH3)4]2[IrF6]NO3 (Fm-3m, a = 11.21210(10) Å) have been synthesized and structurally characterized for the first time. The existence of polymorphs for the DCS has been revealed. The influence of the chemical composition of the initial reagents on the reaction course and, respectively, the products, has been demonstrated. A hypothesis on the influence of the second coordination sphere on the formation of one or the other polymorph of the DCS has been suggested. It has been shown that the series α-[Pd(NH3)4][МF6]·H2O (M = Pt, Pd) exhibits isostructurality.  相似文献   

4.
The complex [(HOCH2)3CNH3] 2 + [HgI4]2? (I) was synthesized by reacting (trioxymethyl)methylammonium iodide with mercury dioide (2: 1 mol/mol) in acetone. X-ray crystallography shows that the complex consists of two types of crystallographically independent [(HOCH2)3CNH3]+ cations and tetrahedral anions [HgI4]2? (IHgI, 106.49(2)°–113.99(4)°; Hg-I, 2.7849(8)-2.8105(8) Å. [(HOCH2)3CNH3]+ cations are linked via hydrogen bonds O…H-N and O-H…N (O…N, 2.84–2.92 Å) to form polymer chains, which are cross-linked with one another via anions (I…H, 2.81, 2.82 Å).  相似文献   

5.
Slow evaporation of water solution of [{Re6S8}(H2O)6]2+ generated in situ from [{Re6S8}(OH)6]4– in presence of γ-cyclodextrin (CD) leads to crystallization of {[{Re6S8}(H2O)6] ? [γ-CD]}(NO3)2·12H2O (1·12H2O) supramolecular complex, which was characterized by single-crystal X-ray diffraction crystallography, IR-spectroscopy, thermogravimetric and elemental analyses. X-ray analysis confirms the formation of 1:1 {[{Re6S8}(H2O)6] ? [γ-CD]}2+ inclusion compound in the solid state. However, no adduct formation was detected between [{Re6S8}(H2O)6]2+ and γ-cyclodextrin in solution, according to 1H NMR spectroscopy. In the case of in situ generated [{Re6Se8}(H2O)6]2+ the reaction solution with γ-cyclodextrin is unstable and during the crystallization only amorphous precipitate has been obtained.  相似文献   

6.
Near-infrared (NIR) quantum cutting phosphors serve as a potential material for fabricating photovoltaic spectral convertors. In many cases, quantum cutting phosphors are obtained via a wet chemical method coupled with a post-annealing treatment—a very costly process. In this report, we used continuous flame spray pyrolysis (FSP) for fabricating Y2O3:Tb3+–Yb3+ quantum-cutting phosphors without any post-treatment. Based on characterizations by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we found that as-synthesized Y2O3:Tb3+–Yb3+ phosphors exhibit hollow and shell-like micro-structures composed of highly crystalline and pure cubic-phase nanoparticles (< 50 nm). Photoluminescence studies of the phosphors revealed that NIR emissions appeared with the introduction of Yb to Y2O3:Tb3+. Phosphor size was successfully controlled by managing the concentration of the metal precursor solution for FSP. The Y2O3:Tb3+–Yb3+ phosphors were then embedded into transparent poly-ethylene-co-vinyl acetate (EVA) film to form a spectral convertor. The composite films of Y2O3:Tb3+–Yb3+ phosphors and poly-EVA were found to be highly transparent in the visible range (> 500 nm), making them suitable as spectral photovoltaic convertors.  相似文献   

7.
Tb3+–Yb3+ co-doped Ca5(PO4)3F inverse opal photonic crystals were prepared by a self-assembly technique in combination with a sol–gel method. Upconversion luminescence characteristics of the inverse opals were investigated. The results indicate that photonic band gap has a significant effect on upconversion luminescence of Tb3+–Yb3+ co-doped Ca5(PO4)3F inverse opal. Significant inhibition of the green or blue upconversion luminescence was inspected if the photonic band gap overlapped with the emission band of Tb3+ ions.  相似文献   

8.
CaAl2Si2O8: Eu2+, Mn2+ phosphors have been prepared by a sol–gel method. X-ray diffractometer, spectrofluorometer and UV–Vis spectrometer were used to characterize structural and optical properties of the samples. The results indicate that anorthite (CaAl2Si2O8) directly crystallizes at 1000 °C in the sol–gel process. CaAl2Si2O8: Eu2+, Mn2+ phosphors show two emission bands excited by ultraviolet light. Blue (around 415 nm) and yellow (around 575 nm) emissions originate from Eu2+ and Mn2+, respectively. With appropriate tuning of Mn2+ content, CaAl2Si2O8: Eu2+, Mn2+ phosphors exhibit different hues and relative color temperatures.  相似文献   

9.
The synthesis, IR and Raman spectroscopic study, and X-ray diffraction analysis of [Ni(HL1)3](L2)2 · 4H2O (I), where HL1 is phenylacetic acid hydrazide and L2 is the benzoate monoanion, have been performed. The structural units of a crystal of complex I are complex [Ni(HL1)3]2+ cations, (L2) anions, and crystallization water molecules. The nickel atom is coordinated to the three oxygen atoms at octahedron apices and the three nitrogen atoms of three bidentate chelate (О, N) ligands HL1 in cis,trans-meredianal (fac) conformation. The structural units of a crystal of complex I are bonded by a branched network of О–Н···О and N–H···O hydrogen bonds.  相似文献   

10.
Preparative method in combination with X-ray diffraction and IR spectroscopy is used to study reaction of Sb(III) fluoride with -aminoisovaleric acid (DL-valine) in an aqueous solution in the range of the molar ratios of components (0.25–2) : 1 in the presence of hydrofluoric acid. The molecular complex of Sb(III) fluoride with valine (1 : 1) of the composition SbF3{(CH3)2CHCH(+NH3)COO}(I) and valinium tetrafluoro-antimonate(III) monohydrate {(CH3)2CHCH(+NH3)COOH}SbF4· H2O (II) are synthesized for the first time. Crystal structure was determined for the molecular complex I consisting of SbF3 groups and valine molecules united into polymer chains through bidentate bridging carboxylate groups of amino acid molecules.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 125–131.Original Russian Text Copyright © 2005 by Zemnukhova, Davidovich, Udovenko, Kovaleva.  相似文献   

11.
Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. The anhydrous oxalate mineral moolooite CuC2O4 as the natural copper(II) oxalate mineral is a classic example. Another example of a natural oxalate is the mineral wheatleyite Na2Cu2+(C2O4)2·2H2O. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition of wheatleyite at 255°C. Two higher temperature mass losses are observed at 324 and 349°C. Higher temperature mass losses are observed at 819, 833 and 857°C. These mass losses as confirmed by mass spectrometry are attributed to the decomposition of tennerite CuO. In comparison the thermal decomposition of moolooite takes place at 260°C. Evolved gas mass spectrometry for moolooite shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II) oxalate as compared to the synthetic compound which is the dihydrate.  相似文献   

12.
Nanostructured transparent glass-ceramics with composition of 95SiO2–5LaF3 co-doped with 0.3Yb3+, 0.1Ho3+ and 0.1Tm3+ (mol%) were synthesized by thermal treatment of precursor sol–gel derived glasses. X-ray diffraction and transmission electron microscopy analysis point out the precipitation of hexagonal LaF3 nanocrystals with diameter ranging from 11 to 20 nm in these nano-glass-ceramics. White light generation by means of efficient blue, green and red up-conversion luminescence under infrared excitation at 980 nm was observed and involved mechanisms were analyzed. Colour tuneability is achieved by varying the up-conversion emission ratios as a function of pump power.  相似文献   

13.
Ca3Al6Si2O16: Ce3+, Tb3+ phosphors have been prepared by sol–gel method. The structure and photoluminescence properties were studied with careful. The results indicated that the single-phased Ca3Al6Si2O16 phosphors crystallize at 1,000 °C for 2 h in conventional furnace. With appropriate concentrations of Ce3+ and Tb3+ ions into Ca3Al6Si2O16 matrix, these materials exhibit blue phosphors and white light under ultraviolet radiation. White-light emission can be achieved because of a 400 nm emission ascribed to transitions of Ce3+ ions and three sharp peaks at 487, 543, 585 nm, respectively, resulting from transitions of Tb3+ ions.  相似文献   

14.
A new coordination polymer, [Cd(NH3)4]2{Cd[Re3Mo3S8(CN)6]}·1.5H2O (I), was prepared by the reaction between solutions of Cd(CH3COO)2 · 2H2O in aqueous ammonia and CaK4[Re3Mo3S8(CN)6] · 8H2O in water. The crystals are cubic, space group Fm3m (Prussian blue structural type); a = 15.0268(4) Å (CIF file CSD no. 431555). According to ESR data, compound I is paramagnetic, g-factor is 2.298. Thermal stability investigation by TGA and powder X-ray diffraction showed that elimination of coordinated NH3 molecules is accompanied by sample amorphization.  相似文献   

15.
The complex [Ni(En)2][Ni(CN)4] · 3.5H2O (I) (En = ethylenediamine) was synthesized by the reaction of [Ni(En)2](ClO4)2 and K2[Ni(CN)4] in an H-shaped tube. The crystal structure of I has been determined by single-crystal X-ray analysis. The crystal of complex I is orthorhombic, space group Pnna with a = 28.151(3), b = 8.3946(8), c = 14.5441(13)Å, M =404.76, Z = 8, V = 3437.0(5)Å3. The structure of complex I reveals infinite zigzag chains shaped structure are formed by cis-Ni(En)2-μ-(NC)2, cis-μ-(NC)2Ni(CN)2, and trans-μ-(CN)2Ni(En)2.  相似文献   

16.
Phase equilibria in the reciprocal system 3Tl2S + Sb2Se3 ? 3Tl2Se + Sb2S3 are investigated by DTA, X-ray powder diffraction, and emf measurements. Some polythermal sections, the isothermal section of the phase diagram at 400K, and the liquidus-surface projection for this system are constructed. The types and coordinates of invariant and univariant equilibria are determined. It is shown that the system is non-diagonal. Broad regions of solid solutions are found on the basis of the binary compounds Tl2S and Tl2Se and along the boundary system Sb2S3-Sb2Se3 and the sections Tl3SbS3-Tl3SbSe3, TlSbS2-TlSbSe2, and TlSb3S5-TlSb3Se5 of the phase diagram.  相似文献   

17.
Summary.  The diagram of the ternary system Mg2+/Cl, SO4 2−–H2O was established at 15°C by means of analytical and conductimetric measurements. Three compounds were found in this diagram, which are MgSO4·6H2O, MgSO4·7H2O, and MgCl2·6H2O. The solubility field of MgSO4·7H2O is important whereas those of MgSO4·6H2O and MgCl2·6H2O are small. The compositions (mass-%) of the two invariant points determined by the two methods are: MgSO4:MgCl2=2.73:33.80 and MgSO4: MgCl2=3.38:28.91. Both the measured and the calculated isotherm at 15°C have been used for modelling of the diagram Mg2+/Cl, SO4 2−–H2O between 0 and 35°C. The polythermal invariant point was approximately located between 15 and 10°C.  Corresponding author. E-mail: ariguib@planet.tn Received October 16, 2002; accepted (revised) December 3, 2002 Published online April 24, 2003 RID="a" ID="a" Dedicated to Prof. Dr. Heinz Gamsj?ger on the occasion of his 70th birthday  相似文献   

18.
The reactions of SnMe3Cl with salts of the cluster anionic complexes [Re6Q8(CN)6]4? (Q = S, Se) gave novel complexes [{(SnMe3)2(OH)}2{SnMe3}2{Re6S8(CN)6}] (I), (Me4N)2[{SnMe3(H2O)}2{Re6Se8(CN)6}] (II), [{(SnMe2)43-O)}2{Re6Se8(CN)6}] (III), and [(SnMe2)43-O)22-OH)2(H2O)2][{SnMe3 2{Re6Se8(CN)6}] (IV). The structures of I–IV were determined by X-ray diffraction. Compounds I, IV have the chain structures with the CN-SnMe3-NC bridges between the cluster anions [Re6Q8(CN)6]4?. Compound II contains isolated fragments {SnMe3(H2O)}2{Re6Se8(CN)6}2?. In the polymer framework of compound III, the cluster anionic complexes [Re6Se8(CN)6]4? are bound by the complex cations [(SnMe2)43-O)2]4+ formed due to the hydrolysis of the initial (SnMe3)Cl.  相似文献   

19.
20.
Synthesis of a mixed complex compound Pb2[Fe(CN)6]NO3·5.5H2O is described. The results of its X-ray structural investigation are presented. Crystal data: C6H11FeN7O8.50Pb2: a = 7.2582(6) Å, b = 21.838(3) Å, c = 11.612(1) Å; β = 107.91(1)°, V = 1751.4(3) Å3, Z = 4, dcalc = 2.986 g/cm3, space group P21/m, R = 0.038. The compound has a framework polymer structure.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号