Modifications in band gap and optical properties of Zn0.96−xNd0.04CuxO (x = 0, 0.05, 0.1 and 0.15) nanoparticles

Nd-doped and Nd, Cu co-doped ZnO nanoparticles (Zn_0.96?xNd_0.04Cu_xO, x = 0, 0.05, 0.1 and 0.15) were synthesized by sol–gel method. The structural and optical properties of the samples were investigated by X-ray diffraction (XRD) and UV–visible photo-spectrometer. The synthesized nanoparticles have different microstructure without changing a hexagonal wurtzite structure. CuO phase was noticed in XRD spectra at 38.73° after Cu = 5 % which was formed from remaining un-reacted Cu²⁺ ions. The average crystal size was gradually increased from Cu = 0 % (17 nm) to 15 % (17.6 nm) having lowest value (16.7 nm) at Cu = 5 %. The change in lattice parameters confirmed the substitution of Cu in Zn–Nd–O lattice. The observed constant c/a ratio revealed that there was no change in hexagonal wurtzite structure by Cu-doping. The energy dispersive X-ray spectra confirmed the presence of appropriate amount of Nd and Cu in Zn–O lattice. The optical absorption was increased gradually from Cu = 0–10 % and showed maximum at Cu = 10 % due to the presence of more nucleation centres and defect states. The defects related green band between 487 and 493 nm was due to the oxygen vacancies and intrinsic defects. The higher transmittance (≈ 90 %) noticed at Cu = 15 % leads to the industrial applications. The observed blue shift in energy gap from 3.49 eV (Cu = 0 %) to 3.65 eV (Cu = 10 %) and the red shift from Cu = 10 % (3.65 eV) to Cu = 15 % (3.61 eV) can be explained by the Burstein–Moss effect. Presence of chemical bonding was confirmed by Fourier transform infrared spectra.     

乳状液膜法制备超细碳酸钙

探讨了不同流动载体的煤油、司本 - 80与碳酸钠水溶液制成的乳状液的稳定性 .考察了外相氢氧化钙水溶液中Ca2 + 浓度、膜相磷酸三丁酯的量及乳水比等因素对Ca2 + 迁移率的影响 .经TEM测定 ,破乳后的沉淀颗粒粒径不超过 10 0nm .     

Phase separation temperatures in the ternary system polystyrene/poly(α-methyl styrene)/cyclopentane

Phase separation temperatures of the ternary system polystyrene (PS) (M_w = 1.67 × 10⁴)/poly(α-methyl styrene) (PαMS) (M_w = 9.0 × 10⁴)/cyclopentane with a blend ratio PS/PαMS = 55/45 have been determined over the polymer concentration range 0.02 ≤ ψ_{PS + PαMS} ≤ 0.52, where ψ _{PS + PαMS} is the segment fraction of polymer in ternary system. Phase separation temperatures for the upper critical separation in the ternary system decrease with increasing ψ _{PS + PαMS} over the range 0.1 ≤ ψ _{PS + PαMS} ≤ 0.52. The vapor—liquid equilibrium in this system with a blend ratio PS/PαMS=50/50 has been determined over the concentration range 0.925 ≤ ψ_{PS + PαMS} < 0.995 and the temperature range 60–100°C by the piezoelectric vapor sorption method. The polymer—polymer interaction parameters χ′₁₂ determined are positive except at 100°C and increase with increasing ψ _{PS + PαMS}. Values of χ′₁₂ extrapolated to zero solvent concentration are positive (0.0–1.3) over the temperature range measured. Phase separation behavior is discussed in terms of phase separation temperature in a ternary system and the polymer–polymer interaction parameter.     

Preparation and Superconductivity of a Series of Bi2CaSr2-XBaxCu2O8+δ

By means of the addition of Ba into the Bi-Ca-Sr-Cu-O 2122 system, a series of Bi₂CaSr_2-xBa_xCu₂O_8+δ (0 ≤ × ≤ 2) quinary metal oxides were prepared by the citrate route and by the conventional powder reaction method. The samples prepared by the former method have better properties than the latter. It was found that 5 was not equal to zero for all of them and that it increased with decreasing Tc. Two phases were indentified in the oxides containing all five metal elements. One is the Bi-Ca-Sr-Cu-O 2122 phase, the other is a new insulating phase which probably contains Bi-Ca-Ba-Cu-O with undetermined stoichiometry. Superconductivity was found in those samples for which × ≤ 1.50 with their Tc onsets between 93–78 K by resistivity measurements. Superconductivity decreased monotonically with increasing x. However, residual resistance was found in those samples for which 1.00 ≤ × ≤ 1.50, The Meissner effect appears in the samples where × ≤ 1.00 with Tc onsets between 88–80 K. For x = 1.75 and 2.00, the samples were semiconductors with resistivities of 6.66 × 10² and 6.96 × 10³ Ω cm at 290 K, and activation energies of 0.109, and 0.298 eV, respectively.     

Cu取代对水滑石前驱物及其衍生氧化物性能的影响

The coprecipitation method was used to prepare a series of different oxides (CuO: 0, 5%, 10%, 15%, 20%, 30% and 40%) derived from Cu substituted Mg/Al mixed anionic clay precursors (hydrotalcites) at the ratio of M2+/M3+ =3. In order to study influences of Cu and Mg content upon the performance of these materials, such characterization techniques as X-ray diffraction, thermogravimetrical analysis, differential scanning calorimetry, temperature programmed reaction and Fourier transform infrared reflectance spectra, were used. The results showed that complete structure of hydrotalcite precursors could be formed when CuO≤30%. When CuO≥40%, Cu(OH)2 phase appeared. Homogeneous composite oxides can be obtained by high temperature calcination at CuO≤20%. When CuO>20%, CuO phase was isolated. The content of Cu and Mg had significant influences on thermal stability of materials. The reduction ability of materials was related to calcination temperatures and material composition.     

Kinetics of metal exchange reaction of Cu(II)-poly(vinyl alcohol) complex with Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between the Cu(II)-poly(vinyl alcohol) complex (Cu(II)-PVA) and Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid (Ca(II)-EDTA) were studied by mixing both solutions in a spectrophotometer at pH 9.7–11.0, at μ = 0.10(KNO₃) and at 25°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA by the attack of H⁺ to Cu(II)-PVA, and while both ligand exchange and metal exchange steps occur, the latter may be rate-determining. The kinetic expression of this reaction was determined as -d[Cu(II)-PVA]/dt = k[Cu(II)-PVA] [H⁺] [PVA]/[Ca(II)-EDTA], where k = k₁ + k′₂[H⁺], k₁ = 3.85 × 10⁻² sec⁻¹, k₂ = k′₂ · K^−H_Cu(II)-H-PVA 9.59 × 10⁵ 1 mol⁻¹ sec⁻¹.     

State of water in amorphous calcium and calcium-magnesium phosphates

Fourier-transform infrared spectra of three samples of deposited amorphous phosphates, calcium monodiphosphate (orthopyrophosphate) with a molar ratio 2P/(2P + 1P) of ～0.3, calcium magnesium monophosphate with an atomic ratio Mg/(Mg + Ca) of ～0.3, and calcium-magnesium monodiphosphate with a molar ratio 2P/(2P + 1P) of ～0.1 and atomic ratio Mg/(Mg + Ca) of ～0.1, were analyzed. On the basis of the observed similarity between the v(OH), δ(OH) and (δ + ω)(OH) lines in the spectra of these phosphates and liquid water analogous states of water molecules therein were assumed. It was presumed that the formation of amorphous phosphates involves deposition of poorly soluble substances on the surface of water nanoclusters.     

Synthesis,Crystal Structure and Reducibility of K2NiF4 Type Oxides Sm2—xSrxCuO4

K2NiF4 type compounds Sm2-xSrxCuO4(0≤x≤1.2)were prepared.Rietveld refinement of powder diffraction data shows that the crystal system of these compounds belongs to T′ type tetragonal structure of space group I4/mmm,and the addition of Sr causes a dramatic shift of the O(I) ions along the c axis from Sm(Sr) toward Cu while scarcely affecting the Cu-O(Ⅱ）bond in basal CuO4 phane.From XRD data,it can be seen that when 0.0≤x≤0.6,Sm2-xSrxCuO4 belongs to a singlephase K2NiF4 type structure,while at x≥0.7,both the free SrO phase and the CuO phase exist in these compounds.From the results of XPS and rietveld refinement,it can be seen that after replacing Sm^3 with Sr^2 of lower valence,the valence of Cu and Sm does not change apparently,and thus some defect must be formed at the oxygen ion positions and/or position A on A2BO4 to keep charge balance and to stabilize the structure.     

Structural chemistry of A3CuBO6 (A = Ca, Sr; B = Mn, Ru, Ir) as a function of temperature

Variable temperature X-ray and neutron powder diffraction techniques have been used to identify structural phase transitions in Cu-rich A(3)A'BO(6) phases. A transition from monoclinic to rhombohedral symmetry was observed by X-ray diffraction between 700 and 500 K in Sr(3)Cu(1-x)M(x)IrO(6) (M = Ni, Zn; 0 < or = x < or = 0.5). The temperature of the phase change decreased in a linear manner with Cu-content and was essentially independent of the nature of M. Ca(3.1)Cu(0.9)MnO(6) was shown to pass from a rhombohedral phase to a triclinic phase on cooling below 290 K; the structure of the triclinic phase was refined against neutron diffraction data collected at 2 K. Ca(3.1)Cu(0.9)RuO(6) undergoes a transition between a disordered rhombohedral phase and an ordered monoclinic phase when cooled below 623 K. Neutron diffraction has been used to determine the structure as a function of temperature in the range 523 < or =T/K < or = 723 and hence to determine an order parameter for the low temperature phase; the second-order transition is shown to be incomplete 100 K below the critical temperature.     

Electrometric titrations of Bi(III), Cu(II), Pt(IV), Te(VI) and Te(IV) with standard iron(II) solution in alkaline medla containing hexitols

Potentiometric, bipotentiometric and biamperometric titrations with an iron(II) salt in alkaline solutions containing sorbitol are reported. Suitable conditions are discussed for determinations based on the Bi(III) → Bi°, Cu(II) → Cu(I) → Cu°, Pt(IV) → Pt(II) → Pt° and Te(VI) → Te(IV) → Te° → telluride systems.     

Effect of the ionic strength and prostaglandin E2 on the free Ca2+ concentration and the Ca2+ influx in human red blood cells

Human red blood cells (RBCs) were loaded with the Ca(2+)-sensitive fluorescent dye fura-2 to investigate the effects of media ionic strength and prostaglandin E2 (PGE2) on the intracellular free Ca2+ concentration ([Ca2+]i). [Ca2+]i of intact RBCs in a Ca(2+)-containing physiological (high) ionic strength (HIS) solution was 75.1 +/- 8.3 nM after 5 min incubation, increasing to 114.9 +/- 9.6 nM after 1 h. In Ca(2+)-containing low ionic strength (LIS) solutions, [Ca2+]i was significantly lower than in the Ca(2+)-containing HIS solution (p = 0.041 or 0.0385 for LIS solutions containing 200 or 250 mM sucrose, respectively), but, as in HIS solution, an increase of [Ca2+]i was seen after 1 h. In Ca(2+)-free (0 Ca2+ plus 15 microM EGTA) media, [Ca2+]i decreased (ranging from 15 to 21 nM), but were not significantly different in HIS or LIS, and did not change following 1 h incubation. The effect of the ionic strength and PGE2 on passive Ca2+ influx was investigated on ATP-depleted RBCs. Ca2+ influx was faster during the initial 10 min in comparison with the subsequent time period (10-45 min), both in HIS and LIS media, decreasing from 20.3 +/- 1.9 to 12.9 +/- 1.3 micromol/(lcells x h) in HIS, and from 36.7 +/- 5.3 to 8.6 +/- 1.2 micromol/(lcells x h) in LIS. Prostaglandin E2 (PGE2; 10(-7)-10(-11) M), dissolved in deionised water or in ethanol, did not affect [Ca2+]i in either normal or in ATP-depleted RBCs suspended in Ca(2+)-containing HIS medium. Finally, the addition of carbachol (100 microM) did not affect [Ca2+]i. The present findings suggest that stimulation of the Ca(2+)-activated K+ channel by PGE2, reported in [J. Biol. Chem. 271 (1996) 18651], cannot be mediated via increased [Ca2+]i.     

Synthesis, Crystal Structure, Transport, and Magnetic Properties of Novel Ternary Copper Phosphides, A(2)Cu(6)P(5) (A = Sr, Eu) and EuCu(4)P(3)

Three new ternary copper phosphides, Sr(2)Cu(6)P(5), Eu(2)Cu(6)P(5), and EuCu(4)P(3), have been synthesized from the elements in evacuated silica capsules. Eu(2)Cu(6)P(5) and Sr(2)Cu(6)P(5) adopt the Ca(2)Cu(6)P(5)-type structure, while EuCu(4)P(3) is isostructural to BaMg(4)Si(3) and still remains the only representative of this structure type among the ternary Cu pnictides. All three materials show metallic conductivity in the temperature range 2 K ≤ T ≤ 290 K, with no indication for superconductivity. For Eu(2)Cu(6)P(5) and EuCu(4)P(3), long-range magnetic order was observed, governed by 4f local moments on the Eu atoms with predominant ferromagnetic interactions. While Eu(2)Cu(6)P(5) shows a single ferromagnetic transition at T(C) = 34 K, the magnetic behavior of EuCu(4)P(3) is more complex, giving rise to three consecutive magnetic phase transitions at 70, 43, and 18 K.     

An investigation of homogeneity within micro-areas of IAEA Urban Dust reference materials by the scanning proton microprobe technique

In order to develop new reference materials for microanalytical nuclear techniques, the Scanning Proton Microprobe (SPM) technique was used to determine homogeneity levels within 100 × 200 μm² areas on small pieces of IAEA Urban Dust reference materials. The experimental methods are described in detail. The results show that IAEA-396A/M Vienna Urban Dust is homogeneous enough for an SRM (≤ 10% for Si, S, K, Ca, Fe, Cu, Zn) for small sample analysis.     

Syntheses,Crystal Structures,and Antibacterial Activities of Four Schiff Base Complexes of Copper and Zinc

Four Schiff base complexes, [Cu₂(L1)₂(μ‐NCS)₂] ( 1 ), [Cu₂(L2)₂(μ‐N₃)₂] ( 2 ), Cu[Cu(CH₃COO)(L3)]₂ ( 3 ), and [Zn{Zn(C₃H₄N₂)(L3)}₂(NO₃)](NO₃) ( 4 ) (where L1 = 2‐[(pyridin‐2‐ylmethylimino)methyl]phenol, L2 = 1‐[(pyridin‐2‐ylmethylimino)methyl]naphthalen‐2‐ol, and L3 = bis(salicylidene)‐1, 3‐propanediamine), were synthesized and characterized by elemental analyses, infrared spectroscopy, and single crystal X‐ray determinations. Both 1 and 2 are structurally similar di‐nuclear complexes, which are located at crystallographic inversion centers (with the center of the central Cu₂N₂ ring). In 1 , each copper atom has a slightly distorted square pyramidal configuration, coordinated by two nitrogen atoms and one oxygen atom from L1 and another two terminal nitrogen atoms from two bridging thiocyanate anions. The Cu···Cu separation is 3.466(3) Å. The structure of 2 is similar to that of 1 , with Cu···Cu separation of 3.368(2) Å. Both 3 and 4 are linear tri‐nuclear complexes. In 3 , the central Cu²⁺ ion is located on an inversion centre and has a distorted octahedral coordination involving four bridging O atoms from two Schiff base ligands (L3) in the equatorial plane and one O atom from each bridging acetate group in the axial positions. The coordination around the terminal Cu²⁺ ions is irregular‐square pyramidal, with two O and two N atoms of L3 in the basal plane and one O atom from an acetate group in the apical position. The acetate bridges linking the central and terminal Cu²⁺ ions are mutually trans. The Cu···Cu separation is 3.009(3) Å. In 4 , the coordination configuration of the central and the terminal zinc atoms are similar to that of the 3 , with Zn···Zn separation of 3.153(4) Å. The three Schiff bases and the corresponding three copper complexes exhibit good antibacterial properties, while the zinc complex 4 has nearly no.     

Mössbauer Spectroscopy and Preparation of Hg-1223, Tl-1223 and Tl-1212 Superconductors

Introduction of the Mössbauer nuclei ⁵⁷Fe into Hg-1223 phase and that of ⁵⁷Fe and ¹⁵¹Eu into Tl-1212 and Tl-1223 superconductors were investigated. Samples of high phase purity were obtained. Scanning electron microscopy and optical microscopy in normal and polarized light were employed to study the microstructure of the specimens. Energy dispersive X-ray analysis showed that ⁵⁷Fe in the Hg-based samples and ⁵⁷Fe as well as ¹⁵¹Eu in the Tl-based compounds, entered superconducting phases. Incorporation of Eu³⁺ into the superconducting phase favored the formation of the Tl-1212 phase. Mössbauer spectroscopy showed that Eu³⁺ entered the Ca-site. Two doublets found in the ⁵⁷Fe Mössbauer spectra in both the Hg-1223 and the Tl-1223 phase referred to two different micro-environments of Fe³⁺. The assignment of the ⁵⁷Fe Mössbauer spectra was made under the assumption that Fe favored the 1223 phase. Fe³⁺ may replace Cu in both the square pyramidal, five-fold oxygen coordinated Cu sites between the Ca and Ba-(Sr)-O layers, and in the square planar, four-fold oxygen coordinated Cu sites the Ca layers in the superconducting phases in both the Hg- and the Tl-based materials. From the relative areas of the two doublets, we concluded that the Fe³⁺ preferred the square planar Cu site.     

Growth and Spectral Characterization of Nd3+∶(Sr0.7Ca0.3)3Y(BO3)3 Crystal

A Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal with dimensions of 17×23 mm3 has been grown by the Czochralski method. The spectroscopic characterization of Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal was investigated. The polarized absorption cross-sections of Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal are 2.81×10-20 cm2 with full width at half maximum (FWHM) of 14 nm at 808 nm for σ-polarization and 2.04×10 -20 cm 2 with FWHM of 19 nm at 807 nm for σ-polarization, respectively. The polarized emission cross-sections of Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal are 12.2×10-20 cm2 at 1062 nm for the π-polarization and 13.6×10-20 cm2 at 1061 nm for the σ-polarization, respectively. After the Ca 2+ ion partly substitutes for Sr2+ ion in the Sr3Y(BO3)3 crystal to form the (Sr0.7Ca0.3)3Y(BO3)3 solid solution, it can improve the quantum efficiency of Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal. The quantum efficiency is 31.7%. These results may be regarded Nd3+ :(Sr0.7Ca0.3)3Y(BO3)3 crystal as a potential solid-state laser material.     

Über den Einfluß von Substitution auf die Kristallstruktur von SrNi2P2

About the Effect of Substitution on the Crystal Structure of SrNi₂P₂ With several series of mixed crystals the effect of substitution on the crystal structure of SrNi₂P₂ (polymorphic, the structures are variants of the ThCr₂Si₂ type) is investigated by X-ray methods. In the compound Ni completely can be substituted by Co and Cu respectively and also P by As; in Sr_1–xCa_xNi₂P₂ there is a gap of the miscibility between 0.3 ≤ x ≤ 0.6. A low substitution of the several elements more than proportionally changes the structure parameters. In this range the mixed crystals with Ca, Cu, and As, respectively, undergo first order phase transitions with significant changes of the bond distances, which will be interpreted by the results of band structure calculations.     

Syndiospecific polymerization of styrene in the presence of new titanium complexes with dialkanolamines: Titanocanes and bistitanocanes

The syndiospecific polymerization of styrene is studied in the presence of titanium complexes with dialkanolamines—bistitanocanes and titanocane—activated by individual MAO or the combined cocatalyst MAO/TIBA. It is shown that these catalysts are more active and stereospecific after their activation with the combined cocatalyst ([TIBA]: [MAO] ≤ 0.13) than that in the case of the activation with MAO: The activities of the catalysts are ≤18 and 9 kg PS/(mol Ti h), and the syndiotacticities of PS are ≤76 and 60%, respectively. Polymers synthesized in the presence of bistitanocanes are characterized by M _n ≤ 4.5 × 10⁴ and T _m ≤ 268°C and a narrow molecular-mass distribution (≤2.5).     

Synthesis, structure and dielectric properties of Ba1-xSrx My Ti1-yO3 (M = Zr, Sn)

A series of Ba1-xSrxMyTi1-yO3 (M = Zr, Sn, 0≤x≤0.4, 0≤y≤0.3) solid solutions were synthesized with the soft chemical method below 100 ℃. XRD pattern and cell parameters-composition figures of the prepared powder demonstrate that they are completely miscible solid solutions based on BaTiO3. Furthermore, TEM shows that they have a shape of uniform, substantially spherical particles with an average particle size of 70 nm in diameter. The sintered ceramics of the powder doped with Sr2 and Zr4 or Sn4 have dielectric constant eight times higher and dielectric loss thirty per cent lower than those of pure BaTiO3 phase at room temperature.     

Preparation and characterization of carbonated barium-calcium hydroxyapatite solid solutions

Particles of carbonated barium-calcium hydroxyapatite solid solutions (BaCaHap) with different Ba/(Ba+Ca) (X(Ba)) atomic ratios were prepared by a wet method at 100 degrees C and characterized by various means. The crystal phases and structures of the products strongly depended on the composition of the starting solution, that is, the Ba/(Ba+Ca) atomic ratio ([X(Ba)]) and H3PO4 concentration ([H3PO4]) in the solution. BaCaHap with X(Ba)0.43 could be prepared at [X(Ba)]0.7 by changing [H3PO4], but could never be obtained at [X(Ba)]=0.8-0.95 regardless of [H3PO4]. The carbonated calcium hydroxyapatite particles prepared at [X(Ba)]=0 were fine and short rod-shaped particles (ca. 14x84 nm). With increasing [X(Ba)] from 0 to 0.8, the particles obtained became large spherical agglomerates. The carbonated barium hydroxyapatite particles formed at [X(Ba)]=1 were long rod-shaped agglomerates (ca. 0.2x2 microm) of fine primary particles. The amount of CO2 adsorbed irreversibly on a series of BaCaHaps showed a minimum at (Ba+Ca)/(P+C) atomic ratio of around 1.56, which agreed well with the minimum cation/P ratio obtained for the other hydroxyapatites, as already reported.