Effect of the Zn2+ and Hg2+ ions on the structure of liquid water

The effect of ions on the structure of liquid water is still not completely understood, despite extensive experimental and theoretical studies. A combined XANES and molecular dynamics investigation on diluted Zn(2+) and Hg(2+) aqueous solutions reveals that the influence of a single ion on the bonding pattern of water molecules is strongly dependent on the nature of the ion. While the structure of water is not altered by the presence of the Zn(2+) ion, the Hg(2+) cation has a strong impact on the hydrogen-bond network of water that extends beyond the first coordination shell.     

Synthesis of CaWO4:Er3+@SiO2 and CaWO4:Tm3+@SiO2 nano-particles via a combustion pathway and study of their optical properties

Use of citric acid as a chelating agent and fuel, ammonium nitrate as fuel, boric acid as flux material and silica as supports, CaWO₄:Ln³⁺@SiO₂ (Ln = Er and Tm) nanoparticles were synthesized via a combustion reaction at 800 °C. Characterization of the samples was performed by X-ray diffractometer (XRD), reflectance UV–Vis spectrophotometer, fluorescence spectrophotometer (PL) and transmission electron microscope (TEM). XRD patterns showed that tetragonal crystalline structure of scheelite and silica supports were formed, and that the formation of a silica support could enhance the luminescence intensity of CaWO₄:Ln³⁺. The reflectance UV–Vis and PL spectra indicated the broad absorption band of WO₄ ^2? groups about 240 nm, the WO₄ ^2? wide excitation band with maximum at 240 nm, a broad emission band of WO₄ ^2? with maximum about 420 nm, and characteristic emissions of Ln³⁺ ions. According to the TEM analysis, CaWO₄:Er³⁺@SiO₂ and CaWO₄:Tm³⁺@SiO₂ nanoparticles have almost the same morphology with average particle sizes about 50 nm.     

Investigations of the optical spectra and EPR parameters in CaWO4:Yb3+

In this paper, we calculate the optical spectra data (crystal-field energy levels), the electron paramagnetic resonance (EPR) g factors gparallel, gperpendicular of Yb3+ and hyperfine structure constants Aparallel, Aperpendicular of 171Yb3+ and 173Yb3+ isotopes in CaWO4 crystal in a unified way from the crystal-field theory. All the calculated results are in good agreement with the experimental values. The signs of Aparallel and Aperpendicular for both isotopes 171Yb3+ and 173Yb3+ are suggested.     

Effect of sol temperature on the structure,morphology, optical and photoluminescence properties of nanocrystalline zirconia thin films

Transparent nanocrystalline zirconia thin films were prepared by sol–gel dip coating technique using Zirconium oxychloride octahydrate as source material on quartz substrates, keeping the sol at room temperature (SET I) and 60 °C (SET II). X-ray diffraction (XRD) pattern shows the formation of mixed phase [tetragonal (T) + monoclinic (M)] in SET I and a pure tetragonal phase in SET II ZrO₂ thin films annealed at 400 °C. Phase transformation from tetragonal to monoclinic was achieved in SET II film annealed at 500 °C. Atomic force microscopy analysis reveals lower rms roughness and skewness in SET II film annealed at 500 °C indicating better optical quality. The transmittance spectra gives a higher average transmittance >85% (UV–VIS region) in SET II films. Optical spectra indicate that the ZrO₂ films contain direct—band transitions. The sub- band in the monoclinic ZrO₂ films introduced interstitial O⁻defect states above the top of the valance band. The energy bandgap increased (5.57–5.74 eV) in SET I films and decreased (5.74–5.62 eV) in SET II films, with annealing temperature. This is associated with the variations in grain sizes. Photoluminescence (PL) spectra give intense band at 384 and 396 nm in SET I and SET II films, respectively. A twofold increase in the PL intensity is observed in SET II film. The “Red” shift of SET I films and “Blue” shift of SET II films with annealing temperature, originates from the change of stress of the film due to lattice distortions.     

Effect of metal ions on structural,morphological and optical properties of nano-crystallite spinel cobalt-aluminate (CoAl2O4)

The bright blue nano crystallite cobalt aluminate (CoAl₂O₄) was synthesized by sol–gel method using a mixture of chelating agent of glycerol and citric acid. The effects of changing (0.05, 0.075, 0.10, 0.25, 0.50, and 0.75 mol/L) metal ion concentration on the structural, morphological and color properties of synthesized CoAl₂O₄ were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Nanoparticle size analyzer, Simultaneous Thermal Analyzer (STA), UV–vis absorption spectroscopy, and CIE-LAB colorimetric analysis. From the X-ray peak profile analysis, the crystallite size was measured by Debye-Scherrer (D-S) equation, and three different models presenting average crystallite sizes between 88.3 and 125.4 nm.The average lattice strain, dislocation density, lattice constant, cell volume, and zeta potential were between 0.00021 and 0.0058, (1.73 to 12.8) × 10¹⁴ (lines/m²), 8.10658 to 8.11181 Å, 533.60 to 533.81 Å³, ?56.4 to ? 63.5 mV, respectively. Using UV–vis absorption spectroscopy, the band gap was calculated from Kubelka-Munk method, and the values of band gap increasing from 1.82 to 1.84 eV, respectively. The reflectance spectra and the CIE-L*a*b* values of cobalt aluminate is also measured which confirmed the formation of blue nano crystallite cobalt aluminate.     

Sorption behavior of Co2+, Zn2+ and Ba2+ ions on alumina,kaolinite and magnesite

The sorption behavior of Ba²⁺, Co²⁺ and Zn²⁺ ions on alumina, kaolinite and magnesite have been investigated using the batch method.⁶⁰Co,⁶⁵Zn and¹³³Ba were used as radiotracers. The mineral samples were separated into different particle size fractions using an Andreasen Pipette. The particle sizes used in the sorption experiments were all less than 38 m. Synthetic groundwaters were used which had compositions similar to those from the regions where the minerals were recovered. The samples were shaken with a lateral shaker at 190 rpm, the phases were separated by centrifuging and adioactivity counted using a NaI(Tl) detector. Kinetic studies indicated that sorption onto the minerals took place in two stages with the slower process dominating. The highest sorption was observed on alumina. Both Freundlich and Dubinin-Radushkevich type isotherms were found to describe the sorption process well. The distribution ratio,R _d was found to be a function of the liquid volume to solid mass ratio. TheR _d 's for sorption on binary mixtures of minerals were experimentally determined and compared with those predicted fromR _d values of each individual mineral.     

Effect of crystal structure and ions concentration on luminescence in Yb and Tm codoped fluoride microcrystals

A facile hydrothermal method is used for the preparation of Tm³⁺/Yb³⁺ codoped fluoride microphosphors. The effect of crystal structure and ions concentration on the spectra and lifetimes of the radiative levels of Tm³⁺ ions in the different fluoride microcrystals is studied in detail. XRD analysis of Tm³⁺/Yb³⁺ codoped LaF₃ microcrystals shows that 20% Yb³⁺ doping is sufficient for hexagonal LaF₃ microparticles to crystallize completely in the orthorhombic phase. And lifetime analysis suggests that the average lifetimes of the radiative levels of Tm³⁺ ions increased when the matrix phase structure changing from orthorhombic phase to hexagonal phase with ytterbium dopant concentration changing.     

Effect of PSS on morphology and optical properties of ZnO

ZnO micrometer-sized rods with tunable aspect ratios and 3D hollow spherical superstructures are selectively fabricated by a simple poly(sodium 4-styrene-sulfonate) (PSS)-mediated hydrothermal crystallization and assembly strategy. When PSS concentration is relatively low (0-0.5 g L), the aspect ratios of as-obtained microrods steadily decrease with increasing PSS concentration due to the selective adsorption of PSS on the polar ZnO (001) crystal plane. When PSS concentration is relatively high (1 g L), 3D nanosheets-built hollow microspheres form probably due to the organic-inorganic interfacial cooperative assembly. Raman, photoluminescence and UV-vis diffuse reflectance spectra show that the optical properties of as-obtained ZnO microstructures are highly related to their specific morphologies.     

Controllable synthesis and luminescent properties of three-dimensional nanostructured CaWO4:Tb3+ microspheres

Three-dimensional (3D) nanostructured CaWO(4):Tb(3+)microspheres assembled by submicrospindles were synthesized via a mild sonochemical route from an aqueous solution of CaCl(2), TbCl(3) and Na(2)WO(4) with the aid of surfactant Polyglycol 600 (PEG-600). The crystal structure and morphology of the as-prepared products were characterized by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Rietveld refinement was carried out on the XRD data. The results showed that the CaWO(4):Tb(3+)nanoparticles can be formed without ultrasonic irradiation or addition of PEG-600. With continuously increasing irradiation time the submicrospindles and microspheres could be self-assembled. The central diameter and length of the submicrospindles are around 190 and 500 nm, respectively. The 3D CaWO(4):Tb(3+)nanostructured microspheres with diameter of 2-4 μm were assembled by the submicrospindles. A possible formation mechanism for the 3D-structured CaWO(4):Tb(3+)microspheres was proposed. The Photoluminescent (PL) properties of Tb(3+) ions in the nanostructured CaWO(4) microspheres were studied. The energy transfer processes in CaWO(4):Tb(3+)microspheres were analyzed. The electric dipole-dipole energy transfers related to (5)D(3) level were studied by inspecting the fluorescence decay of (5)D(3) level. The energy transfer critical distance was estimated.     

Tracer-diffusion of Zn2+ ions in cobalt sulphate

Tracer-diffusion of Zn²⁺ ions in the presence of CoSO₄ is studied at 25°C in 1% agar gel over a concentration range of 10^–5 to 0.25M using a zone-diffusion technique. The deviations observed between experimental and theoretical values of diffusion coefficients are explained by considering different types of interactions occurring in the ion-gel-water system. Further, study of the obstruction, effect in the diffusion of Zn²⁺ ions at different concentrations of CoSO₄ reveals that the -value decreases with increasing concentration of the electrolyte. This observation is accounted on the basis of competitive hydration between ions and agar molecules.     

A pure inorganic 2-D framework based on paradodecatungstate and Mn2+ ions: syntheses,structure, and properties

A pure inorganic 2-D framework based on paradodecatungstate polyanions and [Mn(H₂O)_n]²⁺ (n = 2, 3) ions, Na₁₀{[Mn(H₂O)₃]₂[H₂W₁₂O₄₂]}{[Mn(H₂O)₃]₂[Mn(H₂O)₄][H₂W₁₂O₄₂]}·56H₂O (1), has been synthesized and characterized by IR spectra, UV–vis spectra, thermogravimetric analysis (TGA), single-crystal X-ray diffraction, and magnetic measurements. Single-crystal X-ray diffraction analysis indicates that [H₂W₁₂O₄₂]^10? in 1 is a tetradentate ligand and coordinates to four [(Mn(H₂O)₃]²⁺ cations through terminal oxygens to form manganese doubly bridged 1-D chains, which are further linked through [Mn(H₂O)₄]²⁺ ions into a 2-D layer. The catalytic activities of 1 are tested in the selective oxidation of benzyl alcohol to benzaldehyde with 30% aqueous H₂O₂ as oxidant in toluene, exhibiting 90% conversion and 93% selectivity. Magnetic studies indicate that weak antiferromagnetic couplings exist between the Mn(II) ions in 1.     

Synthesis,structure, and optical properties of CsU2(PO4)3

CsU₂(PO₄)₃ was synthesized in highest yield by the reaction in a fused-silica tube of U, P, and Se in a CsCl flux at 1273 K. It crystallizes with four formula units in space group P2₁/n of the monoclinic system in a new structure type. The structure of CsU₂(PO₄)₃ is composed of U and Cs atoms coordinated by PO₄^3? units in distorted octahedral arrangements. Each U atom corner shares with six PO₄^3? units. Each Cs atom face shares with one, edge shares with two, and corner shares with three PO₄^3? units. The structure shares some features with the sodium zirconium phosphate structure type. X-ray powder diffraction results demonstrate that the present CsU₂(PO₄)₃ compound crystallizes in a structure different from the previously reported β′- and γ-CsU₂(PO₄)₃ compounds. CsU₂(PO₄)₃ is highly pleochroic, as demonstrated by single-crystal optical absorption measurements.     

Synthesis and study of properties of the polyhexamethyleneguanidine complexes with the ions Cu2+, Zn2+, and Ni2+

The reaction products of polyhexamethyleneguanidine hydrochloride with the Cu²⁺, Zn²⁺, and Ni²⁺ ions, which are the polyligand coordination compounds formed by polyguanidine and hydroxyl ligands, were studied using IR, UV, and ESR spectroscopy. The influence of the nature of the chelating agent on the structure of the complexes formed was revealed. Antibacterial properties of the synthesized complexes were assessed.     

Effects of DNA on the growth and optical properties of luminescent organic microcrystals

The reprecipitation method, which is a solvent-exchange process, was used to prepare free-standing microcrystals from an organic fluorescent dye, 4-n-octylamino-7-nitrobenz-2-oxa-1,3-diazole. Calf thymus DNA was introduced as an additive into the reprecipitation medium, strongly accelerating the process. The reprecipitation kinetics was monitored by UV/vis absorption spectroscopy, and the analysis of the rate constants allowed the role played by the additive to be clarified. DNA was also found to affect the shape and size of the dye microcrystals obtained. In particular, its presence induced the formation of a new type of microcrystal that displays original two-color fluorescence. The emission properties were first analyzed on the suspensions, using a traditional fluorimeter, and then on individual microcrystals by means of a space- and time-correlated photon-counting photomutiplier installed on a microscope. The study on single microcrystals suggests that the dual coloration observed originates from the reabsorption of the blue component of the emitted light, whereas the remaining red component propagates through the microcrystal body and is scattered by the edges. However, the color of the other types of microcrystals can be explained only by specific arrangements of molecules at the surface of the crystal.     

Effect of electron beam irradiation on structure,morphology, and optical properties of PVDF-HFP/PEO blend polymer electrolyte films

Journal of Radioanalytical and Nuclear Chemistry - The effect of 8 MeV energy electron beam (EB) on poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/polyethylene oxide (PEO) (@...     

High-pressure synthesis, crystal structure, and properties of BiPd2O4 with Pd2+ and Pd4+ ordering and PbPd2O4

BiPd(2)O(4) and PbPd(2)O(4) were synthesized at high pressure of 6 GPa and 1500 K. Crystal structures of BiPd(2)O(4) and PbPd(2)O(4) were studied with synchrotron X-ray powder diffraction. BiPd(2)O(4) is isostructural with PbPt(2)O(4) and crystallizes in a triclinic system (space group P1, a = 5.73632(4) ?, b = 6.02532(5) ?, c = 6.41100(5) ?, α = 114.371(1)°, β = 95.910(1)°, and γ = 111.540(1)° at 293 K). PbPd(2)O(4) is isostructural with LaPd(2)O(4) and BaAu(2)O(4) and crystallizes in a tetragonal system (space group I4(1)/a, a = 5.76232(1) ?, and c = 9.98347(2) ? at 293 K). BiPd(2)O(4) shows ordering of Pd(2+) and Pd(4+) ions, and it is the third example of compounds with ordered arrangements of Pd(2+) and Pd(4+) in addition to Ba(2)Hg(3)Pd(7)O(14) and KPd(2)O(3). In PbPd(2)O(4), the following charge distribution is realized Pb(4+)Pd(2+)(2)O(4). PbPd(2)O(4) shows a structural phase transition from I4(1)/a to I2/a at about 240 K keeping basically the same structural arrangements (space group I2/a, a = 5.77326(1) ?, b = 9.95633(2) ?, c = 5.73264(1) ?, β = 90.2185(2)° at 112 K). BiPd(2)O(4) is nonmagnetic while PbPd(2)O(4) exhibits a significant temperature-dependent paramagnetic moment of 0.46μ(B)/f.u. between 2 and 350 K. PbPd(2)O(4) shows metallic conductivity, and BiPd(2)O(4) is a semiconductor between 2 and 400 K.     

Concentration of Co2+, Fe3+ and Zn2+ ions with microbiological collectors

By means of Spicaria Violacea Abbott fungus, a microbiological method of concentration and separation of cobalt, iron and zinc is given. The influence of the experimental conditions, i.e. pH, time and concentration have been investigated.