A three-dimensional highly stable cobalt(II) metal–organic framework based on terephthalic acid: synthesis, crystal structure, thermal and physical properties

A metal?Corganic framework complex, [Co(??₃?Ctp)(??₂?pyz)] _n , where H₂tp?=?1,4-benzenedicarboxylic acid (terephthalic acid) and pyz?=?pyrazine, has been synthesized under hydrothermal conditions and characterized by physico-chemical and spectroscopic methods, thermogravimetric analysis and single-crystal X-ray diffraction. Each Co(II) center is surrounded by four carboxylate oxygen atoms from three tp ligands and two nitrogen atoms from two pyrazine ligands, giving a distorted octahedral geometry. The entire framework is made up of two-dimensional sheets of dicobalt ions linked via terephthalate ligands to form rectangles. The sheets are then linked into each other via the axial pyrazine ligands, forming an interlocked 3-D network, which is finally arranged as an ABAB interconnected pattern. Photoluminescence measurements for the polymer in the solid state show an emission at 414?nm, which suggests this complex as a potential blue-light material. The electrochemical behavior of a modified carbon paste electrode prepared from the complex has been studied by cyclic voltammetry, indicating quasi-reversible redox behavior.     

A novel Lu fluorescent nano-chemosensor using new functionalized mesoporous structures

A new Lu³⁺ sensitive fluorescent chemosensor is designed using 8-hydroxyquinoline functionalized mesoporous silica with highly ordered structure (LUS-SPS-Q). The characterization of LUS-SPS-Q showed that the organized structure has been preserved after the post grafting procedure. The synthesized material showed a selective interaction with Lu³⁺ ion, most probably due to the presence of the fluorophore moiety at its surface. The emission intensity of the Lu³⁺-bound mesoporous material increases with an increase in concentrations of Lu³⁺ ion. Addition of other mono-, di-, trivalent ions resulted in insignificant change in the fluorescent intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Lu³⁺ ion. The linear response range of Lu³⁺ chemo-sensor was from 1.6 × 10⁻⁷ to 1.0 × 10⁻⁵ mol L⁻¹. The Limit of detection obtained was 8.2 × 10⁻⁸ mol L⁻¹ and the pH range which the proposed chemo-sensor can be applied was 3.3–8.3.     

Investigation of environmental and concentration effects on fluorescence properties of AlQ<Subscript>3</Subscript> using mesoporous silica and polyacrylate

In this work, for the first time, control over the position of maximum emission peak for fluorophore, using embedded tris(8-hydroxyquinoline) aluminum (AlQ₃) complexes into different types of host materials, can be achieved. Moreover, the environmental and concentration effects on luminescent properties were studied. In this regard, different concentrations of AlQ₃ were embedded into the poly(methyl methacrylate-co-butyl acrylate) (PMMA-co-PBuA) nanoparticles as organic host materials by emulsion polymerization. It is established that the dilution of AlQ₃ in the polymer matrix leads to blue-shift of the luminescence maximum up to 0.32 eV compared to pure AlQ₃. Moreover, AlQ₃ was embedded in SBA-15 type mesoporous silica as an inorganic host material by physical adsorption. Finally, this functionalized mesoporous silica was incorporated into PMMA-co-PBuA transparent matrix by blending method to obtain Co-Poly-AlQ₃-SBA-15 as organic–inorganic composite material. It was found that there is no significant wavelength shift on the maximum emission peak of the organic–inorganic composite at various concentrations of AlQ₃-SBA-15. The prepared materials were characterized by powder X-ray diffraction (XRD), N₂ adsorption–desorption, NMR, Fourier transform infrared (FT-IR), dynamic light scattering (DLS), scanning electron microscopy (SEM) and fluorescence spectra.     

A study on the formation of strontium hexaferrite nanopowder by a sol–gel auto-combustion method in the presence of surfactant

Strontium hexaferrite is a hard magnetic material and has been extensively used as a permanent magnet. In this work, a novel sol–gel auto-combustion method was used to synthesize ultra-fine strontium hexaferrite, and the effect of the surfactant on the crystallite size of the final product was investigated for the first time. The DTA/TGA plot exhibited the formation temperature of hexaferrite. The XRD results show that adding surfactant to the sol does not change the composition of the combustion product and the surfactant burns completely during the combustion process. The average crystallite size of hexaferrite powders was also measured by the X-ray line broadening technique employing the Scherrer formula. The results show that adding surfactant to the gel makes the particle size of the final product much smaller.     

The synthesis and spectroscopic characterization of nano calcium fluorapatite using tetra-butylammonium fluoride

Pure homogeneous nano sized biocompatible fluorapatite (FAp) particles were synthesized by a wet chemical procedure using water soluble tetra-butylammonium fluoride (TBAF) without using high temperatures and any purification processes. Combination of the Bragg's law and the plane-spacing equation for the two high intensity lines, namely, (002) and (300), gives a=9.3531 ?, c=6.8841 ?, confirms the identity of the highly crystalline synthetic material as well as its purity. The effect of various pH's in crystal formation and on their size was also evaluated. The calculated crystallinities were excellent with a rate around 5.0. The synthesized nano FAp was fully characterized by spectroscopic techniques (XRD, SEM, EDS, BET, FT-IR and ICP-AES). The nitrogen adsorption-desorption isotherm showed a type IV diagram and calculation of the surface area was investigated as well.